LOP operation

[Roger Long]

Is anyone in this group interested in or experimenting with Lean of Peak
operation? I'm especially interested in the experience of anyone doing it
with a fixed pitch carb engine with single EGT and CHT probes.
--
Roger Long

[[email protected]]

On Wed, 14 Apr 2004 19:15:21 GMT, "Roger Long"
m> wrote:

>Is anyone in this group interested in or experimenting with Lean of Peak
>operation? I'm especially interested in the experience of anyone doing it
>with a fixed pitch carb engine with single EGT and CHT probes.
>--
>Roger Long

I am Roger, but I've got a ways to go yet before I'll be able to try
it. I'll be using a Ford V6, and I'm just now getting ready to
fabricate the headers. I'll be drilling each exhaust tube for an EGT
probe and hope to scrounge the money to get one of the multi cylinder
types.

Then I have to run the engine for an extended period while documenting
the tests so that the DAR who looks things over will at least be able
to see that the engine was run at flight power settings for extended
periods.

During the runs, I'll be seeing if I can bring the mixture to lean of
peak without misfiring.

In theory, the engine should lean way down without getting rough
because I've modified the intake manifold and also am fabricating the
exhaust system with equal length runners, which collect into two
pipes.

But theories have a way of not working out as planned. I'll report
once the engine is running.

Corky Scott

[Rod Madsen]

Every thing I've read indicates that you really can't do it with carbureted
engine and single EGT probe. The mixture is quite different in each
cylinder due to the poor mixing in the intake manifold. Rather, you need
matched fuel injectors and an EGT probe on each cylinder to avoid problems.

Rod
"Roger Long" m> wrote in
message ...
> Is anyone in this group interested in or experimenting with Lean of Peak
> operation? I'm especially interested in the experience of anyone doing it
> with a fixed pitch carb engine with single EGT and CHT probes.
> --
> Roger Long
>
>

[Roger Long]

I did it on a flight Monday with the O-320 H2AD in our 172 N. It's been
discovered in the past few months that using carb heat improves the mixture
distribution, probably by the heat increasing vaporization. Not all engines
will do it and there may even be individual variation among the same models
in the same airframes.

Without matched injectors and an engine monitor, you can't be sure one or
more of the cylinders haven't gone over to the high stress region just ROP
so it's probably a good idea to limit LOP operation to 60% power. My engine
was just a hair rough but I saw the CHT go down 25 degrees. It was
roughness you would have to listen carefully for, not something that would
be annoying.

I did a lot of fiddling to be sure that I really was LOP and watching of
gauges. Now that I know what to listen and look for, I think it will be a
lot easier.
--
Roger Long

[Marc J. Zeitlin]

Roger Long wrote:

> Is anyone in this group interested in or experimenting with Lean of
Peak
> operation? I'm especially interested in the experience of anyone
doing it
> with a fixed pitch carb engine with single EGT and CHT probes.

I don't have exactly that setup, but pretty close. I've got an O-360
A2A with an Ellison throttle body carb on my COZY MKIV, with four
EGT/CHT's. I've started trying to run LOP lately, but only under 75%
power. I generally find that I can get to 50 degrees LOP or so on the
hottest cylinder (haven't checked all four cylinders all the time yet -
I've got a manual rotary switch - maybe on the way to S&F tomorrow from
MA I'll have some time to play with it). If I try to lean it out more
than that, it starts running pretty rough, I get uncomfortable, and the
canard shakes.

Now, I DON'T have a fuel flow gauge, so I really don't know what effect
this is having, other than slowing me down a few mph. I've just been
playing with it to see what happens.

--
Marc J. Zeitlin
http://marc.zeitlin.home.comcast.net/
http://www.cozybuilders.org/
Copyright (c) 2004

[Roger Long]

The LOP guru (Walter Atkinson one of the Advanced Pilot Seminar people) told
me in a post on a Cessna Pilot Association forum that 25 degrees LOP is all
you need to do at these power settings with our O-320. Your 360 shouldn't
be very different.

The advantages are a cleaner burning engine, less stress on pistons and
connecting rods due to peak pressures occurring later when the rod has more
mechanical advantage on the crankshaft and lower cylinder head temperatures.
CO production will also be lower to non-existent.

The fuel savings probably wouldn't be significant in terms of range unless
the flight was a squeaker but could add up to something pretty substantial
over the life of the engine.

Lot's of good stuff on this in the Pelican's Pearch columns over on Avweb.
These articles mostly predate the discovery that carb heat makes it more
feasible on simple engines.

--
Roger Long

[kage]

>>The advantages are a cleaner burning engine, less stress on pistons and
connecting rods due to peak pressures occurring later when the rod has more
mechanical advantage on the crankshaft and lower cylinder head temperatures.
CO production will also be lower to non-existent.>>

The engine will burn plenty clean enough ROP.
Stress levels are well within limits ROP
Cylinder temps are well within limits ROP
CO? So what! Goes out the exhaust.

The only advantage to running LOP is an engine that runs at a lower BSFC.
Which increases range, not so much by decreasing fuel consumption, but by
slowing the airplane down closer to best range speed.

Walter Atkinson is a dentist. He once told me that my IO-520D was more like
a Wright 3350 "Cyclone" engine than a O-470U. He is in well over his head.

Karl

[Tom Sixkiller]

"kage" > wrote in message
...
>
> The engine will burn plenty clean enough ROP.
> Stress levels are well within limits ROP
> Cylinder temps are well within limits ROP
> CO? So what! Goes out the exhaust.
>
> The only advantage to running LOP is an engine that runs at a lower BSFC.
> Which increases range, not so much by decreasing fuel consumption, but by
> slowing the airplane down closer to best range speed.
>
> Walter Atkinson is a dentist. He once told me that my IO-520D was more
like
> a Wright 3350 "Cyclone" engine than a O-470U. He is in well over his head.


Man...10,000 hours on test stands, tons of computer analysis and you know
more than the guys with dirt under their nails. I'm impressed!!!

And your qualifications are, what, again?

[kage]

My gripe is with Walter, not GAMI.

Walter is a dentist, and clearly not an engineer. His association with GAMI
was never that of an engineer. He should leave the engineering to George
Braly and the talking to John Deakin.

You also totally missed the point. GAMIjectors are great. They do everything
as advertised. But most of what they do is an answer to a problem that
doesn't exist. I've used them since GAMI serial #19. Engines ran great
before GAMIs however. Twenty years ago Continentals ran easily to TBO. That
is not the case today and a set of GAMIs will not help the longevity of
these poorly built engines at all. Even John Deakin burned out a set of
Continental cylinders in 500 hours LOP in his Bonanza. And their highly
touted fuel savings are, for the most part, due to a decrease in speed. You
know, all that drag increase with V squared.

CHTs are just fine ROP.
Engines run clean enough ROP.
Engine stresses have been doing just fine now for 100 years ROP.
CO is not a problem in maintained exhaust systems.
Airplanes fly faster ROP.
Even the LOP diehards admit engines run smoother ROP.
Gamis have more value in a turbocharged engine.

And, I have plenty of dirt under my nails, thank you for asking.

