Ignition timing ref points

[Todd Knighton]

Kalle Pihlajasaari wrote:
> 
> I want to do the timing with no interpolation so that the counter
> can be very dumb and just count pulses ant any RPM and then go blip.
> 


Well, about the simplest system I've seen for that has to be the early
Bosch Motronics.  On a six cylinder, the use a 129 tooth flywheel that
gives you 1.4 degree resolution.  They just count to the proper tooth,
then wait for the proper rising or falling edge to fire the thing.  No
counters wasted, very simple, no interpolation, no problems with crank
angle acceleration because it always references the crank not a timer. 
The only problem is interrupt time.  At high rpm the interrupt starts
taking up a lot of time, but it will go to about 8500 rpm's or so with
an old 8051 and a 6mhz oscillator, the same deal with a faster processor
and upped oscillator could easily go to the 20,000 rpm range.

Just my two cents, have fun.

Todd Knighton
Protomotive Engineering