Spark signal generation

[Mark Mason]

Dave Zug wrote:
> 
> to get my ECM to run on a bench, i think i read that some sort of
> feedback spark reference is needed to simulate a "running" engine, in
> addition to, of coarse, key sensors attatched, or POTs. can someone
> explain what is basically needed and how it can be simulated?


It depends on the type of pickup circuitry used. If your ECM receives
the spark reference directly, you can use a sine wave generator to
simulate the signal because the ECM will turn this into a square wave
and sense the falling edge as the spark reference. If the pickup is
amplified with a module, you can use a square wave generator with its DC
offset adjusted so the signal swings from 0 to 12 or so volts. For a GM
product, you'd use the square wave. The frequency in hertz for a given
RPM would then be :

  RPM x 8
------------
  60 x 2

Hope this helps.

Mark.