Differences between automotive & airplane engines [Archive]

February 10th 06, 05:37 AM

Chris Wells wrote:
> How are "normal" airplane engines tuned to run at a lower rpm? What
> changes would have to be made to an automotive engine to shift the
> power band down accordingly?
>
-----------------------------------------------------------------------------

Dear Chris,

They are not 'tuned' to run at lower rpms, they are DESIGNED to do so.
Indeed, although both are engines, in purely engineering terms they
have surprisingly little in common.

In mechanical terms the two main differences between variable-speed
engines, such as found in cars, and 'normal' aircraft engines are in
the cam timing and the sizing of the bearings. But you're really
looking at an entirely different engineering philosophy, in that with
an aircraft engine reliability is given a higher priority than any
other factor.

Another major difference is the ratio between nominal and peak power.
The service life of a car's engine is based on a nominal output equal
to about 25% (or less) of the engine's peak output. That is the level
of output the engine is expected to produce for approximately 98% of
its service-life. The only time it will be asked to produce more is
when accellerating or climbing a grade. By comparison, the nominal
output of an aircraft engine is about 70% of its peak (or take-off)
rating, dropping to about 55% if the objective is to achieve maximum
time between overhauls.

A major problem in the on-going contraversy about converting car
engines for use in airplanes is that most Americans are not well versed
in automotive engineering and the best example of that may be seen in
the comments produced any time an engineer uses the term.
'Automotive,' of course, means ANYTHING that moves under its own
power and 'automotive engineering' covers everything from the space
shuttle to motorbikes... unless you happen to be one of the millions of
superbly ill-educated Americans who use 'automotive' when they mean
'automobile.' This is far more than grammatical nit-picking, in that
it is impossible to carry on a meaningful dialogue without properly
defined terms.

A by-product of that lack of education is how Americans view
'horsepower,' typically insisting that 50hp (at 5000rpm) is EXACTLY THE
SAME as 50hp (at 1000rpm). Indeed, most will whip out their calculator
and 'prove' they are identical :-) But as the Wright brothers
discovered more than a hundred years ago, horsepower is not a factor in
the equation of flight. With powered flight, the factor we must
concern ourselves with most is thrust. Working back through the
equation, for a given propeller efficiency & rpm we will eventually
arrive at a given quanta of torque which then may be converted into
units of 'horsepower,' should we wish to do so, although it serves no
useful purpose. But when we DO use 'horsepower' we must be careful to
never use it in isolation, always identifing the rotational speed at
which that 'horsepower' is being produced.

And along about here someone will discover the simple solution of
putting a gear-train between the thing producing all that lovely
'horsepower' and the propeller producing all that necessary thrust.
Indeed, the more astute will point out that the Wright brothers did
exactly that, using an arrangement of bicycle chains as a a
torque-multiplier :-)

-R.S.Hoover

Alan Baker

February 10th 06, 06:12 AM

In article . com>,
wrote:

> A by-product of that lack of education is how Americans view
> 'horsepower,' typically insisting that 50hp (at 5000rpm) is EXACTLY THE
> SAME as 50hp (at 1000rpm). Indeed, most will whip out their calculator
> and 'prove' they are identical :-) But as the Wright brothers
> discovered more than a hundred years ago, horsepower is not a factor in
> the equation of flight. With powered flight, the factor we must
> concern ourselves with most is thrust. Working back through the
> equation, for a given propeller efficiency & rpm we will eventually
> arrive at a given quanta of torque which then may be converted into
> units of 'horsepower,' should we wish to do so, although it serves no
> useful purpose. But when we DO use 'horsepower' we must be careful to
> never use it in isolation, always identifing the rotational speed at
> which that 'horsepower' is being produced.

Absolutely and utterly wrong.

It is *torque* which must always be associated with the rotational speed
at which it is being produced.

--
Alan Baker
Vancouver, British Columbia
"If you raise the ceiling 4 feet, move the fireplace from that wall
to that wall, you'll still only get the full stereophonic effect
if you sit in the bottom of that cupboard."

Kyle Boatright

February 10th 06, 11:54 AM

"Alan Baker" > wrote in message
...
> In article . com>,
> wrote:
>
>> A by-product of that lack of education is how Americans view
>> 'horsepower,' typically insisting that 50hp (at 5000rpm) is EXACTLY THE
>> SAME as 50hp (at 1000rpm). Indeed, most will whip out their calculator
>> and 'prove' they are identical :-) But as the Wright brothers
>> discovered more than a hundred years ago, horsepower is not a factor in
>> the equation of flight. With powered flight, the factor we must
>> concern ourselves with most is thrust. Working back through the
>> equation, for a given propeller efficiency & rpm we will eventually
>> arrive at a given quanta of torque which then may be converted into
>> units of 'horsepower,' should we wish to do so, although it serves no
>> useful purpose. But when we DO use 'horsepower' we must be careful to
>> never use it in isolation, always identifing the rotational speed at
>> which that 'horsepower' is being produced.
>
> Absolutely and utterly wrong.
>
> It is *torque* which must always be associated with the rotational speed
> at which it is being produced.
>
> --
> Alan Baker

Alan,

You do understand that if you know the HP at a given rpm, you can easily
calculate torque.

KB

Philippe Vessaire

February 10th 06, 12:34 PM

Chris Wells wrote:

> How are "normal" airplane engines tuned to run at a lower rpm? What
> changes would have to be made to an automotive engine to shift the
> power band down accordingly?

the airplane enemy is weight.

Any engine may fit, the lighter is the better.

An automotive engine, with PSRU is always heavier than an airplane one.
An automotive engine burn the same amount of gas than an airplane one

Is automotive engines cheaper than a 2000h core of airplane engine? (with
the PSRU).

By
--
Pub: http://www.slowfood.fr/france
Philippe Vessaire ҿӬ

stol

February 10th 06, 01:33 PM

Philippe Vessaire wrote:
> Chris Wells wrote:
>
>
> > How are "normal" airplane engines tuned to run at a lower rpm? What
> > changes would have to be made to an automotive engine to shift the
> > power band down accordingly?
>
> the airplane enemy is weight.

Ya got that one right....

> Any engine may fit, the lighter is the better.

That makes two in a row for correctness.

> An automotive engine, with PSRU is always heavier than an airplane one

Ya wanna bet?????

..
> An automotive engine burn the same amount of gas than an airplane one

Bull****....
>
> Is automotive engines cheaper than a 2000h core of airplane engine? (with
> the PSRU).

This answer doesn't make sense....
>
> By
> --
> Pub: http://www.slowfood.fr/france
> Philippe Vessaire ҿӬ
>

Lou

February 10th 06, 01:55 PM

I'll agree with the automotive engine with PSRU being heavier, but are
you sure about your other statement "the lighter the better"?
I'm currently looking at an engine that is 100lbs lighter than the one
recommended for my plane. Although cutting 100lbs from the total
weight is a dream come true, it brings up the question of weight and
balance. I can move the engine forward to make up the difference in
balance, but I don't know how far or how to find out.
Lou

[email protected]

February 10th 06, 03:40 PM

[email protected]

February 10th 06, 03:41 PM

>> An automotive engine burn the same amount of gas than an airplane one

>Bull****....

It can, too. The volumetric efficiency of a high-RPM engine
suffers at that higher RPM, and I have experience with a Soob to prove
it.

Dan

[email protected]

February 10th 06, 03:46 PM

>>But when we DO use 'horsepower' we must be careful to
>> never use it in isolation, always identifing the rotational speed at
>> which that 'horsepower' is being produced.

>Absolutely and utterly wrong.

>It is *torque* which must always be associated with the rotational speed
>at which it is being produced.

Read that first sentence again. He's not wrong; he just
didn't specify "torque" for those who don't know the relationship
between it and RPM and HP.
When you say "absolutely and utterly" it should be used
only where it applies. Clearly, that's not here.

Stealth Pilot

February 10th 06, 03:46 PM

On 10 Feb 2006 05:55:48 -0800, "Lou" > wrote:

>I'll agree with the automotive engine with PSRU being heavier, but are
>you sure about your other statement "the lighter the better"?
>I'm currently looking at an engine that is 100lbs lighter than the one
>recommended for my plane. Although cutting 100lbs from the total
>weight is a dream come true, it brings up the question of weight and
>balance. I can move the engine forward to make up the difference in
>balance, but I don't know how far or how to find out.
> Lou

calculate it out yourself.
weight times distance from the datum for the original engine will need
to equal weight times distance for the new engine.

ie moment arm of the old engine needs to equal the moment arm of the
new engine.

for your calculation purpose you can select an arbitrary point on the
fuselage as your datum point.
the manufacturer's data for the engine should show the cg position of
the engine. measure the distance from that cg point to the datum.
multiply the engine weight by the distance you just measured.
the result is the moment arm.

now divide the answer above by the new engine weight and you will get
a number. that number is the distance from the datum to the cg
position of the new engine that maintains the original aircraft
balance.

if you dont have the cg position of the engine you can work it out
easily.
(think about the consequences of dropping the engine as you consider
this next bit. it needs to be done carefully!)
just hang the engine up on a rope from a part somewhere on the engine
and draw a vertical line from the rope down across the engine.
hang it up by a different position on the engine and draw another
vertical line. the vertical lines will intersect at the cg.

(btw hang it so that you can see the side elevation of the engine)

just to work out a hypothetical answer.
suppose you make the pilot's door knob the datum point.
measuring from there to the engine cg gives say 52 inches.
the engine weighs 180 lbs.
multiplying that gives a moment of 9,360 inch lbs.

the new engine is 100 lb lighter. say 80lbs.
9,360 divided by 80 = 117.

the CG of the new engine needs to be positioned 117 inches from our
datum of the the pilots doorknob to keep the existing aircraft cg.

there you go lou. that should make it easier.
btw take into account all the stuff that changes as well.
cowlings and engine mount if they have any significant weight.
and include the prop and spinner in the engine weight.
Stealth Pilot
Australia

Richard Lamb

February 10th 06, 04:01 PM

Lou wrote:

> I'll agree with the automotive engine with PSRU being heavier, but are
> you sure about your other statement "the lighter the better"?
> I'm currently looking at an engine that is 100lbs lighter than the one
> recommended for my plane. Although cutting 100lbs from the total
> weight is a dream come true, it brings up the question of weight and
> balance. I can move the engine forward to make up the difference in
> balance, but I don't know how far or how to find out.
> Lou
>

Googling this group for weight and balance yields 25 pages...
So I picked up one of mine here (Dec 10, 2002) and included
Brian's note at the bottom...
(Unfortunately, there was no link attached, so here is the text).

There is a lot of smoke and mirror magic around weight and balance
because so many people understand it so poorly.

At the heart of all of it, though, is a rotational force about a
reference point. the rotational force is called a MOMENT, and
the reference point is called the DATUM.

Sometimes the datum is located at the tip of the spinner.
Sometimes it's located at the main gear axles.
Sometimes its located at the leading edge of the wing.
It doesn't particularly matter where it is located, as long
as you use the same location to work the problem.

You'll often see the term STATION. This is the distance from the
datum to a particular place on the aircraft. Say, for instance,
the instrument panel?

The station numbers change according to where the datum is placed.
But the instrument panel stays in the same physical location.
It's all an offset from a zero point.

One reason to place the datum at the tip of the spinner is because
all the station numbers are positive. No negative distances to
confuse things.

One reason to place the datum at the axles is because the datum
is station zero.zero. Multiply the weight on the wheel times
zero (the ARM is zero at the datum) and the moments for that
wheel come out to zero. Makes the arithmetic a little easier?

And, the reason to place the datum at the leading edge of the wing
it because that's where we are going to wind up anyway. The results
of our CG calculations will finally boil down to a point some given
distance aft of the leading edge.

CG range is often refereed to in terms of a percentage of the wing
chord. Say 25% would be the forward CG limit, maybe 33% would be the
aft limit. So our end number actually refers to a distance aft of
the leading edge. The actual numbers will be different, depending
on where the datum is located, but they all (hopefully) come out
at the same place on the airplane.

First rule:

weight x distance = moments pounds x inches = pound inches (!)
So,
moments / inches = pounds
and
moments / pounds = inches

Practical example:

A bowling ball, held at the chest, has a certain weight.
Held at arms length, it has exactly the same weight!

But due to the longer distance (called ARM) it has a much higher moment.
\
THAT's what feels so heavy.
That rotational force.

So, to solve your little weight and balance question.

The only distance from anything. that matters, is the
distance from the CG of the instrument to the DATUM
specified for that aircraft.

If you have a "before" weight and balance already done,
multiply the weight of the instrument times the distance
from the datum given in the "before" problem.

Then add that moment to the airplane's moment,
and the instrument weight to the airplane's weight.

Divide the new moments by the new weight and you get the
new CG location.

Does that help?

Or do you maybe feel like I sometimes do after some
of your answers???

From: Brian Anderson - view profile
Date: Tues, Dec 10 2002 12:22 am

Jim,

EE's are the brightest of the lot - - - they can measure and calculate
things you can't even see.

The revised CG calculation is straightforward, but you need to calculate the
original moment first, i.e. the total weight [W] x the arm from the datum
[D]. Add to this the additional moment for the instrument, i.e. 8 lbs x the
distance of the instrument CG from the datum [d]. The resulting moment is
[W*D] + [8*d]. Divide this by the new total weight [W+8], and the result is
the new CG location from the datum.

Hence, new CG location = [[W x D] + [8 x d]]/[W+8]

I know even an elderly EE can follow that. After all, I is one too.

Brian

Alan Baker

February 10th 06, 04:26 PM

In article >,
"Kyle Boatright" > wrote:

> "Alan Baker" > wrote in message
> ...
> > In article . com>,
> > wrote:
> >
> >> A by-product of that lack of education is how Americans view
> >> 'horsepower,' typically insisting that 50hp (at 5000rpm) is EXACTLY THE
> >> SAME as 50hp (at 1000rpm). Indeed, most will whip out their calculator
> >> and 'prove' they are identical :-) But as the Wright brothers
> >> discovered more than a hundred years ago, horsepower is not a factor in
> >> the equation of flight. With powered flight, the factor we must
> >> concern ourselves with most is thrust. Working back through the
> >> equation, for a given propeller efficiency & rpm we will eventually
> >> arrive at a given quanta of torque which then may be converted into
> >> units of 'horsepower,' should we wish to do so, although it serves no
> >> useful purpose. But when we DO use 'horsepower' we must be careful to
> >> never use it in isolation, always identifing the rotational speed at
> >> which that 'horsepower' is being produced.
> >
> > Absolutely and utterly wrong.
> >
> > It is *torque* which must always be associated with the rotational speed
> > at which it is being produced.
> >
> > --
> > Alan Baker
>
> Alan,
>
> You do understand that if you know the HP at a given rpm, you can easily
> calculate torque.
>
> KB

Yes. But if you know torque without knowing RPM, you can't tell what
performance you can get out of an engine, but if you know horsepower,
you do know what performance you can get.

--
Alan Baker
Vancouver, British Columbia
"If you raise the ceiling 4 feet, move the fireplace from that wall
to that wall, you'll still only get the full stereophonic effect
if you sit in the bottom of that cupboard."

Alan Baker

February 10th 06, 04:28 PM

In article . com>,
wrote:

> >>But when we DO use 'horsepower' we must be careful to
> >> never use it in isolation, always identifing the rotational speed at
> >> which that 'horsepower' is being produced.
>
>
> >Absolutely and utterly wrong.
>
> >It is *torque* which must always be associated with the rotational speed
> >at which it is being produced.
>
> Read that first sentence again. He's not wrong; he just
> didn't specify "torque" for those who don't know the relationship
> between it and RPM and HP.
> When you say "absolutely and utterly" it should be used
> only where it applies. Clearly, that's not here.

But that's my point. He is absolutely and utterly wrong, when he says
that you need to know the rotational speed before you know all you need
to know when you know the horsepower.

With horsepower, you can use gearing to get any rotational speed you
want; the horsepower remains constant. Torque changes with gearing.

--
Alan Baker
Vancouver, British Columbia
"If you raise the ceiling 4 feet, move the fireplace from that wall
to that wall, you'll still only get the full stereophonic effect
if you sit in the bottom of that cupboard."

