In rec.aviation.owning Newps wrote:
: I can lean to that fuel flow without any undue engine sounds, too. But my
: EGTs go well over 1500 degrees, and my CHTs push 350 when I do.

: EGT is irrelavant and 350 is not hot.

Exactly. The absolute value of EGT does not matter... almost all of the
cooling of the exhaust valves is done through the valve seat (and stem in Lycoming).
Thus, the "cold sink" is the cylinder, and CHT is what's important. Lycoming redlines
CHT at 500, recommends 450 as a max, and general wisedom dictates anything under
375-400 in cruise is fine.

Also remember that EGT and CHT probes are often uncompensated thermocouples.
That means they read the difference between the "hot" thing, and the temperature of
the "cold" (where the J thermocouple wires connect to the copper wires going to the
meter, etc). They're generally set to be accurate at about 70 degrees F. If it's 0
F, the temp will read 70 degrees hotter than it actually is. Wintertime temps read
higher for that reason.

I don't know about the fancy JPI, etc, by my dumb gauges definately do this.

-Cory



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* Cory Papenfuss *
* Electrical Engineering candidate Ph.D. graduate student *
* Virginia Polytechnic Institute and State University *
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