..
"Tom Sixkiller" > wrote in message
...
>
> "kage" > wrote in message
> ...
> >
> > The engine will burn plenty clean enough ROP.
> > Stress levels are well within limits ROP
> > Cylinder temps are well within limits ROP
> > CO? So what! Goes out the exhaust.
> >
> > The only advantage to running LOP is an engine that runs at a lower
BSFC.
> > Which increases range, not so much by decreasing fuel consumption, but
by
> > slowing the airplane down closer to best range speed.
> >
> > Walter Atkinson is a dentist. He once told me that my IO-520D was more
> like
> > a Wright 3350 "Cyclone" engine than a O-470U. He is in well over his
head.
>
>
> Man...10,000 hours on test stands, tons of computer analysis and you know
> more than the guys with dirt under their nails. I'm impressed!!!
>
> And your qualifications are, what, again?
>
>

[Thomas Borchert]

Roger,

> I'm especially interested in the experience of anyone doing it
> with a fixed pitch carb engine with single EGT and CHT probes.
>

How would you know you're LOP on all cylinders with that kind of
set-up? Our Tobago (O-360) will not run smoothly LOP. I haven't tried
to enhance smoothness by adding carb heat, which some say helps even
out fuel distribution.

--
Thomas Borchert (EDDH)

[Roger Long]

I set my engine up LOP and flew it at 2350 RPM which is my normal cruise RPM
at that altitude. Then I set the same RPM 100 degrees ROP. Since this is a
fixed pitch prop and I was in level flight, horsepower was exactly the same.
Airspeed was the same. CHT was 10 - 15 degrees cooler and 25 below where I
usually see it. The engine was rougher but it was not vibration. It was
more like the difference between listening to the upright piano at the
elememtary school play and a Steinway, very noticable if you were focused on
the quality of the sound but not objectionable in the first case.

Although the engine was rougher LOP, when I listened closely, the sound had
a hard to describe quality of "easiness". Combustion actually has to start
while the piston is still compressing. LOP slows the combustion so that
there is less pressure against the piston as it is moving up. Peak
pressures occur at a more favorable point on the down stroke. Perhaps this
accounts for the way LOP sounds if you listen closely.

At anything above 60% power, I would go ROP with my minimal engine
instrumentation but this looks like a great thing to have in your bag of
tricks for hot days or need to maximize fuel reserves without slowing way
down.

We have been leaning aggressively on the ground and about 100 ROP in the
air. Our engine was opened up at 1030 hours due to lifter failure. There
was a normal but impressive amount of crud on the piston tops and exhaust
valves. Anything that reduces that has got to be good for the engine.

Walter can drill on my teeth anytime:)

--
Roger Long

[Allen]

"Roger Long" m> wrote in
message ...
> Is anyone in this group interested in or experimenting with Lean of Peak
> operation? I'm especially interested in the experience of anyone doing it
> with a fixed pitch carb engine with single EGT and CHT probes.
> --
> Roger Long
>

While you are fiddling with that mixture control trying to set the elusive
25 degrees LOP you are spending considerable time at PEAK, which will cause
damage to cylinders and exhaust in a short time.

Just my thought on the matter.
Allen

[James M. Knox]

"Roger Long" m> wrote
in :

> The LOP guru (Walter Atkinson one of the Advanced Pilot Seminar
> people) told me in a post on a Cessna Pilot Association forum that 25
> degrees LOP is all you need to do at these power settings with our
> O-320. Your 360 shouldn't be very different.

A big part of the "magic" starts to happen as soon as you hit peak
(assuming all cylinders peak together). Anything past that and you are
cooling with air rather than fuel. The reason you hear about running "50
LOP" for example, as opposed to 25 LOP or 1 LOP is to keep temperatures
down at high power settings. It lower power, if 25 LOP keeps your temps
within limits, then great...


-----------------------------------------------
James M. Knox
TriSoft ph 512-385-0316
1109-A Shady Lane fax 512-366-4331
Austin, Tx 78721
-----------------------------------------------

[Roger Long]

Not at 60% power, at least with a simple engine that has wide detonation
margins like an O-320. The greatest stress on the engine will be at 50 ROP
which is where Lycoming says to run it. If they aren't turning into gliders
at that setting, a few minutes at peak aren't going to hurt them.

EGT doesn't exactly relate to the temperatures inside the cylinder. For
example, if you let the hot gas out sooner, EGT will go up while the gas
won't be in the cylinder as long to heat it up. CHT would go down in that
case.

I was fiddling to learn more about the engine and confirm where the sweet
spot related to peak. I think that's something you have to go through to
get to know your engine and to confirm that your FA ratios are balanced
enough to run this way, not all engines are. What takes some getting used
to is how small the adjustments are and doing them slowly. That doesn't
mean they are fussy. They are accompanied by engine sounds and changes that
you can learn.

Once you have confirmed that your engine can be operated in a regime where
enriching the mixture increases power, is running acceptably smooth (but
yes, it will never be as smooth sounding as ROP), and CHT is lower than the
corresponding ROP RPM or MP, try it this way:

1) Put on carb heat. Probably different amount for each engine. If there
is a point when you slowly pull the heat knob where the drop in RPM seems to
increase, try it about there.

2) Set RPM 100 above the 60% power setting for that altitude. This will be
nearly WOT for a carb 172 at 4000 - 6000 feet.

3) Lean until RPM goes way down.

4) Enrich until you and the engine are comfortable or to the 60% power RPM
(or MP). Forget the EGT gauge.

You should check your POH to be sure about the 60% power settings. Go
through the fiddling and peak finding steps first to get to know how your
engine reacts. If you can't get it to run as described above without
roughness that creates airframe vibration or is really annoying, your engine
will have to be run ROP.

I'm still experimenting with this so it isn't expert advice. I'd really
like to hear the results of others experiments as opposed to OWT repetition.
If it's a small bore engine, you aren't going to hurt it fiddling with
mixture at these power settings unless it's too rich in which case you'll
foul the plugs.

--
Roger Long


Allen > wrote in message
m...
>
> "Roger Long" m> wrote
in
> message ...
> > Is anyone in this group interested in or experimenting with Lean of Peak
> > operation? I'm especially interested in the experience of anyone doing
it
> > with a fixed pitch carb engine with single EGT and CHT probes.
> > --
> > Roger Long
> >
>
> While you are fiddling with that mixture control trying to set the elusive
> 25 degrees LOP you are spending considerable time at PEAK, which will
cause
> damage to cylinders and exhaust in a short time.
>
> Just my thought on the matter.
> Allen
>
>

[Roger Long]

Air is free. 100 LL is heading towards $3.75 a gallon. Which would you
rather cool with?

--
Roger Long

James M. Knox > wrote in message
...
> "Roger Long" m> wrote
> in :
>
> A big part of the "magic" starts to happen as soon as you hit peak
> (assuming all cylinders peak together). Anything past that and you are
> cooling with air rather than fuel.

[Ron Rosenfeld]

On Thu, 15 Apr 2004 13:34:30 GMT, "Roger Long"
m> wrote:

>The greatest stress on the engine will be at 50 ROP
>which is where Lycoming says to run it.

