LOP operation

I set my engine up LOP and flew it at 2350 RPM which is my normal cruise RPM
at that altitude. Then I set the same RPM 100 degrees ROP. Since this is a
fixed pitch prop and I was in level flight, horsepower was exactly the same.
Airspeed was the same. CHT was 10 - 15 degrees cooler and 25 below where I
usually see it. The engine was rougher but it was not vibration. It was
more like the difference between listening to the upright piano at the
elememtary school play and a Steinway, very noticable if you were focused on
the quality of the sound but not objectionable in the first case.

Although the engine was rougher LOP, when I listened closely, the sound had
a hard to describe quality of "easiness". Combustion actually has to start
while the piston is still compressing. LOP slows the combustion so that
there is less pressure against the piston as it is moving up. Peak
pressures occur at a more favorable point on the down stroke. Perhaps this
accounts for the way LOP sounds if you listen closely.

At anything above 60% power, I would go ROP with my minimal engine
instrumentation but this looks like a great thing to have in your bag of
tricks for hot days or need to maximize fuel reserves without slowing way
down.

We have been leaning aggressively on the ground and about 100 ROP in the
air. Our engine was opened up at 1030 hours due to lifter failure. There
was a normal but impressive amount of crud on the piston tops and exhaust
valves. Anything that reduces that has got to be good for the engine.

Walter can drill on my teeth anytime

--
Roger Long

"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


While you are fiddling with that mixture control trying to set the elusive
25 degrees LOP you are spending considerable time at PEAK, which will cause
damage to cylinders and exhaust in a short time.

Just my thought on the matter.
Allen

"Roger Long" om wrote
in :

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.

A big part of the "magic" starts to happen as soon as you hit peak
(assuming all cylinders peak together). Anything past that and you are
cooling with air rather than fuel. The reason you hear about running "50
LOP" for example, as opposed to 25 LOP or 1 LOP is to keep temperatures
down at high power settings. It lower power, if 25 LOP keeps your temps
within limits, then great...


-----------------------------------------------
James M. Knox
TriSoft ph 512-385-0316
1109-A Shady Lane fax 512-366-4331
Austin, Tx 78721
-----------------------------------------------

Not at 60% power, at least with a simple engine that has wide detonation
margins like an O-320. The greatest stress on the engine will be at 50 ROP
which is where Lycoming says to run it. If they aren't turning into gliders
at that setting, a few minutes at peak aren't going to hurt them.

EGT doesn't exactly relate to the temperatures inside the cylinder. For
example, if you let the hot gas out sooner, EGT will go up while the gas
won't be in the cylinder as long to heat it up. CHT would go down in that
case.

I was fiddling to learn more about the engine and confirm where the sweet
spot related to peak. I think that's something you have to go through to
get to know your engine and to confirm that your FA ratios are balanced
enough to run this way, not all engines are. What takes some getting used
to is how small the adjustments are and doing them slowly. That doesn't
mean they are fussy. They are accompanied by engine sounds and changes that
you can learn.

Once you have confirmed that your engine can be operated in a regime where
enriching the mixture increases power, is running acceptably smooth (but
yes, it will never be as smooth sounding as ROP), and CHT is lower than the
corresponding ROP RPM or MP, try it this way:

1) Put on carb heat. Probably different amount for each engine. If there
is a point when you slowly pull the heat knob where the drop in RPM seems to
increase, try it about there.

2) Set RPM 100 above the 60% power setting for that altitude. This will be
nearly WOT for a carb 172 at 4000 - 6000 feet.

3) Lean until RPM goes way down.

4) Enrich until you and the engine are comfortable or to the 60% power RPM
(or MP). Forget the EGT gauge.

You should check your POH to be sure about the 60% power settings. Go
through the fiddling and peak finding steps first to get to know how your
engine reacts. If you can't get it to run as described above without
roughness that creates airframe vibration or is really annoying, your engine
will have to be run ROP.

I'm still experimenting with this so it isn't expert advice. I'd really
like to hear the results of others experiments as opposed to OWT repetition.
If it's a small bore engine, you aren't going to hurt it fiddling with
mixture at these power settings unless it's too rich in which case you'll
foul the plugs.

--
Roger Long


Allen wrote in message
m...

"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


While you are fiddling with that mixture control trying to set the elusive
25 degrees LOP you are spending considerable time at PEAK, which will
cause
damage to cylinders and exhaust in a short time.

Just my thought on the matter.
Allen

Air is free. 100 LL is heading towards $3.75 a gallon. Which would you
rather cool with?

--
Roger Long

James M. Knox wrote in message
...
"Roger Long" om wrote
in :

A big part of the "magic" starts to happen as soon as you hit peak
(assuming all cylinders peak together). Anything past that and you are
cooling with air rather than fuel.

On Thu, 15 Apr 2004 13:34:30 GMT, "Roger Long"
om wrote:

The greatest stress on the engine will be at 50 ROP
which is where Lycoming says to run it.

I am asuming, since your email suggests that you are US based, that you are
talking degrees Farenheit. I agree that 50°F ROP is a bad place to run the
engine.

Which engine does Lycoming say to run 50°F ROP? Lycoming does NOT make
that recommendation for the O360 series of engines.

In my Lycoming O360 series engine manual, the recommendations for normally
aspirated engines a

1. Full Rich for take-off, climb and maximum cruise powers (above
75% power), with a caveat to lean just to a smooth running engine for
take-off from a high-elevation airport or during climb.

