Originally Posted by Jabawocky
What I said was the ACTUAL spark timing , when the plug actually fires is anywhere up to 13-16 degrees BTDC. I can show you this on the dyno runs during the APS class.
When you set the timing to e.g. 22 degrees before top dead centre, the engine is not running. (That's why some people call it 'static' timing.)
When the engine is running the crank is moving. During the short period between the points opening and the spark occurring the crank has moved about half a dozen to a dozen degrees. It depends on RPM of course.
That's 'actual' timing.
The dyno data shows it.
And no, yr right, there are not multiple sparks out of a bog standard aero engine magneto after each points opening event. Just one spark, then some secondary 'ringing'.