I am asuming, since your email suggests that you are US based, that you are
talking degrees Farenheit. I agree that 50°F ROP is a bad place to run the
engine.

Which engine does Lycoming say to run 50°F ROP? Lycoming does NOT make
that recommendation for the O360 series of engines.

In my Lycoming O360 series engine manual, the recommendations for normally
aspirated engines are:

1. Full Rich for take-off, climb and maximum cruise powers (above
75% power), with a caveat to lean just to a smooth running engine for
take-off from a high-elevation airport or during climb.

2. Maximum Power cruise (75% power): 150°F on the rich side of
peak EGT.

3. Best Economy cruise (below 75% power): operate at peak EGT

For turbocharged engines:

1. Best Economy Cruise: Lean to peak TIT or 1650°F, whichever
occurs first.

2. Maximum Power Cruise: 125°F on the rich side of the temperature
determined in step 1 (peak TIT vs 1650°F).

Certain "airframe" manufacturers may have different recommendations in
their POH's, and those take precedence. But, even though Lycoming states
that a manufacturer's POH takes precedence, that's a far cry from stating
that "Lycoming" says to run the engine at 50°F ROP.


Ron (EPM) (N5843Q, Mooney M20E) (CP, ASEL, ASES, IA)

[EDR]

In article >, kage
> wrote:

> Walter Atkinson is a dentist. He once told me that my IO-520D was more like
> a Wright 3350 "Cyclone" engine than a O-470U. He is in well over his head.

So was/is Dick VanGrunsen (sic) ,IIRC, but that hasn't stopped him from
designing a great series of airplanes.

[Roger Long]

Quite right. However our 172 N did not come with EGT as standard equipment.
The "lean to rough, enrich till smooth" I was taught in primary training
(and used for the first couple of years when our EGT didn't work) ends up
about 50 ROP on our engine if you do it quickly and without carb heat. It
was sloppy of me to call it a Lycoming recommendation.

--
Roger Long
Ron Rosenfeld > wrote in message
...
> On Thu, 15 Apr 2004 13:34:30 GMT, "Roger Long"
> m> wrote:
>
> >The greatest stress on the engine will be at 50 ROP
> >which is where Lycoming says to run it.
>
> I am asuming, since your email suggests that you are US based, that you
are
> talking degrees Farenheit. I agree that 50°F ROP is a bad place to run
the
> engine.
>
> Which engine does Lycoming say to run 50°F ROP? Lycoming does NOT make
> that recommendation for the O360 series of engines.
>
> In my Lycoming O360 series engine manual, the recommendations for normally
> aspirated engines are:
>
> 1. Full Rich for take-off, climb and maximum cruise powers (above
> 75% power), with a caveat to lean just to a smooth running engine for
> take-off from a high-elevation airport or during climb.
>
> 2. Maximum Power cruise (75% power): 150°F on the rich side of
> peak EGT.
>
> 3. Best Economy cruise (below 75% power): operate at peak EGT
>
> For turbocharged engines:
>
> 1. Best Economy Cruise: Lean to peak TIT or 1650°F, whichever
> occurs first.
>
> 2. Maximum Power Cruise: 125°F on the rich side of the temperature
> determined in step 1 (peak TIT vs 1650°F).
>
> Certain "airframe" manufacturers may have different recommendations in
> their POH's, and those take precedence. But, even though Lycoming states
> that a manufacturer's POH takes precedence, that's a far cry from stating
> that "Lycoming" says to run the engine at 50°F ROP.
>
>
> Ron (EPM) (N5843Q, Mooney M20E) (CP, ASEL, ASES, IA)

[Ron Rosenfeld]

On Thu, 15 Apr 2004 14:56:57 GMT, "Roger Long"
m> wrote:

>Quite right. However our 172 N did not come with EGT as standard equipment.
>The "lean to rough, enrich till smooth" I was taught in primary training
>(and used for the first couple of years when our EGT didn't work) ends up
>about 50 ROP on our engine if you do it quickly and without carb heat. It
>was sloppy of me to call it a Lycoming recommendation.

I don't think I really learned how to lean until I had an EGT indicator.
and discovered how slowly the engine parameters change with changes in the
mixture control. At least in my fuel injected IO360.

And the lean to rough, enrich to smooth IS Lycoming's recommendation for
carbureted engines without EGT indicators or flowmeters. But they do say
to lean *slowly* and they also state it is for Economy cruise at 75% power
or less).

If you lean slowly in your 172N to rough, then slowly enrich until just
smooth -- where do you wind up with regard to EGT?




Ron (EPM) (N5843Q, Mooney M20E) (CP, ASEL, ASES, IA)

[Michael Houghton]

Howdy!

In article >,
kage > wrote:
>My gripe is with Walter, not GAMI.
>
>Walter is a dentist, and clearly not an engineer. His association with GAMI
>was never that of an engineer. He should leave the engineering to George
>Braly and the talking to John Deakin.
>
>You also totally missed the point. GAMIjectors are great. They do everything
>as advertised. But most of what they do is an answer to a problem that
>doesn't exist. I've used them since GAMI serial #19. Engines ran great
>before GAMIs however. Twenty years ago Continentals ran easily to TBO. That
>is not the case today and a set of GAMIs will not help the longevity of
>these poorly built engines at all. Even John Deakin burned out a set of
>Continental cylinders in 500 hours LOP in his Bonanza. And their highly
>touted fuel savings are, for the most part, due to a decrease in speed. You
>know, all that drag increase with V squared.

What is your agenda? You seem to have an axe to grind, and you get your
facts wrong.

For a given power setting, in general (module altitude effects), there
are two mixture settings to give that power. One ROP, the other LOP.
If you run at, say, 70% power, your airspeed is going to be fixed at
a particular level, assuming stable, level flight. If you run LOP,
you run less fuel through the engine, and you burn all of it up. If
you turn ROP, you use some of it to cool the engine -- using more
fuel than LOP operation. All this for the same speed.

>
>CHTs are just fine ROP.

What CHT level do you think is "just fine"? How does this argue
in favor of ROP?

>Engines run clean enough ROP.

On what do you base this unsupported assertion?

>Engine stresses have been doing just fine now for 100 years ROP.

Oh? Have you ever examined the operations of round engines,
especially the bigger things like R-3350s? IIRC, LOP operations
were mandatory to get satisfactory performance and engine life.

>CO is not a problem in maintained exhaust systems.

What does that have to do with the decision? LOP makes less CO;
isn't that a positive?

>Airplanes fly faster ROP.

That claim is especially brown and smelly, given the orifice it
was pulled from. See discussion above. Speed is all about power
levels.

>Even the LOP diehards admit engines run smoother ROP.

As opposed to the ROP blowhards who can't abide admitting they might
be wrong? See! I can use cheap rhetorical devices, too! Would you
care to try a logical approach, or are you just interested in being
fanatical?

>Gamis have more value in a turbocharged engine.

