I think this discussion
is causing some confusion. I understand and agree with the idea of
avoiding peak EGT; however, how you operate depends on engine controller, and
maybe to some extend on racing vs flying. (Maybe Lynn’s remarks
were specific to Mistral’s EC)
With Tracy EC, once you get the
engine ‘tuned’ (mixture vs MAP); and you set the knob to be rice of peak; it’s ROP no mater what the throttle
setting. You can choose your knob setting to give you something like 1600-1650 EGT
on climb out; pull your throttle back to cruise (or lower power to limit oil
temp if that’s your issue) and not have an EGT issue.
When you’re in stable cruise then
turn the knob to your LOP lean cruise condition. You’ll want to
lean to a point where your EGT is again at 1600 (or lower if it is still
running reasonably smooth). You just don’t want to do your climb-out, or
your cruise at peak EGT.
At least that’s my story,
Al
-----Original Message-----
From: Rotary motors in aircraft
[mailto:flyrotary@lancaironline.net] On Behalf
Of Lehanover@aol.com
Sent: Sunday, February 06, 2011
11:33 AM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: EGT
Values and recovery.
In a
message dated 2/6/2011 10:27:50 A.M. Eastern Standard Time, keltro@att.net
writes:
Do I understand this correctly.................You are saying that for
maximum efficiency that we need to fly
with
full throttle at both climb and cruise and control "EGT"
with mixture control (and /or ECU map settings)
.............Slightly
richer than best power for climb (to reduce EGT to less than 1650 F) then lean
quickly
(to
lean stumble) then slightly richer.............The bottom line that being that
trying to control "EGT" with the
throttle
will not help efficiency since it increases pumping losses and only
slightly reduces "EGT"..............
Kelly Troyer
"DYKE DELTA
JD2" (Eventually)
"13B ROTARY"_
Engine
Pulling
off throttle is a good way to reduce total engine heat as in when you have an
oil cooling problem and EGTs.
From a
climb setting at 1600 on the EGT you are fuel cooling the engine to good
extent. This is a costly way to cool any engine. But no damage will occur, and
power will be good. So instead of fuel cooling.........
the
over-lean mixture cools by removing BTUs. Smaller fire. Less heat.
Better more thorough burn due to excess oxygen. Lower oil temps. And
so-on.
The
rotor face is close to or in front of the spark plugs longer than a
piston engine. More dwell. So less advance is needed, and there is more time
for the over-lean mixture to burn. Thus more efficient than a piston engine?
Not quite but very close. Add a monster ignition system and lean even further.
That
1600 degrees is several hundred degrees from best power. That leaning to lean
of peak EGT must be done very quickly. As you turn the leaning knob or pull on
the cable, you will pass right through the very point we are trying to avoid,
best power and peak EGT. Or, pull of just a bit of throttle, then go lean and
put the throttle back up. One must not diddle at or near peak EGT. Or,
tune "B" for lean of peak and just flip the switch.
This is
not some new idea. If your piston engine has enough compression to run lean of
peak, it should be run so in cruise all of the time. All big radials use fuel
as fast as you can pour it out of a bucket. Were it not for lean of peak
operation they had very limited range, and poor payloads.
In the
Fiat we never ran full throttle. I found on the dyno that more power was
available just short of full throttle. My guess was that the butterflies at
slightly less than straight up and down, helped turn the mixture a bit. An
extra 3 HP every time.
Airplanes
are dynamometers.
Take
advantage. Make one change at a time. Record everything. Use SAE tables to
correct to sea level HP.