Morgans wrote:
"Matt Whiting" wrote

Maybe to another question. You didn't address why having the timing
advanced too far would cause a greater power loss with mogas than with
avgas. And noise from igniting the mixture too soon and detonation are
two different phenomenon.

Sorry, I'll try again.

The higher octane of 100LL will allow more advanced spark settings without
knock and detonation, than will the lower octane mogas.

End result would be that the mogas could show a loss of power, when avgas is
still allowing the engine to function normally.


This is only true for engines that have very advanced ignition timing,
which isn't true for most GA piston engines, or engines with very high
compression ratios, again, not true for most GA piston engines. Keep in
mind that most were designed to run on 80 octane avgas...


I don't disagree with the fact that in normal conditions, and a normal
engine, the power of an engine running 100LL or mogas should be virtually
the same.

Yes, I can't imagine many GA piston engines where this wouldn't be the
case. Maybe a turbocharged engine running very hot.

Matt