HEI HEI

[Shannen Durphey]

Peter Fenske wrote:

> Howday folks
>
> Just finished playing with an EST HEI module in the lab..
>
> To get it to get had to hang a 2K resistor between N and P
> terminals(coil)
>
> Then feed the P terminal through a 680 ohm resistor
> with a square wave. To trigger took a min of 3 volts from
> DC.
>
> The ref output to ecm was the same W.F. about 6 V in
> amplitude not O.C.
>
> The output W.F was inverted.
>
> Driving a 22 ohm resistor instead of a coil the module got
> quite warm in five minutes. So heatsink it..
>
> There was no dwell extend effect noted.
> I presume the cap in not in the est version
> This is prob true since dwell  is ecm controlled
>
> To activate bypass it takes 5V on the bypass pin.
> Even through a 10k.
>
> Well this means you can use Hall effect crank triggers to
> drive the HEI module
>
> Just make sure that there is no tdc double triggers or
> something like that
>
> the vortec 4.3 has a 50% duty cycle 3 pulse per rev..
>
> later:peter

  Not questioning what you did, only asking questions...  An
old GM test is to connect a test light to battery + and touch
it to the P terminal of the module.  If coil fires, module is
supposedly ok.  This has worked for me whether or not the
pickup coil is connected.  Also, for use in firing a remote
coil I tied the N terminal of a module directly to the
negative side of a coil on a running engine. I had nothing on
the P terminal.  The module fired my remote coil every time
the vehicle coil fired, until the engine reached about 1200
RPM.

I'm asking this:  were you providing a complete circuit for
the signal?  P and N connected to the source?  I would think
it would take very low voltage, .5 to .7V, to fire module this
way as I believe that's all it takes from the pickup coil to
trigger.  Why/how did you decide to put the 680 Ohm resistor
in line?

Just thought of something.  The EST line is a digital signal
from the ECM.  If the module was powered on, 5V supplied to
the bypass line, could the pickup coil terminals be completely
bypassed by supplying a square wave on the EST line?

Oh yeah, about heat.  If a module is replaced and dielectric
grease isn't applied to the back before bolting it down, it
usually lives a brief life.

"The ref output to ecm was the same W.F. about 6 V in
amplitude not O.C."
WF=waveform
OC=??

Thanks.

Shannen