Lycoming's views on best economy settings

"Mike Rhodes" wrote in message
...
On 29 Jun 2004 22:13:49 -0700, (John Clear) wrote:

In article ,
Mike Rhodes wrote:

As for Lycoming recommending against LOP, there was an article in
Flying magazine (p. 74-75, 7/02, inset article, J.Mac) , where there
was some sort of lead crystalline deposit (lead oxybromide) forming in
_turbo_ engines only in LOP operations.

I've snipped the rest since it is full of old wives tales. The
theory of lead oxybromide came from a poorly investigated accident
in Austrailia.

John Deakin analyzes the accident, and Flying's coverage of it.

Accident: http://www.avweb.com/news/columns/182152-1.html

Flying's coverage: http://www.avweb.com/news/columns/182153-1.html

Deakin also covers LOP in alot of his articles, specifically the
ones titled 'Where should I run my engine?' He goes into the
science of how an engine actually works, and examines how the
'your engine will burn up if you do that' OWTs relate to reality.

All of Deakin's articles: http://www.avweb.com/news/columns/182146-1.html

John

So I can ignore all the hysterics and lean to roughness, then enrichen
it to smoothness. And we all should do so in any piston engine, as
long as the power is markedly below 75%.


No...you can read the articles and try to LEARN something instead of
shooting your mouth off with your foot still in it.

"John Clear" wrote in message
...
In article ,
Mike Rhodes wrote:
Deakin also covers LOP in alot of his articles, specifically the
ones titled 'Where should I run my engine?' He goes into the
science of how an engine actually works, and examines how the
'your engine will burn up if you do that' OWTs relate to reality.

All of Deakin's articles:
http://www.avweb.com/news/columns/182146-1.html

So I can ignore all the hysterics and lean to roughness, then enrichen
it to smoothness. And we all should do so in any piston engine, as
long as the power is markedly below 75%.

Without an engine analyzer, you have know way of knowing how bad
the fuel/air mixture is in each cylinder. Running at the standard
50F rich of peak EGT puts you right in the 'Red Zone'. Running
100-150F ROP is a better place to run the engine if you can't run
LOP smoothly. Most non-fuel injected engines have such large
differences in fuel/air mixture between cylinders that they can't
be run LOP smoothly.

At lower power settings, it doesn't matter much where you run your
engine since lower power means lower heat and pressure.

Deakin does a much better job of explaining all this.


Save your breath.

Numerous people have pointed out the articles. Evidently Rhodes is unwilling
to read them or cannot comprehend them.

On Thu, 1 Jul 2004 10:45:43 -0700, "Tom Sixkiller"
wrote:

"Mike Rhodes" wrote in message
.. .

All of Deakin's articles: http://www.avweb.com/news/columns/182146-1.html

John

So I can ignore all the hysterics and lean to roughness, then enrichen
it to smoothness. And we all should do so in any piston engine, as
long as the power is markedly below 75%.


No...you can read the articles and try to LEARN something instead of
shooting your mouth off with your foot still in it.


I glanced at one page of Deakin and thought the writing entertaining,
& therefore also distracting. That was not intended as a critique of
his understanding, though there appears to be a bit of desparation in
that regard. Deakin's kind of wordy, especially if its expected to be
used as reference material -- like from this news group.

I think it unusual to be dissed for not reading something, and I got
that feeling even before the above. So I chose not to pour over the
material, which is not written as if it were intended to be used for
reference. If you have a specific page I'd be glad to check it out;
but not all of his articles. If I like that then I may read more, but
on my time.

Otherwise, quoting the header post by Mr. Scott, (and this is general
info as I know/knew it)...

Remember, when you are cruising at 60% power, you cannot hurt the
engine no matter where you set the mixture control. You can't burn
valves or cook the cylinderheads or cause detonation, it just isn't
producing enough power to do that.

Therefore I think I can assume (for I always have), that no 'red zone'
actually exists in cruise throttle, as was mentioned someplace else in
the thread.

My 2nd reply, which is stated on top of this post (leaning to
roughness), is therefore allowed, and without qualification, by the
'can't hurt engine at 60%'. The words "best economy" are in the title
of this thread.

