In the original email, i asked what MP one should use when running LOP.  George Braly suggested i go out and find out for myself.  So I did.

Here are two runs, both LOP at 2500 RPM and 17.5 GPH lean of peak:

30" MAP
EGT  1558  1558  1576  1563  1528  1484
CHT  330  328  332  328  340  324
TIT 1593 / 1634

31.6 MAP
EGT  1542  1544  1556  1540  1514  1472
CHT  326  322  326  324  326  314
TIT 1578 / 1611

The IAS in both cases was the same, so the horsepower must have been the same.  As one can see, higher MP means cooler temperatures.  Which makes sense, since the mixture is leaner.  I think I'm concluding that one sets the fuel flow to pick the horsepower desired, and then adjusts the MP to get the temperature desired (within reason).

I thought 17.5 LOP would be about 75% power.  So I went ROP and reduced MP until i got the same IAS as the LOP runs above.  It took 27" MAP and 20 GPH to match the IAS, which I think is about 65% power (don't know why it isn't 75%...)

-isaac
N7842K ES-P