"CAPACITIVE DISCHARGE The Digital 6A and 6AL feature a capacitive discharge
ignition design.  The majority of stock ignition systems are inductive
ignitions.  In an inductive ignition, the coil must store and step up the
voltage to maximum strength in between each firing.  At higher rpm, since
there is less time to charge the coil to full capacity, the voltage falls
short of reaching maximum energy which results in a loss of power or top end
miss.  The MSD Ignition features a capacitor which is quickly charged with
520 - 535 volts and stores it until the ignition is triggered.  With the CD
design, the voltage sent to the coil positive terminal is always at full
power even at high rpm."

Unlike RX8 or LS1 coils there is no dwell time to charge the coil
requirements, This greatly simplifies the ignition and eliminates the need
for a computer.  It will also work with a carb.

"MULTIPLE SPARKS The MSD produces full power multiple sparks for each firing
of a plug.  The number of multiple sparks that occur decreases as rpm
increases, however the spark series always lasts for 20° of crankshaft
rota

MSD is advertising the the ignition will work up to 15,000 RPM with a
8 cylinder engine and a distributer. That is a lot of sparks per
minute
even though the distributer is running at half crank speed.
Namely 8 sparks times 7500 distributer RPM is 60,000 sparks per
minute.
In effect we need only two sparks per rev for a two rotor.


MSD now has a low cost capacitive discharge ignition system for $150.

In years past the racers used four MSD ignitions systems one for
each plug.
Four sensors could or were used to fire the four systems. Simple
and straight forward but rather expensive. This got very
expensive as you needed an old fashion coil  and one MSD systems
for each plug.

Mazdatrix uses an early model RX7 distributor driven at half
e-shaft RPM with a two story distributer cap two  coils. That
requires an old front cover.

This halved the cost if  two  instead of four MSD systems were used.
That distributer and front cover are getting rare. Won't work
with an RX8
front cover.


There is no need to drive a distributor at half crank speed  on a
rotary.
I had an idea on how to build a distributer directly driven off
the front of the
e-shaft. This cuts the number of MSD systems required down to just 2.
One for leading plugs and one for the trailing plugs. Second gen
coils
trailing coils will work great. The 2nd gen leading coil is a
waste spark type
that can also be used but just on the leading (lower) spark plugs.

Next installment will be a 3D dwg of the distributor mounted on the
front of the e-shaft.

Paul Lamar

I did use the MSD Street Fire on the single rotor driving a single dual
coil. A really simple setup. It fires even an overly rich starting mixture.
The multi-spark only works at the lower RPM.
The problem I ran into is the single trigger firing prevention. Meaning,
unless the cranking reaches a certain RPM the unit does not fire. I found
this to be somewhere between 250 and 350 RPM. My all new seals engine I put
in the airplane cranked at slightly more than 250, and did not fire. And
this after about 40hrs on the test stand engine. That was one of the biggest
set backs I had in the engine installation.
I am using now two independent old fission transistor ignition sets driven
by one CAS.
Just my 2 cents.


Richard Sohn
N2071U

http://www.fairpoint.net/~res12/home.html

If you were using a magnetic sensor the spacing is critical. At low RPM
they don't put out a lot of signal. In that case it is better to use a photo
interrupter circuit. I used these for 20 years with my road test systems.
I sold many of these to motor cycle and car manufactures all over the world.

They work down to zero RPM and are very durable and reliable.
I never put them in a housing to protect them and they always worked in a high
dust environment. It is an infrared light emitting diode and transistor.

Here is a picture.

You could hand prop the engine no problem.

Sell me that MSD system :) How much?

Paul Lamar