Very true. On a turbocharged airplane the EGT is calibrated
and called a TIT [an a jet it is ITT or TPT]
The turbo has designed temperature limits and because it is
rotating at 35,000 to 120,000 rpm it needs very good
strength to stay in one piece. It also needs to be cooled
at a moderate idle speed for 4-5 minutes to allow it to
spool down, cool off and have good oil pressure. A closed
throttle idle doesn't supply enough oil volume to cool the
turn bearing, and a fast idle, particularly a simple fixed
waste gate type won't let it slow down enough.

Bottom line, RTFM for the particular model and serial
number.



"John R. Copeland" wrote in
message . ..
"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.