Originally Posted by
Lead Balloon
Setting the mixture to around 25C ROP is the worst setting for a piston aero-engine
whatever the power setting. It will produce the highest CHT possible for that power.
Given the choice of a 74% power setting with a CHT of X and a 74% power setting with CHT less than X, I choose the latter.
Detonation is not the only thing that is detrimental to engine longevity. So is heat. The manufacturers say so.
The logic here doesn't make sense. Sure, keeping temperatures under control is essential for an engine.
However, to avoid engine overheating, should you:
a) adjust the mixture to settings that are not recommended by the manufacturer?
or
b) ensure that you have adequate cooling?
Thanks for finding that Lycoming doc. I was only able to find the quotes from it by John Deakin.
Key phrases in that document:
Lycoming is in complete agreement that it is possible to operate an engine on the lean side of peak
we can attest to the fact that things that work well in the test laboratory have not always proven successful in service
the technique of operating lean of peak and power recovery was discontinued due to the resulting increase in service issues
For optimum service life, Lycoming suggests operating 50 degrees rich of peak EGT or TIT
Lycoming are in the best position to gather data about service issues. That information is direct enough and specific enough that I am prepared to assume they are not lying, and follow their recommendations.