"Allen" wrote in message et...

"John R. Copeland" wrote in message
.. .
Doug's advice about never leaning above a safe temperature
is well advised, and it's exactly what I've followed for 25 years.
In fact, I found that leaning to RAM's recommended 1550F
still results in a little exhaust-system distortion, and I've held to
1525F max for the last ten years or so, with better results.

I believe their recommendation at 75% power is 100 degrees rich of "peak",
not 100 degrees rich of 1650 degrees. Most engines will peak at a
temperature less than 1650 degrees.

Allen


OK, let me try to rephrase what Doug already said correctly...
*At the higher power settings*, say about 70% and above,
the peak EGT *will* rise above steel's softening temperatures.
If your EGT gauge is calibrated for temperature,
never lean above 900C/1650F, except for very brief time.
Preferably, lean directly to the desired temperature and fuel flow.
RAM recommends operating at 850C/1550F, but my experience says
that's slightly too high, and I lean to about 25F cooler than that.
My penalty is less than 5% additional fuel flow above RAM's figures.
Yes, avgas is expensive, but replacing exhaust parts is expensive, also.

My engines certainly will peak above 1650F at high power settings,
but not so when operated down around economy power settings,
which would typically be below 65%.
I normally cruise my TSIO320s at about the 50% power level,
and even there, my peak EGTs remain above my personal target of 1525F.

From my cockpit, I can see down through louvers in the tops of my
engine nacelles, into the areas around the turbochargers.
I've had passengers at night ask me why I have yellow-orange lights
turned on in the engine compartments. :-/
When you've seen your exhaust components glowing in the dark,
you get a better appreciation of the stress they endure hour after hour.
They are more than red-hot, they are nearly yellow-hot.
Don't abuse your exhaust system any more than necessary.