EGT Accuracy

"O. Sami Saydjari" wrote in
:

Okay, here's something "interesting." You are running pretty high
power settings there... up probably around 85% (at 12 gph LOP).

Well, I should say that my fuel flow gauge says 12 gph, but my actuals
are closer to yours at 10.9 gph.

Those old analog gauges for FF are pretty inaccurate. They aren't
really fuel flow gauges anyway. They are pressure gauges, calibrated to
read out in gph, on the theory that a certain pressure through a certain
combination of injector sizings will equal a certain fuel flow.

When ROP the power setting is pretty much independent of fuel flow,
since excess fuel is discarded out the exhaust. When LOP all of the
fuel is consumed and the power setting is directly a function of the
fuel flow. Of course, then what the power setting actually means is up
for grabs (ever wonder how you can have in your POH two different
performance values for the same "75% power"?).

I hate being blind to my CHT readings. And I just baught my plane,
so I do not know what the CHTs notmally run.

Limit on that plane is 460 F, but that's WAY TOO HOT for normal
operation. The manual recommends 400 or below, and that's good
practice. I like to keep mine under 380. Usually, except when hot and
heavy, I keep them down more like 330 - 350. The big problem isn't the
high temperature so much, but rather the fact that the temperature
around the cylinder is very non-uniform. So while your probe reads 330,
a spot on the other side could be 260, or 420.

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James M. Knox
TriSoft ph 512-385-0316
1109-A Shady Lane fax 512-366-4331
Austin, Tx 78721
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