What does this have to do with deciding to operate LOP? Or are you
just trying to obfuscate with more irrelevancies?
>
>And, I have plenty of dirt under my nails, thank you for asking.
>
Do you have real qualifications to back up your amazing assertions?
How about real data? Sound logical reasoning?

yours,
Michael


--
Michael and MJ Houghton | Herveus d'Ormonde and Megan O'Donnelly
| White Wolf and the Phoenix
Bowie, MD, USA | Tablet and Inkle bands, and other stuff
| http://www.radix.net/~herveus/

[[email protected]]

On Wed, 14 Apr 2004 22:36:41 -0700, "kage" >
wrote:

> Even John Deakin burned out a set of
>Continental cylinders in 500 hours LOP in his Bonanza. And their highly
>touted fuel savings are, for the most part, due to a decrease in speed. You
>know, all that drag increase with V squared.

I'd hesitate to speak for Mr. Deakin but I'd venture that he'd
disagree violently that running lean of peak burned out his cylinders.
Since running lean of peak results in low temperatures and less gas
being burned, how exactly did they get burned out?

To demonstrate that running lean of peak does not necessarily mean a
lost of power, his "Mixture Magic" column showed a color photo of an
instrument panel of a Cessna 410 running one engine ROP and the other
LOP. Both engines were producing exactly the same power but at
different manifold pressures. The LOP engine was using less fuel and
was running at lower CHT temps. How is that bad?

>CHTs are just fine ROP.

Actually they aren't, if you set the engine according to the POH.
Running at 75% or 80% power and set 50 degrees ROP, the CHT's run
above 400 degrees. These are figures that come from Lycoming and
Continental. And yet over 400 degrees is where aluminum begins to
loose strength. Deakin also was able to demonstrate that at certain
POH dictated ROP settings, the cylinders actually distorted from the
heat and began to scuff the pistons. This was during flight testing
with several proprietary probes installed in his engine which could
read what was happening in areas away from the cylinderhead probe.
While these probes were showing alarming increases in heat, the
cylinderhead readings read normal. He had to terminate the testing at
those settings because the readings at the bases of the cylinders were
rapidly rising, indicating that the pistons were beginning to scuff.

>Engines run clean enough ROP.
>Engine stresses have been doing just fine now for 100 years ROP.
>CO is not a problem in maintained exhaust systems.
>Airplanes fly faster ROP.

Not necessarily. Same rpm, same airspeed but higher manifold pressure
at the LOP settings equals the same cruise speed. Yes, if you want to
fly at best power, you should be running ROP.

>Even the LOP diehards admit engines run smoother ROP.
>Gamis have more value in a turbocharged engine.

Once again, not necessarily. Once the GAMI injectors are installed,
Deakin has been able to lean right to the point of having the engine
quit due to a mixture too lean to fire, without any roughness at all.
If there's roughness then the injectors are not matched properly.

Corky Scott

[kage]

> For a given power setting, in general (module altitude effects), there
> are two mixture settings to give that power. One ROP, the other LOP.
> If you run at, say, 70% power, your airspeed is going to be fixed at
> a particular level, assuming stable, level flight. If you run LOP,
> you run less fuel through the engine, and you burn all of it up. If
> you turn ROP, you use some of it to cool the engine -- using more
> fuel than LOP operation. All this for the same speed.
>
Only at very low altitudes. Get YOUR facts straight. LOP is worthless at
altitude because you simply cannot push enough gas through the engine to
develop any meaningful horsepower, unless, like I said, you are
turbocharged.
> >
>
> What CHT level do you think is "just fine"? How does this argue
> in favor of ROP?

For decades we were running ROP and there were no casualties from high CHTs.
I ran several IO520s to overhaul in the 70's without any premature cylinder
pulls.
>
> >Engines run clean enough ROP.
>
Your data is unsupported, not mine. There are, and never were prolems with
Cont/Lyc running "dirty." Where is YOUR data to assert this. You are pulling
this out of thin air. Lack of experience and GAMI propaganda here.

> >Engine stresses have been doing just fine now for 100 years ROP.
>
> Oh? Have you ever examined the operations of round engines,
> especially the bigger things like R-3350s? IIRC, LOP operations
> were mandatory to get satisfactory performance and engine life.

So what? We are talking Walter here, GAMI----remember. They don't make
injectors for R-3350s
>
> >CO is not a problem in maintained exhaust systems.
>
> What does that have to do with the decision? LOP makes less CO;
> isn't that a positive?

No. Not necessarily. Where is your data, as you like to say, that this is
positive? You aren't some tree hugger are you?
>
> >Airplanes fly faster ROP.
>
> That claim is especially brown and smelly, given the orifice it
> was pulled from. See discussion above. Speed is all about power
> levels.

Impossible to pull sufficient power at any reasonable higher altitude
without a turbo. Try running LOP at 10,000 ft. Look at your charts(worthless
LOP) at 10,000 and show me how much power/speed you are making.
>
> >Even the LOP diehards admit engines run smoother ROP.
>
> As opposed to the ROP blowhards who can't abide admitting they might
> be wrong? See! I can use cheap rhetorical devices, too! Would you
> care to try a logical approach, or are you just interested in being
> fanatical?

Again you don't even make a point. Smoother is smoother, period.
>
> >Gamis have more value in a turbocharged engine.
>
> What does this have to do with deciding to operate LOP? Or are you
> just trying to obfuscate with more irrelevancies?

Turbo engines benefit from LOP because they can still pull the necessary
power to run at altitude. You really should get some facts straight about
available power at altitude LOP.
> >
> >And, I have plenty of dirt under my nails, thank you for asking.
> >
> Do you have real qualifications to back up your amazing assertions?
> How about real data? Sound logical reasoning?

This is Usenet. You have shown me NO logical reasoning. Only GAMI claims.
Cooler, cleaner, less stress----irrelevant!

Get some experience and check back in.

[Allen]

> wrote in message
...
> On Wed, 14 Apr 2004 22:36:41 -0700, "kage" >
> wrote:
>
>> To demonstrate that running lean of peak does not necessarily mean a
> lost of power, his "Mixture Magic" column showed a color photo of an
> instrument panel of a Cessna 410 running one engine ROP and the other
> LOP. Both engines were producing exactly the same power but at
> different manifold pressures. The LOP engine was using less fuel and
> was running at lower CHT temps. How is that bad?

Uh, what's a Cessna 410? Is it the predecessor to the 411 with an TCM
GTSIO-520-M engine?

Allen

[[email protected]]

On Thu, 15 Apr 2004 19:32:39 GMT, "Allen" >
wrote:

>Uh, what's a Cessna 410? Is it the predecessor to the 411 with an TCM
>GTSIO-520-M engine?
>
>Allen

Sorry, working on memory from the article. It was a Cessna 414. See
<http://www.avweb.com/news/columns/182084-1.html>

Corky Scott

[Roger Long]

> If you lean slowly in your 172N to rough, then slowly enrich until just
> smooth -- where do you wind up with regard to EGT?
>


I'm going to try and trace my thought processes back here because I think a
lot of 4 banger, fixed pitch pilots are still flying the way I have at
various times.