Mr. Scott's polite reply (thank-you) to my lean-to-roughness said I
"may have leaned to a safe setting, maybe not." But this is in
conflict with his own statement above, for which he then gave no
explanation, except to suggest the engine analyzer. But if the engine
is below 75% power then what difference does it make what mixture is
in any particular cylinder? If I need economy I go to roughness. If
I need speed then I enrichen it to gain power. And I would expect
more wear-and-tear at the higher power of richer mixture settings --
_IF_ I get higher power at richer mixture and don't begin to waste
fuel. I can monitor my airspeed to see where an another optimum
mixture setting exists.

(Apologies for putting all my replies into this post, for my first,
semi-uneducated post. It was an honest question on my part.)

--Mike

On Thu, 01 Jul 2004 21:44:26 -0500, Mike Rhodes
wrote:

But if the engine
is below 75% power then what difference does it make what mixture is
in any particular cylinder? If I need economy I go to roughness. If
I need speed then I enrichen it to gain power. And I would expect
more wear-and-tear at the higher power of richer mixture settings --
_IF_ I get higher power at richer mixture and don't begin to waste
fuel. I can monitor my airspeed to see where an another optimum
mixture setting exists.

I think you've got it, at least as I understand it anyway. My only
concern was that if you are using a high power setting at below 8,000
feet, leaning to roughness and then richening to smooth operation
might put you into the red zone, that zone as defined in Deakin's
graph's, which can cause high cylinderhead temperatures.

I don't know how much you read through the "Mixture Magic" column, but
there's that one, plus four others that go into minute detail on
exactly what happens inside the engine on the Ground, Takeoff/Climb,
Cruise and Descent.

Deakin wrote columns for AVWeb, he wasn't writing NACA white papers.
His "Mixture Magic" column included many graphs from Pratt and Whitney
as well as Lycoming, Continental and actual test stand results from
the GAMI shops. At one point, they boosted turbo pressure to
demonstrate graphically what the onset of detonation looked like on
the graph. Deakin remarked that the engine definately did not sound
happy. This information was represented on a color coded graph. You
could see the traces of detonation represented by squiggly lines on
the pressure rise.

In my opinion, if the subject interests you, you might want to
download all five articles and print them out to a color printer so
that you can read them at your leisure. I also enlarged those graphs
that allowed you to do so and printed them out seperately so I could
refer to them from the text. Otherwise the graphs printed out a bit
small.

It's my opinion that all the information you need to safely and
economically operate your engine is there in those five columns. It
isn't all conversational text, every single claim he makes is backed
up by graphs and/or readouts and pictures.

At one point he casually remarked that he wished he had the time to do
timed climbs leaning as he climbed to plot the savings in gas and time
to climb. One of his readers hopped into his own airplane which was
equipped with a JPI EGT analyzer and flew out from under the LA Class
B space and then made two climbs to 10,000 feet carefully leaning as
he climbed during one climb and leaving it rich for the other. Then
he e-mailed Deakin the electronically recorded information and Deakin
formatted it into Excel and presented the results in his next column.

I have a friend who has just became the owner of a V tail Bonanza,
which is what Deakin flies, only Deakin's is turbocharged. He has
been flying for a number of years and just cannot bring himself to run
it LOP . . . yet. He understands the concept, but was a race driver
and builder and engine assembler in his youth, and recalls what
happened to his engines if they ran lean. As Deakin mentions though,
we aren't talking about leaning during takeoff power operation. We
will be trying out LOP operation in the next few weeks to see if the
engine will tolerate it without running rough. He does not have GAMI
injectors.

Corky Scott

"Ash Wyllie" wrote
GAMI claims something else is going on. Fuel from the upstream injectors is
leaking into the downstream intake ports, making the downstream cylinders
richer than the upstream cylinders.

They can claim anything they want - but if what they were describing
was real, the coke bottle test would show it and adjusting the
injector nozzles would fix it.

AS to intake air distribution, I would assume that it is like the rest of
aviation, reliable junk.

Junk? Yes. Reliable? I've heard of too many cases (from reliable
sources) of the intake system developing leaks, causing cylinders to
run overlean and fail. I think the term you're going for is
UNreliable junk.

Michael

Michael opined

"Ash Wyllie" wrote
GAMI claims something else is going on. Fuel from the upstream injectors is
leaking into the downstream intake ports, making the downstream cylinders
richer than the upstream cylinders.

They can claim anything they want - but if what they were describing
was real, the coke bottle test would show it and adjusting the
injector nozzles would fix it.

