[Diy_efi] Crank trigger resolution

[Rod Hiorns]

Hi guys,

How does crank trigger wheel resolution map into spark (or fuel)
timing resolution? Numerous OEMs use 4-pulse cam-driven sensors
but aftermarket guys like Electromotive push 60 teeth offerings.

I guess I'll know the transient timing better with more teeth,
and can allow for crank twist at high power, but is there more
to it than this? I've seen Mazda publish only minor HP improve-
ments by swapping to crank trigger (at low resolution).

I'm thinking of changing a cam angle sensor for a crank trigger
to get rid of the belt "slop", but I'm wondering how much this
will solve. Timing jitter is obvious at the moment ... if that's
just belt slop I'll modify the cam signal by latching it with a
crank signal, and then advance the cam sensor so it's far enough
ahead of the crank "edge" that the jitter doesn't come into play.

If I need to do more, what else should I be doing? Any advice is
much appreciated.
Cheers
Rod


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