I started out without an EGT knowing only that leaner was hotter, too lean
made the engine rough, and too hot would burn the valves. I also didn't
really believe that the engine would restart if I leaned so much that it
quit. A CFI would have done me a big favor by showing me that you could
lean it until it was producing almost no power and then bring it back again.

So, I would carefully turn the mixture listening intently for the slightest
change in engine sound (Is that rough?) I was afraid to ever lean it enough
to learn what rough actually sounded like. Carefully doesn't mean slowly.
New pilots tend to do everything like this quickly because they look up to
find themselves 200 feet off altitude if they don't. The care was in
jumping like a rabbit back to richer from the slightest burble in the
exhaust sound. I know from later flying with the EGT that this method was
putting me about 50 - 75 ROP.

After I took over as maintenance officer, I had the EGT probe tested and it
was working. The gauge had never been adjusted so it was off scale most of
the time. I leaned and looked at the gauge and it didn't seem to react so I
just ignored it for another couple of years.

Then I learned two new things. You can't hurt the engine at 75% power with
any mixture setting and these engines, which were not designed to burn
100LL, need to be really leaned to avoid plug and valve stem fouling. This
prompted me to dig out and read through the stuff that came with the Alcor
EGT gauge. I'd heard about LOP by this time but thought it was only for
GAMI customers. I also went out and calibrated the EGT according to the POH
supplement which, along with some patience, suddenly made it a usable
instrument. I was still focused on plug fouling so I leaned to peak and
then back 50 degrees to cover the spread in FA ratios and make sure none of
the uninstrumented cylinders were in the "dangerous" LOP zone. So, I was
still flying the same way but with an EGT gauge.

The information that carb heat helps to even out mixture distribution was
coming to light just about the time our plane went down for a three month
refit so it was a frustrating winter. Here's what I know now.

If you keep leaning our engine with carb heat off, it does not get steadily
rougher from the first change in engine sound that used to spook me into
giving the mixture knob a couple turns back. You can keep going to peak and
a little beyond with little change. Jumping back from the first flaw in
smoothness was the mistake I'd been making for years. It's noticeably rough
by peak though. Lean it really smooth again and you'll wind up about 50
ROP.

Now put on the carb heat and forget about roughness, lean it until it really
sags and slowly turn the mixture in. With WOT or close to it, the engine
will settle down to about the same power output and roughness as it had at
25 - 50 ROP without carb heat but CHT will be 15 - 25 degrees lower. With
the ROP operation, the throttle would be pulled back farther to keep the
power in the 60 - 75% range but RPM, not throttle position is the measure of
power output. (For fixed pitch, anyway).

This is clearly only going to work in the lower half of our 172's service
ceiling but that's where a lot of our flying is done. There are also a lot
of subtle factors that effect mixture distribution. It would not surprise
me a bit if another O-320 H2AD in a 172N didn't have good enough mixture
distribution to make this work.

I also don't think you can do it cookbook style. I suspect you have to go
through the fiddling stage, trying different amounts of carb heat and
learning the way the engine sounds and reacts at different points. After
that, it should be easier.

I'm still learning about it which is why I'm curious what kind of experience
other simple engine fliers have if they try it (as opposed to just
pontificating about it).


--
Roger Long

[Tom Sixkiller]

> wrote in message
...
> On Wed, 14 Apr 2004 22:36:41 -0700, "kage" >
> wrote:
>
> > Even John Deakin burned out a set of
> >Continental cylinders in 500 hours LOP in his Bonanza. And their highly
> >touted fuel savings are, for the most part, due to a decrease in speed.
You
> >know, all that drag increase with V squared.
>
> I'd hesitate to speak for Mr. Deakin but I'd venture that he'd
> disagree violently that running lean of peak burned out his cylinders.
> Since running lean of peak results in low temperatures and less gas
> being burned, how exactly did they get burned out?

I addressed Kage's comments to Deakin and he responded in a private email.
You're completely right that Deakin disagrees...well, vehemently.

[Ron Rosenfeld]

On Thu, 15 Apr 2004 22:34:24 GMT, "Roger Long"
m> wrote:

>> If you lean slowly in your 172N to rough, then slowly enrich until just
>> smooth -- where do you wind up with regard to EGT?
>>
>
>
>I'm going to try and trace my thought processes back here because I think a
>lot of 4 banger, fixed pitch pilots are still flying the way I have at
>various times.
>

>I also don't think you can do it cookbook style. I suspect you have to go
>through the fiddling stage, trying different amounts of carb heat and
>learning the way the engine sounds and reacts at different points. After
>that, it should be easier.
>
>I'm still learning about it which is why I'm curious what kind of experience
>other simple engine fliers have if they try it (as opposed to just
>pontificating about it).

Interesting and educational story. It is clear that, in your engine,
following Lycoming's recommendations does result in running 50°F ROP. That
may not be what L intended, but that surely seems to be the result.

I, too, was never taught to properly lean. And I probably didn't really
learn to do it correctly until I'd owned my own airplane for five or ten
years (or maybe longer). There were a number of Mooniacs who were
recommending leaning to 50° rich for best power. In retrospect, although I
probably was aiming for that, I was likely a lot richer due to making the
adjustments too quickly.

But my "mature" Mooney would never show cruise CHT's much above 325°; and
my engine problems necessitating early O/H have not been related to
leaning.


Ron (EPM) (N5843Q, Mooney M20E) (CP, ASEL, ASES, IA)

[kage]

If you recall, I said Deakin burned out his cylinders despite his GAMIs, not
because of them. GAMIs will never correct Continentals poor build quality
and crummy warranty service.

All the hype that GAMI puts out about cooler, cleaner, peak pressure etc.
doesn't do a thing for longevity of junk. See Deakin's cylinders, for
example. And if you need to privately discuss this with Deakin, at least get
your "facts" straight. Plus, go get some aviation experience so you can have
something to offer Usenet besides poor manners.

Best,

>Get a brain and start using it.
"Tom Sixkiller" > wrote in message
...
>
> > wrote in message
> ...
> > On Wed, 14 Apr 2004 22:36:41 -0700, "kage" >
> > wrote:
> >
> > > Even John Deakin burned out a set of
> > >Continental cylinders in 500 hours LOP in his Bonanza. And their highly
> > >touted fuel savings are, for the most part, due to a decrease in speed.
> You
> > >know, all that drag increase with V squared.
> >
> > I'd hesitate to speak for Mr. Deakin but I'd venture that he'd
> > disagree violently that running lean of peak burned out his cylinders.
> > Since running lean of peak results in low temperatures and less gas
> > being burned, how exactly did they get burned out?
>
> I addressed Kage's comments to Deakin and he responded in a private email.
> You're completely right that Deakin disagrees...well, vehemently.
>
>
>
>
>
>

[kage]

Hey Charles,

If your reading is better than your Cessna model number knowledge, be aware
that I've always maintained GAMIs and Turbo engines are a good deal. A
Cessna 410(sic) is turbocharged. For normally aspirated engines, however,
their benefit is greatly diminished by the FACT that LOP reduces power,
especially where you need it most---at cruise at altitude.