The coke bottle test won't find this, as it is an artifact of the way air
flows in the intake manifold. And adjusting the injector nozzles is what GAMI
is doing. By making accurate injectors designed for each cylinder all
cylinders provide the same power.

AS to intake air distribution, I would assume that it is like the rest of
aviation, reliable junk.

Junk? Yes. Reliable? I've heard of too many cases (from reliable
sources) of the intake system developing leaks, causing cylinders to
run overlean and fail. I think the term you're going for is
UNreliable junk.

Aircraft engines don't fail in the air, too often...


-ash
Cthulhu for President!
Why vote for a lesser evil?

On 02 Jul 04 12:03:47 -0500, "Ash Wyllie" wrote:

Michael opined

"Ash Wyllie" wrote
GAMI claims something else is going on. Fuel from the upstream injectors is
leaking into the downstream intake ports, making the downstream cylinders
richer than the upstream cylinders.

They can claim anything they want - but if what they were describing
was real, the coke bottle test would show it and adjusting the
injector nozzles would fix it.

The coke bottle test won't find this, as it is an artifact of the way air
flows in the intake manifold. And adjusting the injector nozzles is what GAMI
is doing. By making accurate injectors designed for each cylinder all
cylinders provide the same power.

snipped....

Do they provide the same power or do they provide the same air/fuel
ratio? I don't believe that they can do both. If they are providing
the same air/fuel ratio to all cylinders the power that they develop
will be dependent upon the volume of air that was getting to each
cylinder. If all cylinders are providing the same power, then they
must be receiving the same amount of air, which is not the case with
most aircraft induction systems that I've seen (not that that is a
lot). Not an expert, just curious and want to understand the
situation correctly.
Rich Russell

Ash,

causing cylinders to
run overlean and fail.


NO, NO, NO!!!

Running "overlean" does NOT hurt cylinders! This is the core of the OWT
surrounding all this. Run the cylinder leaner and leaner - and it will
get cooler until combustion quits. A little more correct would be to
say "not running lean enough and fail". The correct description is
"changing the mixture to a point where the temperatures and pressures
in the cylinder failed it". But this is in NO WAY the leanest point, or
"overleanest" - whatever that may be.

--
Thomas Borchert (EDDH)

Richard Russell opined

On 02 Jul 04 12:03:47 -0500, "Ash Wyllie" wrote:

Michael opined

"Ash Wyllie" wrote
GAMI claims something else is going on. Fuel from the upstream injectors
is leaking into the downstream intake ports, making the downstream
cylinders richer than the upstream cylinders.

They can claim anything they want - but if what they were describing
was real, the coke bottle test would show it and adjusting the
injector nozzles would fix it.

The coke bottle test won't find this, as it is an artifact of the way air
flows in the intake manifold. And adjusting the injector nozzles is what
GAMI is doing. By making accurate injectors designed for each cylinder all
cylinders provide the same power.

snipped....

Do they provide the same power or do they provide the same air/fuel
ratio? I don't believe that they can do both. If they are providing
the same air/fuel ratio to all cylinders the power that they develop
will be dependent upon the volume of air that was getting to each
cylinder. If all cylinders are providing the same power, then they
must be receiving the same amount of air, which is not the case with
most aircraft induction systems that I've seen (not that that is a
lot). Not an expert, just curious and want to understand the
situation correctly.

Same mixture.

-ash
Cthulhu for President!
Why vote for a lesser evil?

Thomas Borchert wrote
NO, NO, NO!!!

Running "overlean" does NOT hurt cylinders!

It does at takeoff power. At takeoff power, a VERY rich mixture
(probably 200 degrees rich of peak, or more) is normally and properly
used. An induction leak can cause the mixture to be significantly
leaner, meaning much closer to peak. Running at peak EGT at takeoff
power most certainly will hurt the cylinders.

If the induction leak was bad enough that a cylinder was running well
lean of peak, that would probably be OK - but in that case, there
would be noticeable roughness and loss of power. The insidious thing
about a slight induction leak is that there is no loss of power - in
fact there is a slight gain - and smooth operation is maintained right
to peak on the affected cylinder. Without all-cylinder EGT, this is
undetectable. The design of the induction systems in certified
aircraft engines is such that they are prone to this problem of having
one jug running at close to peak due to an induction leak while the
other jugs run well rich. Thus they are, by design, unreliable junk.

I'm sorry if you found the term "overlean" confusing. In this
context, it simply means leaner than is proper for the operation.

Michael