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There seem to be recurring questions about EGT - Is
it too high?
Given the fact that EGT for a particualr
engine/exhaust will vary slightly from other identical engines as a
function of "where the EGT sensor is placed ", and stating at the start
that we are talking about "cruise" power settings - not "full throttle at sea
level" (in other words, we are, by definition only talking about leaning at a
lower power setting, with proper timing and proper octane, where there is ZERO
possibility of detonation) isn't it true that if one adjusts mixture from rich
to lean, that the EGT will "peak" at "best fuel-air ratio" for complete
combustion, and that max power will be achieved by richening a bit from that
(richen until you get max RPM for that immediate flight condition) which will
result in a slight drop in EGT? Then, if one leans back to "peak" and then
continues to lean, one will get "better economy", and, again, EGT will decrease
from what it was at "peak".
From reading of what others have said, one
can lean past "peak" maybe 50 degrees and have a safe, economical cruise
setting, maybe taking a slight increase in throttel or manifold pressure to keep
HP up to what you want to cruise at.
- The old Air Force BIG
radial engines used to cruise at 80 degrees lean of peak for long flights
requiring max economy.
A point I like to think of is that 50 or 80 degrees
"from" "peak" on the rich side and on the lean side is, the same
temperature. For piston engines, running 50 deg lean of peak is the same
temp as running 50 deg rich of peak, so the valves are seeing the same temp - so
why are some engine "gurus" so adament about cruising 50 deg rich of
peak? It makes no sense to me.
So, I believe there is no such thing as "EGT too
high". There is only "peak EGT", whatever it is for your
installation.
David
----- Original Message -----
Sent: Tuesday, May 03, 2005 8:55 PM
Subject: [FlyRotary] Re: EGT temps
Paul,
My EGT temps normally range from 1450 (lean) to
1600 and have gone as high as 1750F, so no, I don't think yours are too
high. However, part of the equation is where are your EGTs located - close
the ports, far from the ports? Mine are approx 8" from the
ports.
Mold for enlarge duct opening nearly completed
today, fiberglass (ugh {:>)) tomorrow. Then an air filter/plenum to
build and I should be ready in plenty of time for the Mid-Atlantic Fly in 12
May.
Ed A
----- Original Message -----
Sent: Wednesday, May 04, 2005 1:37
PM
Subject: [FlyRotary] EGT temps
Hi all...I flew the SQ2000 again. Engine ran
great. Just flew around enjoying the thing. After removing the
thermostat, I found that upon reaching the end of the runway my water temps
were only 120 degrees instead of the normal 160 to 170 degrees. Temps rose
much slower than normal on climb-out. Actually fun to fly when you don't
have to keep focusing on temps all the time. Cruising at 4500 rpm's, the
temps were very cool....stabilized at around 180 degrees at 1500' AGL. Temos
on the ground were around 78. When I increased the throttle to 5300
rpm's in level flight, temps slowly started rising. I then noted the EGT at
5300 rpm's. It was 1425. Does this sound a little too high? If so,
my mixture settings may be a little lean at those rpm's. Just wondering
what others are seeing for EFT temps for around 5300 rpm's. Thanks in
advance for any and all replies. Paul
Conner
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