Lycoming's views on best economy settings

"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

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

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

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?

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)

"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

"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

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