February 10th 06, 05:24 PM

"Chris Wells" > wrote in message
...
>
> How are "normal" airplane engines tuned to run at a lower rpm? What
> changes would have to be made to an automotive engine to shift the
> power band down accordingly?
>
Lengthen the stroke. High RPM engines have a large bore, and short stroke.
Low RPM engines have a longer stroke, and smaller bore, all else remaining
equal.

Al

Peter Dohm

February 10th 06, 05:46 PM

> wrote in message
oups.com...
>
> Lou wrote:
> > I'll agree with the automotive engine with PSRU being heavier, but are
> > you sure about your other statement "the lighter the better"?
> > I'm currently looking at an engine that is 100lbs lighter than the one
> > recommended for my plane. Although cutting 100lbs from the total
> > weight is a dream come true, it brings up the question of weight and
> > balance. I can move the engine forward to make up the difference in
> > balance, but I don't know how far or how to find out.
> > Lou
>
> You weigh the airplane without the engine installed and
> calculate a balance point for it. Knowing the weight of the engine, you
> then figure the arm at which it needs to be located to bring the
> airplane's empty CG to the point the designer calls for it. Not a big
> deal at all. Pages 134 and 135 of William Kerschner's Advanced Pilot's
> Flight Manual shows how.
>
> Dan
>
However, you will also be changing the area and arm relationships of the
side view of the aircraft (there is a name for this which I cannot recall)
and the size of the verticall fin will need to be increased if you are to
retain the same yaw stability. Then, because of the increased area of the
vertical stabilizer, a larger rudder would be needed to retain the original
crosswind landing capability. In addition, due to the increased planform
area forward of the CG, a larger horizontal stabilizer may well be required
to prevent any sort of deep stall or flat spin tendency. Finally, just as a
larger vertival stabilizer requires a larger rudder, a larger horizontal
stabilizer will very likely require a larger elevator.

To put it another way: Engineering is the science of compromise, and an
airplane is a series of compromises flying in close formation.

Peter

ORVAL FAIRAIRN

February 10th 06, 07:10 PM

In article >,
Chris Wells > wrote:

> How are "normal" airplane engines tuned to run at a lower rpm? What
> changes would have to be made to an automotive engine to shift the
> power band down accordingly?

You are entering an engineering thicket when you decide to convert
automobile engines to aeronautical use.

One item nobody has yet mentioned is the matter of thrust bearings. An
automobile engine is designed to deliver its power through a clutch, to
a gearbox, with relatively low axial forces imparted to the crankshaft.

A direct-drive aircraft engine, however, delivers its power to a
propeller, which pulls (or pushes) axially on the crankshaft. If you
took an automobile engine and hung a prop on the end of the crank, you
amy or may not have enough thrust bearing to take the loads.

A properly-designed PSRU will have a thrust bearing to take those loads.
Some PSRUs, however, may impart side loads to the power end of the crank
and result in wear and fatigue issues.

There is an axiom for homebuilders: If you want to develop engines,
convert automobile engines; if you wish to fly, use aircraft engines.

Chris Wells

February 10th 06, 07:43 PM

I'm well aware of the purpose of the PSRU, I'd like to know if it's feasible to convert an automobile (or other) engine to run at an RPM low enough so that a PSRU wouldn't be necessary. I'm thinking a custom camshaft would be needed, and different ignition timing, what else?

February 10th 06, 08:08 PM

Also level the plane as it would fly though the air.Only my $0.02.
LJ

Richard Lamb wrote:
> Lou wrote:
>
>> I'll agree with the automotive engine with PSRU being heavier, but are
>> you sure about your other statement "the lighter the better"?
>> I'm currently looking at an engine that is 100lbs lighter than the one
>> recommended for my plane. Although cutting 100lbs from the total
>> weight is a dream come true, it brings up the question of weight and
>> balance. I can move the engine forward to make up the difference in
>> balance, but I don't know how far or how to find out.
>> Lou
>>
>
> Googling this group for weight and balance yields 25 pages...
> So I picked up one of mine here (Dec 10, 2002) and included
> Brian's note at the bottom...
> (Unfortunately, there was no link attached, so here is the text).
>
>
>
> There is a lot of smoke and mirror magic around weight and balance
> because so many people understand it so poorly.
>
> At the heart of all of it, though, is a rotational force about a
> reference point. the rotational force is called a MOMENT, and
> the reference point is called the DATUM.
>
> Sometimes the datum is located at the tip of the spinner.
> Sometimes it's located at the main gear axles.
> Sometimes its located at the leading edge of the wing.
> It doesn't particularly matter where it is located, as long
> as you use the same location to work the problem.
>
> You'll often see the term STATION. This is the distance from the
> datum to a particular place on the aircraft. Say, for instance,
> the instrument panel?
>
> The station numbers change according to where the datum is placed.
> But the instrument panel stays in the same physical location.
> It's all an offset from a zero point.
>
> One reason to place the datum at the tip of the spinner is because
> all the station numbers are positive. No negative distances to
> confuse things.
>
> One reason to place the datum at the axles is because the datum
> is station zero.zero. Multiply the weight on the wheel times
> zero (the ARM is zero at the datum) and the moments for that
> wheel come out to zero. Makes the arithmetic a little easier?
>
> And, the reason to place the datum at the leading edge of the wing
> it because that's where we are going to wind up anyway. The results
> of our CG calculations will finally boil down to a point some given
> distance aft of the leading edge.
>
> CG range is often refereed to in terms of a percentage of the wing
> chord. Say 25% would be the forward CG limit, maybe 33% would be the
> aft limit. So our end number actually refers to a distance aft of
> the leading edge. The actual numbers will be different, depending
> on where the datum is located, but they all (hopefully) come out
> at the same place on the airplane.
>
> First rule:
>
> weight x distance = moments pounds x inches = pound inches (!)
> So,
> moments / inches = pounds
> and
> moments / pounds = inches
>
> Practical example:
>
> A bowling ball, held at the chest, has a certain weight.
> Held at arms length, it has exactly the same weight!
>
> But due to the longer distance (called ARM) it has a much higher moment.
> \
> THAT's what feels so heavy.
> That rotational force.
>
> So, to solve your little weight and balance question.
>
> The only distance from anything. that matters, is the
> distance from the CG of the instrument to the DATUM
> specified for that aircraft.
>
> If you have a "before" weight and balance already done,
> multiply the weight of the instrument times the distance
> from the datum given in the "before" problem.
>
> Then add that moment to the airplane's moment,
> and the instrument weight to the airplane's weight.
>
> Divide the new moments by the new weight and you get the
> new CG location.
>
> Does that help?
>
> Or do you maybe feel like I sometimes do after some
> of your answers???
>
>
> From: Brian Anderson - view profile
> Date: Tues, Dec 10 2002 12:22 am
>
> Jim,
>
> EE's are the brightest of the lot - - - they can measure and calculate
> things you can't even see.
>
> The revised CG calculation is straightforward, but you need to calculate
> the
> original moment first, i.e. the total weight [W] x the arm from the datum
> [D]. Add to this the additional moment for the instrument, i.e. 8 lbs x the
> distance of the instrument CG from the datum [d]. The resulting moment is
> [W*D] + [8*d]. Divide this by the new total weight [W+8], and the
> result is
> the new CG location from the datum.
>
> Hence, new CG location = [[W x D] + [8 x d]]/[W+8]
>
> I know even an elderly EE can follow that. After all, I is one too.
>
> Brian
>

Capt. Geoffrey Thorpe

February 10th 06, 10:57 PM

"Chris Wells" > wrote in message
...
>
> How are "normal" airplane engines tuned to run at a lower rpm? What
> changes would have to be made to an automotive engine to shift the
> power band down accordingly?

Longer stroke.

--
Geoff
the sea hawk at wow way d0t com
remove spaces and make the obvious substitutions to reply by mail
Spell checking is left as an excercise for the reader.

Morgans

February 10th 06, 11:42 PM

"Peter Dohm" > wrote

> However, you will also be changing the area and arm relationships of the
> side view of the aircraft (there is a name for this which I cannot recall)
> and the size of the verticall fin will need to be increased if you are to
> retain the same yaw stability. Then, because of the increased area of the
> vertical stabilizer, a larger rudder would be needed to retain the
original
> crosswind landing capability. In addition, due to the increased planform
> area forward of the CG, a larger horizontal stabilizer may well be
required
> to prevent any sort of deep stall or flat spin tendency. Finally, just as
a
> larger vertival stabilizer requires a larger rudder, a larger horizontal
> stabilizer will very likely require a larger elevator.
>
> To put it another way: Engineering is the science of compromise, and an
> airplane is a series of compromises flying in close formation.

It should not change all that much, I'll bet. If you look at that heavy
engine moving a few inches, and the increased cowl area in front of
aerodynamic center pressure, then look at that long, long arm back to the
fin and rudder, it should only take about a third of the area the engine
added to make it all work out. Increase the fin/rudder height a couple
inches, or add a small dorsal fin, and all will be well in the world. :-

Reminder: all usenet advice is worth what you pay for the advise.

To the OP; what are you using that is 100 lbs lighter, and what was the
original? That is a nice weight savings!
--
Jim in NC

Kyle Boatright

February 11th 06, 12:46 AM

"Chris Wells" > wrote in message
...
>
> I'm well aware of the purpose of the PSRU, I'd like to know if it's
> feasible to convert an automobile (or other) engine to run at an RPM
> low enough so that a PSRU wouldn't be necessary. I'm thinking a custom
> camshaft would be needed, and different ignition timing, what else?
>
>
> --
> Chris Wells

Changing a cam has *some* impact, but it doesn't change the amount of
fuel/air mixture the engine can burn on each combustion stroke, which is
what really determines the output of an engine. That's why small engines
have to spin fast to develop, say 200 hp, while larger engines can run
considerably slower. Changing the timing? Well, the slower an engine
turns, the more the timing must be retarded to prevent knocking. Most
engines (auto or aviation) have their ignition timing set to produce the
most power possible while leaving a margin against knock or pre-ignition.
So changing the timing may not be practical, nor is it likely to turn a
pig's ear into a silk purse.

The bottom line is that unless you're willing to turn a <relatively> large,
heavy engine slowly and with a disappointing power/wt ratio, there really
isn't a good way to take an automobile engine, bolt it onto an airplane, and
go flying.

Auto engines are designed for what they do, as are airplane engines. Same
thing for horses and camels. You won't win the Kentucky Derby with a camel,
but neither is a thoroughbred going to survive long in the desert...

KB

[email protected]

February 11th 06, 12:48 AM

>I'm well aware of the purpose of the PSRU, I'd like to know if it's
>feasible to convert an automobile (or other) engine to run at an RPM
>low enough so that a PSRU wouldn't be necessary. I'm thinking a custom
>camshaft would be needed, and different ignition timing, what else?

You need much longer stroke, which would mean a crank with longer
throws which won't fit in the crankcase anymore, and a longer cylinder
to accomodate the longer piston travel, which you're not going to get,
either. Take a look inside any auto engine crankcase sometime, and see
how close all that stuff is running; there's not much extra room. Chevy
took the 283 and made the subsequent 305/307/327/350/400 engines out of
it by boring larger diameter cylinders (which required just a bit more
casting thickness) and a crank with a tiny bit more throw, which they
managed to squeeze into the case. See
http://www.aces.edu/~gparmer/sbc.html
The Chev 350 V8 has a bore of 4" and a stroke of 3.48, while my
old Gypsy Major, a four-banger that had about the same displacement,
had a 4 5/8" bore and 6 1/2" stroke. Big torque. Redlined about 2650
rpm. Modern aircraft engines like the O-320 are more oversquare like
the auto engines, but still have longer strokes of about 4".
The car engine's crank, as someone else pointed out, won't take
prop thrust loads well, and certainly can't handle the gyroscopic loads
the prop places on it. Even the direct-drive conversions usually have
some sort of extension and bearings to take those loads; those that
don't, like many of the VW and Subaru conversions, have had crankshafts
break in flight. Special forged cranks are required, but the bearings
in the case are still too light.
Try picking up a Lycoming 0-320 sometime: 280 lbs or so. Then
try picking up the Chev 327, almost the same displacement, and see what
it weighs: 575 lbs. Then pile on the radiator and some water, too. Your
airplane has to lift all that.

Dan

[email protected]

February 11th 06, 01:01 AM

>It should not change all that much, I'll bet. If you look at that heavy
>engine moving a few inches, and the increased cowl area in front of
>aerodynamic center pressure, then look at that long, long arm back to the
>fin and rudder, it should only take about a third of the area the engine
>added to make it all work out. Increase the fin/rudder height a couple
>inches, or add a small dorsal fin, and all will be well in the world. :-

It will change it some. My Jodel came out considerably heavier
than designed, mostly to the use of birch instead of the mahogany
specified in the original French drawings, fabric over all ply surfaces
to meet Canadian requirements, a tailwheel insterad of a skid, and so
on. Since most of the added weight is behind the CG, it was tailheavy
and the engine had to go 11" further forward.
The longer nose side area results in a little less directional
stability with the same tail, and I won't spin it because I don't know
just what the effect of the extra weight in the tail (and the longer
nose arm to balance it) might do to the spin; it might flatten into an
unrecoverable situation. Sure does an awesome slip, though.

Dan

stol

February 11th 06, 02:10 AM

ORVAL FAIRAIRN wrote:
> In article >,
> Chris Wells > wrote:
>
> > How are "normal" airplane engines tuned to run at a lower rpm? What
> > changes would have to be made to an automotive engine to shift the
> > power band down accordingly?
>
> You are entering an engineering thicket when you decide to convert
> automobile engines to aeronautical use.
>
> One item nobody has yet mentioned is the matter of thrust bearings. An
> automobile engine is designed to deliver its power through a clutch, to
> a gearbox, with relatively low axial forces imparted to the crankshaft.
>
> A direct-drive aircraft engine, however, delivers its power to a
> propeller, which pulls (or pushes) axially on the crankshaft. If you
> took an automobile engine and hung a prop on the end of the crank, you
> amy or may not have enough thrust bearing to take the loads.
>
> A properly-designed PSRU will have a thrust bearing to take those loads.
> Some PSRUs, however, may impart side loads to the power end of the crank
> and result in wear and fatigue issues.
>
> There is an axiom for homebuilders: If you want to develop engines,
> convert automobile engines; if you wish to fly, use aircraft engines.

Well put.. Converting an auto engine for aircraft use is not for the
novice to try. As Orval says. If ya want to fly now,, install a
Lyc/Cont/Rotax. My Zenith 801 is coming up on 100 hours and so far it
hasn't killed me yet. In fact I am headed out first thing in the mornin
in my auto engine powered toy to Idaho for breakfast to take advantage
of this good thick cold air. It's -6f now and headed to -20 by morning.
That always helps when one is based at 6600 MSl...
Ben
Jackson Hole Wy
www.haaspowerair.com

clare at snyder.on.ca

February 11th 06, 03:05 AM

On Fri, 10 Feb 2006 06:12:41 GMT, Alan Baker >
wrote:

>In article . com>,
> wrote:
>
>> A by-product of that lack of education is how Americans view
>> 'horsepower,' typically insisting that 50hp (at 5000rpm) is EXACTLY THE
>> SAME as 50hp (at 1000rpm). Indeed, most will whip out their calculator
>> and 'prove' they are identical :-) But as the Wright brothers
>> discovered more than a hundred years ago, horsepower is not a factor in
>> the equation of flight. With powered flight, the factor we must
>> concern ourselves with most is thrust. Working back through the
>> equation, for a given propeller efficiency & rpm we will eventually
>> arrive at a given quanta of torque which then may be converted into
>> units of 'horsepower,' should we wish to do so, although it serves no
>> useful purpose. But when we DO use 'horsepower' we must be careful to
>> never use it in isolation, always identifing the rotational speed at
>> which that 'horsepower' is being produced.
>
>Absolutely and utterly wrong.
>
>It is *torque* which must always be associated with the rotational speed
>at which it is being produced.

You are both arguing the same thing, since horsepower is the product
of torque and speed. With the commonly understood units of RPM and ft
lbs, the product needs to be devided by the constant 5252 to provide
horsepower.

I can say my engine produces 91 HP at 3000 RPM, or I can say it
produces 160 ft lbs torque at 3000 rpm, and I am saying exactly the
same thing. The fact the engine may also produce 140 hp at 5000 rpm is
totally immaterial except to indicate it MIGHT be able to stand up to
producing 90 hp for a significant amount of time without overheating.

