Paul,


I don't wish to use a waste spark for various reasons I won't
go into now.   It is my understanding that both plugs can be
fired together.   If so then wouldn't a simple system just
rely on two trigger wheels, a magnet on each wheel, with those
magnets 180 degree opposed to each other?


Use two EDIS systems to fire  inductive coils on the
leading plugs and multi spark MSD capacitance on the trailing.

Doug in Japan

<Ford-EDIS-system2.pdf>

If you fire both plugs at the same time the same CAS
signal can be used.  If you use the LM311 it probably
can be used to fire at least six ignition systems
simultaneously.

That of course is not what you need. For a simple
system you need two CAS's one for the front rotor
and one for the rear rotor mounted 180 degrees out of phase
on the front cover. Then you need one wheel with one tit.
When the tit passes the front CAS both front plugs are fired.
When it pass's the second CAS  both plugs on rotor #2 fire.
That works for a CD system like the MSD.

That is not to say it will fire a GM V8 coil on plug system
such as the one Tracy uses. I think you will need
some additional electronics to do that. I have some of those
GM coils and they are on my list of things to try. I suspect
they need some sort of timing to provide a dwell
time as they are an inductive system. Perhaps a fixed width
pulse from a 555 one shot will serve that purpose. Longer
negative going pulse less dwell. Sorter pulse more
dwell.

I am not sure exactly what the EDIS system does.
There is a computer in there and it is doing something.
I don't know if it handles dwell time but it
must as it does not appear to be a high voltage
CD pulse system. It must get the energy some place so it
is probably an inductive system like the GM coils.

It does require many teeth on the trigger wheel
so it can figure out when to turn the current
on in the coil prior to interrupting
the current to fire the plug. It uses those teeth
to figure the RPM of the engine as the dwell time
ideally is a constant while the engine can run over
a wide RPM range.

It also uses those teeth to decide when to fire the other
rotor. The same as a four cylinder. The RX8 system works
in the same way with a missing tooth detector. The
computer decides when to fire rotor 2. It probably just
counts teeth.

If you have an EDIS system  I suggest you set it
up on the bench to see if it is working the way you want
it to work.  I think you could use any old fashioned stand
alone coil with it.

Here is the patent on the EDIS system so this might
help.

Back in the old points days the dwell was variable along
with the RPM. The plugs fired when the points opened.
The dwell was set by the gap in the points when the points
were wide open. More gap shorter dwell. Less gap longer dwell.

At low RPM the coils would run hot as a lot of
DC current was flowing through the coils. A ballast resistor
was used to limit the current flowing through the coil.

http://www.jag-lovers.org/xjlovers/xjfaq/ballastresistor.htm

I am a couple of days away from getting my CD system to
work. CD systems work differently. No DC current is needed
in the coil so there is no dwell time. It is just a high
voltage pulse transformer when the tit passes the CAS.


Paul Lamar