Lycoming's views on best economy settings

[[email protected]]

I was searching via Google for informational schematics, or even just
a written description, on Lycoming's fuel injection system because
it's different from Continental's.

I came across Lycoming's website in which a number of technical and
informational articles reside.

One of them
<http://www.lycoming.textron.com/main.jsp?bodyPage=support/publications/keyReprints/operation/leaningEngines.html>

discusses various mixture settings for their fuel injected engines.

Here is item no. 5 from that article, it's a description of how to
achieve "best power" and "best economy" when an EGT guage is
available:

5. The exhaust gas temperature (EGT) offers little improvement in
leaning the float-type carburetor over the procedures outlined above
because of imperfect mixture distribution. However, if the EGT probe
is installed, lean the mixture to 100oF on the rich side of peak EGT
for best power operation. For best economy cruise, operate at peak
EGT. If roughness is encountered, enrich the mixture slightly for
smooth engine operation. ***editorial note*** If you do this (richen
slightly from peak), the only place for the cylinderhead temperatures
to go is up. Slightly to the rich side of peak on the graph described
below is where the cylinderhead temps peak. So it would pay to be
careful how much you richen from the peak setting, if the engine is
running rough at that point. The Cessna 172 I rent has the EGT guage,
but no CHT guage. So you can richen from peak and drone happily along
not knowing that you are cooking the cylinderheads.

This particular section of the website includes a nice graph, which,
if you are familiar with John Deakin's "Mixture Magic" article, will
look very familiar. It should because all fixed spark engines will
show the exact same performance curves for things like EGT, CHT,
percent power and BSFC.

What was interesting to me is if you look at where peak EGT is
occuring and then go down to the BSFC curve is, you will see that you
have not yet reached the lowest BSFC. That doesn't occur until you've
leaned a bit further. But then you would be **LOP**. Notice it does
not take much additional leaning to get the lowest BSFC the engine is
capable of producing.

Here's the interesting part: At peak EGT, the cylinderhead temps are
already starting down from their peak, and the downward curve is
pretty steep once you get to peak EGT.

Just a tiny bit more leaning and the cylinderhead temps dive down
another full ten degrees, while the EGT has hardly gone down at all.

While this is going on, the percentage of power is dropping off too,
which is why economy cruise is slower than best power, of course.

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
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

[Julian Scarfe]

> wrote in message
...
> 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.

http://www.lycoming.textron.com/support/engineOperationTips/SSP700A.pdf

sets out their case, at least for larger turbos. (I'm not suggesting I
endorse it.)

Another thing to bear in mind is that mixture distribution is imperfect in
most factory engines. If you operate at a steep part of the power vs
mixture curve, small differences in mixture mean large imbalances of power
between the cylinders. That can't be good for the engine. The point of
Braly's Gamijectors is to even out the mixture distribution so that the
imbalance disappears.

Julian Scarfe

[Stan Prevost]

"Julian Scarfe" > wrote in message
...
> The point of
> Braly's Gamijectors is to even out the mixture distribution so that the
> imbalance disappears.
>

They don't even out a power imbalance, they just make all the cylinders
reach peak EGT at the same mixture setting.

[Tom Sixkiller]

"Stan Prevost" > wrote in message
...
>
> "Julian Scarfe" > wrote in message
> ...
> > The point of
> > Braly's Gamijectors is to even out the mixture distribution so that the
> > imbalance disappears.
> >
>
> They don't even out a power imbalance, they just make all the cylinders
> reach peak EGT at the same mixture setting.

Which likely produces a balancing of power, no?

Also, IIRC, it leads to the piston achieving ignition at the optimal point
in the stroke (at LOP??).

[Tom Sixkiller]

> wrote in message
...
> 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.

Corky,

Isn't it also true that LOP optimizes the point in the stroke that the
cylinder achieves the peak ignition point?

Considering the wear on the engines moving parts that provides, maybe George
Patterson is right, that they'd like us to buy new engines? :~) I also
wonder how they are trying to cover their legal asses if they were spreading
wrong (negligent) information for all these years, or merely just PP QC on
their engines??

