On Tue, 09 Mar 2004 05:33:57 GMT, tony roberts wrote:

Hi
I had to pull cylinder 3 due to low compression.
The shop said that there is some minute pitting on the valve which
indicates that the EGT is too hot.

I use an engine analyzer and run 50 rich of peak for leanest cylinder.
This puts CHT's between 300 & 350 and EGT's between 1350 and 1450.
I can't run the cylinders cooler than that and the EGT's tend to follow
the CHT's.

Does 1350 - 1450 sound too hot?
If so where do I go from here?

Tony

Tony,

If you look at a bunch of engine test data, 50°F ROP is about the worst
place you can run a cylinder. CHT's are hottest; peak cylinder pressures
are highest, etc.

Whether the EGT itself is "too high" depends on the kind of valve in your
engine. It's probably not too high for a Lycoming; but I don't know about
Continentals. It also depends on the location of the EGT probe and how
well that reflects the actual temperature at the valve.

So far as "where to go", you have a few options.

If you restrict your operations to less than 65% power, it probably doesn't
matter where you run the engine.

For higher power operations, you can either run richer or run on the lean
side of peak EGT. The latter will give you cooler EGT's, CHT's and lower
peak cylinder pressures as well as better fuel consumption (BSFC) figures.
It may not be possible if your fuel flow is not evenly distributed to the
cylinders. If that's the case, and your engine is fuel injected, you could
opt for GAMI injectors.

Or you could run richer -- 100°-125°F ROP. That would keep you out of the
"danger zone", and also allow higher power operation.


Ron (EPM) (N5843Q, Mooney M20E) (CP, ASEL, ASES, IA)