All the torque in the world won't move anything if it is not allowed
to cause motion, or speed.

clare at snyder.on.ca

February 11th 06, 03:10 AM

On Fri, 10 Feb 2006 16:28:10 GMT, Alan Baker >
wrote:

>In article . com>,
> wrote:
>
>> >>But when we DO use 'horsepower' we must be careful to
>> >> never use it in isolation, always identifing the rotational speed at
>> >> which that 'horsepower' is being produced.
>>
>>
>> >Absolutely and utterly wrong.
>>
>> >It is *torque* which must always be associated with the rotational speed
>> >at which it is being produced.
>>
>> Read that first sentence again. He's not wrong; he just
>> didn't specify "torque" for those who don't know the relationship
>> between it and RPM and HP.
>> When you say "absolutely and utterly" it should be used
>> only where it applies. Clearly, that's not here.
>
>But that's my point. He is absolutely and utterly wrong, when he says
>that you need to know the rotational speed before you know all you need
>to know when you know the horsepower.
>
>With horsepower, you can use gearing to get any rotational speed you
>want; the horsepower remains constant. Torque changes with gearing.

Yes, you CAN use gearing, at the expense of complexity.And efficiency.
Much better to design the engine to produce the power you need at the
speed you need it. However, sometimes you trade efficiency and
durability for weight - and a geared 1.2 liter 80 hp engine running
at 6000 RPM can weigh significantly less than a direct drive 2.7 liter
engine providing the same power at 2800 rpm. (well, about 40 lbs less,
anyway)

[email protected]

February 11th 06, 03:10 AM

Alan Baker wrote:
> ...that's my point. He is absolutely and utterly wrong, when he says
> that you need to know the rotational speed before you know all you need
> to know when you know the horsepower.
>
> With horsepower, you can use gearing to get any rotational speed you
> want; the horsepower remains constant. Torque changes with gearing.

Fantastic! I've been trying to solve the following problem, and
clearly you know how to do it. Please help: I have a 40 horsepower
motor but no idea what the rotational speed is. What gearing should I
use? Thanks in advance.

Daniel

clare at snyder.on.ca

February 11th 06, 03:14 AM

On Fri, 10 Feb 2006 13:34:18 +0100, Philippe Vessaire
> wrote:

>Chris Wells wrote:
>
>
>> How are "normal" airplane engines tuned to run at a lower rpm? What
>> changes would have to be made to an automotive engine to shift the
>> power band down accordingly?
>
>the airplane enemy is weight.
>
>Any engine may fit, the lighter is the better.
>
>An automotive engine, with PSRU is always heavier than an airplane one.
>An automotive engine burn the same amount of gas than an airplane one
>
>Is automotive engines cheaper than a 2000h core of airplane engine? (with
>the PSRU).
>
>By
Not ALWAYS heavier, but usually. How much depends on a lot of
factors. An automotive engine without a psru can be very close. It can
also burn less fuel, under some circumstances.

An O200 and a Corvair weigh virtually the same (within 30 lbs), with
electrical systems, and provide virtually the same hp and thrust.

Cheaper? most definitely can be - and certainly is cheaper to overhaul
when the time comes. And the automotive engine MAY run longer between
major overhauls.
I can build a zero timed Corvair for not much more than the cost of
rebuilding one cyl on a Lycoming.

clare at snyder.on.ca

February 11th 06, 03:18 AM

clare at snyder.on.ca

February 11th 06, 03:20 AM

On Fri, 10 Feb 2006 12:46:28 -0500, "Peter Dohm"
> wrote:

> wrote in message
oups.com...
>>
>> Lou wrote:
>> > I'll agree with the automotive engine with PSRU being heavier, but are
>> > you sure about your other statement "the lighter the better"?
>> > I'm currently looking at an engine that is 100lbs lighter than the one
>> > recommended for my plane. Although cutting 100lbs from the total
>> > weight is a dream come true, it brings up the question of weight and
>> > balance. I can move the engine forward to make up the difference in
>> > balance, but I don't know how far or how to find out.
>> > Lou
>>
>> You weigh the airplane without the engine installed and
>> calculate a balance point for it. Knowing the weight of the engine, you
>> then figure the arm at which it needs to be located to bring the
>> airplane's empty CG to the point the designer calls for it. Not a big
>> deal at all. Pages 134 and 135 of William Kerschner's Advanced Pilot's
>> Flight Manual shows how.
>>
>> Dan
>>
>However, you will also be changing the area and arm relationships of the
>side view of the aircraft (there is a name for this which I cannot recall)
>and the size of the verticall fin will need to be increased if you are to
>retain the same yaw stability. Then, because of the increased area of the
>vertical stabilizer, a larger rudder would be needed to retain the original
>crosswind landing capability. In addition, due to the increased planform
>area forward of the CG, a larger horizontal stabilizer may well be required
>to prevent any sort of deep stall or flat spin tendency. Finally, just as a
>larger vertival stabilizer requires a larger rudder, a larger horizontal
>stabilizer will very likely require a larger elevator.
>
>To put it another way: Engineering is the science of compromise, and an
>airplane is a series of compromises flying in close formation.
>
>Peter
>
You are correct - but 4-6 inches on a 20 foot plane does not make a
significant difference in the yaw and required rudder size. And 4 to 6
inches can correct for a fair amount of weight.

clare at snyder.on.ca

February 11th 06, 03:24 AM

On Fri, 10 Feb 2006 19:10:21 GMT, ORVAL FAIRAIRN
> wrote:

>In article >,
> Chris Wells > wrote:
>
>> How are "normal" airplane engines tuned to run at a lower rpm? What
>> changes would have to be made to an automotive engine to shift the
>> power band down accordingly?
>
>You are entering an engineering thicket when you decide to convert
>automobile engines to aeronautical use.
>
>One item nobody has yet mentioned is the matter of thrust bearings. An
>automobile engine is designed to deliver its power through a clutch, to
>a gearbox, with relatively low axial forces imparted to the crankshaft.
>
>A direct-drive aircraft engine, however, delivers its power to a
>propeller, which pulls (or pushes) axially on the crankshaft. If you
>took an automobile engine and hung a prop on the end of the crank, you
>amy or may not have enough thrust bearing to take the loads.
>
>A properly-designed PSRU will have a thrust bearing to take those loads.
>Some PSRUs, however, may impart side loads to the power end of the crank
>and result in wear and fatigue issues.
>
>There is an axiom for homebuilders: If you want to develop engines,
>convert automobile engines; if you wish to fly, use aircraft engines.
The thrust bearing area on a corvair is almost the same as on a 100HP
Lycoming. It's at the wrong end of the crank, but??

clare at snyder.on.ca

February 11th 06, 03:26 AM

On Fri, 10 Feb 2006 09:24:41 -0800, "Al"
> wrote:

>
>"Chris Wells" > wrote in message
...
>>
>> How are "normal" airplane engines tuned to run at a lower rpm? What
>> changes would have to be made to an automotive engine to shift the
>> power band down accordingly?
>>
>Lengthen the stroke. High RPM engines have a large bore, and short stroke.
>Low RPM engines have a longer stroke, and smaller bore, all else remaining
>equal.
>
>Al
>
Not necessarily so. The myth that high speed engines must be over
square, and low speed engines under square is just that. Piston speed
is what matters, to a large extent, and rod angle - which dictates rod
length.

When you say all else remaining equal, you leave yourself wide open,
because it seldom is.

clare at snyder.on.ca

February 11th 06, 03:32 AM

On Fri, 10 Feb 2006 19:43:24 +0000, Chris Wells
> wrote:

>
>I'm well aware of the purpose of the PSRU, I'd like to know if it's
>feasible to convert an automobile (or other) engine to run at an RPM
>low enough so that a PSRU wouldn't be necessary. I'm thinking a custom
>camshaft would be needed, and different ignition timing, what else?

Valve timing is a good start. Particularly exhaust valve opening
timing. Intake and exhaust tuning also changes - longer and smaller
runners for lower speeds. Look at the short intake runners on a Rotax
912, compared to the long intakes on a Lyco. Smaller runners promote
higher intake and exhaust velocities on slower engines, causing better
filling and purging of the cyls.

Anything you can do to pack more air into the cyl, and to get it ( the
products of combustion ) out will provide more power.
The more air an engine consumes in a minute, the more power it
produces. Turning it faster consumes more air. Supercharging consumes
more air, power tuning the intake and exhaust consumes more air (at
the same, proper, designed speed)

Then make sure the engine can get rid of the heat produced by
consuming all that air. This can be the limitting factor, as on the VW
engine.

Peter Dohm

February 11th 06, 04:47 AM

<clare at snyder.on.ca> wrote in message
...
> On Fri, 10 Feb 2006 12:46:28 -0500, "Peter Dohm"
> > wrote:
>
> > wrote in message
> oups.com...
> >>
> >> Lou wrote:
> >> > I'll agree with the automotive engine with PSRU being heavier, but
are
> >> > you sure about your other statement "the lighter the better"?
> >> > I'm currently looking at an engine that is 100lbs lighter than the
one
> >> > recommended for my plane. Although cutting 100lbs from the total
> >> > weight is a dream come true, it brings up the question of weight and
> >> > balance. I can move the engine forward to make up the difference in
> >> > balance, but I don't know how far or how to find out.
> >> > Lou
> >>
> >> You weigh the airplane without the engine installed and
> >> calculate a balance point for it. Knowing the weight of the engine, you
> >> then figure the arm at which it needs to be located to bring the
> >> airplane's empty CG to the point the designer calls for it. Not a big
> >> deal at all. Pages 134 and 135 of William Kerschner's Advanced Pilot's
> >> Flight Manual shows how.
> >>
> >> Dan
> >>
> >However, you will also be changing the area and arm relationships of the
> >side view of the aircraft (there is a name for this which I cannot
recall)
> >and the size of the verticall fin will need to be increased if you are to
> >retain the same yaw stability. Then, because of the increased area of
the
> >vertical stabilizer, a larger rudder would be needed to retain the
original
> >crosswind landing capability. In addition, due to the increased planform
> >area forward of the CG, a larger horizontal stabilizer may well be
required
> >to prevent any sort of deep stall or flat spin tendency. Finally, just
as a
> >larger vertival stabilizer requires a larger rudder, a larger horizontal
> >stabilizer will very likely require a larger elevator.
> >
> >To put it another way: Engineering is the science of compromise, and an
> >airplane is a series of compromises flying in close formation.
> >
> >Peter
> >
> You are correct - but 4-6 inches on a 20 foot plane does not make a
> significant difference in the yaw and required rudder size. And 4 to 6
> inches can correct for a fair amount of weight.

You are right. I should have at least asked the weight of the original
engine.

Peter Dohm

February 11th 06, 06:23 AM

<clare at snyder.on.ca> wrote in message
...
> On Fri, 10 Feb 2006 16:28:10 GMT, Alan Baker >
> wrote:
>
> >In article . com>,
> > wrote:
> >
> >> >>But when we DO use 'horsepower' we must be careful to
> >> >> never use it in isolation, always identifing the rotational speed at
> >> >> which that 'horsepower' is being produced.
> >>
> >>
> >> >Absolutely and utterly wrong.
> >>
> >> >It is *torque* which must always be associated with the rotational
speed
> >> >at which it is being produced.
> >>
> >> Read that first sentence again. He's not wrong; he just
> >> didn't specify "torque" for those who don't know the relationship
> >> between it and RPM and HP.
> >> When you say "absolutely and utterly" it should be used
> >> only where it applies. Clearly, that's not here.
> >
> >But that's my point. He is absolutely and utterly wrong, when he says
> >that you need to know the rotational speed before you know all you need
> >to know when you know the horsepower.
> >
> >With horsepower, you can use gearing to get any rotational speed you
> >want; the horsepower remains constant. Torque changes with gearing.
>
> Yes, you CAN use gearing, at the expense of complexity.And efficiency.
> Much better to design the engine to produce the power you need at the
> speed you need it. However, sometimes you trade efficiency and
> durability for weight - and a geared 1.2 liter 80 hp engine running
> at 6000 RPM can weigh significantly less than a direct drive 2.7 liter
> engine providing the same power at 2800 rpm. (well, about 40 lbs less,
> anyway)

Ya' know ... there is a real problem with this entire discussion. Not just
this latest thread, but the discussion in general, and I really feel a need
to mention it before I turn in for the night--which is another ting that I
fell a need to do.

The problem, as I see it, is that there may be nearly as much difference
between different kinds of airplanes as there is between the different kinds
of ground vehicles that can be operated on public roads. That's just
counting airplanes, not helicopters, etc...

And we can probably all agree that a faster airplane can efficiently use a
smaller, and faster turning, prop for its horsepower than can a slower
airplane.

Some of us are mostly interested in airplanes that really need a redrive to
get good propeller efficiency from a 40 HP VW. Others are interested in
slippery airplanes that cruise at 150 to 200 kts. My interest is in the
faster type of airplane, and the only reason the specification isn't for
something even faster is a desire to keep the simplicity of a fixed pitch
prop. Therefore, if I want to use the old formula of 0.2G static thrust for
good takeoff performance on a 150 kt airplane, I only need to divide the
expected gross weight of the airplane by 10 to arrive at a reasonable
horsepower figure. (Since I want a static thrust of one fifth of the gross
weight, and also since each horsepower results in 2 pounds of thrust at the
150 kt speed--or would if efficiency was 100%) I really DON'T care about
efficiency, because I only intend to operate at low speed and high power for
less than a minute per flight. Propeller efficiency will always be zero, by
mathematical definition, at the beginning of the take off roll; and my
numbers work just fine with 40% efficiency during the initial climb to clear
the obstacles. On the other hand, if your plan is to cruise at 60 kts, with
a proportionately slower initial climb speed, then you probably need a
larger diameter prop than I do, even with a much lighter and less powerful
airplane.

We really need to look at what is workable, reliable, and affordable for
each specific application. I admit to being a long time advocate of
automotive conversions, and the various GM and D-C all aluminum 60 degree
V6s from 3.0 to 3.7 liters really do look promising; but I really would have
to think long and hard before I trying to adapt one to an airplane that has
already been designed around a standard airplane engine. Just making the
cooling system work reliably, with reasonable drag, would probably cause
insomnia!

Peter

Smitty Two

February 11th 06, 07:07 AM

In article >,
Sparkle > wrote:

> clare at snyder.on.ca wrote:
> > Alan Baker > wrote:
> >
> >> wrote: ...
> >>> But when we DO use 'horsepower' we must be careful to never use
> >>> it in isolation, always identifing the rotational speed at which
> >>> that 'horsepower' is being produced.
> >>
> >> Absolutely and utterly wrong.
> >>
> >> It is *torque* which must always be associated with the rotational
> >> speed at which it is being produced.
> >
> > You are both arguing the same thing, since horsepower is the product
>
> They're saying two very different things. Alan is correct.
>
> > All the torque in the world won't move anything if it is not allowed
> > to cause motion, or speed.
>
> That's why Alan said torque must always be associated with rotational speed.

In the context of engines turning airplane propellers (or any other
attempt to do what physicists call "work,") I'll agree that it's
meaningless to talk about torque without talking about RPM. But, since
horsepower varies with RPM, isn't it also meaningless to talk about
horsepower without talking about RPM?

It seems to me that Mr. Hoover is correct, and so is Mr. Baker, with the
exception of his comment about Mr. Hoover being wrong.

Alan Baker

February 11th 06, 07:13 AM

In article >,
clare at snyder.on.ca wrote:

> On Fri, 10 Feb 2006 06:12:41 GMT, Alan Baker >
> wrote:
>
> >In article . com>,
> > wrote:
> >
> >> A by-product of that lack of education is how Americans view
> >> 'horsepower,' typically insisting that 50hp (at 5000rpm) is EXACTLY THE
> >> SAME as 50hp (at 1000rpm). Indeed, most will whip out their calculator
> >> and 'prove' they are identical :-) But as the Wright brothers
> >> discovered more than a hundred years ago, horsepower is not a factor in
> >> the equation of flight. With powered flight, the factor we must
> >> concern ourselves with most is thrust. Working back through the
> >> equation, for a given propeller efficiency & rpm we will eventually
> >> arrive at a given quanta of torque which then may be converted into
> >> units of 'horsepower,' should we wish to do so, although it serves no
> >> useful purpose. But when we DO use 'horsepower' we must be careful to
> >> never use it in isolation, always identifing the rotational speed at
> >> which that 'horsepower' is being produced.
> >
> >Absolutely and utterly wrong.
> >
> >It is *torque* which must always be associated with the rotational speed
> >at which it is being produced.
>
> You are both arguing the same thing, since horsepower is the product
> of torque and speed. With the commonly understood units of RPM and ft
> lbs, the product needs to be devided by the constant 5252 to provide
> horsepower.
>
> I can say my engine produces 91 HP at 3000 RPM, or I can say it
> produces 160 ft lbs torque at 3000 rpm, and I am saying exactly the
> same thing. The fact the engine may also produce 140 hp at 5000 rpm is
> totally immaterial except to indicate it MIGHT be able to stand up to
> producing 90 hp for a significant amount of time without overheating.
>
> All the torque in the world won't move anything if it is not allowed
> to cause motion, or speed.

