I'm running along at normal mixture,
and settle into a cruise configuration. When I start to lean the
mixture, EGT's go immediately up to 1800 plus degrees (about 10 inches
from the port). This trips the alarm that Tracy had pre-set in the EM-2, and
I richened it back up. What should I shoot for on leaning the
rotary? Is there a rule of thumb such as X number of degrees on the rich
side of peak EGT?
Rusty;
One question is at what percent power are
these temps. Clearly they are on the high side. I found on dyno
runs with my 20B, WOT max power enrichment was somewhere around 100-150 degrees
rich of peak in the 5000 -6500 RPM range; that being about 1600F. Peak
was about 1700 – 1750. 5000 RPM, 90% power EGTs at 1520. My TCs
are about 2.5 inches from the port.
Normally you’d want to lean to
about 100 – 150 F lean of peak. I did a lean-of-peak run at 60%
power with EGTs of 1500 and a BSFC of 0.49. Did you ever get it over to
lean of peak?
I’m running 9.0 : 1 rotors, so
that keeps things a bit cooler. What are yours? Going to 9.7 shouldn’t
make that much difference. And I wouldn’t think that a bit of
fractionating in the runners would more than 25 F difference in EGT. I
would get quite nervous when running EGTs over 1700. I’d be very
nervous at 1800. Could it be unburned fuel burning out into the pipe?
Timing? Plugs? Are you producing lots of power?
Al