Tom
--
"Flying an airplane is just like riding
a bike -- it's just a lot harder to put
baseball cards in the spokes" -- Capt. Rex Cramer

[Mike Rhodes]

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

[John Clear]

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

[Peter Duniho]

"Stan Prevost" > wrote in message
...
> > The point of
> > Braly's Gamijectors is to even out the mixture distribution so that the
> > imbalance disappears.
>
> They don't even out a power imbalance, they just make all the cylinders
> reach peak EGT at the same mixture setting.

Which they do by ensuring the same actual fuel/air mixture at a given
mixture setting. Further, since the difference in fuel/air mixture at a
given mixture setting plays a big part in the power differences between each
cylinder, why wouldn't the Gamijectors help improve the power imbalance?

Pete

[Julian Scarfe]

"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

[Dylan Smith]

In article >, Mike Rhodes wrote:
> 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.
<snip>

I've never bought the argument of "don't get in the habit of this,
because if you move to X type of different aircraft, it's bad".
Operating one engine sub-optimally because it's not done in another type
seems a bit silly to me - surely pilots should fly each different type
appropriately, instead of by habit?

If someone tells me "don't operate your C140/Auster/Champ [...] like
this because if you move to a turbo Bonanza, doing that will be
harmful", I tend to ignore them and continue to operate each aircraft
appropriately.

--
Dylan Smith, Castletown, Isle of Man
Flying: http://www.dylansmith.net
Frontier Elite Universe: http://www.alioth.net
"Maintain thine airspeed, lest the ground come up and smite thee"

[Thomas Borchert]

Mike,

> 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.

Complete, total poppycock, as many sources available on the web show.


> Running lean, by a moment of carelessness (pilots have lots of
> things to tend to) invites catastrophic trouble in any engine.

Yes? Says who?

--
Thomas Borchert (EDDH)

[[email protected]]

On Tue, 29 Jun 2004 14:33:56 -0700, "Tom Sixkiller" >
wrote:

>Isn't it also true that LOP optimizes the point in the stroke that the
>cylinder achieves the peak ignition point?

Yup. I think what you are refering to is the Peak Power Pulse (PPP),
which needs to occur at or about 16 degrees After Top Dead Center
(ATDC). This is vitally important during takeoff as high temps and
pressures inside the engine at that point can cause destruction of the
engine. But during cruise, high temperatures can cause the engine to
have a shortened TBO.

I should make it clear I'm referring only to NON turbocharged engines
in the information below.

The situation is a bit complex and is also the result of aircraft
engines having fixed timing. Since the timing is fixed, the only way
to assure that the PPP occurs at the proper 16 degrees ATDC is by
varying the mixture. The Fuel Air Mixture (FAM) burns more slowly on
either side of the stochiometrically correct ratio of approximately
14.7 to 1 in mass.

Takeoff power is where bad things happening cause BIG problems, so the
engineers optimized the engine for this particular regime. Since the
timing is fixed at 26 or so degrees Before Top Dead Center (BTDC), and
the takeoff RPM is known, the speed of the piston is also known. The
engineers calculated that in order to cause the PPP at 16 degrees
ATDC, the mixture must be overly rich. The over rich mixture delays
the PPP just long enough for it to occur at about 16 degrees ATDC.
Why is it necessary for the PPP to occur there? Because at that
point, the connecting rod has swiveled past TDC and the PPP is working
to force the crankshaft throw downward. If the PPP occurs closer to
TDC, the PPP cannot apply the downward force to the crankshaft, it has
nowhere to go and heat and pressure skyrocket. If the PPP occurs
BEFORE TDC, this is a worst case scenario called pre-ignition and
assures the quick destruction of the engine.

THIS is why running the engine rich on takeoff is necessary. The
extra rich mixture doesn't keep the engine running cool by hosing down
the cylinders, it keeps it cool by making sure the PPP occurs at 16
degrees ATDC.

As I mentioned in a previous post, if there was a way to vary the
timing on the engine, there would be no need to use an overly rich
mixture for takeoff or any other time because the PPP could be kept at
16 degrees ATDC regardless the rpm or power setting or mixture. Well
that's not really true, the mixture would still affect burn rate, but
the timing could vary to make the PPP occur where we want it anyway.

During cruise, the engine is slowed down. If you have a constant
speed prop, you can slow the prop down, but it does not necessarily
mean that you reduce the throttle. Deakin is an advocate of leaving
the throttle full forward because as he quoted a friend of his: "I
didn't buy a fast airplane to fly slow."