No. Incorrect.

You can simply say your engine produces 91 hp, and then you can use a
gearbox to produce any combination of torque and RPM whose product is
that HP.

Answer this question:

Would you prefer an engine that produces 2000 ft-lbs of torque and 20
hp, or one that makes 20 ft-lbs of torque and 2000 hp?

--
Alan Baker
Vancouver, British Columbia
"If you raise the ceiling 4 feet, move the fireplace from that wall
to that wall, you'll still only get the full stereophonic effect
if you sit in the bottom of that cupboard."

Alan Baker

February 11th 06, 07:14 AM

In article . com>,
wrote:

> Alan Baker wrote:
> > ...that's my point. He is absolutely and utterly wrong, when he says
> > that you need to know the rotational speed before you know all you need
> > to know when you know the horsepower.
> >
> > With horsepower, you can use gearing to get any rotational speed you
> > want; the horsepower remains constant. Torque changes with gearing.
>
>
> Fantastic! I've been trying to solve the following problem, and
> clearly you know how to do it. Please help: I have a 40 horsepower
> motor but no idea what the rotational speed is. What gearing should I
> use? Thanks in advance.
>
> Daniel

I don't know. But whatever rotational speed it turns at, you can convert
that into any other rotational speed and still be getting 40 hp.

You can't say the same about torque.

--
Alan Baker
Vancouver, British Columbia
"If you raise the ceiling 4 feet, move the fireplace from that wall
to that wall, you'll still only get the full stereophonic effect
if you sit in the bottom of that cupboard."

Ernest Christley

February 11th 06, 07:28 AM

Peter Dohm wrote:
but I really would have
> to think long and hard before I trying to adapt one to an airplane that has
> already been designed around a standard airplane engine. Just making the
> cooling system work reliably, with reasonable drag, would probably cause
> insomnia!
>
> Peter
>
>

Designing a proper cooling system for a wet engine really isn't that
difficult. Air cooled engines have a much higher delta-T, but their
cooling surface area is extremely limited. Radiators have a much lower
delta-T, but thousands of square inches of surface. The problem is that
most people havn't the slightest clue or any inclination to get one as
to what the air is doing around the cooling surfaces or how to make it
better.

The secret is to make the air pass straight through the radiator vanes
so that both sides are cooled. Rotaries using air-conditioner cores as
radiators are flying very successfully. Have been for years. Only
requires 2 13'x9'x3' cores. Mine will be installed in the wing strakes.

--
This is by far the hardest lesson about freedom. It goes against
instinct, and morality, to just sit back and watch people make
mistakes. We want to help them, which means control them and their
decisions, but in doing so we actually hurt them (and ourselves)."

Ernest Christley

February 11th 06, 07:35 AM

clare at snyder.on.ca wrote:

>>To put it another way: Engineering is the science of compromise, and an
>>airplane is a series of compromises flying in close formation.
>>
>>Peter
>>
>
> You are correct - but 4-6 inches on a 20 foot plane does not make a
> significant difference in the yaw and required rudder size. And 4 to 6
> inches can correct for a fair amount of weight.

There is also the issue of the CG of the engine. They don't all balance
at the same point. One could be 100lbs lighter but have most of the
weight shifted to the front. Mounting in the same geometrical position
would not move the planes CG. (Just a theoretical. I don't know of a
specific case.)

--
This is by far the hardest lesson about freedom. It goes against
instinct, and morality, to just sit back and watch people make
mistakes. We want to help them, which means control them and their
decisions, but in doing so we actually hurt them (and ourselves)."

Ernest Christley

February 11th 06, 07:37 AM

LJ wrote:
> Also level the plane as it would fly though the air.Only my $0.02.
> LJ
>

And use the measurement to the engines CG. You do know where the CG is
on each of the engines, don't you?

--
This is by far the hardest lesson about freedom. It goes against
instinct, and morality, to just sit back and watch people make
mistakes. We want to help them, which means control them and their
decisions, but in doing so we actually hurt them (and ourselves)."

Ernest Christley

February 11th 06, 07:51 AM

ORVAL FAIRAIRN wrote:

> You are entering an engineering thicket when you decide to convert
> automobile engines to aeronautical use.

Anything you do with an airplane is an engineering thicket. There is
nothing about the engine that makes it sacrosant. (I munged that
spelling, didn't I?)

> There is an axiom for homebuilders: If you want to develop engines,
> convert automobile engines; if you wish to fly, use aircraft engines.

No, the axiom is: If you wish to build, build. If you wish to fly, buy.

Using an automobile engine to power an aircraft is no crazier or any
more difficult than spending $200 for a stack of papers with the
intention of turning it into a flying machine some day.

Had a conversation in our local chapter, with one of the guys having a
cracked prop. He was going to have to wait a couple months for a
replacement. He's flying an RV and is a member of EAA. I ask, "Why
don't you just build one?" "I would never try such a thing," he replies
haughtily. I was just a little to confused by that sad attitude to
continue the conversation. Sad. Just sad.

--
This is by far the hardest lesson about freedom. It goes against
instinct, and morality, to just sit back and watch people make
mistakes. We want to help them, which means control them and their
decisions, but in doing so we actually hurt them (and ourselves)."

Ernest Christley

February 11th 06, 07:54 AM

stol wrote:

> Well put.. Converting an auto engine for aircraft use is not for the
> novice to try.
>

Neither is building airplanes. Or flying. Or driving a car. Or using
power tools... Or playing a sport... Or eating solid food...

--
This is by far the hardest lesson about freedom. It goes against
instinct, and morality, to just sit back and watch people make
mistakes. We want to help them, which means control them and their
decisions, but in doing so we actually hurt them (and ourselves)."

Kyle Boatright

February 11th 06, 02:15 PM

<clare at snyder.on.ca> wrote in message
...

<<<snip>>>

> An O200 and a Corvair weigh virtually the same (within 30 lbs), with
> electrical systems, and provide virtually the same hp and thrust.
>
> Cheaper? most definitely can be - and certainly is cheaper to overhaul
> when the time comes. And the automotive engine MAY run longer between
> major overhauls.
> I can build a zero timed Corvair for not much more than the cost of
> rebuilding one cyl on a Lycoming.

The issue there goes back to reliability. What is the reliability of a
Corvair in an aviation application with the crank and bearings taking loads
they were never designed to deal with?

KB

[email protected]

February 11th 06, 06:41 PM

>> Well put.. Converting an auto engine for aircraft use is not for the
>> novice to try.

>Neither is building airplanes. Or flying. Or driving a car. Or using
>power tools... Or playing a sport... Or eating solid food...

Building the airplane involves following published
instructions. Flying involves taking lessons with someone who both
knows what they're doing and how to teach it. Driving a car is similar.
Using power tools without knowing something about how to use them
sometimes involves some hard lessons and a missing digit or two, or an
eye. Playing a sport involves rules, and we can step aside anytime if
the risks mount. The food should get gradually more solid while we
learn to eat it, but even then it's not pretty and even fatal once in a
long while.
Converting engines, for the uninitiated, seems to involve
making a prop hub and bolting it on and expecting reliability,
performance, good fuel economy and great engine life. Those of us
who've done it know otherwise; we have run into many obstacles. There
are a few really good, established conversions out there, and most
builders should buy the plans or the kit or the entire engine and stick
with that rather than assume they can easily make an auto engine fly.
Hanging around homebuilding since 1972 has taught me much, particularly
about the "fantastic" conversions that drop out of sight within a year
or two. Something like the new, improved, futuristic internal
combustion engines that Popular Mechanics seemed to have in their
magazines about every third issue back then. There's no shortage of
hype.
Geschwender sold (still sells, maybe?) converted Ford 351s
that flew all day in cropdusters like the Pawnee. That tells me
something about their credibility. A fella should look for established
machinery like that, or something close to what he needs, and build on
that experience.

Dan

clare at snyder.on.ca

February 11th 06, 08:19 PM

On Sat, 11 Feb 2006 07:13:03 GMT, Alan Baker >
wrote:

>In article >,
> clare at snyder.on.ca wrote:
>
>> On Fri, 10 Feb 2006 06:12:41 GMT, Alan Baker >
>> wrote:
>>
>> >In article . com>,
>> > wrote:
>> >
>> >> A by-product of that lack of education is how Americans view
>> >> 'horsepower,' typically insisting that 50hp (at 5000rpm) is EXACTLY THE
>> >> SAME as 50hp (at 1000rpm). Indeed, most will whip out their calculator
>> >> and 'prove' they are identical :-) But as the Wright brothers
>> >> discovered more than a hundred years ago, horsepower is not a factor in
>> >> the equation of flight. With powered flight, the factor we must
>> >> concern ourselves with most is thrust. Working back through the
>> >> equation, for a given propeller efficiency & rpm we will eventually
>> >> arrive at a given quanta of torque which then may be converted into
>> >> units of 'horsepower,' should we wish to do so, although it serves no
>> >> useful purpose. But when we DO use 'horsepower' we must be careful to
>> >> never use it in isolation, always identifing the rotational speed at
>> >> which that 'horsepower' is being produced.
>> >
>> >Absolutely and utterly wrong.
>> >
>> >It is *torque* which must always be associated with the rotational speed
>> >at which it is being produced.
>>
>> You are both arguing the same thing, since horsepower is the product
>> of torque and speed. With the commonly understood units of RPM and ft
>> lbs, the product needs to be devided by the constant 5252 to provide
>> horsepower.
>>
>> I can say my engine produces 91 HP at 3000 RPM, or I can say it
>> produces 160 ft lbs torque at 3000 rpm, and I am saying exactly the
>> same thing. The fact the engine may also produce 140 hp at 5000 rpm is
>> totally immaterial except to indicate it MIGHT be able to stand up to
>> producing 90 hp for a significant amount of time without overheating.
>>
>> All the torque in the world won't move anything if it is not allowed
>> to cause motion, or speed.
>
>No. Incorrect.

I am NOT incorrect. Torque is static. Without motion or speed no work
is done. That is unarguable scientific fact.
>
>You can simply say your engine produces 91 hp, and then you can use a
>gearbox to produce any combination of torque and RPM whose product is
>that HP.
>

Yes you can, with a cost in efficiency, weight, and complexity - which
translates to reduced reliability and increased cost.
>Answer this question:
>
>Would you prefer an engine that produces 2000 ft-lbs of torque and 20
>hp, or one that makes 20 ft-lbs of torque and 2000 hp?

No comparison at all but 2000 ft lb of torque and 20 HP is 52.52 RPM.
Gearing THAT up to useable RPM is not going to be simple.
Your second example is actually not too far from a turboprop -
525,200 RPM. Still not a simple gearing situation.

My preference? 200 HP at 2000 RPM, or even 100 HP at 3000 RPM. Useable
right "out of the box" with no gearing required.

clare at snyder.on.ca

February 11th 06, 08:23 PM

On Sat, 11 Feb 2006 09:15:06 -0500, "Kyle Boatright"
> wrote:

>
><clare at snyder.on.ca> wrote in message
...
>
><<<snip>>>
>
>> An O200 and a Corvair weigh virtually the same (within 30 lbs), with
>> electrical systems, and provide virtually the same hp and thrust.
>>
>> Cheaper? most definitely can be - and certainly is cheaper to overhaul
>> when the time comes. And the automotive engine MAY run longer between
>> major overhauls.
>> I can build a zero timed Corvair for not much more than the cost of
>> rebuilding one cyl on a Lycoming.
>
>The issue there goes back to reliability. What is the reliability of a
>Corvair in an aviation application with the crank and bearings taking loads
>they were never designed to deal with?
>
>KB
>
They have flown thousands of hours over the years - and untill the
last couple months in high speed planes, crank failures have been
extremely rare. (assuming light weight props, no more than 3000 RPM,
and planes flying in normal category at less than 150MPH)

The cranks have not been any more problematic than Lycos or Contis.
flown within their design parameters.

As stated before, a full thrust bearing on a Corvair engine is almost
identical in thrust are as on an O-200.

Peter Dohm

February 11th 06, 08:30 PM

> wrote in message
oups.com...
> >> Well put.. Converting an auto engine for aircraft use is not for the
> >> novice to try.
>
>
> >Neither is building airplanes. Or flying. Or driving a car. Or using
> >power tools... Or playing a sport... Or eating solid food...
>
> Building the airplane involves following published
> instructions. Flying involves taking lessons with someone who both
> knows what they're doing and how to teach it. Driving a car is similar.
> Using power tools without knowing something about how to use them
> sometimes involves some hard lessons and a missing digit or two, or an
> eye. Playing a sport involves rules, and we can step aside anytime if
> the risks mount. The food should get gradually more solid while we
> learn to eat it, but even then it's not pretty and even fatal once in a
> long while.
> Converting engines, for the uninitiated, seems to involve
> making a prop hub and bolting it on and expecting reliability,
> performance, good fuel economy and great engine life. Those of us
> who've done it know otherwise; we have run into many obstacles. There
> are a few really good, established conversions out there, and most
> builders should buy the plans or the kit or the entire engine and stick
> with that rather than assume they can easily make an auto engine fly.
> Hanging around homebuilding since 1972 has taught me much, particularly
> about the "fantastic" conversions that drop out of sight within a year
> or two. Something like the new, improved, futuristic internal
> combustion engines that Popular Mechanics seemed to have in their
> magazines about every third issue back then. There's no shortage of
> hype.
> Geschwender sold (still sells, maybe?) converted Ford 351s
> that flew all day in cropdusters like the Pawnee. That tells me
> something about their credibility. A fella should look for established
> machinery like that, or something close to what he needs, and build on
> that experience.
>
> Dan
>
Fred Geschwender has pssed on to the big engine factory in the sky.
However, the project lives on. I am not sure which of the several vendors
and developers of Hy-Vo chain based PSRUs is his direct successor; but IIRC
one of them is.

Peter

P.S.: Until further notice, the Hy-Vo chain also remains my first choice
for offset drives; although the proponents of toothed belts do raise a few
meritorious arguments.

Peter Dohm

February 11th 06, 08:35 PM

<clare at snyder.on.ca> wrote in message
...
> On Sat, 11 Feb 2006 09:15:06 -0500, "Kyle Boatright"
> > wrote:
>
> >
> ><clare at snyder.on.ca> wrote in message
> ...
> >
> ><<<snip>>>
> >
> >> An O200 and a Corvair weigh virtually the same (within 30 lbs), with
> >> electrical systems, and provide virtually the same hp and thrust.
> >>
> >> Cheaper? most definitely can be - and certainly is cheaper to overhaul
> >> when the time comes. And the automotive engine MAY run longer between
> >> major overhauls.
> >> I can build a zero timed Corvair for not much more than the cost of
> >> rebuilding one cyl on a Lycoming.
> >
> >The issue there goes back to reliability. What is the reliability of a
> >Corvair in an aviation application with the crank and bearings taking
loads
> >they were never designed to deal with?
> >
> >KB
> >
> They have flown thousands of hours over the years - and untill the
> last couple months in high speed planes, crank failures have been
> extremely rare. (assuming light weight props, no more than 3000 RPM,
> and planes flying in normal category at less than 150MPH)
>
> The cranks have not been any more problematic than Lycos or Contis.
> flown within their design parameters.
>
> As stated before, a full thrust bearing on a Corvair engine is almost
> identical in thrust are as on an O-200.

