John:

** You see, I just said that there was no timing change at > 26" MAP, so, then,
a stronger spark is not going to cause a power loss.**

Again, that all depends.

Assume takeoff power.

Let's assume a timing of 22 degrees with a magneto.
Now, assume a timing of 22 degrees with a very hot spark from an electronic ignition.

The two will NOT result in the same *effective* timing or thetaPP.  It is quite likely in ANY aircraft engine so set up that the earlier thetaPP of the second example WILL have less HP and higher stress on the engine.  That is not open for debate.  It is a measurable effect we can demonstrate repeatedly.

If that is not what we are talking about, please help me understand so we can be more accurate in the discussion.

Walter