So even though the engine is producing less power because it's been
slowed down some, it's still making heat and now the pistons are
moving more slowly. Because they are moving more slowly, the PPP is
now occuring closer to TDC. If you lean out the mixture to something
close to the ideal of 14.7 to 1, the mixture will burn as fast as is
physically possible and the PPP will be very close to TDC. Physics is
physics, even though the air is now pushing through the engine MUCH
faster than was occuring during takeoff and climb, you can produce
high cylinderhead temperatures by using a not quite lean enough
mixture setting. This is what Deakin called the "RED ZONE" and he
warns pilots to avoid mixture settings between LOP and Best Power.

So he advocates either running the engine significantly rich of peak
(in the best power zone), to slow down the burning, or leaning it past
peak again due to the slower burning lean mixture. As we said, either
side of ideal and the rate of burn slows down.

Deakin is also leery of allowing cylinderhead temps to get anywhere
near 400 degrees because aluminum begins to soften at that point.
Lycoming does not worry about temps being that high. They recommend
"400 degrees or below." Deakin strongly suggests not exceeding 380
degrees.

So what Deakin is advocating is setting the mixture where you can fly
the fastest for the best fuel burn and lowest engine temperatures
possible. Note: LOP won't produce the fastest cruise speed, nor will
it produce the best economy, but he feels it's the most reasonable
compromise in that it for sure won't hurt the engine because the
engine will be running cooler.

Corky Scott

PS, I am not an engine expert. I used to be an auto mechanic and am a
lifetime motorhead but all the information above is from John Deakin's
columns, and he got the information from Pratt and Whitney, Lycoming,
Continental and GAMI and their test stand work. The information
stands the test of critical review.

[Michael]

"Tom Sixkiller" > wrote
> > They don't even out a power imbalance, they just make all the cylinders
> > reach peak EGT at the same mixture setting.
>
> Which likely produces a balancing of power, no?

No.

What happens is this - the engines have crappy, obsolete induction
systems, by design. By crappy induction systems, I mean they deliver
a different amount of air to each identical cylinder. Modern engines
(meaning auto engines) don't have this problem because their induction
systems are designed by people who understand fluid mechanics and
model the air flow in the induction system, making changes until all
cylinders have equal (to a reasonable tolerance) air flow at all
normal operating conditions. This process doesn't occur in aero
engines because their induction systems were designed decades ago,
before CFD tools were generally available. I suppose they could be
tweaked now, but there are two things preventing this - it would
require changes in the design of the induction system, which would
mean getting the FAA to recertify the engines, and neither Lycoming
nor Continental have design engineers on staff anymore.

The GAMI 'fix' for the problem is really a bandaid solution - instead
of actually fixing the real problem, you measure the extent of it
(with your all-cylinder EGT) and then change the bores of the
injectors until the fuel distribution is off in exactly the same way
as the air distribution. In fact, since both Lycoming and Continental
make injectors with a variety of bores, you could do this yourself
(though probably not legally).

The problem here is that once you've installed the GAMI's, you STILL
don't have equal power output on each cylinder. Each cylinder is
getting a different amount of air, and the injectors make sure it gets
just the right amount of fuel to go with that amount of air, so each
cylinder produces a different amount of power at every stroke.

The real question is - is that any worse than what happens in normal
operation? A little. Remember, best power mixture is a little bit
rich of peak. Let's say we leaned to peak on the leanest cylinder
(meaning the one that gets the most air). Since it gets the most air,
it should produce the most power. However, the other cylinders are a
little rich of peak, and that compensates a little.

How important is all this? Probably not very. After all, it's not
like the cyclinders are firing simultaneously and we're depending on
the forces of the power strokes to cancel out.

Michael

[Thomas Borchert]

Michael,

> The GAMI 'fix' for the problem is really a bandaid solution - instead
> of actually fixing the real problem, you measure the extent of it
> (with your all-cylinder EGT) and then change the bores of the
> injectors until the fuel distribution is off in exactly the same way
> as the air distributio
>

That's not quite what GAMI says, IIRC. They claim the fuel nozzle specs
from TCM and Lyc are so vague that the fuel delivered will vary widely
between cylinders - and that's what's also evened out.

--
Thomas Borchert (EDDH)

[Tom Sixkiller]

"Mike Rhodes" > wrote in message
...
> 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.

