triggering an HEI module

[bcroe at juno.com]

I think the HEI is designed (haven't checked this all
out) to trigger on the steep NEGATIVE edge as seen
on my scope.  There is no corresponding steep
positive edge, so turning the pickup wires around would
make the trigger (if it worked) very inaccurate and 
sensitive to RPM as amplitude varied.  I'm not sure
what you are saying.  Bruce Roe

On Fri, 9 Mar 2001 09:01:05 -0500 "Bruce Plecan" <nacelp at bright.net>
writes:
> 
> IF that were true there would be  no timing change reguardless of 
> how the
> reluctor is wired up.   What you mention is what GM teaches, which 
> ain't the
> truth on that item.  Sorry to crush you with the horrors of the 
> truth.
> <g>...
> Bruce
> 
> 
> > The signal into an HEI module is far from a sine wave. It
> > looks like a slowly rising voltage which rises faster and
> > faster as the pole pieces come together.  Just as the poles
> > pass peak, the voltage very, very  quickly reverses polarity
> > to about the same but opposite voltage.  Then it decreases
> > like a mirror of the first part.  Then it crosses zero and starts
> > climbing again for the next pole alignment
> >
> > The spark is triggered by that very rapid voltage reversal at
> > the peak pole alignment.  The amplitude varies a lot with
> > speed, but the point of reversal is consistant.  Bruce Roe

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