An excellent point. Racers, acrobatic pilots, and some experimenters with
midified metal props have broken their share of Lycomings and Continentals.

stol

February 12th 06, 04:46 AM

Fred Geschwender has pssed on to the big engine factory in the sky.
However, the project lives on. I am not sure which of the several
vendors
and developers of Hy-Vo chain based PSRUs is his direct successor; but
IIRC
one of them is.

Peter

P.S.: Until further notice, the Hy-Vo chain also remains my first
choice
for offset drives; although the proponents of toothed belts do raise a
few
meritorious arguments

////////////////////////////////////////

I am very comfortable with my toothed belt redrive set up. I am feeding
about twice as much power through it as Jess@belted air advertises it
can handle. So far it shows no sign of failing. Go to my web site,
www.haaspowerair.com

and look close at the pics of the engine/redrive set up, simple,
bulletproof and not that costly.

Ben.
N801BH

Ernest Christley

February 12th 06, 05:51 AM

wrote:
>>>Well put.. Converting an auto engine for aircraft use is not for the
>>>novice to try.
>
>
>
>>Neither is building airplanes. Or flying. Or driving a car. Or using
>>power tools... Or playing a sport... Or eating solid food...
>
>
> Building the airplane involves following published
> instructions.

You never seen published standards for engines? The physics involved
are well understood. All the data necessary relatively easy to come by.

Flying involves taking lessons with someone who both
> knows what they're doing and how to teach it.

Who taught Orville and Wilbur?

Driving a car is similar.
> Using power tools without knowing something about how to use them
> sometimes involves some hard lessons and a missing digit or two, or an
> eye. Playing a sport involves rules, and we can step aside anytime if
> the risks mount. The food should get gradually more solid while we
> learn to eat it, but even then it's not pretty and even fatal once in a
> long while.
> Converting engines, for the uninitiated, seems to involve
> making a prop hub and bolting it on and expecting reliability,
> performance, good fuel economy and great engine life. Those of us
> who've done it know otherwise; we have run into many obstacles.

I agree with you 100%, and will take it one further. Building an
airplane for the uninitiated seems to involve bolting an unquantified
entity called a 'wing' to an equally unquantified entity called a
'frame' then heading off into the clear blue. Quick and easy. A few
weeks work. That's the way I thought of it...four years ago.
Fortunately, the less we know of a subject, the more we think we know;
otherwise, I might not have started.

All of your responses reinforce my point. Every endeavour we choose to
undertake, whether it be converting an engine, buiding an airplane,
playing a musical instrument, the first requirement is always to study
and understand the problem space. I believe that the only point we
disagree on is the degree of difficulty you perceive in an engine
conversion.

My argument is that an engine conversion just adds another facet to the
long list of things to learn. Which brings us back to the original
addage. If you want to build, build, even if that build involves an
auto conversion and with all the study and education that involves. If
you want to fly, buy.

--
This is by far the hardest lesson about freedom. It goes against
instinct, and morality, to just sit back and watch people make
mistakes. We want to help them, which means control them and their
decisions, but in doing so we actually hurt them (and ourselves)."

stol

February 12th 06, 02:27 PM

I agree with you 100%, and will take it one further. Building an
airplane for the uninitiated seems to involve bolting an unquantified
entity called a 'wing' to an equally unquantified entity called a
'frame' then heading off into the clear blue. Quick and easy. A few
weeks work. That's the way I thought of it...four years ago.
Fortunately, the less we know of a subject, the more we think we know;
otherwise, I might not have started.

All of your responses reinforce my point. Every endeavour we choose to

undertake, whether it be converting an engine, buiding an airplane,
playing a musical instrument, the first requirement is always to study
and understand the problem space. I believe that the only point we
disagree on is the degree of difficulty you perceive in an engine
conversion.

My argument is that an engine conversion just adds another facet to the

long list of things to learn. Which brings us back to the original
addage. If you want to build, build, even if that build involves an
auto conversion and with all the study and education that involves. If

you want to fly, buy.

--

Thats whythe FAA clearly states " building a homebuilt plane is for
educational purposes" Ernest, you will reap the satisfaction when you
safely land after your first flight in a creation you built. It is a
feeling that CANNOT be duplicated. Trust us on that..Forgive me if I
didn't catch in an previous post but what are you building and how
close are you to getting in the air????

Ernest Christley

February 12th 06, 08:46 PM

stol wrote:

> Thats whythe FAA clearly states " building a homebuilt plane is for
> educational purposes" Ernest, you will reap the satisfaction when you
> safely land after your first flight in a creation you built. It is a
> feeling that CANNOT be duplicated. Trust us on that..Forgive me if I
> didn't catch in an previous post but what are you building and how
> close are you to getting in the air????
>

I'm building a Dyke Delta JD-2. I'm at the point of skinning it, but I
keep finding little things that I'm not happy with. Lots of rework.
Like we were saying, everything looks easy until you start trying to do
it. I'm 80% done, with 80% to go. For more information:

http://ernest.isa-geek.org

--
This is by far the hardest lesson about freedom. It goes against
instinct, and morality, to just sit back and watch people make
mistakes. We want to help them, which means control them and their
decisions, but in doing so we actually hurt them (and ourselves)."

Robert Bonomi

February 12th 06, 11:11 PM

In article >,
Chris Wells > wrote:
>
>I'm well aware of the purpose of the PSRU, I'd like to know if it's
>feasible to convert an automobile (or other) engine to run at an RPM
>low enough so that a PSRU wouldn't be necessary. I'm thinking a custom
>camshaft would be needed, and different ignition timing, what else?
>
Lessee, possibilities include:
cylinder diameter
cylinder stroke
cylinder displacement
valve diameter
number of valves
valve placement
valve timing (that's the new camshaft)

You _can_ run an automotive (*not* 'automobile', BTW 'automobile' is *any*
'self-propelled' device) engine at a speed such that a PSRU isn't needed.
Doing so, however, gives a 'power to weight' ratio that can be considered
'medium dreadful' at best. If you're lugging around an extra 100 lbs
(or whatever) of engine weight, that's 100 lbs _less_ "usable" carrying
capacity.

Which leads back to the real issues:
power vs weight vs size vs longevity vs cost vs operational reliability

Balancing those 'competing' requirements is a _very_ complex and difficult
task. Taking an engine that is designed for one set of those conditions,
and attempting to modify it to a significantly different 'balance point'
is *not* terribly practical. You essentially re-design, and then 'modify'
the existing hardware to *be* the new design.

*OR*, you use the engine in the operating realm for which it was designed,
and 'adapt' the output as appropriate. Thus, PSRU 'adapters', or other
forms of a gearbox/transmission..

clare at snyder.on.ca

February 13th 06, 01:28 AM

On Sun, 12 Feb 2006 23:11:48 -0000,
(Robert Bonomi) wrote:

>In article >,
>Chris Wells > wrote:
>>
>>I'm well aware of the purpose of the PSRU, I'd like to know if it's
>>feasible to convert an automobile (or other) engine to run at an RPM
>>low enough so that a PSRU wouldn't be necessary. I'm thinking a custom
>>camshaft would be needed, and different ignition timing, what else?
>>
>Lessee, possibilities include:
> cylinder diameter
> cylinder stroke
> cylinder displacement
> valve diameter
> number of valves
> valve placement
> valve timing (that's the new camshaft)
>
>You _can_ run an automotive (*not* 'automobile', BTW 'automobile' is *any*
>'self-propelled' device) engine at a speed such that a PSRU isn't needed.
>Doing so, however, gives a 'power to weight' ratio that can be considered
>'medium dreadful' at best. If you're lugging around an extra 100 lbs
>(or whatever) of engine weight, that's 100 lbs _less_ "usable" carrying
>capacity.
>
>Which leads back to the real issues:
> power vs weight vs size vs longevity vs cost vs operational reliability
>
>Balancing those 'competing' requirements is a _very_ complex and difficult
>task. Taking an engine that is designed for one set of those conditions,
>and attempting to modify it to a significantly different 'balance point'
>is *not* terribly practical. You essentially re-design, and then 'modify'
>the existing hardware to *be* the new design.
>
>*OR*, you use the engine in the operating realm for which it was designed,
>and 'adapt' the output as appropriate. Thus, PSRU 'adapters', or other
>forms of a gearbox/transmission..

2.6 lbs per horsepower is "medium dreadful"? 235 lbs and 91 HP at 3000
RPM from an automotive power plant - including cooling system and
fluids. ANd that is NOT using a custom cam, changing bore, or stroke.
No PSRU. No valve diameter change. By changing cam I might squeeze
another 6 HP out of it.
*** Free account sponsored by SecureIX.com ***
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Highflyer

February 13th 06, 05:10 AM

"Chris Wells" > wrote in message
...
>
> How are "normal" airplane engines tuned to run at a lower rpm? What
> changes would have to be made to an automotive engine to shift the
> power band down accordingly?
>

Some minor changes in valve timing, basically a bit less overlap on the
exhaust/intake crossover. You realize that you don't REALLY shift the
"power band" down. What you actually do is settle for a lot less
horsepower. Virtually all direct drive aircraft engines produce about 1/2
horsepower per cubic inch. I could probably expect about 175 horsepower
from my aviation conversion of a Chevy 350 engine at around 2700 rpm.
Most hop up mods to automotive engines are designed to let you get a bit
more RPM before they come apart or float the valves or ignition. Airplane
engines put out a lot more than their rated power if you overrev them. Of
course, they also go into automatic disassembly mode quicker too!

Highflyer
Highflight Aviation Services
Pinckneyville Airport ( PJY )

Highflyer

February 13th 06, 05:21 AM

"Peter Dohm" > wrote in message
...
> Some of us are mostly interested in airplanes that really need a redrive
> to
> get good propeller efficiency from a 40 HP VW. Others are interested in
> slippery airplanes that cruise at 150 to 200 kts. My interest is in the
> faster type of airplane, and the only reason the specification isn't for
> something even faster is a desire to keep the simplicity of a fixed pitch
> prop. Therefore, if I want to use the old formula of 0.2G static thrust
> for
> good takeoff performance on a 150 kt airplane, I only need to divide the
> expected gross weight of the airplane by 10 to arrive at a reasonable
> horsepower figure. (Since I want a static thrust of one fifth of the
> gross
> weight, and also since each horsepower results in 2 pounds of thrust at
> the
> 150 kt speed--or would if efficiency was 100%) I really DON'T care about
> efficiency, because I only intend to operate at low speed and high power
> for
> less than a minute per flight. Propeller efficiency will always be zero,
> by
> mathematical definition, at the beginning of the take off roll; and my
> numbers work just fine with 40% efficiency during the initial climb to
> clear
> the obstacles. On the other hand, if your plan is to cruise at 60 kts,
> with
> a proportionately slower initial climb speed, then you probably need a
> larger diameter prop than I do, even with a much lighter and less powerful
> airplane.
>
> We really need to look at what is workable, reliable, and affordable for
> each specific application. I admit to being a long time advocate of
> automotive conversions, and the various GM and D-C all aluminum 60 degree
> V6s from 3.0 to 3.7 liters really do look promising; but I really would
> have
> to think long and hard before I trying to adapt one to an airplane that
> has
> already been designed around a standard airplane engine. Just making the
> cooling system work reliably, with reasonable drag, would probably cause
> insomnia!
>
> Peter
>
>

I recommend Fred Weick's book on Propellor Design. I think you will find
that the thrust per horsepower is not a constant but rather decays
proportionately to the log of the RPM. The pounds of thrust per horsepower
gets pretty punk past about 2500 RPM of the prop. At 1000 RPM you get great
thrust out of 25 or 30 horsepower! At 2500 RPM you can get the same thrust
from 100 HP with a good prop! :-)

Highflyer
Highflight Aviation Services
Pinckneyville Airport ( PJY )

Highflyer

February 13th 06, 05:26 AM

"Alan Baker" > wrote in message
...
> In article . com>,
> wrote:
>
>> >
> I don't know. But whatever rotational speed it turns at, you can convert
> that into any other rotational speed and still be getting 40 hp.
>
> You can't say the same about torque.
>

Right. Horsepower is equal to torque multiplied by RPM times a constant.
For any given horsepower if torque goes up the RPM must go down and vice
versa.

Of course, if you know any two of HP, torque, or RPM you can easily find the
third.

Gearing adds weight and wear points. However, many aircraft engines have
been geared. It does get a little tricky, since the prop serves as the
flywheel, so you are putting your gears inbetween the crankshaft and the
flywheel. That is not a good place for gears if you hope for reasonable
service life!

Highflyer
Highflight Aviation Services
Pinckneyville Airport ( PJY )

Highflyer

February 13th 06, 05:37 AM

"stol" > wrote in message
oups.com...

Philippe Vessaire wrote:
>
> An automotive engine burn the same amount of gas than an airplane one

Bull****....

Any engine that burns gasoline will burn very close to the same amount of
gasoline per horsepower hour. Conservatively figure .5 pounds per
horsepower per hour. The best you are likely to get is .43 or so. The
worst is probably not more than .6. To get much better than that you would
have to be able to use your exhaust stacks to make ice cubes.

An automobile engine burns the same amount of gas an an aircraft engine per
horsepower hour.

Is that better!

>
> Is automotive engines cheaper than a 2000h core of airplane engine? (with
> the PSRU).

This answer doesn't make sense....
>

The folks I have seen who go out and buy a converted automobile engine for
their airplane have spent around $15,000 by the time they got it flying.
That is about the price of a field overhauled Lycoming or Continental of
similiar horsepower.
That is what he just said. I bought a midtime Lycoming O-290-D 135HP engine
for my Cavalier 102.5. I paid $1200 for the engine ready to run. All I
have to do to it is bolt it into the airplane and put a prop on it, which I
bought from the same gentleman for $400. I am going with an aircraft
engine. :-)

Highflyer
Highflight Aviation Services
Pinckneyville Airport ( PJY )

Highflyer

February 13th 06, 05:52 AM

"Chris Wells" > wrote in message
...
>
> I'm well aware of the purpose of the PSRU, I'd like to know if it's
> feasible to convert an automobile (or other) engine to run at an RPM
> low enough so that a PSRU wouldn't be necessary. I'm thinking a custom
> camshaft would be needed, and different ignition timing, what else?
>
>

If the cam in the engine is pretty mild it is probably OK. Ignition timing
depends on the RPM and most aircraft engines run a fixed timing advance of
around 25 degrees. Plus or minus about 5. Not a big deal. You can trash
the advance stuff on the engine.

Then just work out a decent way to attach a prop hub to the crankshaft. One
easy way is to machine up an adaptor that bolts onto the crankshaft instead
of the flywheel. If you do it that way you can use ordinary aircraft
props, which is a plus. Then just pick a prop so that you can't pull more
than about 2700 RPM. You will get right around 1/2 horsepower for every
cubic inch if everything else is fine. Actually you probably want the
engine to lug down to about 2400 RPM static at full throttle. The RPM will
pick up some when you start to move and the horsepower will go up with it.

For best efficiency put in a cam that gives you max torque at around 2400
RPM. That will give you the best specific fuel consumption, because you
will be cruising at about torque peak.

Highflyer
Highflight Aviation Services
Pinckneyville Airport ( PJY )

Alan Baker

February 13th 06, 07:42 AM

In article >, "Highflyer" >
wrote:

> "Alan Baker" > wrote in message
> ...
> > In article . com>,
> > wrote:
> >
> >> >
> > I don't know. But whatever rotational speed it turns at, you can convert
> > that into any other rotational speed and still be getting 40 hp.
> >
> > You can't say the same about torque.
> >
>
> Right. Horsepower is equal to torque multiplied by RPM times a constant.
> For any given horsepower if torque goes up the RPM must go down and vice
> versa.
>
> Of course, if you know any two of HP, torque, or RPM you can easily find the
> third.

But the point is that if you know torque, you *must* also know RPM if
you're going to know what kind of performance to expect.

With horsepower, you instantly know whether or not an engine offers
enough performance for the application you are considering.

>
> Gearing adds weight and wear points. However, many aircraft engines have
> been geared. It does get a little tricky, since the prop serves as the
> flywheel, so you are putting your gears inbetween the crankshaft and the
> flywheel. That is not a good place for gears if you hope for reasonable
> service life!
>
> Highflyer
> Highflight Aviation Services
> Pinckneyville Airport ( PJY )

--
Alan Baker
Vancouver, British Columbia
"If you raise the ceiling 4 feet, move the fireplace from that wall
to that wall, you'll still only get the full stereophonic effect
if you sit in the bottom of that cupboard."