Junk Science more than likely.

http://www.avweb.com/news/columns/182152-1.html
http://www.avweb.com/news/columns/182153-1.html

> 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

[Mike Rhodes]

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

[[email protected]]

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

[John Clear]

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

[Michael]

Thomas Borchert > wrote
> > The GAMI 'fix' for the problem is really a bandaid solution - instead
> > of actually fixing the real problem, you measure the extent of it
> > (with your all-cylinder EGT) and then change the bores of the
> > injectors until the fuel distribution is off in exactly the same way
> > as the air distributio
> >
> That's not quite what GAMI says, IIRC. They claim the fuel nozzle specs
> from TCM and Lyc are so vague that the fuel delivered will vary widely
> between cylinders - and that's what's also evened out.

That's disingenuous (on their part, not yours).

It is true that the specs on the fuel nozzles are vague. It is also
true that some of the engines out there are not set up properly with
respect to fuel flow. It is NOT true that this is the major problem.

When setting up an injected engine, there is a classic "coke bottle"
test. Basically, you unscrew the nozzles from the jugs, stick them
into coke bottles, then run the boost pump. After a few minutes, you
have a very good idea of how the fuel distribution is working.
Everyone knows this part of it.

The part that used to be common knowledge, but isn't anymore, is that
(at least with Lycomings) there are different bores of fuel nozzle.
All of them meet spec. By playing with the diameters of the nozzles
(putting smaller ones on the jugs that flow too much and larger ones
on the ones that flow too little) you can very easily make the fuel
flows right - without GAMI's. If you're not too terribly worried
about legalities, you can open up the bores yourself. Like you said -
the specs are so vague, nobody will ever know even if your nozzles are
inspected. In fact, the old style Lyc nozzles were two-part affairs
where the actual nozzle portion was a piece inserted into the bleeder.

If the big issue was fuel rather than air flow, there would not be any
need for test flights and expensive instrumentation. The coke bottle
test would be all you would need. However, that is simply not the
case.

This procedure actually works very well for the baby injected Lycs -
IO-320/360. The air distribution on those is so good that there's no
need to match the fuel flows to the individual jugs, only to each
other. This is why it can be so difficult to lean Lyc O-320/360
engines. We've all met the engine that can be leaned so much that
there is obvious power loss - and it's still running smooth. There is
a tendency to blame the pilot ("you just can't feel the roughness")
but the reality is that some of them have such even air flow (and with
carbureted engines that means the fuel flow is even too, since it's
vapor) that you simply can't feel the onset of roughness.

Such is not the case with the big Continentals. In fact, if you do a
coke bottle test with one of those engines that has GAMI's, you will
see differences in the fuel flows.

Michael

[Ash Wyllie]

Michael opined

>Thomas Borchert > wrote
>> > The GAMI 'fix' for the problem is really a bandaid solution - instead
>> > of actually fixing the real problem, you measure the extent of it
>> > (with your all-cylinder EGT) and then change the bores of the
>> > injectors until the fuel distribution is off in exactly the same way
>> > as the air distributio
>> >
>> That's not quite what GAMI says, IIRC. They claim the fuel nozzle specs
>> from TCM and Lyc are so vague that the fuel delivered will vary widely
>> between cylinders - and that's what's also evened out.

>That's disingenuous (on their part, not yours).

>It is true that the specs on the fuel nozzles are vague. It is also
>true that some of the engines out there are not set up properly with
>respect to fuel flow. It is NOT true that this is the major problem.

>When setting up an injected engine, there is a classic "coke bottle"
>test. Basically, you unscrew the nozzles from the jugs, stick them
>into coke bottles, then run the boost pump. After a few minutes, you
>have a very good idea of how the fuel distribution is working.
>Everyone knows this part of it.

>The part that used to be common knowledge, but isn't anymore, is that
>(at least with Lycomings) there are different bores of fuel nozzle.
>All of them meet spec. By playing with the diameters of the nozzles
>(putting smaller ones on the jugs that flow too much and larger ones
>on the ones that flow too little) you can very easily make the fuel
>flows right - without GAMI's. If you're not too terribly worried
>about legalities, you can open up the bores yourself. Like you said -
>the specs are so vague, nobody will ever know even if your nozzles are
>inspected. In fact, the old style Lyc nozzles were two-part affairs
>where the actual nozzle portion was a piece inserted into the bleeder.