*****Once again, not necessarily. Once the GAMI injectors are installed,
> Deakin has been able to lean right to the point of having the engine
> quit due to a mixture too lean to fire, without any roughness at all.
> If there's roughness then the injectors are not matched properly.*****

That is just simply incorrect. There is roughness that anyone, including
Deakin and Braly notice. It has nothing to do with the injectors being
mismatched. It has everything to do with the need for the engine's timing to
be adjustable. LOP REQUIRES the timing to be further advanced. GAMI knows
this, and is the reason they are developing their Prism system of engine
management.

Best,




And
> wrote in message
...
> On Wed, 14 Apr 2004 22:36:41 -0700, "kage" >
> wrote:
>
> > Even John Deakin burned out a set of
> >Continental cylinders in 500 hours LOP in his Bonanza. And their highly
> >touted fuel savings are, for the most part, due to a decrease in speed.
You
> >know, all that drag increase with V squared.
>
> I'd hesitate to speak for Mr. Deakin but I'd venture that he'd
> disagree violently that running lean of peak burned out his cylinders.
> Since running lean of peak results in low temperatures and less gas
> being burned, how exactly did they get burned out?
>
> To demonstrate that running lean of peak does not necessarily mean a
> lost of power, his "Mixture Magic" column showed a color photo of an
> instrument panel of a Cessna 410 running one engine ROP and the other
> LOP. Both engines were producing exactly the same power but at
> different manifold pressures. The LOP engine was using less fuel and
> was running at lower CHT temps. How is that bad?
>
> >CHTs are just fine ROP.
>
> Actually they aren't, if you set the engine according to the POH.
> Running at 75% or 80% power and set 50 degrees ROP, the CHT's run
> above 400 degrees. These are figures that come from Lycoming and
> Continental. And yet over 400 degrees is where aluminum begins to
> loose strength. Deakin also was able to demonstrate that at certain
> POH dictated ROP settings, the cylinders actually distorted from the
> heat and began to scuff the pistons. This was during flight testing
> with several proprietary probes installed in his engine which could
> read what was happening in areas away from the cylinderhead probe.
> While these probes were showing alarming increases in heat, the
> cylinderhead readings read normal. He had to terminate the testing at
> those settings because the readings at the bases of the cylinders were
> rapidly rising, indicating that the pistons were beginning to scuff.
>
> >Engines run clean enough ROP.
> >Engine stresses have been doing just fine now for 100 years ROP.
> >CO is not a problem in maintained exhaust systems.
> >Airplanes fly faster ROP.
>
> Not necessarily. Same rpm, same airspeed but higher manifold pressure
> at the LOP settings equals the same cruise speed. Yes, if you want to
> fly at best power, you should be running ROP.
>
> >Even the LOP diehards admit engines run smoother ROP.
> >Gamis have more value in a turbocharged engine.
>
> Once again, not necessarily. Once the GAMI injectors are installed,
> Deakin has been able to lean right to the point of having the engine
> quit due to a mixture too lean to fire, without any roughness at all.
> If there's roughness then the injectors are not matched properly.
>
> Corky Scott
>

[Friedrich Ostertag]

Hi Corky,

> > Even John Deakin burned out a set of
> >Continental cylinders in 500 hours LOP in his Bonanza. And their
highly
> >touted fuel savings are, for the most part, due to a decrease in
speed. You
> >know, all that drag increase with V squared.
>
> I'd hesitate to speak for Mr. Deakin but I'd venture that he'd
> disagree violently that running lean of peak burned out his
cylinders.

Even if it did - Mr. Deakin is one of the key people in developing LOP
operations for today's GA Piston Aircraft. I guess he did experiment a
bit with it before getting it right.

However I fully agree: If done right running LOP puts less (thermal)
stress on the engine and is certainly not going to "burn out"
cylinders.

regards,
Friedrich

--
please remove entfernen from my adress for personal email

[[email protected]]

On Thu, 15 Apr 2004 20:53:48 -0700, "kage" >
wrote:

>*****Once again, not necessarily. Once the GAMI injectors are installed,
>> Deakin has been able to lean right to the point of having the engine
>> quit due to a mixture too lean to fire, without any roughness at all.
>> If there's roughness then the injectors are not matched properly.*****
>
>That is just simply incorrect. There is roughness that anyone, including
>Deakin and Braly notice. It has nothing to do with the injectors being
>mismatched. It has everything to do with the need for the engine's timing to
>be adjustable. LOP REQUIRES the timing to be further advanced. GAMI knows
>this, and is the reason they are developing their Prism system of engine
>management.
>
>Best,

According to Deakin's article "Mixture Magic", the speed at which the
fuel air mixture burns varies depending on the stochiometric ratio.
At the ideal mixture ratio of about 15 to 1 by volume, the mixture
burns fastest. On either side of that ratio, the burning slows down.

Because the timing is fixed, adjusting the mixture is the only way to
vary where the Peak Pressure Point (the point at which the combustion
process produces the highest pressure within the cylinder. It's
important that this occur when the crankshaft throw is about 16
degrees past TDC so that maximum leverage is applied to the piston.
If PPP occurs when the piston is closer to TDC, there is little
mechanical advantage and the pressure of the combustion pushes against
a piston that just pushes back instead of accelerating away and adding
thrust to the rotation of the crankshaft). The timing of the engines
and the mixture setup (full rich) is specifically adjusted such that
during full power operation, the PPP occurs at about 16 degrees past
top dead center. This is the source of the common knowledge that a
rich mixture cools the engine. The rich mixture doesn't hose down the
inside of the combustion chamber, it merely slows down the rate of
burning such that PPP occurs at 16 degrees past top dead center. When
the mixture is leaned out so that it approaches the ideal burning
ratio, the mixture burns faster and the PPP begins to occur while the
piston is much closer to TDC. This increases the pressure inside the
combustion chamber and heat goes up. This is the "peak" part of the
LOP or ROP operation. Either side of "peak" the mixture burns slower
which allows the engine to run cooler.

But lean the mixture further, beyond the ideal, and the rate of burn,
as mentioned above, slows down. This allows the piston to be at 16
degrees past TDC again which greatly reduces heat. It also reduces
the amount of gas you use.

As Deakin points out, at about 8,000 feet and full throttle, the
engine is only producing about 60% power and at that power setting you
cannot hurt the engine no matter where you put the mixture, so you
might as well lean to best power setting (which is rich of peak) and
leave it there, if you want to fly at your fastest cruise speed and
range is not an issue.

If the timing ***COULD*** be varied, there would be no need for a
mixture control knob, it could be set for best ratio by the mechanic
and the variable timing would take care of keeping the PPP at the
proper location. Variable timing would also simplify starting.
Engines start much easier when the timing can be retarded to fire the
plugs when the piston is at about TDC, or perhaps even a little after
TDC.

So in answer to your last statement above, LOP operation does not
require that the timing be further advanced. LOP operation actually
has the affect of retarding the timing because it slows down the
combustion process just as an over-rich mixture likewise slows down
the combustion process, allowing the PPP to occur in the desired
place.

Corky Scott

[Michael Houghton]

Howdy!

