Does anybody know the "proper" way to determine what the correct ignition
timing is on a given engine?
My Martin 1865cc engine is an unknown quantity as far as timing is
concerned. When we dyno'd it, we got it to run well at 36 - 37 deg. BTDC at
full advance, but on the weekend I found some documentation in the files
that came with the car that called out timing of 47 deg BTDC. Since the
engine had a power peak of 135 hp at 5800 rpm on our dyno (with 37 deg
advance), and the original manufacturer (Ted Martin) claimed quite a bit
higher power, at up to 7500 rpm, AND since Mr Martin also noted that the
burn quality of the combustion chamber was less than optimal, I wonder if
the high ignition advance of 47 deg was used to compensate for slow burn
characteristics in the chamber, and get a better power output at higher rpms?
Any engineers/technoids out there care to comment? Other details are A-6
cam, 10.5:1 compression, 85mm bore by 82mm stroke in a Ford 120E block.
What I'm wondering is if I get the ignition to far advanced, on the dyno,
will the power fall off before I burn down the engine, or will I be able to
tell (from what indicators) that I've gone too far? Same for on-track
tuning - how do I tell when the ignition timing is close to optimum?
Thanks, and I really hope I get some good ideas from the crowd.
Brian
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