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


  Paul

  On 12/29/10 you posted Part 3 on using the Denso GM coil and had run it
  up to
  12,000 rpm and showed a spark plug at 9,000. How does this jive with
the
  latest
  concern that it takes 5ms to charge these coils, which corresponds to
  7,500,
  yet the coils apparently work well at 9,000?

  Dan F



  I did not have the scope on the trigger wire so it was probably self
  triggering at some lower frequency. I was just looking at the dial of
  the signal
  generator. They will do that. They will sit there and spark on thier
own
  until they die. It does this at dwell time frequency. In the case of
the
  GM 5 millisecond period. If I had let it cook longer it would probably
  have
  committed suicide. :)

  It had me fooled :)

  Paul Lamar

 May I suggest a less expensive and perhaps more reliable way of getting
 an ignition spark.
 http://www.fairchildsemi.com/markets/automotive/auto_igbt_ig_std.html#ign

 Use these or similar from other manufactures and a standard or wasted
 spark coil.

 Sample of chip.

 csmale

 That appearers to be the chip used in the Mazda and maybe the GM coil.
 That would work but you would have to find a stand alone inductive
 coil that will build max current in about 3 ms. Do you know of any
 fast charging
 stand alone coils?

 Paul Lamar .

No but maybe a CD ignition coil would work if the dwell is
controlled.Or a
coil requiring a resistor and use it without a resistor
c smale

The CD coils might work but so does any old fashion inductance coil
work with a CD. The coil becomes merely a pulse transformer when
used with a CD system. In my experience with CD systems dating back
to the early 60's just about any ignition coil worked.

Too bad I cannot find a chemical to dissolve the epoxy
potting compound in failed RX8 coils. I'll bet they are
a dime a dozen. I could use them with a separated IGBT
switch :)

Paul Lamar

Mogas with ethanol famously dissolves the epoxy in fiberglass epoxy fuel
tanks. Probably takes time to soak in.

Al Rees

I think I'll try it>

Paul Lamar