Morgans

February 13th 06, 07:48 AM

> > An automotive engine burn the same amount of gas than an airplane one
>
> Bull****....
>
> Any engine that burns gasoline will burn very close to the same amount of
> gasoline per horsepower hour. Conservatively figure .5 pounds per
> horsepower per hour. The best you are likely to get is .43 or so. The
> worst is probably not more than .6. To get much better than that you
would
> have to be able to use your exhaust stacks to make ice cubes.
>
> An automobile engine burns the same amount of gas an an aircraft engine
per
> horsepower hour.
>
> Is that better!

If you are saying that an air cooled aircraft engine burns the same amount
of gas as a water cooled engine (auto or aircraft), then I say you are
wrong.

The water cooled engine is able to burn less fuel per HP produced because of
many factors, major ones being the cooler cylinder, non tapered bore, and
ability to run leaner with less danger of preignition and detonation.
Backing that up is the fact that air cooled engines disappeared from
automobiles, primarily because they could not meet emission standards.
Wasted gas, unburned, going out with the exhaust is one of the things that
could not be improved on enough. Also, it is interesting that the Scaled
Composite's around the world piston engine was to be liquid cooled,
primarily to improve on fuel economy.

There are too many examples of water cooled airplane engines that are
flying, and reporting lower fuel burns compared to the air cooled examples,
to argue that water cooled engines are not superior (in fuel burn) to air
cooled engines. The difference is even greater for the conversions using a
computer to control fuel mixtures.

There is no arguing that converting and working out the bugs in an auto
conversion is a tricky, and expensive proposition. Some people thrive on
that, just like people who drag race and build hot rods. If the person is
not in to that kind of thing, then they should stick to the proven,
standard, aircraft engine.

It is a shame that Lycoming and Continental (and others) are not making
faster progress on creating easy to substitute water cooled engines, and jet
fuel burning piston engines for the GA fleet. Small tubojet and turboprop
engines would be nice, too. It could open up options that would be
beneficial to many people, and many designs.
--
Jim in NC

Ron Webb

February 13th 06, 07:51 AM

Not quite "Bull****"

An aircraft engine is normally either run full rich, or "leaned" to max RPM-
that's usually an air fuel ratio of around 10:1. An auto engine (at least a
fuel injected auto engine) is kept right at the stoichiometric point of 14.7
to 1 air fuel ratio. It makes a little less power there, but not much, and
burns 30% or so less fuel.

For an auto engine, BSFC of 0.45 lb/hp/hr is expected, but I have seen
figures as low as 0.39. Some ECU's even run very lean (~17:1 or so)
returning to stoich every now and then just to make sure they know where
it's at (the Oxygen sensor puts out a characteristic sawtooth pattern at
stoich). An aircraft engine running full rich is lucky to see 0.55.

Anyway - anyone with much experience with an auto conversion will tell you
it burns much less fuel than a Lycosaur of the same HP. That's one reason
why.

Another is the pattern of torque pulses. A geared V6 or V8 has a lot of
overlap on the torque pulses. A direct drive 4 does not. If you plot torque
vs time, you see a series of BIG spikes, that drop way down between piston
firings. A prop does completely different things when twisted with a series
of jerks, than it does with a smooth twisting force. I'll leave you to guess
which is more efficient, even if both are getting the same average
horsepower.

>> An automotive engine burn the same amount of gas than an airplane one
>
> Bull****....
>
> Any engine that burns gasoline will burn very close to the same amount of
> gasoline per horsepower hour. Conservatively figure .5 pounds per
> horsepower per hour. The best you are likely to get is .43 or so. The
> worst is probably not more than .6. To get much better than that you
> would have to be able to use your exhaust stacks to make ice cubes.
>
> An automobile engine burns the same amount of gas an an aircraft engine
> per horsepower hour.
>
> Is that better!
>
>>
>> Is automotive engines cheaper than a 2000h core of airplane engine? (with
>> the PSRU).
>
> This answer doesn't make sense....
>>
>
> The folks I have seen who go out and buy a converted automobile engine for
> their airplane have spent around $15,000 by the time they got it flying.
> That is about the price of a field overhauled Lycoming or Continental of
> similiar horsepower.
> That is what he just said. I bought a midtime Lycoming O-290-D 135HP
> engine for my Cavalier 102.5. I paid $1200 for the engine ready to run.
> All I have to do to it is bolt it into the airplane and put a prop on it,
> which I bought from the same gentleman for $400. I am going with an
> aircraft engine. :-)
>
> Highflyer
> Highflight Aviation Services
> Pinckneyville Airport ( PJY )
>
>
>

Peter Dohm

February 13th 06, 02:48 PM

"Morgans" > wrote in message
...
>
> > > An automotive engine burn the same amount of gas than an airplane one
> >
> > Bull****....
> >
> > Any engine that burns gasoline will burn very close to the same amount
of
> > gasoline per horsepower hour. Conservatively figure .5 pounds per
> > horsepower per hour. The best you are likely to get is .43 or so. The
> > worst is probably not more than .6. To get much better than that you
> would
> > have to be able to use your exhaust stacks to make ice cubes.
> >
> > An automobile engine burns the same amount of gas an an aircraft engine
> per
> > horsepower hour.
> >
> > Is that better!
>
> If you are saying that an air cooled aircraft engine burns the same amount
> of gas as a water cooled engine (auto or aircraft), then I say you are
> wrong.
>
> The water cooled engine is able to burn less fuel per HP produced because
of
> many factors, major ones being the cooler cylinder, non tapered bore, and
> ability to run leaner with less danger of preignition and detonation.
> Backing that up is the fact that air cooled engines disappeared from
> automobiles, primarily because they could not meet emission standards.
> Wasted gas, unburned, going out with the exhaust is one of the things that
> could not be improved on enough. Also, it is interesting that the Scaled
> Composite's around the world piston engine was to be liquid cooled,
> primarily to improve on fuel economy.
>
> There are too many examples of water cooled airplane engines that are
> flying, and reporting lower fuel burns compared to the air cooled
examples,
> to argue that water cooled engines are not superior (in fuel burn) to air
> cooled engines. The difference is even greater for the conversions using
a
> computer to control fuel mixtures.
>
> There is no arguing that converting and working out the bugs in an auto
> conversion is a tricky, and expensive proposition. Some people thrive on
> that, just like people who drag race and build hot rods. If the person is
> not in to that kind of thing, then they should stick to the proven,
> standard, aircraft engine.
>
> It is a shame that Lycoming and Continental (and others) are not making
> faster progress on creating easy to substitute water cooled engines, and
jet
> fuel burning piston engines for the GA fleet. Small tubojet and turboprop
> engines would be nice, too. It could open up options that would be
> beneficial to many people, and many designs.
> --
> Jim in NC
>
I am not really sure which side of some of these issues I really want to be
on; for a lot of reasons.

First, I too, was instructed in the mythology of *real* airplane engines.
However, I have come to doubt much of what I was taught, and the two
examples which I can think of at the moment are:
1) Full rich on take-off, except at high altitude airports, to cool the
engine. Wrong! The real reason is far more important, and failure to
follow the directive is far more destructive. We *really* do it to prevent
detonation, because we can't retard the spark. The obvious defense of the
procedure is that it works, and will continue to work as long as we use
fuel(s) with a radical change of performance number between lean and rich
operation.
2) Dual magneto ignition makes them ultra-reliable. Well, yeah, sort-of,
assuming that you keep them e-gapped correctly, and timed correctly, and
understand mag-drop, and ...

My point is that the ECM for a modern automotive controls mixture and intake
temperature far better than I ever could or ever will, handles timing quite
nicely as well, and provides pretty good early warning of most failure modes
as well. That is not to say that the redundancy of dual magnetos, if fully
maintained, can't provide better reliability for a long flight than a single
ignition ECM; but I strongly suspect that a single ignition ECM with a coil
per cylinder (as is now typical) may provide equal or better reliability
than a typical dual mag installation in the real world--at least in the real
world that I saw years ago.

I also have doubts whether the emissions problems that we saw 30 years ago
with air cooled automotive engines would be true today. We can now meter
fuel and airflow, and measure temperature and residual oxygen levels quite
reliably. Therefore, air cooled engines might be capable of the same fuel
efficiency as liquid cooled engines--or slightly better if I correctly
understand the Carnot Cycle. OTOH, I doubt there is any real motivation for
any automotive manufacture to bother.

As to liquid cooling in airplanes, there are not only a considerable number
currently flying; many were quite well developed long ago and played a roll
roughly equal to their air cooled counterparts in WWII. And they did so on
behalf of the US, UK, Germany, USSR, Japan and probably others.

Everything is a compromise. Speed and drag (induced plus equivalent flat
plate area) pretty much dictate the size of propeller disk area required.
Propeller disk area defines diameter. Propeller diameter strongly
influenced RPM. And so forth.

One size does not fit all. Just as an example, a VW powered STOL with a
cruising speed around 60 kts requires a larger diameter prop (and probably a
redrive) than does a KR-2. We do not all need 84 inch props turning 2000
rpm. There really are designs that perform much better with 48 to52 inch
props. And most homebuilts fall in between those figures.

Peter

[email protected]

February 13th 06, 03:45 PM

>It is a shame that Lycoming and Continental (and others) are not making
>faster progress on creating easy to substitute water cooled engines, and jet
>fuel burning piston engines for the GA fleet. Small tubojet and turboprop
>engines would be nice, too. It could open up options that would be
>beneficial to many people, and many designs.

Liability issues. Better stuff means the old stuff was
defective, or so a lawyer will argue and a jury will swallow.
R&D costs. Everybody wants at least $100K a year. The
governments want big certification fees, at least here in Canada.
The old stuff is making money. For how long yet, no one can
guess, but it's probably a shortsighted strategy, seeing that the
Europeans are building certified diesels that drop into existing
airframes. See http://www.centurion-engines.com/c17/c17_start.htm
Small turboprops and jets are inefficient because of the
very small diameter/area of the compressors and turbines, similar to
the low efficiencies of very small propellers. Rule of thumb says that
anything below 400 HP is going to get too thirsty for the power it
produces. Converted APUs like the one I saw at Arlington a few years
ago generated 150 hp but burned 18 GPH, which is at around 50% worse
than an O-320 running at full throttle at sea level and producing the
same 150 HP. And that's 18 GPH of diesel or jet, which has more energy
per gallon than gasoline and weighs more.

Dan

[email protected]

February 13th 06, 07:14 PM

On Mon, 13 Feb 2006 02:48:12 -0500, "Morgans"
> wrote:

>The water cooled engine is able to burn less fuel per HP produced because of
>many factors, major ones being the cooler cylinder, non tapered bore, and
>ability to run leaner with less danger of preignition and detonation.
>Backing that up is the fact that air cooled engines disappeared from
>automobiles, primarily because they could not meet emission standards.
>Wasted gas, unburned, going out with the exhaust is one of the things that
>could not be improved on enough. Also, it is interesting that the Scaled
>Composite's around the world piston engine was to be liquid cooled,
>primarily to improve on fuel economy.

I used to think so too, but after reading about the physics of fuel
economy I've come to the conclusion that aircraft engines, under very
specific circumstances, usually beat out auto engines in terms of
BSFC.

When properly leaned for best economy, aircraft engines will turn in a
BSFC of under .40. Auto engines normally run in the range of .50,
even during cruise.

So why do auto engine conversions seem to get a better fuel burn in
real life? Mostly because most pilots do not lean their engines as
much as is possible. Plus, they do not lean on the ground, or during
climb. I'm generalizing here, some pilots do lean on the ground and
during climb of course.

With a auto conversion, even one that's carburated, the fuel mixture
setting is normally much closer to ideal than the overly rich initial
setup the aircraft engine is set to.

So even during full power takeoffs, the auto conversion is not running
as rich as the aircraft engine becuase it does not need to do so in
order to prevent overheating or detonation.

Most aircraft engines have fixed timing, which requires that they run
excessively rich during full power takeoffs in order to prevent
overheating and detonation. Auto engines have variable timing so they
do not need to run excessively rich mixtures in order to reduce
detonation and overheating.

So it may seem that the auto engines are getting better fuel economy
when used as aircraft power plants, but their BSFC usually is not as
good as that of a properly leaned aircraft engine.

Corky Scott

Richard Lamb

February 14th 06, 02:18 AM

I'm rather curious, considering the current fuel situation,

What would a healthy dose of alcohol do the the BSFC and power
output?

I'm a little familiar with some of the handling and corrosion
issues from a friend that races quarter midgets.

Richard

Orval Fairbairn

February 14th 06, 04:42 AM

In article .net>,
Richard Lamb > wrote:

> I'm rather curious, considering the current fuel situation,
>
> What would a healthy dose of alcohol do the the BSFC and power
> output?
>
> I'm a little familiar with some of the handling and corrosion
> issues from a friend that races quarter midgets.
>
> Richard

Alcohol contains only some 79% of the energy of gasoline.

mark

February 14th 06, 04:10 PM

"Orval Fairbairn" > wrote in message
...
> In article .net>,
> Richard Lamb > wrote:
>
>> I'm rather curious, considering the current fuel situation,
>>
>> What would a healthy dose of alcohol do the the BSFC and power
>> output?
>>
>> I'm a little familiar with some of the handling and corrosion
>> issues from a friend that races quarter midgets.
>>
>> Richard
>
> Alcohol contains only some 79% of the energy of gasoline.

Racers use alcohol for a lot of reasons, but mainly that water can put out
the fires when they happen. The corrosion issues for race cars are easier
to deal with because the life of a race car is short. A 3 or 4 year old
race car is seldom still run at most of the higher levels. Lower levels
they tend to last longer, but you won't see many 50 year old race cars
running (though with vintage racing thats changing too) An airplane has to
be designed to last.

clare at snyder.on.ca

February 14th 06, 08:21 PM

On Tue, 14 Feb 2006 16:10:15 GMT, "mark" >
wrote:

>
>"Orval Fairbairn" > wrote in message
...
>> In article .net>,
>> Richard Lamb > wrote:
>>
>>> I'm rather curious, considering the current fuel situation,
>>>
>>> What would a healthy dose of alcohol do the the BSFC and power
>>> output?
>>>
>>> I'm a little familiar with some of the handling and corrosion
>>> issues from a friend that races quarter midgets.
>>>
>>> Richard
>>
>> Alcohol contains only some 79% of the energy of gasoline.

But alky also has a significantly higher octane rating.
>
>Racers use alcohol for a lot of reasons, but mainly that water can put out
>the fires when they happen. The corrosion issues for race cars are easier
>to deal with because the life of a race car is short. A 3 or 4 year old
>race car is seldom still run at most of the higher levels. Lower levels
>they tend to last longer, but you won't see many 50 year old race cars
>running (though with vintage racing thats changing too) An airplane has to
>be designed to last.
>

*** Free account sponsored by SecureIX.com ***
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Bill Daniels

February 14th 06, 10:04 PM

<clare at snyder.on.ca> wrote in message
...
> On Tue, 14 Feb 2006 16:10:15 GMT, "mark" >
> wrote:

snip-------
>>> Alcohol contains only some 79% of the energy of gasoline.
>
> But alky also has a significantly higher octane rating.

The higher octane rating (~115 - 130) allows a higher compression ratio
and/or higher boost pressure. If the alky is allowed to fully evaporate in
the intake (as opposed to direct injection) you get a cooler, denser intake
charge. To get the most out of ethanol, the engine has to be designed for
it from the beginning. If this is done, my understanding is that the BSFC
is about the same as with gasoline.

Bush II is hot for cellulose (Sawgrass) to ethanol as a fuel source. Why
stop there? If you are bioengineering the bugs to do that, why not
bioengineer them to produce Iso Octane instead? Iso Octane is a perfect
motor fuel if made available in commercial quantities - no engine mods
needed

Bill Daniels

Orval Fairbairn

February 15th 06, 01:09 AM

In article >,
"Bill Daniels" <bildan@comcast-dot-net> wrote:

> <clare at snyder.on.ca> wrote in message
> ...
> > On Tue, 14 Feb 2006 16:10:15 GMT, "mark" >
> > wrote:
>
> snip-------
> >>> Alcohol contains only some 79% of the energy of gasoline.
> >
> > But alky also has a significantly higher octane rating.
>
> The higher octane rating (~115 - 130) allows a higher compression ratio
> and/or higher boost pressure. If the alky is allowed to fully evaporate in
> the intake (as opposed to direct injection) you get a cooler, denser intake
> charge. To get the most out of ethanol, the engine has to be designed for
> it from the beginning. If this is done, my understanding is that the BSFC
> is about the same as with gasoline.
>
> Bush II is hot for cellulose (Sawgrass) to ethanol as a fuel source. Why
> stop there? If you are bioengineering the bugs to do that, why not
> bioengineer them to produce Iso Octane instead? Iso Octane is a perfect
> motor fuel if made available in commercial quantities - no engine mods
> needed
>
> Bill Daniels

Damn good point! I'm sure that somewhere, a smart bioscientist will see
the obvious!

