shadowplane676:
hmm, I wonder if I could code the lower RPMs to be less sensitive to rpm change than higher rpms. that might keep a more stable idle ignition timing.
I don't think that's something that you can control. The problem is that if you're cranking at (say) 3 revolutions per second and your crank signal is coming in at an average of 3Hz, the previous crank signal came in 300 ms ago and you've just received the next signal. How long before the crank is at the right position for ignition? The answer is mainly a guess, because the speed is varying all the place, not consistent within a cycle and not consistent from cycle to cycle. By trial and error, hopefully you can come up with a guess that is good enough to get the ignition timing close enough for the thing to eventually fire. The problem with this is that starting a cold engine can be problematic at the best of times, and you would only need to 'miss' the correct timing a few times to make it very difficult to fire at all even when the timing is right.