Lycoming's views on best economy settings

On Tue, 29 Jun 2004 12:55:39 -0400,
wrote:

[trim]

Lycoming finishes the graph with the following statement: "Textron
Lycoming does not recommend operating on the lean side of peak EGT."

Yet as their own graph shows, best economy is ONLY achieved lean of
peak. What extremely interesting to me is that the difference between
peak and lean of peak where best economy occurs is only a matter of a
very few degrees EGT.

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

That since an aircraft engine will not usually detonate at the lower
power. But turbo engines, I've read, may have difficulty...

valves or cook the cylinderheads or cause detonation, it just isn't
producing enough power to do that. Lycoming themselves recommends
that for maximum engine life, cruise power should be limited to 65%
and CHT's kept below 400 F. But since the instrument panel doesn't
include a CHT guage, the only way to avoid high temps is to be way
rich, or at peak EGT or below.

Why Lycoming recommends against LOP operation is a mystery. MUCH
cooler CHT's and less fuel being burned... what am I missing here?
Does the engine run roughly at this setting? Only those who try LOP
will know.

Corky Scott

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. That deposit would cause a
"light" detonation, and eventually destroy the engine. The deposit
apparently does not form in normally aspirated engines, regardless of
mixture. Lead oxybromide was also found to harm the rod and
crankshaft bearings.
If true, I would think this would be common knowledge, and pilots
would not have to run to Lycoming for it. And other authorities would
not suggest lean in turbo engines. (Do they?)
Running lean, by a moment of carelessness (pilots have lots of
things to tend to) invites catastrophic trouble in any engine. And
for the pilot to get in that habit in normally-aspirated engines can,
after the pilot upgrades, apparently inflict harm on turbo engines.
Anyone else familiar with this?

--Mike

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
--
John Clear - http://www.panix.com/~jac

"John Clear" wrote in message
...

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

You missed the best bit, where the coroner slates the ATSB investigation.
:-)

http://www.airsafety.com.au/whyalla/default.htm

has the chronology.

Julian Scarfe

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%.

Mike

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.

John
--
John Clear - http://www.panix.com/~jac

"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 Wed, 30 Jun 2004 13:16:14 -0500, Mike Rhodes
wrote:

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%.

Mike

What Deakin suggests is that you get yourself a multi cylinder EGT
guage that can tell you what the temperatures are for the EGT and CHT
for ALL the cylinders.

Without that instrument and even with a single point EGT guage, you
have no idea where the CHT's are when you lean by that method. He
frequently characterized the typical Lycoming/Continental engine as a
group of cylinders flying along loosely in formation because the
temperature readings from one cylinder to the other can vary so much
you'd think they were from some other engine.

Maybe you've leaned to a safe settng but maybe not. Deakin advocates
knowing for sure. Seems like good, albeit expensive advice.

Corky Scott

"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.

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