>If the big issue was fuel rather than air flow, there would not be any
>need for test flights and expensive instrumentation. The coke bottle
>test would be all you would need. However, that is simply not the
>case.

>This procedure actually works very well for the baby injected Lycs -
>IO-320/360. The air distribution on those is so good that there's no
>need to match the fuel flows to the individual jugs, only to each
>other. This is why it can be so difficult to lean Lyc O-320/360
>engines. We've all met the engine that can be leaned so much that
>there is obvious power loss - and it's still running smooth. There is
>a tendency to blame the pilot ("you just can't feel the roughness")
>but the reality is that some of them have such even air flow (and with
>carbureted engines that means the fuel flow is even too, since it's
>vapor) that you simply can't feel the onset of roughness.

>Such is not the case with the big Continentals. In fact, if you do a
>coke bottle test with one of those engines that has GAMI's, you will
>see differences in the fuel flows.

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.

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


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

[Tom Sixkiller]

"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.

[Tom Sixkiller]

"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.

[Mike Rhodes]

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

[[email protected]]

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

[Michael]

"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

[Ash Wyllie]

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?

[Richard Russell]

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

[Thomas Borchert]

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)

[Ash Wyllie]

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?

[Michael]

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

[Michael]

"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.

I think we're talking at cross-purposes here. If you mean that the
problem is caused by improper air flow in the induction system, then
we have no argument. This is indeed the issue.

> And adjusting the injector nozzles is what GAMI
> is doing. By making accurate injectors designed for each cylinder all
> cylinders provide the same power.

Well, no. If the air flow in the induction system is such that it
causes fuel to be carried from one cylinder to another after it leaves
the injector nozzles, there's no chance at all that the cylinders are
all getting an equal charge of air. Air flow requires changes in air
pressure.

Thus the cylinders DO NOT all provide the same power - they run the
same mixture, which is not the same thing.

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

Really? Compared to what? Certainly not to car engines failing on
the road...

Michael

[kage]

>>>It does at takeoff power<<<

No, running sufficiently LOP at "Takeoff Power" would do NO damage. REPEAT
NONE! First, you can't get anywhere near 100% power LOP, and second, the CHT
and EGT will STILL be significantly lower LOP than ROP. Besides nobody would
ever takeoff LOP, including the zealots at Advanced? and GAMI. Although,
Braly runs his 550 at 90% continuously with no long term effects.

>>>>> I'm sorry if you found the term "overlean" confusing<<<<

YOU are the one who is seriously confused!

Karl

"Michael" > wrote in message
om...
> 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

[kage]

>>>>Thus the cylinders DO NOT all provide the same power <<<<

Wrong again, Bozo!

The air distribution is very good. The fuel distribution is poor due to the
"occult" migration of fuel. Gami's solve that and the power from each
cylinder is equal, at least MUCH better than from TCM. That is why there is
no vibration LOP with GAMI's.

Karl

If you had any engineering skills, you could read the graphs of the
converted engines.


"Michael" > wrote in message
om...
> "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.
>
> I think we're talking at cross-purposes here. If you mean that the
> problem is caused by improper air flow in the induction system, then
> we have no argument. This is indeed the issue.
>
> > And adjusting the injector nozzles is what GAMI
> > is doing. By making accurate injectors designed for each cylinder all
> > cylinders provide the same power.
>
> Well, no. If the air flow in the induction system is such that it
> causes fuel to be carried from one cylinder to another after it leaves
> the injector nozzles, there's no chance at all that the cylinders are
> all getting an equal charge of air. Air flow requires changes in air
> pressure.
>
> Thus the cylinders DO NOT all provide the same power - they run the
> same mixture, which is not the same thing.
>
> > Aircraft engines don't fail in the air, too often...
>
> Really? Compared to what? Certainly not to car engines failing on
> the road...
>
> Michael

[Ash Wyllie]

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.

>I think we're talking at cross-purposes here. If you mean that the
>problem is caused by improper air flow in the induction system, then
>we have no argument. This is indeed the issue.

I agree.

>> And adjusting the injector nozzles is what GAMI
>> is doing. By making accurate injectors designed for each cylinder all
>> cylinders provide the same power.