In article >,
kage > demonstrated an amazing lack of reading
comprehension when he/she wrote:
>
>
>> For a given power setting, in general (module altitude effects), there
>> are two mixture settings to give that power. One ROP, the other LOP.
>> If you run at, say, 70% power, your airspeed is going to be fixed at
>> a particular level, assuming stable, level flight. If you run LOP,
>> you run less fuel through the engine, and you burn all of it up. If
>> you turn ROP, you use some of it to cool the engine -- using more
>> fuel than LOP operation. All this for the same speed.
>>
>Only at very low altitudes. Get YOUR facts straight. LOP is worthless at
>altitude because you simply cannot push enough gas through the engine to
>develop any meaningful horsepower, unless, like I said, you are
>turbocharged.

You didn't read a thing I wrote, apparently.

If you are running at, say, 70% power, you are spinning your fixed-pitch
prop at a particular RPM. At sufficient altitude, you may not be able to get
70% power, but that is irrelevant to the discussion.

It doesn't matter whether you are LOP or ROP. If you are getting X RPM,
you are getting Y% power. For a constant speed prop, the indicator is
different, but the concept is the same.

Of course, at high power levels, LOP is bad, but usually 75% power and under
is safe (from a detonation perspective).

To effectively operate LOP, you also need better control over the fuel
distribution from cylinder to cylinder -- particularly problematic with
carburetted engines. However, that doesn't change the essential fact that
operating LOP uses less fuel for a given power level than operating ROP.
>> >
>>
>> What CHT level do you think is "just fine"? How does this argue
>> in favor of ROP?
>
>For decades we were running ROP and there were no casualties from high CHTs.
>I ran several IO520s to overhaul in the 70's without any premature cylinder
>pulls.

You didn't answer my question, and you left out your assertion that I
responded to. If your engine is capable of running LOP, you can manage
CHTs just fine.
>>
>> >Engines run clean enough ROP.
>>
>Your data is unsupported, not mine. There are, and never were prolems with
>Cont/Lyc running "dirty." Where is YOUR data to assert this. You are pulling
>this out of thin air. Lack of experience and GAMI propaganda here.

Ummm...now you leave out my response and continue with the bald assertions.
You made the claim -- now back it up, unless you are just making stuff up.
>
>> >Engine stresses have been doing just fine now for 100 years ROP.
>>
>> Oh? Have you ever examined the operations of round engines,
>> especially the bigger things like R-3350s? IIRC, LOP operations
>> were mandatory to get satisfactory performance and engine life.
>
>So what? We are talking Walter here, GAMI----remember. They don't make
>injectors for R-3350s

You didn't make that distinction. You simply asserted a century of ROP
operation without distinguishing particular engine types. I, once again,
note that LOP operations were essential to satisfactory operation of
round engines, especially the large ones, and may have been part of
stardard operating practices for other engine types as well. I don't
know all the answers, but I'm not claiming universal use of ROP as the
normal operating regime for all (aircraft) engines for the last century.
>>
>> >CO is not a problem in maintained exhaust systems.
>>
>> What does that have to do with the decision? LOP makes less CO;
>> isn't that a positive?
>
>No. Not necessarily. Where is your data, as you like to say, that this is
>positive? You aren't some tree hugger are you?

CO is formed when there is more carbon (fuel) than oxygen -- the definition
of a "rich" mixture.

You didn't answer the part about how CO production has any real relation
to deciding whether to operate LOP or ROP. I guess that means you don't
have a reason for including that point in your list -- it was just padding.

Your ad hominem ("tree hugger") further reinforces that conclusion. You
resort to name calling when you can't make a substantive response.

Busted!
>>
>> >Airplanes fly faster ROP.
>>
>> That claim is especially brown and smelly, given the orifice it
>> was pulled from. See discussion above. Speed is all about power
>> levels.
>
>Impossible to pull sufficient power at any reasonable higher altitude
>without a turbo. Try running LOP at 10,000 ft. Look at your charts(worthless
>LOP) at 10,000 and show me how much power/speed you are making.

Non sequitur. As in, that does not follow. Reread the response to your first
non-point.

Oh, I don't have charts available to me, but somehow I don't think they
really reference the mixture setting when telling you how much power you
can get at a given altitude, or how to get it. If you'd care to provide
a citation that we can all see to the contrary, I'll concede the points
where I am actually mistaken.
>>
>> >Even the LOP diehards admit engines run smoother ROP.
>>
>> As opposed to the ROP blowhards who can't abide admitting they might
>> be wrong? See! I can use cheap rhetorical devices, too! Would you
>> care to try a logical approach, or are you just interested in being
>> fanatical?
>
>Again you don't even make a point. Smoother is smoother, period.

I made as much of a point as you did, and I even admitted that I was using
cheap rhetorical devices. You just say "did too".
>>
>> >Gamis have more value in a turbocharged engine.
>>
>> What does this have to do with deciding to operate LOP? Or are you
>> just trying to obfuscate with more irrelevancies?
>
>Turbo engines benefit from LOP because they can still pull the necessary
>power to run at altitude. You really should get some facts straight about
>available power at altitude LOP.

What do you mean by "at altitude"? 10,000 feet? 20,000 feet?

I'm pretty sure you can get your normally aspirated light single up to 10k,
for many values of "light single".
>> >
>> >And, I have plenty of dirt under my nails, thank you for asking.
>> >
>> Do you have real qualifications to back up your amazing assertions?
>> How about real data? Sound logical reasoning?
>
>This is Usenet. You have shown me NO logical reasoning. Only GAMI claims.
>Cooler, cleaner, less stress----irrelevant!

....and just because it's Usenet doesn't mean you get a free ride when you
make ridiculous claims and don't back them up. You still have not offered
any checkable facts, or any credentials that would tell us why we should
take your word on this.

I have shown (though you clearly ignored it) how more than one mixture
setting can produce the same power level, but you continue to assert
something else. You gave us a laundry list of "reasons" why LOP was a
bad thing but offered no reason for us to take your word for it. When
called on that, you simply continue to repeat, deny, and change the
subject.
>
>Get some experience and check back in.
>
You first.

yours,
Michael

--
Michael and MJ Houghton | Herveus d'Ormonde and Megan O'Donnelly
| White Wolf and the Phoenix
Bowie, MD, USA | Tablet and Inkle bands, and other stuff
| http://www.radix.net/~herveus/

[Michael Houghton]

Howdy!

In article >,
kage > wrote:
>Hey Charles,
>
>If your reading is better than your Cessna model number knowledge, be aware
>that I've always maintained GAMIs and Turbo engines are a good deal. A
>Cessna 410(sic) is turbocharged. For normally aspirated engines, however,
>their benefit is greatly diminished by the FACT that LOP reduces power,
>especially where you need it most---at cruise at altitude.
>
>*****Once again, not necessarily. Once the GAMI injectors are installed,
>> Deakin has been able to lean right to the point of having the engine
>> quit due to a mixture too lean to fire, without any roughness at all.
>> If there's roughness then the injectors are not matched properly.*****
>
>That is just simply incorrect. There is roughness that anyone, including
>Deakin and Braly notice. It has nothing to do with the injectors being
>mismatched. It has everything to do with the need for the engine's timing to
>be adjustable. LOP REQUIRES the timing to be further advanced. GAMI knows
>this, and is the reason they are developing their Prism system of engine
>management.
>
Are you calling John Deakin a liar? It sure looks that way.