2. Maximum Power cruise (75% power): 150°F on the rich side of
peak EGT.

3. Best Economy cruise (below 75% power): operate at peak EGT

For turbocharged engines:

1. Best Economy Cruise: Lean to peak TIT or 1650°F, whichever
occurs first.

2. Maximum Power Cruise: 125°F on the rich side of the temperature
determined in step 1 (peak TIT vs 1650°F).

Certain "airframe" manufacturers may have different recommendations in
their POH's, and those take precedence. But, even though Lycoming states
that a manufacturer's POH takes precedence, that's a far cry from stating
that "Lycoming" says to run the engine at 50°F ROP.


Ron (EPM) (N5843Q, Mooney M20E) (CP, ASEL, ASES, IA)

In article , kage
wrote:

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.

So was/is Dick VanGrunsen (sic) ,IIRC, but that hasn't stopped him from
designing a great series of airplanes.

Quite right. However our 172 N did not come with EGT as standard equipment.
The "lean to rough, enrich till smooth" I was taught in primary training
(and used for the first couple of years when our EGT didn't work) ends up
about 50 ROP on our engine if you do it quickly and without carb heat. It
was sloppy of me to call it a Lycoming recommendation.

--
Roger Long
Ron Rosenfeld wrote in message
...
On Thu, 15 Apr 2004 13:34:30 GMT, "Roger Long"
om wrote:

The greatest stress on the engine will be at 50 ROP
which is where Lycoming says to run it.

I am asuming, since your email suggests that you are US based, that you
are
talking degrees Farenheit. I agree that 50°F ROP is a bad place to run
the
engine.

Which engine does Lycoming say to run 50°F ROP? Lycoming does NOT make
that recommendation for the O360 series of engines.

In my Lycoming O360 series engine manual, the recommendations for normally
aspirated engines a

1. Full Rich for take-off, climb and maximum cruise powers (above
75% power), with a caveat to lean just to a smooth running engine for
take-off from a high-elevation airport or during climb.

2. Maximum Power cruise (75% power): 150°F on the rich side of
peak EGT.

3. Best Economy cruise (below 75% power): operate at peak EGT

For turbocharged engines:

1. Best Economy Cruise: Lean to peak TIT or 1650°F, whichever
occurs first.

2. Maximum Power Cruise: 125°F on the rich side of the temperature
determined in step 1 (peak TIT vs 1650°F).

Certain "airframe" manufacturers may have different recommendations in
their POH's, and those take precedence. But, even though Lycoming states
that a manufacturer's POH takes precedence, that's a far cry from stating
that "Lycoming" says to run the engine at 50°F ROP.


Ron (EPM) (N5843Q, Mooney M20E) (CP, ASEL, ASES, IA)

On Thu, 15 Apr 2004 14:56:57 GMT, "Roger Long"
om wrote:

Quite right. However our 172 N did not come with EGT as standard equipment.
The "lean to rough, enrich till smooth" I was taught in primary training
(and used for the first couple of years when our EGT didn't work) ends up
about 50 ROP on our engine if you do it quickly and without carb heat. It
was sloppy of me to call it a Lycoming recommendation.

I don't think I really learned how to lean until I had an EGT indicator.
and discovered how slowly the engine parameters change with changes in the
mixture control. At least in my fuel injected IO360.

And the lean to rough, enrich to smooth IS Lycoming's recommendation for
carbureted engines without EGT indicators or flowmeters. But they do say
to lean *slowly* and they also state it is for Economy cruise at 75% power
or less).

If you lean slowly in your 172N to rough, then slowly enrich until just
smooth -- where do you wind up with regard to EGT?




Ron (EPM) (N5843Q, Mooney M20E) (CP, ASEL, ASES, IA)

Howdy!

In article ,
kage wrote:
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.

What is your agenda? You seem to have an axe to grind, and you get your
facts wrong.

For a given power setting, in general (module altitude effects), there
are two mixture settings to give that power. One ROP, the other LOP.
If you run at, say, 70% power, your airspeed is going to be fixed at
a particular level, assuming stable, level flight. If you run LOP,
you run less fuel through the engine, and you burn all of it up. If
you turn ROP, you use some of it to cool the engine -- using more
fuel than LOP operation. All this for the same speed.


CHTs are just fine ROP.

What CHT level do you think is "just fine"? How does this argue
in favor of ROP?

Engines run clean enough ROP.

On what do you base this unsupported assertion?

Engine stresses have been doing just fine now for 100 years ROP.

Oh? Have you ever examined the operations of round engines,
especially the bigger things like R-3350s? IIRC, LOP operations
were mandatory to get satisfactory performance and engine life.

CO is not a problem in maintained exhaust systems.

What does that have to do with the decision? LOP makes less CO;
isn't that a positive?

Airplanes fly faster ROP.

That claim is especially brown and smelly, given the orifice it
was pulled from. See discussion above. Speed is all about power
levels.

Even the LOP diehards admit engines run smoother ROP.

As opposed to the ROP blowhards who can't abide admitting they might
be wrong? See! I can use cheap rhetorical devices, too! Would you
care to try a logical approach, or are you just interested in being
fanatical?

Gamis have more value in a turbocharged engine.

What does this have to do with deciding to operate LOP? Or are you
just trying to obfuscate with more irrelevancies?

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

Do you have real qualifications to back up your amazing assertions?
How about real data? Sound logical reasoning?

yours,
Michael


--
Michael and MJ Houghton | Herveus d'Ormonde and Megan O'Donnelly
| White Wolf and the Phoenix
Bowie, MD, USA | Tablet and Inkle bands, and other stuff
| http://www.radix.net/~herveus/