One of the vexing problems we have had for years was the difficulty of
installing  off the shelf capacitor discharge ignition systems on the rotary.
The very common 2nd gen crank angle sensor put out only one pulse per engine rev
while two were required. One 180 degrees out of phase with the other. One pulse
for each rotor.

A four cylinder piston engine puts out four pulses per rev of the 1/2 speed cam
shaft and the distributor sends the spark to the right cylinder as needed and
one CD system is used. If we could somehow get two pulses 180 degrees out of
phase we could use two CD systems with the benefit of multiple sparks at a much
higher RPM than would be possible with a 4 cylinder engine and a single CD system.

Yes we could use two trigger wheels on the e-shaft and two sensors mounted 180
degrees out. The spark wheels would have to be slotted so the spark timing could
be adjusted.  The 2nd gen CAS has two sensors and it is already slotted for
timing adjustments. They are a dime a dozen on e-bay and are the most common way
of triggering  rotary engines.

The top sensor puts out one spark per E-shaft rev and the lower sensor puts out
12 sparks per E-shaft rev. The lower sensor is used to send RPM data to the
computer. Why does the top sensor have two tits on the trigger wheel? Simple!
The CAS runs at half E-shaft speed left over from the days when the rotary had a
distributor.

  What I have come up with is a simple and cheap two chip counter circuit that
counts six pulses on the lower sensor and puts out one pulse for the second
rotor. Ideally I'll sell an assembled PC board unless someone else wants to do
it. We don't need variable advance as the engine runs in a narrow RPM range of
5000 to 7500 RPM and real aircraft engines don't have variable advance. If you
want variable advance get a computer and program it yourself :)

Here is the timing diagram. The counter chip I will try to use is a CMOS 4017
decade counter. A hex inverter chip will provide both positive and negative
going triggers for different CD systems depending on their needs.

http://www.kpsec.freeuk.com/components/cmos.htm#4002
The count advances as the clock input becomes high (on the rising-edge). Each
output Q0-Q9 goes high in turn as counting advances. For some functions (such as
flash sequences) outputs may be combined using diodes.

The reset input should be low (0V) for normal operation (counting 0-9). When
high it resets the count to zero (Q0 high). This can be done by the top trigger
  pulse.

The disable input should be low (0V) for normal operation. When high it disables
counting so that clock pulses are ignored and the count is kept constant.


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With the right drill motor you can pull the roll pin and gear and chuck the CAS for testing the circuit. The shaft diameter is just under 1/2 inch.

BTW you can use two CD systems on the leading plugs and two Corvette style LS1 coil on plug systems for the trailing plugs I think. I'll have to test that as I think the coil on plug systems require a certain limited dwell time. I suspect if the dwell time is too long the GM coil on plug systems over heat. In that case perhaps a couple of 555s will put out a fixed pulse width to the coil-on-plug systems. One can always use 4 CD systems. Racing Beat uses 4 CD systems on their racing engines. Six on a 3 rotor.

Also BTW I have a report on the GM LS1 coil on plug systems:
"Turns out that LS1 igniters always draw power whenever available.  Not much -- only about .02 amp each.  But that will (and did) drain the battery over time for sure.  So I rewired to put a switch inline to disable them the same way the
injectors need a similar switch to not keep sucking juice.  Ammeter and
voltage level testing now confirm batteries don't get run down anymore."

Paul Lamar