LOP operation

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

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

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

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

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

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

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

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

Corky Scott

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

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

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

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

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

Roger Long wrote:

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

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

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

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

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

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

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

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

--
Roger Long

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

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

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

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

Karl

"kage" wrote in message
...

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

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

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


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

And your qualifications are, what, again?

My gripe is with Walter, not GAMI.

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

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

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

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

..
"Tom Sixkiller" wrote in message
news

"kage" wrote in message
...

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

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

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


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

And your qualifications are, what, again?

Roger,

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


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

--
Thomas Borchert (EDDH)