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