Peter Dohm

February 15th 06, 01:55 AM

"Orval Fairbairn" > wrote in message
...
> In article >,
> "Bill Daniels" <bildan@comcast-dot-net> wrote:
>
> > <clare at snyder.on.ca> wrote in message
> > ...
> > > On Tue, 14 Feb 2006 16:10:15 GMT, "mark" >
> > > wrote:
> >
> > snip-------
> > >>> Alcohol contains only some 79% of the energy of gasoline.
> > >
> > > But alky also has a significantly higher octane rating.
> >
> > The higher octane rating (~115 - 130) allows a higher compression ratio
> > and/or higher boost pressure. If the alky is allowed to fully evaporate
in
> > the intake (as opposed to direct injection) you get a cooler, denser
intake
> > charge. To get the most out of ethanol, the engine has to be designed
for
> > it from the beginning. If this is done, my understanding is that the
BSFC
> > is about the same as with gasoline.
> >
> > Bush II is hot for cellulose (Sawgrass) to ethanol as a fuel source.
Why
> > stop there? If you are bioengineering the bugs to do that, why not
> > bioengineer them to produce Iso Octane instead? Iso Octane is a perfect
> > motor fuel if made available in commercial quantities - no engine mods
> > needed
> >
> > Bill Daniels
>
>
> Damn good point! I'm sure that somewhere, a smart bioscientist will see
> the obvious!

I certainly hope that you're right. One of the especially good things about
purely petroleum based products is that they are not especially
hydroscopic--and that they are easily separated from water with nothing more
than a very fine mesh strainer. I don't know of any easy way to accomplish
that with any of the flammable alcohols. And any re-refining of ethanol,
whether by distillation or fractional freezing, undoubtedly requires a
special license--at least in the U.S.

Ernest Christley

February 15th 06, 02:14 AM

wrote:

> When properly leaned for best economy, aircraft engines will turn in a
> BSFC of under .40. Auto engines normally run in the range of .50,
> even during cruise.
>

Those caveats are the killer, aren't they? You CAN'T 'properly lean'
the average aircraft engine, because they have horribly designed intake
manifolds. The mixture isn't distributed evenly. So to get two of them
properly leaned, you have to send the other two down into detonation
territory. Not knowing who's on first, the best bet is to **** your
money away in wasted fuel out the exhaust pipe.

--
This is by far the hardest lesson about freedom. It goes against
instinct, and morality, to just sit back and watch people make
mistakes. We want to help them, which means control them and their
decisions, but in doing so we actually hurt them (and ourselves)."

JStricker

February 15th 06, 03:59 AM

Bill,

Having built and tuned alcohol drag boat engines that WERE designed and
built to run alcohol, I've never seen this. Our alcohol fuel lines and pump
volumes were typically twice the area. That is, if a 3/8 line would
normally be used, we'd go to 1/2" line.

Alcohol (at least Methanol, which is what we ran) is actually a little bit
heavier than gasoline by about 10% at around 6.75#, and the specific gravity
of pure methanol is .81 while normal regular gasoline is .72. (Yes, we
jetted the pill in the Hilborns by chart initially based on density altitude
and specific gravity of the alcohol. I can probably find the conversion
charts somewhere if I looked hard enough.)

Anyway, higher volume and higher density does not equal the same or lower
BSFC. While Alcohol has a higher octane, it has a significantly lower BTU
content and that's what makes the heat that makes the engine run.

John Stricker

"Bill Daniels" <bildan@comcast-dot-net> wrote in message
...
>
> To get the most out of ethanol, the engine has to be designed for it from
> the beginning. If this is done, my understanding is that the BSFC is
> about the same as with gasoline.
>
> Bill Daniels
>

[email protected]

February 15th 06, 02:33 PM

JStricker wrote:

> Anyway, higher volume and higher density does not equal the same or lower
> BSFC. While Alcohol has a higher octane, it has a significantly lower BTU
> content and that's what makes the heat that makes the engine run.
>
-----------------------------------------------------------------------------------

Roger that.

-R.S.Hoover

Chris Wells

February 15th 06, 03:43 PM

Ok, I've been scolded for using the word "automotive" and then I was scolded for using "automobile". It would seem to me that in this context, "automobile" would be correct, but can someone give me a final ruling?

BTW, this has been a very informative thread. This is exactly what I read message boards for.

[email protected]

February 15th 06, 03:48 PM

On Wed, 15 Feb 2006 02:14:33 GMT, Ernest Christley
> wrote:

>Those caveats are the killer, aren't they? You CAN'T 'properly lean'
>the average aircraft engine, because they have horribly designed intake
>manifolds. The mixture isn't distributed evenly. So to get two of them
>properly leaned, you have to send the other two down into detonation
>territory. Not knowing who's on first, the best bet is to **** your
>money away in wasted fuel out the exhaust pipe.

It gets worse. According to John Deakin who wrote a series of very
very interesting articles on AVWeb (still available by the way) about
how to properly lean an aircraft engine, it's not just useless but may
be harmful to the engine to attempt to lean below peak if you do not
have an EGR guage that reads all cylinders.

He had a chart that showed that "properly" leaned, that is leaned
according to the POH using rpm drop, you could very easily have one of
the cylinders reaching a redline cylinderhead temperature, while
others were safe.

That is, if you are above about 65% power. At or below 65% power, it
doesn't matter where you set the mixture, you won't be able to
overheat the engine.

He also advocated leaning even to the point of roughness, if you could
stand it and were at 65% power, saying that the roughness wouldn't
hurt anything and was just the result of relatively unbalanced
fuel/air charges in the cylinder combustion chamber. This is the kind
of thing you feel because the cylinders of the four cylinder 0-360's
are so big. Any unbalanced fuel charge results in substantially
different pressures inside the combustion chambers from one cylinder
to the other, which can result in a perceptably rough running engine.

Smaller displacement engines with more cylinders would be less
susceptible to this syndrome.

Adjusting the injectors such that they produce aproximately equal
fuel/air distribution within the combustion chambers allows the pilot
to lean to the point where the engine quits, without any roughness to
that point.

Corky Scott

Peter Dohm

February 15th 06, 06:10 PM

> wrote in message
...
> On Wed, 15 Feb 2006 02:14:33 GMT, Ernest Christley
> > wrote:
>
> >Those caveats are the killer, aren't they? You CAN'T 'properly lean'
> >the average aircraft engine, because they have horribly designed intake
> >manifolds. The mixture isn't distributed evenly. So to get two of them
> >properly leaned, you have to send the other two down into detonation
> >territory. Not knowing who's on first, the best bet is to **** your
> >money away in wasted fuel out the exhaust pipe.
>
> It gets worse. According to John Deakin who wrote a series of very
> very interesting articles on AVWeb (still available by the way) about
> how to properly lean an aircraft engine, it's not just useless but may
> be harmful to the engine to attempt to lean below peak if you do not
> have an EGR guage that reads all cylinders.
>
> He had a chart that showed that "properly" leaned, that is leaned
> according to the POH using rpm drop, you could very easily have one of
> the cylinders reaching a redline cylinderhead temperature, while
> others were safe.
>
> That is, if you are above about 65% power. At or below 65% power, it
> doesn't matter where you set the mixture, you won't be able to
> overheat the engine.
>
> He also advocated leaning even to the point of roughness, if you could
> stand it and were at 65% power, saying that the roughness wouldn't
> hurt anything and was just the result of relatively unbalanced
> fuel/air charges in the cylinder combustion chamber. This is the kind
> of thing you feel because the cylinders of the four cylinder 0-360's
> are so big. Any unbalanced fuel charge results in substantially
> different pressures inside the combustion chambers from one cylinder
> to the other, which can result in a perceptably rough running engine.
>
> Smaller displacement engines with more cylinders would be less
> susceptible to this syndrome.
>
> Adjusting the injectors such that they produce aproximately equal
> fuel/air distribution within the combustion chambers allows the pilot
> to lean to the point where the engine quits, without any roughness to
> that point.
>
> Corky Scott

I don't always agree with Mr. Deakin; but on the above points, I believe
that you have it nailed!

On the related, though not identical, automotive conversion issue; I am
comming around to a hypothesis that the complete ECM and sensor package of
an unmodified automotive engine may be useable with leaded fuel. I mention
this because the ECM systems in automobiles and trucks to a commendable job
of managing mixture under a wide range of conditions.

My reasoning is that the higher average power levels in aircraft use may
keep the oxigen sensors in the exhaust system hot enough for the inevitable
lead deposits to sublimate off as fast as they would otherwise build. My
best guess is that average power levels in automotive use run around 10% of
maximum, due to a lot of time spent idling. Even allowing for very
substantial derating, aircraft use would involve much higher power. For
example, I just drove a Plymouth Neon on a 450 mile road trip and, judging
by fuel burn, the 130 HP engine produces less than 25% power at 70 MPH (or
about 70-75% rpm).

I regret that I will not be testing my hypothesis, to possibly make it a
theory, in the near future; so I am only offering it for comment at this
time.

Peter

stol

February 15th 06, 06:46 PM

On the related, though not identical, automotive conversion issue; I am

comming around to a hypothesis that the complete ECM and sensor package
of
an unmodified automotive engine may be useable with leaded fuel. I
mention
this because the ECM systems in automobiles and trucks to a commendable
job
of managing mixture under a wide range of conditions.

My reasoning is that the higher average power levels in aircraft use
may
keep the oxigen sensors in the exhaust system hot enough for the
inevitable
lead deposits to sublimate off as fast as they would otherwise build.
My
best guess is that average power levels in automotive use run around
10% of
maximum, due to a lot of time spent idling

////////////////////////////////////////////////////////////////////////
Alot of ECM controlled motors have optional ECMs for "offshore" markets
and those don't use a O2 sensor. The LS1 Gm motor can be bought with
the US puter or the "offshore" one. The offshore one doesn't need
Oxygen info to run properly. I agree the high output of a aircraft
engine will burn off alot of the lead plating that happens on a O2
sensor but it still will lose value and give the ECM a bad reading
after a 100 hours or so. Ya just make it a givin that during every
annual ,oops, conditional inspection you just replace the O2 sensor
with a new one and toss out the old one. They are less then 45 bucks.
That equates to about 1.78 Faa approved certified spakplugs...

Montblack

February 15th 06, 07:38 PM

("Chris Wells" wrote)
> Ok, I've been scolded for using the word "automotive" and then I was
> scolded for using "automobile". It would seem to me that in this context,
> "automobile" would be correct, but can someone give me a final ruling?

Have you floated the term horseless carriage yet? :-)

Montblack

abripl

February 15th 06, 08:20 PM

Ernest Christley wrote:
> ....................................... You CAN'T 'properly lean'
> the average aircraft engine, because they have horribly designed intake
> manifolds. The mixture isn't distributed evenly. .............

Don't know about lycoming, etc. but my Franklin 200+ hp has two long
curved intake tubes from the carb before going to the manifolds. Near
160kts cruise I easily get 8gph overal average - with near 2000 lbs. If
I slow down to about 120kts that jumps to about 5gph.
I think the long tubes allow the fuel to mix better and the mixture
floats around until sucked in by cylinders. In fact the engine was
uprated by 5hp from one model to another just by lenghtening the tubes
a little.
-----------------------------------------------------------------
SQ2000 canard: http://www.abri.com/sq2000

February 15th 06, 11:07 PM

Not realy.I don't know what your asken me?

Ernest Christley wrote:
> LJ wrote:
>
>> Also level the plane as it would fly though the air.Only my $0.02.
>> LJ
>>
>
> And use the measurement to the engines CG. You do know where the CG is
> on each of the engines, don't you?
>

Morgans

February 15th 06, 11:17 PM

"abripl" > wrote

> In fact the engine was
> uprated by 5hp from one model to another just by lenghtening the tubes
> a little.

You are probably dealing with tuned intakes, or in other words, the pulses
of the valve opening and closing causes a high pressure wave to reach the
intake valve, just as it closes. That gives a small supercharging effect,
thus more power.
--
Jim in NC

[email protected]

February 15th 06, 11:50 PM

>> ....................................... You CAN'T 'properly lean'
>> the average aircraft engine, because they have horribly designed intake
>> manifolds. The mixture isn't distributed evenly. .............

>Don't know about lycoming, etc. but my Franklin 200+ hp has two long
>curved intake tubes from the carb before going to the manifolds.

The length of tube doesn't affect the mixture distribution.
The length of manifold immediately after the carbe and before the
divisions to the various cylinders does affect it, and in most of these
engines the intake divides within a couple of inches of the carb. Fuel
spraying from the main nozzle hits the throttle plate at anything less
than full throttle and is deflected to one side or another, striking
the manifold wall and clinging to it, so that cylinders that feed from
that side get more fuel than others.

Dan

abripl

February 16th 06, 01:18 AM

> The length of tube doesn't affect the mixture distribution.
> The length of manifold immediately after the carbe and before the
> divisions to the various cylinders does affect it,....

These tubes are about as wide as manifolds - so should have the same
as your effect "length of manifold after carb(e) and before divisions".
Have you actually seen a working Franklin 6A-350?

> and in most of these
> engines the intake divides within a couple of inches of the carb. Fuel
> spraying from the main nozzle hits the throttle plate at anything less
> than full throttle and is deflected to one side or another, striking
> the manifold wall and clinging to it, so that cylinders that feed from
> that side get more fuel than others.

The throttle plate rotates perpendicular to the engine line, so fuel
should
get deflected symmetrically to both sides and not to one side.
Its really a fairly symmetrical arrangement. Probably not as
good a fuel injection but pretty good as far as carbs go.

Peter Dohm

February 16th 06, 03:20 AM

"stol" > wrote in message
ups.com...
> On the related, though not identical, automotive conversion issue; I am
>
> comming around to a hypothesis that the complete ECM and sensor package
> of
> an unmodified automotive engine may be useable with leaded fuel. I
> mention
> this because the ECM systems in automobiles and trucks to a commendable
> job
> of managing mixture under a wide range of conditions.
>
>
> My reasoning is that the higher average power levels in aircraft use
> may
> keep the oxigen sensors in the exhaust system hot enough for the
> inevitable
> lead deposits to sublimate off as fast as they would otherwise build.
> My
> best guess is that average power levels in automotive use run around
> 10% of
> maximum, due to a lot of time spent idling
>
>
> ////////////////////////////////////////////////////////////////////////
> Alot of ECM controlled motors have optional ECMs for "offshore" markets
> and those don't use a O2 sensor. The LS1 Gm motor can be bought with
> the US puter or the "offshore" one. The offshore one doesn't need
> Oxygen info to run properly. I agree the high output of a aircraft
> engine will burn off alot of the lead plating that happens on a O2
> sensor but it still will lose value and give the ECM a bad reading
> after a 100 hours or so. Ya just make it a givin that during every
> annual ,oops, conditional inspection you just replace the O2 sensor
> with a new one and toss out the old one. They are less then 45 bucks.
> That equates to about 1.78 Faa approved certified spakplugs...
>
Your points are well taken. The cost of just replacing the O2 sensor is not
exorbitant.

Is there any really easy way to tell what engines are available with non O2
sensing ECMs?

Ernest Christley

February 16th 06, 03:54 AM

LJ wrote:
> Not realy.I don't know what your asken me?
>
> Ernest Christley wrote:
>
>> LJ wrote:
>>
>>> Also level the plane as it would fly though the air.Only my $0.02.
>>> LJ
>>>
>>
>> And use the measurement to the engines CG. You do know where the CG
>> is on each of the engines, don't you?
>>
>

CG isn't something unique to airplanes. Every object within the reach
of gravity has a 3-dimensional point where all the objects weight could
be thought of as being concentrated...engines included.

