Percent power altitude

As a first approximation, it should be the same for any normally
aspirated engine (and yes it would be based on DENSITY altitude). The
engine develops 100% HP only at sealevel. As the altitude goes up what
changes? The density of the air decreases and in response the fuel
delivered decreases (from both the carb delivering less fuel and the
pilot leaning the mixture). This is the same for all the normally
aspirated engines.

Now at somewhere around 65-70% power it becomes impossible to get
excess EGTs and CHTs due to overleaning the engine. So run the engine
at that altitude and lean for max rpm and note the EGT. This is
guaranteed to be a safe EGT! Now use this EGT for leaning at ALL
altitudes. Thus you have found 100 or so degrees rich of peak without
ever having to run the engine at peak (which is too hot and hazardous
in itself).

Doug wrote:
Anyone tell me at what altitude I get 75% and 65% power respctively
(with full throttle, normally aspirated).

"Doug" wrote in message
oups.com...
altitudes. Thus you have found 100 or so degrees rich of peak without
ever having to run the engine at peak (which is too hot and hazardous
in itself).

What makes you think that?

Karl
"Curator" N185KG
Gami ser# 19

Doug,

Thus you have found 100 or so degrees rich of peak without
ever having to run the engine at peak (which is too hot and hazardous
in itself).


Come again? That part in parenthesis is completely wrong.

--
Thomas Borchert (EDDH)

"Thomas Borchert" wrote in message ...
Doug,

Thus you have found 100 or so degrees rich of peak without
ever having to run the engine at peak (which is too hot and hazardous
in itself).


Come again? That part in parenthesis is completely wrong.

--
Thomas Borchert (EDDH)


Thomas, I think you snipped away an important part of Doug's post.
He was trying to stress the need for leaning to a temperature limit.
Stainless steels approach their softening points above 900C (1650F).
Doug's "too hot and hazardous" remark referred only to the peak EGT
reached at a high power setting, where the peak temperature is high
enough to enter the softening region of the exhaust collectors.
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.

"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

"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.

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.

Beechcraft, for example, calls it "TIT" instead of "EGT".
Some others still call it "EGT" on turbocharged airplanes.
But they all mean the same measurement.

"Jim Macklin" wrote in message ...
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.

I agree I didn't say it right. But the procedure has some value. You
lean to peak at 10000', you are leaning to a safe EGT. THAT EGT will be
well rich (or lean) of peak at "dangerous" power settings (like 75% or
more) and you have found this rich (or lean) of peak by never leaning
all the way to peak.

That is what I meant. Sorry about the poor (actually incorrect) wording.

"Jim Macklin" wrote in message
...
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's airplane, a Cessna 340, came from the factory with an EGT (when
installed), not TIT. EGT is located forward of the turbo and actually has a
higher temperature than the TIT. Some airplanes, such as the P-Baron and
58TC have TIT, the probe is actually located in the turbo inlet. I was just
commenting to John that I have never seen RAM recommend any particular EGT,
only the 1650 degree max. I agree with the rest of your post.

Allen