If we're evaluating centrifugal advance at a particular RPM, for instance, find the maximum torque developed at a particular WOT speed, and start advancing timing one degree at a time and recording the torque change. You'll find the "sweet spot" where torque is at a maximum. Advancing the timing further results in a loss of torque, due to the engine trying to run backwards as the flame front reaches the piston crown too soon. Record the torque loss from the over-advance. Go back to max torque, and start retarding the timing, recording the torque loss as the timing is retarded. You'll find that it takes approximately 5 degrees of timing retard from the max power point to equal the torque loss from ONE DEGREE of over-advance. It's always a good idea to err on the side of "not enough" centrifugal advance, as the law of diminishing returns kicks in very quickly!
Jerry
I'm pretty sure I understand what you're telling me Jerry, but you didn't answer my question.
Given a constant amount of time for the spark to get the air/fuel mix to burn completely and a decreasing amount of time (as RPM increases) for a piston to be in the proper place in it's travel in the cylinder to take full advantage of the expanding pressure of the air/fuel mix, why not continue to increase the timing advance past 3000 (or so) RPM?
There must be a reason that "centrifugal timing advance numbers are remarkably similar between engine manufacturers".