Listen, howzabout you provide us with some way to verify your claims besides
taking your word for it. Links to verifiable accounts, etc.

yours,
Michael


--
Michael and MJ Houghton | Herveus d'Ormonde and Megan O'Donnelly
| White Wolf and the Phoenix
Bowie, MD, USA | Tablet and Inkle bands, and other stuff
| http://www.radix.net/~herveus/

[kage]

*****So in answer to your last statement above, LOP operation does not
require that the timing be further advanced. LOP operation actually
has the affect of retarding the timing because it slows down the
combustion process just as an over-rich mixture likewise slows down
the combustion process, allowing the PPP to occur in the desired
place.*******


Oh GREAT. Tell that ot GAMI. They can stop their work on PRISM right away.


> wrote in message
...
> On Thu, 15 Apr 2004 20:53:48 -0700, "kage" >
> wrote:
>
> >*****Once again, not necessarily. Once the GAMI injectors are installed,
> >> Deakin has been able to lean right to the point of having the engine
> >> quit due to a mixture too lean to fire, without any roughness at all.
> >> If there's roughness then the injectors are not matched properly.*****
> >
> >That is just simply incorrect. There is roughness that anyone, including
> >Deakin and Braly notice. It has nothing to do with the injectors being
> >mismatched. It has everything to do with the need for the engine's timing
to
> >be adjustable. LOP REQUIRES the timing to be further advanced. GAMI knows
> >this, and is the reason they are developing their Prism system of engine
> >management.
> >
> >Best,
>
> According to Deakin's article "Mixture Magic", the speed at which the
> fuel air mixture burns varies depending on the stochiometric ratio.
> At the ideal mixture ratio of about 15 to 1 by volume, the mixture
> burns fastest. On either side of that ratio, the burning slows down.
>
> Because the timing is fixed, adjusting the mixture is the only way to
> vary where the Peak Pressure Point (the point at which the combustion
> process produces the highest pressure within the cylinder. It's
> important that this occur when the crankshaft throw is about 16
> degrees past TDC so that maximum leverage is applied to the piston.
> If PPP occurs when the piston is closer to TDC, there is little
> mechanical advantage and the pressure of the combustion pushes against
> a piston that just pushes back instead of accelerating away and adding
> thrust to the rotation of the crankshaft). The timing of the engines
> and the mixture setup (full rich) is specifically adjusted such that
> during full power operation, the PPP occurs at about 16 degrees past
> top dead center. This is the source of the common knowledge that a
> rich mixture cools the engine. The rich mixture doesn't hose down the
> inside of the combustion chamber, it merely slows down the rate of
> burning such that PPP occurs at 16 degrees past top dead center. When
> the mixture is leaned out so that it approaches the ideal burning
> ratio, the mixture burns faster and the PPP begins to occur while the
> piston is much closer to TDC. This increases the pressure inside the
> combustion chamber and heat goes up. This is the "peak" part of the
> LOP or ROP operation. Either side of "peak" the mixture burns slower
> which allows the engine to run cooler.
>
> But lean the mixture further, beyond the ideal, and the rate of burn,
> as mentioned above, slows down. This allows the piston to be at 16
> degrees past TDC again which greatly reduces heat. It also reduces
> the amount of gas you use.
>
> As Deakin points out, at about 8,000 feet and full throttle, the
> engine is only producing about 60% power and at that power setting you
> cannot hurt the engine no matter where you put the mixture, so you
> might as well lean to best power setting (which is rich of peak) and
> leave it there, if you want to fly at your fastest cruise speed and
> range is not an issue.
>
> If the timing ***COULD*** be varied, there would be no need for a
> mixture control knob, it could be set for best ratio by the mechanic
> and the variable timing would take care of keeping the PPP at the
> proper location. Variable timing would also simplify starting.
> Engines start much easier when the timing can be retarded to fire the
> plugs when the piston is at about TDC, or perhaps even a little after
> TDC.
>
> So in answer to your last statement above, LOP operation does not
> require that the timing be further advanced. LOP operation actually
> has the affect of retarding the timing because it slows down the
> combustion process just as an over-rich mixture likewise slows down
> the combustion process, allowing the PPP to occur in the desired
> place.
>
> Corky Scott

[[email protected]]

On Fri, 16 Apr 2004 06:54:49 -0700, "kage" >
wrote:

>*****So in answer to your last statement above, LOP operation does not
>require that the timing be further advanced. LOP operation actually
>has the affect of retarding the timing because it slows down the
>combustion process just as an over-rich mixture likewise slows down
>the combustion process, allowing the PPP to occur in the desired
>place.*******
>
>
>Oh GREAT. Tell that ot GAMI. They can stop their work on PRISM right away.

I guess I don't understand your remark. What I've been explaining is
that GAMI has been saying. The fact that a lean or rich mixture burns
more slowly than the ideal mixture isn't made up, it's what happens
inside air cooled certified aircraft engines with fixed timing.

Why would GAMI want to stop work on their variable timing electronic
ignition?

Corky Scott

[Rick Durden]

Thomas,

How are you, Sir? Hope things are going well.

I so enjoy the nay-sayers to LOP operation and get a lot of laughs out
of their remarks and repeated recitation of OWTs. It's funny how many
people are content to rely on myth rather than data. Ah, well.

Just finished 10 days of flying a Cessna 206 in Belize for LightHawk
in support of environmental research and data collection. Fuel there
is about $4.25 U.S. per gallon, so on top of 90 degree F temps,
keeping the fuel burns minimized is one of those very high priority
items in one's operating plan. Plus, one may only purchase fuel at
one airport in a country the size of the U.S. state of Mass.
Therefore, GAMIs and LOP ops are essential. I very much appreciate
the fact that when I've got the rear doors off the 206, with
photographers hanging outside, I'm able to maintain the requested 85
knots indicated with the cowl flaps closed and CHTs in the 350 degree
F range. If I go ROP, the CHTs hit 400 degrees F immediately and even
opening the cowl flaps, which adds a bunch to drag at those speeds,
and requires a power increase, doesn't cool things off much. When I
can burn 11 gph in that IO-520 at 24 inches and 2200 rpm LOP while
keeping the engine very happily cool in the tropical heat, I just
shake my head in wonder at those who still don't get it. Plus, even
with the questional quality control on the cylinders, that engine is
running clean and doing a very nice job of hanging in there in terms
of an absence of gunk in the various areas where you get the products
of incomplete combustion in ROP operated engeines.

Warmest regards,
Rick

Thomas Borchert > wrote in message >...
> Roger,
>
> > I'm especially interested in the experience of anyone doing it
> > with a fixed pitch carb engine with single EGT and CHT probes.
> >
>
> How would you know you're LOP on all cylinders with that kind of
> set-up? Our Tobago (O-360) will not run smoothly LOP. I haven't tried
> to enhance smoothness by adding carb heat, which some say helps even
> out fuel distribution.