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Oh boy I'm so glad we finally started a inteligent, fact finding conversation
about LOP, instead of just hitting on Old Wife's Tail again and again.
Dan Schaefer's -235 engine, you probably don't have good fuel distribution or
you're having spark timing issues. Before you can run LOP agressively, you need
an engine that is getting very similar fuel-air mixtures on all cylinders. Most
engines don't go nearly close enough. Pretty much any non fuel injected engine
won't have good fuel-air mixture distribution. I have the same issues on the
Skyhawk's O-320's I use to fly until my lancair gets of the ground.
Jim Scales TCM IO 550G, as long as you're high enough that you don't have enough
MP available to exceed 65% power, you can lean your engine as you'd like, to get
the best performance. You have too little air in the engine to cause detonation
anyhow. In your case, I would run the engine just barely lean of peak to get as
close as possible to 100% fuel and air consumption. This will give the best fuel
consumption with very little power loss. If you're low enough that you still
have over 23" of power available, run full MP and lean to a fuel flow that will
give you the desired power output, LOP.
George, one issue brought a few days ago was that the excess lead (from excess
fuel operating ROP) actually helps lubricate the exaust valves. Another theory
was thrown that excess hot oxygen from an agressive LOP combustion would help
oxydize things in the engine while a ROP mixture having consumed all oxygen
wouldn't suffer from this. I don't believe that's true, but have no technical
data to counteract that, except that because an agressively LOP mixture runs way
cooler, that should reduce any kind of oxydation issues on exaust valves and
other components.
Marcelo Pacheco
PP-ASEL IFR
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