Timing Jump on 165/TPI System

[Bruce Plecan]

If you read some of the hacs for the gm ecms you'll see a timing correction
per K of rpm.  If you ever get to see a true scope pattern (or for those you
who haven't) you'll see that it doesn't really resemble a sine wave other
then going + and-.  The peaks are very drastic. and the pattern going from +
to- near max values is very steep.
   A good afternoon's project is using an op-amp (714), and/or comparator, a
1K resistor, a LED, and old dissy.  Then mock up a "module" for turning on
the LED, interesting how slow, you can get trigger, and how early you can
detect the "stars" lining up.
  It's also been said that it zero crossing triggers.  Well maybe in some
applications, just none that I've seen........
Grumpy

| My understanding is that the module triggers on the falling peak of the AC
| signal. If so it would not be affected by speed, only the amplitude of the
| signal would rise ( the frequency changes, but in direct proportion to the
| engine speed, therfore no net timing change. I would think the jump in
timing
| you experience is software driven for the sake of driveability in case the
| connector is left unplugged.  Just a thought. Wallace O
|