Lynn,

      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.

 

Lynn E. Hanover