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Date: Tue, 30 May 2006 20:58:38 -0400
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From: "colyncase on earthlink" <colyncase@earthlink.net>
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Subject: Re: [LML] Lean of Peak question
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John,
    It's well worth taking the APS course, available on line at a good price 
now.   In the meantime, go to avweb and find the Pelican's Perch (John 
Deakin) series on engine management.
    but to answer your question, the shape of the power vs. mixture curve is 
much steeper on the lean side than on the rich side.  Therefore if your 
cylinders are not perfectly matched, and you are on the lean side, you feel 
it as roughness.    On the rich side, the mixtures in each cylinder can be 
as divergent as your "rough" setting but you won't feel it as much because 
the power output of each cylinder is not that different.   This can actually 
be worse for your engine, particularly in the zone just rich of peak, where 
cylinder pressures are the highest.
    The short story is you need to be a little (50+) lean of peak or a LOT 
(150+ or even more) rich of peak to keep cylinder pressures in a safe place 
at high power settings.   The procedure you describe results in neither on 
most airplanes.

Colyn