what's funny about all this, is i get grief from people (not inliners, i'd like to point out! :-) about "advance til ping, back off". i've tried multiple times to put some rigor into tuning.
the supertuner website info is correct, as far as it goes -- the problem is that the dominant variable is virtually unknowable -- flame propagation at at particular load/rev/chamber shape/stoichiometry point.
i'm very glad i made the spreadsheet though -- it allowed me to do what-ifs. Often, this sort of process in other areas (gearing, cams even, chassis stuff, electronics, ...) converges on a workable range of values from which to choose and tune. In this case both the slope and intercept of the spark curve (assuming a linear approximation) is all over the place.
so basically i can now justify what we've all known and done -- start with what you've got and tune on the road!
I still want to have some physical justification/verification for settings though. I will pursue exhaust gas temperature, first to get F/A mixture right then for spark.
However, i had NOT done the math on my engine until now -- the loooooong rod and stroke and slow turning mean that I really don't need a lot of spark lead -- unless the combustion chamber shape, which really is bizarre and terrible, hugely slows down flame propagation.
Thanks for humoring me here.
