In a message dated 8/17/2006 6:09:26 A.M. Eastern Daylight Time, atlasyts@bellsouth.net writes:
Rusty, I did not play with the mixture too much, but I could see
changes as I was turning the knob up and down. I'll do that with the
timing also, but later. I have to fabricate the heat shields, but
working with stainless sheet is a bitch if you don't have the right
forming tools. Keeps springing back, unlike aluminum.
Buly
Remember that the timing is reported as crankshaft degrees. The rotor is going one third as fast, and it is the position of the rotor that is our interest. A total advance of 20-22 degrees (at the crank) is plenty for up to 9,000 RPM. The object of the advance point is to generate the highest cylinder pressure between 40 and 50 degrees (crankshaft) after top dead center.

More than 22 degrees would be needed for RPM over 9,000 RPM to keep maximum cylinder pressure below 50 degrees after top dead center. You can run some very poor quality fuel and very low octane fuel at 22 degrees of advance. If you are stuck with 100 or 110  then 25 degrees is plenty. When the timing is anywhere around this point, the rotor is by any observation, at TDC. So for 21 degrees of  advance the rotor is 7 degrees BTDC. At 24 degrees it is at 8 degrees BTDC.

In street cars some timings were near zero with the trailing firing after TDC.


Mixture to rich enough to cost a few RPM off of peak, for take off and climb to help with temperature control. Once at speed, then lean to well lean of peak EGT as quickly as possible. In the 150 degrees lean of peak area. The airplane is a dyno and you can see the result of any timing or mixture changes. Best power is near ideal timing, and is just rich of peak EGT. And peak EGT can be real high as in 1800 degrees and that is bad for apex seals.  A/F can be below 12 to 1. EGT can be in the high 1400s, like 1490 or so. Not far off of a piston engine.

A strong running 12A can do 173 HP at 6,500 with 12.3 A/F and 25 degrees of advance,
( for the ideal power above 9,000 RPM shifting at 9,600 RPM) BSFC is .666 so it is using plenty of fuel. Front EGT is 1515, rear EGT is 1491.

The engine is not used below 7,000 RPM we just pass through that 6,500 RPM on a dyno pass.

Lynn E. Hanover