>Well, no. If the air flow in the induction system is such that it
>causes fuel to be carried from one cylinder to another after it leaves
>the injector nozzles, there's no chance at all that the cylinders are
>all getting an equal charge of air. Air flow requires changes in air
>pressure.

>Thus the cylinders DO NOT all provide the same power - they run the
>same mixture, which is not the same thing.

True. But by running the same mixture the engines run much smoother. And they
can be leaned to LOP with big fuel savings. GAMI equiped engines can to a
limited extent be controlled by the mixture.

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

>Really? Compared to what? Certainly not to car engines failing on
>the road...

How often do auto engines fail these days?


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

[Thomas Borchert]

Michael,

what Karl says.

> Running at peak EGT at takeoff
> power most certainly will hurt the cylinders.
>

Sure. Is that "overlean"? Or "not quite overlean"? Or "not overlean
enough"? "Overlean" has no sensible meaning.

> If the induction leak was bad enough that a cylinder was running well
> lean of peak, that would probably be OK -
>

Perzactly!

--
Thomas Borchert (EDDH)

[Michael]

"kage" > wrote
> >>>>Thus the cylinders DO NOT all provide the same power <<<<
>
> Wrong again, Bozo!
>
> The air distribution is very good. The fuel distribution is poor due to the
> "occult" migration of fuel. Gami's solve that and the power from each
> cylinder is equal, at least MUCH better than from TCM.

Much better than TCM I buy, Bozo. Equal I don't buy.

> That is why there is
> no vibration LOP with GAMI's.

In fact there is, and I've personally observed it. I know more than
one person who installed GAMI's and still won't run LOP because it's
not as smooth as running ROP.

> If you had any engineering skills, you could read the graphs of the
> converted engines.

I've read the graphs. If you had real engineering skills, you would
notice what they DON'T show - such as individual power output from
each cylinder. As for my engineering skills, well, let's just say
that everyone who knows me and is reading this is chuckling right now.

Michael

[Julian Scarfe]

"kage" > wrote in message
...
> >>>It does at takeoff power<<<
>
> No, running sufficiently LOP at "Takeoff Power" would do NO damage. REPEAT
> NONE! First, you can't get anywhere near 100% power LOP, and second, the
CHT
> and EGT will STILL be significantly lower LOP than ROP.

So that's not "Takeoff Power", is it.

The problem is that for a given CHT, you can get about 95% of maximum power
operating at a very rich mixture, but to achieve the same CHT lean of peak
you'll be down at maybe 80% of maximum power. Where power is not critical,
e.g. in the cruise, that's not a problem, but as you recognize, you don't
take off like that. If you try to achieve the same 95% power lean of peak,
you do end up frying the cylinders, albeit while saving gas.

Julian Scarfe

[Michael]

Thomas Borchert > wrote
> what Karl says.

is mostly rude.

> > Running at peak EGT at takeoff
> > power most certainly will hurt the cylinders.
>
> Sure. Is that "overlean"? Or "not quite overlean"? Or "not overlean
> enough"? "Overlean" has no sensible meaning.

You can argue semantics forever. Overlean, in my opinion, has a
perfectly sensible meaning - too lean for the conditions. In this
case, the condition is takeoff power. To produce takeoff power, you
need a mixture well rich of peak. If you are leaner than about
150-200 degrees ROP, you are overlean for takeoff. Depending on how
lean you are, one of two things will happen - both bad:

> > If the induction leak was bad enough that a cylinder was running well
> > lean of peak, that would probably be OK -
>
> Perzactly!

But you missed the second part:

> >but in that case, there
> >would be noticeable roughness and loss of power

In other words - it would be OK, in the sense that you would not hurt
the engine - but you won't develop takeoff power either, and that can
hurt the engine in another way - it will be about the first thing at
the scene of the crash when you don't clear the obstacle because you
didn't make full takeoff power.

If the induction leak is only slight, and only causes the jug to be
slightly lean (meaning at or just slightly rich of peak) - that's
still overlean. You will make takeoff power (and a bit more) and save
fuel - but keep doing it and you will destroy the jug.

The reality is that you just can't run lean of peak at takeoff power.
You can't run at or slightly rich of peak either. You must run well
rich of peak. Anything less is overlean.

Sure, you can run LOP at full throttle (and max RPM if equipped with a
CS prop) but you still won't be running takeoff power - it will be
more like 85-90% of what's available at that density altitude.

Michael