Take the riduculous case. You have an aircraft engine that stretches
from station 8 to station 10, as the designer put it on paper. The
engine weighs 100# and the CG is at the center. The moment arm is 900.

But you want to substitute the new SuperRev engine, 'cause it only
weighs 75#. 900/75 = 12, so you need to move the engine out 3 stations.
Now the engine will stretch from station 11 to 13. Now what if it is
the same length, but somehow all the weight got concentrated in the
front end. The front end would need to be placed on station 12, and the
back end would be on station 10.

Engines are not homogeneous chunks of metal, and the CG can vary
considerably from one configuration to another. When I bought my
rotary, it was nice and balanced around the center. When I removed the
manual flywheel (~30#) the thing practically flipped up onto the other end.

--
This is by far the hardest lesson about freedom. It goes against
instinct, and morality, to just sit back and watch people make
mistakes. We want to help them, which means control them and their
decisions, but in doing so we actually hurt them (and ourselves)."

John

February 16th 06, 11:42 AM

> My ignition system consists of dual MSD boxes,one fed
> throught the main buss and the other fed straight from the battery. I
> run a Optima gel cell unit that has 950 cca and can deliver enough
> voltage to run the ign for hours. The DAR that inspected my plane asked
> that very question and together we calculed I would have to land three
> times for fuel before the ign would fail from low voltage. I would like
> to think I am not dumb enough to take off the second time in that
> failure mode. <G>
>
> Ben
> www.haaspowerair.com

Ben
Your ignition that is "fed straight from the battery." is it straight or do
you have a high current isolation diode in there (and hopefully fused!)?
If not it could fail and take down the battery/alternator and main buss
also.
John
Just curious, no flames ;-)

Lou

February 16th 06, 11:55 AM

Richard Lamb wrote:
> Lou wrote:
>
> > I'll agree with the automotive engine with PSRU being heavier, but are
> > you sure about your other statement "the lighter the better"?
> > I'm currently looking at an engine that is 100lbs lighter than the one
> > recommended for my plane. Although cutting 100lbs from the total
> > weight is a dream come true, it brings up the question of weight and
> > balance. I can move the engine forward to make up the difference in
> > balance, but I don't know how far or how to find out.
> > Lou
> >
>
> Googling this group for weight and balance yields 25 pages...
> So I picked up one of mine here (Dec 10, 2002) and included
> Brian's note at the bottom...
> (Unfortunately, there was no link attached, so here is the text).
>
>
>
> There is a lot of smoke and mirror magic around weight and balance
> because so many people understand it so poorly.
>
> At the heart of all of it, though, is a rotational force about a
> reference point. the rotational force is called a MOMENT, and
> the reference point is called the DATUM.
>
> Sometimes the datum is located at the tip of the spinner.
> Sometimes it's located at the main gear axles.
> Sometimes its located at the leading edge of the wing.
> It doesn't particularly matter where it is located, as long
> as you use the same location to work the problem.
>
> You'll often see the term STATION. This is the distance from the
> datum to a particular place on the aircraft. Say, for instance,
> the instrument panel?
>
> The station numbers change according to where the datum is placed.
> But the instrument panel stays in the same physical location.
> It's all an offset from a zero point.
>
> One reason to place the datum at the tip of the spinner is because
> all the station numbers are positive. No negative distances to
> confuse things.
>
> One reason to place the datum at the axles is because the datum
> is station zero.zero. Multiply the weight on the wheel times
> zero (the ARM is zero at the datum) and the moments for that
> wheel come out to zero. Makes the arithmetic a little easier?
>
> And, the reason to place the datum at the leading edge of the wing
> it because that's where we are going to wind up anyway. The results
> of our CG calculations will finally boil down to a point some given
> distance aft of the leading edge.
>
> CG range is often refereed to in terms of a percentage of the wing
> chord. Say 25% would be the forward CG limit, maybe 33% would be the
> aft limit. So our end number actually refers to a distance aft of
> the leading edge. The actual numbers will be different, depending
> on where the datum is located, but they all (hopefully) come out
> at the same place on the airplane.
>
> First rule:
>
> weight x distance = moments pounds x inches = pound inches (!)
> So,
> moments / inches = pounds
> and
> moments / pounds = inches
>
> Practical example:
>
> A bowling ball, held at the chest, has a certain weight.
> Held at arms length, it has exactly the same weight!
>
> But due to the longer distance (called ARM) it has a much higher moment.
> \
> THAT's what feels so heavy.
> That rotational force.
>
> So, to solve your little weight and balance question.
>
> The only distance from anything. that matters, is the
> distance from the CG of the instrument to the DATUM
> specified for that aircraft.
>
> If you have a "before" weight and balance already done,
> multiply the weight of the instrument times the distance
> from the datum given in the "before" problem.
>
> Then add that moment to the airplane's moment,
> and the instrument weight to the airplane's weight.
>
> Divide the new moments by the new weight and you get the
> new CG location.
>
> Does that help?
>
> Or do you maybe feel like I sometimes do after some
> of your answers???
>
>

Thanks Rich,
This information does help quite a bit, and I'm happy that I could
make you feel a little smarter everytime I answer one of your posts.
Lou

Richard Lamb

February 16th 06, 12:28 PM

Lou wrote:

>
>
> Thanks Rich,
> This information does help quite a bit, and I'm happy that I could
> make you feel a little smarter everytime I answer one of your posts.
> Lou
>

Than YOU, Lou, but

Looks like I missed the "level the aircraft first".
I think it was in the original thread somewhere prior.

Minor little detail, but So important.

So much for smarter...

Richard

stol

February 16th 06, 02:54 PM

Your points are well taken. The cost of just replacing the O2 sensor
is not
exorbitant.

Is there any really easy way to tell what engines are available with
non O2
sensing ECMs?

////////////////////////////////////////////////////////////////////////

I would assume any engine that is marketed to a foreign country that
doesn't require the use of unleaded fuel would be compatable. I know
for sure the GM LS1 series are available with both style puters, I
think the Caddy northstar engine comes that way too. There are
companies that manufactuer "test" units that mimic O2 sensors so that
is an option. On my Firewall forward package I kept things VERY simple.
One Holley carb with the Mcneilly mixture leaning block installed gives
precise fuel metering, is cost effective and bulletproof. In my
application I have a high wing so if by a million to one shot I lose
both fuel pumps ,gravity flow should keep the motor running till I get
her down safely. My ignition system consists of dual MSD boxes,one fed
throught the main buss and the other fed straight from the battery. I
run a Optima gel cell unit that has 950 cca and can deliver enough
voltage to run the ign for hours. The DAR that inspected my plane asked
that very question and together we calculed I would have to land three
times for fuel before the ign would fail from low voltage. I would like
to think I am not dumb enough to take off the second time in that
failure mode. <G>

Ben
www.haaspowerair.com

[email protected]

February 16th 06, 03:02 PM

Chris Wells wrote:
> Ok, I've been scolded for using the word "automotive" and then I was
> scolded for using "automobile". It would seem to me that in this
> context, "automobile" would be correct, but can someone give me a final
> ruling?
>

Well if it makes use of the Otto cycle you can call it an Ottomobile
too.

> BTW, this has been a very informative thread. This is exactly what I
> read message boards for.
>

--

FF

stol

February 16th 06, 05:10 PM

John wrote:
> > My ignition system consists of dual MSD boxes,one fed
> > throught the main buss and the other fed straight from the battery. I
> > run a Optima gel cell unit that has 950 cca and can deliver enough
> > voltage to run the ign for hours. The DAR that inspected my plane asked
> > that very question and together we calculed I would have to land three
> > times for fuel before the ign would fail from low voltage. I would like
> > to think I am not dumb enough to take off the second time in that
> > failure mode. <G>
> >
> > Ben
> > www.haaspowerair.com
>
>
> Ben
> Your ignition that is "fed straight from the battery." is it straight or do
> you have a high current isolation diode in there (and hopefully fused!)?
> If not it could fail and take down the battery/alternator and main buss
> also.
> John
> Just curious, no flames ;-)

Yes to the later of the above.................................

February 16th 06, 05:24 PM

I agree,Ernest!
I was merrily adding to the problem,as I fly a tail dragger.
Just nit picking I guess. The old one,LJ

Ernest Christley wrote:
> LJ wrote:
>
>> Not realy.I don't know what your asken me?
>>
>> Ernest Christley wrote:
>>
>>> LJ wrote:
>>>
>>>> Also level the plane as it would fly though the air.Only my $0.02.
>>>> LJ
>>>>
>>>
>>> And use the measurement to the engines CG. You do know where the CG
>>> is on each of the engines, don't you?
>>>
>>
>
> CG isn't something unique to airplanes. Every object within the reach
> of gravity has a 3-dimensional point where all the objects weight could
> be thought of as being concentrated...engines included.
>
> Take the riduculous case. You have an aircraft engine that stretches
> from station 8 to station 10, as the designer put it on paper. The
> engine weighs 100# and the CG is at the center. The moment arm is 900.
>
> But you want to substitute the new SuperRev engine, 'cause it only
> weighs 75#. 900/75 = 12, so you need to move the engine out 3 stations.
> Now the engine will stretch from station 11 to 13. Now what if it is
> the same length, but somehow all the weight got concentrated in the
> front end. The front end would need to be placed on station 12, and the
> back end would be on station 10.
>
> Engines are not homogeneous chunks of metal, and the CG can vary
> considerably from one configuration to another. When I bought my
> rotary, it was nice and balanced around the center. When I removed the
> manual flywheel (~30#) the thing practically flipped up onto the other end.
>

Montblack

February 16th 06, 05:30 PM

("stol" wrote)
> My ignition system consists of dual MSD boxes,one fed throught the main
> buss and the other fed straight from the battery. I run a Optima gel cell
> unit that has 950 cca and can deliver enough voltage to run the ign for
> hours.

Ignoring paperwork issues for the moment: Is this an ignition system that
could be easily(?) retrofitted to a standard Cessna 172 / Piper Warrior?

If yes, (guesstimating) what would the performance gains be over the factory
stock ignition systems they're running now? 1%? 5%? 10%?

Or is it mostly a reliability issue?

Montblack

stol

February 16th 06, 05:46 PM

Ignoring paperwork issues for the moment: Is this an ignition system
that
could be easily(?) retrofitted to a standard Cessna 172 / Piper
Warrior?

If yes, (guesstimating) what would the performance gains be over the
factory
stock ignition systems they're running now? 1%? 5%? 10%?

Or is it mostly a reliability issue?

Montblack

//////////////////////////////////
It is VERY reliable for sure. If I were to"experiment" with this
concept all one would have to do is install a crank trigger to fire the
boxes, have it set up so the plugs would fire every 360 degrees as to
keep the distributing simple, who cares if the plugs spark during the
overlap period, Two strokes do this. The MSD units can be fitted with
timing curves so that will give a performance gain for sure. As for
amount of HP gain, if I were younger and still had my R&D dyno I sold
to Jasper engines a few years back I would experiment just to see what
numbers would come up. My gut feeling is................8-12%

[email protected]

February 17th 06, 03:36 PM

>Ignoring paperwork issues for the moment: Is this an >ignition system that
>could be easily(?) retrofitted to a standard Cessna >172 / Piper Warrior?

Here's something to ease the paperwork issues:

http://www.unisonindustries.com/products/lasar_performance_gains/lasar_perform_gains_menu.html

This system varies the timing on certified aircraft engines,
but does not advance timing beyond the setting specified by the engine
manufacturere. I don't know if this is because there are no gains to be
had (25 degrees BTDC on an O-320, for example, should be plenty for
2700 RPM), or if the engine's TC would prohibit it. They do claim
better performance at any power setting below max, though, and smoother
operation.

Dan

Ron Webb

February 18th 06, 06:25 PM

Yea...all of them.

The OBD-2 standard, which all cars sold in the US have had to meet since
1996, demands that if the O2 sensor goes bad, the "limp home" or "open loop"
mode (in other words just what you want) must be good enough to not only run
fine, but it's gotta still pass the smog check (750 PPM In my state).

If your computer has a "closed loop" mode, great, but there is no advantage
to insisting on a computer that CAN'T use an O2 sensor if one's available.

Just put some black electrical tape over the "check engine" light and you're
as good as if you'd spent $2K on an aftermarket ECU!

>
> Is there any really easy way to tell what engines are available with non
> O2
> sensing ECMs?
>
>

Capt. Geoffrey Thorpe

February 18th 06, 10:38 PM

> wrote in message
...
> On Wed, 15 Feb 2006 02:14:33 GMT, Ernest Christley
> > wrote:
>
> Adjusting the injectors such that they produce aproximately equal
> fuel/air distribution within the combustion chambers allows the pilot
> to lean to the point where the engine quits, without any roughness to
> that point.
>
> Corky Scott

You will get roughness due to the slow burns and ocassional misfires before
it quits no matter how well you match cylinder to cylinder air fuel.
There is considerable cycle to cycle variation in the burn rates and
effective power for a single cylinder when you get too lean.
BSFC also goes up around that point as well.

--
Geoff
The Sea Hawk at Wow Way d0t Com
remove spaces and make the obvious substitutions to reply by mail
Spell checking is left as an excercise for the reader.

Capt. Geoffrey Thorpe

February 18th 06, 10:49 PM

"Peter Dohm" > wrote in message
...

> My reasoning is that the higher average power levels in aircraft use may
> keep the oxigen sensors in the exhaust system hot enough for the
> inevitable
> lead deposits to sublimate off as fast as they would otherwise build.

Sorry, no. If you want to run lean - then you want a wide range sensor - I
don't recall the operating temperature on those, I'm embaressed to admit,
but if you look in the holes in the protection tube, you can see the sensor
element glowing (At least the NTK brand has a hole right on the end that
lets you see the element directly - I never tried to look into a Bosch or
Denso sensor). And, if you get the sensor much hotter than the normal heated
temperature, they will be damaged and give inaccurate readings (guess how I
know.) The element temperature is actually controlled via a closed loop
controller that reacts to the measured impedance of the sensor.

The more common swicthing sensors are not as sensitive to variations in
temperature and generally don't run as hot.

If you want to put in Oxygen sensors, you are pretty much stuck with
unleaded fuel.

My
> best guess is that average power levels in automotive use run around 10%
> of
> maximum, due to a lot of time spent idling. Even allowing for very
> substantial derating, aircraft use would involve much higher power. For
> example, I just drove a Plymouth Neon on a 450 mile road trip and, judging
> by fuel burn, the 130 HP engine produces less than 25% power at 70 MPH (or
> about 70-75% rpm).

Sounds close.

--
Geoff
The Sea Hawk at Wow Way d0t Com
remove spaces and make the obvious substitutions to reply by mail
Spell checking is left as an excercise for the reader.

Capt. Geoffrey Thorpe

February 18th 06, 10:53 PM

"Peter Dohm" > wrote in message
...

>
> Is there any really easy way to tell what engines are available with non
> O2
> sensing ECMs?

Yes, just visit a dealer in Saudi Arabia and see what they sell.

:-)

--
Geoff
The Sea Hawk at Wow Way d0t Com
remove spaces and make the obvious substitutions to reply by mail
Spell checking is left as an excercise for the reader.

Capt. Geoffrey Thorpe

February 18th 06, 11:00 PM

"Ron Webb" > wrote in message
...
>
> Yea...all of them.
>
> The OBD-2 standard, which all cars sold in the US have had to meet since
> 1996, demands that if the O2 sensor goes bad, the "limp home" or "open
> loop" mode (in other words just what you want) must be good enough to not
> only run fine, but it's gotta still pass the smog check (750 PPM In my
> state).

OBD-II requires you to set a code and turn on a light. It does not require
any kind of performance once the failure has been detected. On the other
hand, I don't know about EVERY brand, but the ones I work on will run just
fine with the O2 sensor disconnected. We try very hard to make sure you can
make it home in the event of just about any sensor failure.

>
> If your computer has a "closed loop" mode, great, but there is no
> advantage to insisting on a computer that CAN'T use an O2 sensor if one's
> available.
>
> Just put some black electrical tape over the "check engine" light and
> you're as good as if you'd spent $2K on an aftermarket ECU!

Yea, the bulb takes a LONG time to burn out on it's own.

--
Geoff
The Sea Hawk at Wow Way d0t Com
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