Electronic spark timing ! PLEASE HELP !

[Ken Kelly]

For the Jag to work it must have another sensor to indicate
the Cam position, or use wastefire coils that fire both
cylinders at top dead center on that crank position.
		Ken.

Walter Petermann wrote:
> 
> Jose,
> I don't know if this would help at all, but have you tried averaging
> your y counts? Now that you have a 40 tooth wheel you could take ten
> y counts, maybe remove the highest and lowest values then average the
> rest.
> Just for encouragement, the Jaguar XJ40 uses only 3 notches for the
> timing or 120 degrees!
> 
>  Walter  (pushing the envelope over my head)
> 
> > Jose Carlos Rublescki wrote:
> >
> ...
> > The problem comes with the ignition part. In my first system, the MCU
> > received  from the engine one pulse each 90-degrees of engine rotation
> > (on TDC's). For each 90 degree period the MCU counted the number of clock
> > pulses (2 Mhz clock), let's say n, and then it did simple aritmethics as
> > follows:
> >
> > 90 DEGREES = n clock pulses
> > x  DEGREES = y pulses.
> >
> > So if I wanted a spark to appear x DEGREES after the 90-degree mark, I
> > should just have to program the MCU to generate the spark after y clock
> > pulses.
> ...
> > I should work fine in theory, but the problem I found is that there was
> > sometimes too much variation from one 90-degree period to the next.
> ...
> > My BIG question is that there are here lots of cars made by Volkswagen
> > where the ECU only reads one pulse each 90-degree of engine rotation. Do
> > they just live with the fact that they will have spark timing variations
> > or do they have some misterious way (at least to me) make this
> > calculation?
> >
> > After I gave up using the system above cited, I decided to use a 40-teeth
> > wheel attached to the engine like FIAT and GM do here (only they have
> > different teeth count). I now get much better results, but they're still
> > not as great as I would expect.
> ...