Posted for John Hafen <j.hafen@comcast.net>:

Fred:

Many thanks for this great information.  Extracting a few summary points:

* Factory recommended setting is 50F rich of peak for many engines.  This
turns out to be the worst place to operate for many engines, particularly at
high power settings.
* The hottest CHT occurs at the point where EGT is about 50F rich of peak.
* We could lean a lot and only lose a little power.
* If we lean to max CHT, wešll have max power for that MP/RPM setting.

So if a guy looks at the factory recommended setting of 50F rich of peak,
and that historically gas has been pretty cheap, one wonders if the 50F ROP
recommended by the factory was simply to extract maximum power out of the
engine at the expense of gas and cooking the engine in the process (at max
CHT for max power).  So you go a little faster (perhaps) at the expense of
gas and the longevity of the engine.

And I doubt, like you say, the factory will ever change their
recommendations, opening them łto criticism that past advice may be wrong.˛

Thanks for the John Deakin Pelican Perch site.  Most excellent.

John Hafen
IVP N413AJ 101 hours (would be more if I didnšt live in Seattle!)