LOP operation

"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
-----------------------------------------------

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.

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)

Thomas,

How are you, Sir? Hope things are going well.

I so enjoy the nay-sayers to LOP operation and get a lot of laughs out
of their remarks and repeated recitation of OWTs. It's funny how many
people are content to rely on myth rather than data. Ah, well.

Just finished 10 days of flying a Cessna 206 in Belize for LightHawk
in support of environmental research and data collection. Fuel there
is about $4.25 U.S. per gallon, so on top of 90 degree F temps,
keeping the fuel burns minimized is one of those very high priority
items in one's operating plan. Plus, one may only purchase fuel at
one airport in a country the size of the U.S. state of Mass.
Therefore, GAMIs and LOP ops are essential. I very much appreciate
the fact that when I've got the rear doors off the 206, with
photographers hanging outside, I'm able to maintain the requested 85
knots indicated with the cowl flaps closed and CHTs in the 350 degree
F range. If I go ROP, the CHTs hit 400 degrees F immediately and even
opening the cowl flaps, which adds a bunch to drag at those speeds,
and requires a power increase, doesn't cool things off much. When I
can burn 11 gph in that IO-520 at 24 inches and 2200 rpm LOP while
keeping the engine very happily cool in the tropical heat, I just
shake my head in wonder at those who still don't get it. Plus, even
with the questional quality control on the cylinders, that engine is
running clean and doing a very nice job of hanging in there in terms
of an absence of gunk in the various areas where you get the products
of incomplete combustion in ROP operated engeines.

Warmest regards,
Rick

Thomas Borchert wrote in message ...
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.

"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

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

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)

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)