Because that additional 100 degrees of exhaust temperature translates back
to far more than an additional 100 degrees in combustion flame temperature,
and requires the heads, and the oil, and especially the exhaust valves, to
remove a larger total heat load than the additional 100 degrees on your egt
gauge looks like to you... Engineering is not always intuitive...
denny

"O. Sami Saydjari" wrote in message
...
OK. I have a basic question. Why is running an engine at peak
temperature (as in Rich-of-Peak operation) not good for the engine? In
the scheme of things 50-100 degress cooler than peak temperature (where
many folks recommend the engine be run) does not seem significantly
lower in temperature than the peak temperature. It would seem if the
engine parts can stand Peak-100 degrees, they would be able to stand
peak. What am I missing? (Oh, and I have read Deakin's articles on
AVWEB, and still have this question).

-Sami (N2057M, Piper Turbo Arrow III)