Here’s the quote:

“So as the mixture is leaned, power peaks first, with CHT peaking at very close to the same point. In practical terms, if we lean to max CHT, we'll have max power for that MP/RPM setting. Doesn't that make sense, intuitively? Max power, max CHT? It's not precisely true, but it's close enough.”

John


On 2/8/09 11:23 AM, "Colyn Case at earthlink" <colyncase@earthlink.net> wrote:

John,
    Did they really print that about CHT?
    I don't remember that max CHT equates to anything useful although it may correlate very well to max internal cylinder pressure (ICP), which is a bad thing.  ...but it's also affected by cylinder cooling, while EGT is (mostly) not. Max EGT would be stoichiometric which is most efficient if your engine can take it.   Usually slightly rich of that (e.g. 50 dF ROP) is better power but also involves more pressure before top dead center and is close to max ICP.
    There's a really scary picture you get early in the APS course which shows how the internal cylinder pressure varies in relation to crank position when you are running at "best power".  A measurable amount of the combustion expansion is actually pushing backwards on the crank until it comes over the top.   Great for torsional stress.

Colyn