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.


 -------------------------------------------------------------
 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
 ----------------------------------------------------------------------

 Or, grind off all but 2 of the 12 gear teeth for the bottom pickup coil.
 Run the MSDs from each of the coils.
 The top pick up for the front housing and the lower pick up for the rear
 housing. Have the MSD drive a double ended MSD (or other suitable) coil to
 fire  both plugs at once.

 No advance curve is required. The engine will start and run fine with
 anything from 20 to 27 degrees of advance. Mark out two sets of timing
 marks in
 the spaces between the teeth on the flex plate. One set for the front
 housing  and one set for the rear housing. Use epoxy paint. Very easy to
 see.
 Make a  fixed pointer on the PSRU mounting plate.

 Keep the plug wires short and use spiral core wire.

 Lynn E. Hanover


 That will work no doubt but it makes a mess if you do it while the wheels
 are still in there. Easy to have the die grinder slip. If you take the
shaft
 out it is a fair amount of work to take it out and put it back in.

 I like my electronic way as it gives more flexibility on the type of
output
 trigger. Up or down and width. Here is the counter out put and the final
 output trigger for the lower pickup or rotor 2.

 Take your pick. Both ways will work.

 Paul Lamar

Paul,

I'm guessing this approach wouldn't work on a 3-rotor?

When I first received my 3-rotor I wanted to hear it run, but didn't have
the engine computer.  Not wanting to invest a lot of money into a temporary
ignition system, I modified the CAS to accept 3 separate pickups, one for
each rotor, triggering off the dual-pointer rotor.  I fed the signals into
three late 70's GM electronic ignition modules which I used to trigger
three
GM dual tower coils, each coil firing the leading and trailing plugs on the
same rotor.  And low and behold...it worked.

I'm thinking that I could use this basic design to trigger three MSD CDI
units instead of the three GM ignition modules/GM dual coils. With each
MSD-CDI firing only one set of plugs, it should be able to provide multiple
sparks up to 7500 rpm.

How much (if any) improvement in bsfc do you think this would give?


Mark S.

----------------------------------------------------------

I would like to see some pictures of that 2nd gen CAS you
modified for 3 rotor use. That is real interesting.

I have not figured out how to do that yet so I am reluctant
to say it won't work :) Some bright electronics type might
come up with a solution without using a computer.  It can
always be done with a computer. Electronically dividing by
4 instead of six might work.  I think one may need 2 4017
decade counter chips instead of just one. Perhaps it could
be done with a 4518 dual decade counter.

In your case you could always use 3 pickups
and one tooth on an e-shaft trigger wheel which
would constitute the sledge hammer approach :)

I am hoping for a lot of BSFC improvement but I don't
really now if one can measure it short of a dyno run.
Perhaps getting one of those HyTek Automation data ack
systems and recording the injector pulse width, the intake
manifold pressure and the RPM and you have what you need
for a pretty good way of measuring the relative BSFC as you
will know the relative HP and the absolute fuel burn.  You
have 8 channels of 12 bit A to D to work with.  That is
pretty high resolution in anybodies book.  That is one part
4096 parts.  The other five channels can record outside air
temp, air speed and altitude among other things.

To re-word what you said MSD claims there is not enough time
to fire the plugs more than once over 3000 RPM.  I am
hoping that translates to 6000 RPM since we would be using
one unit per rotor.  A one rotor engine is equal to two
cylinders while a 2 rotor engine is equal to four cylinders
as far ignition requirements are concerned.  MSD is talking
about a four cylinder engine in this pdf I think.

There is little doubt in my
mind that multiple sparks at high RPM would be beneficial
as our combustion chamber moves past the spark plugs unlike
a piston engine combustion chamber where the plugs are on
one end.


Paul Lamar

Paul,

I'll look around and see if I can find it and send you a picture.

Mark S.

You are up early :)

I just had an idea. A way of testing a highly multi spark
system in a rotary with off the shelf hardware.

Since we have a moving
combustion chamber that stays in contact with the leading spark
plug for over 270 E-shaft degrees we need an entirely different
type of ignition. If we fire 20 degrees BTDC the combustion
chamber is still in contact with the leading spark plug for 220
degrees  of e-shaft rotation.

In fact it is more than that. The center
of the fire stays in contact with the spark plugs much
longer than a piston engine due to the geometry and
centrifugal force on the mixture molecules.

Here is the idea. Use 3 MSD units per rotor.
MSD claims the spark duration is 20 degrees.
One fires at 20 degrees BTDC. The second fires at
TDC and the third 20 degrees ATDC for a total spark
duration of 60 degrees. Three times longer than what
MSD claims.

One tooth on the trigger wheel and 3 pickups for
each group of 3 MSD units. The groups of three are
180 degrees out for a 2 rotor. For a 3 rotor of course
you would need nine and 120 degrees out.

What do you think?

If that does not improve the BSFC I don't know what
will.

This is for testing purposes only of course.
It is far too expensive for production. A custom
designed ignition system for the rotary is what we
really need.

Paul Lamar