Victor,

  I am down to my last three workable RX8 coils and
  one of those might be dead.

  Here is the schematic on the GM coils.
  Why do you think they ran a separate signal ground.


  Paul Lamar

  The GM coils do the same thing. Retrigger with as much as
  2.2 K in series. However they only limit the in put trigger
  to 5 volts from five. The schematic calls out a .05 uf across
  the trigger line. That seems to help.

  It also seems to be highly configuration sensitive.

  By that I mean how the wires are placed.

  Perhaps the close proximity to the spark is feeding
  back to the trigger. In the car there would be
  a short piece of spark plug wire to the spark plug.

  In any event the GM coils seems to be more robust but they
  don't like a dwell time less than 5 milli seconds.

  I'll get some spark plugs wires and move the spark away
  from the trigger input.

  I also moved the battery and the coil a couple of feet away
  and shielded the trigger wire. All this changes things.

  IMHO coils should not have electronics in them.
  MSD ignitions do not do that.


  Paul Lamar

I finally figure it out. Both the RX8 and the GM coils do NOT
like a spark anywhere NEAR themselves. You MUST us a plug wire
and the spark gap must be at least a foot away from the coil.
For example if the HV connector on the top of the coil comes
loose and the coil sparks to a ground spot in the vicinity it will
destroy itself in short order by re-trigging it self. That will cause
it to over heat. The RX8 coils fail faster than the GM coils.

What had me fooled is I had mounted spark gaps on the top of
coils with no problems in the past. What is different is the
fact that transistors and integrated circuits that are now built
in to the GM and Mazda coils. See the attached picture below.

Now as for the GM coils for a rotary engine that is running at 7000 RPM.
The GM coils DO NOT like dwell times less than 5 milliseconds.
At 7000 RPM the rotary must fire the plug in less than
8.57 milliseconds. At 7500 RPM the time to fire once
is down to 8 milliseconds. IMHO you will have misfire problems
with the GM coils. Perhaps getting the dwell  down to 4 millseconds
MIGHT help but don't hold your breath and don't bet on it.

These coils are designed for engines that NEVER require the
coil to fire half that often.

Good luck with a dwell that is only
5 milliseconds.

This situation is marginal and the RX8 coils require less
dwell time.

Mark in Texas, hook up a scope and check your dwell time.
Let me know what it is.


"The first wireless transmissions (1888-1905) employed spark
technology. Marconi systems were based on spark technology."

http://www.physics.otago.ac.nz/ursi/belrose/spark.html

"By 1924 spark was forbidden on the new 80, 40, 20 and 5-metre amateur bands. But spark was still used on the lower bands, and for another decade or more in the maritime service as a back-up for distress messages on the international distress frequency of 500 kHz (600 metres) right up to the beginning of the WW2. Had it not been for the war, spark would have been completely phased out in the maritime service except for emergency (lifeboat) purposes by the end of 1939."

If you find yourself crashed out in the bush salvage all the wire
you can and connected it all together and make a long wire antenna.
Then make a spark gap out of a coil and the battery. Learn morse
code :)

Paul Lamar