The RX8 coils are the only coils on the market
that will fire 9000 times a minute.

The GM LS2 or LS3 or GM truck coils are only designed
to fire 3500 times a minute at the most.
Some are using them on the rotary and there is some
evidence they start having trouble around 6500 to 7000 RPM.

The reason for this  is the four stroke piston engine
fires the plug every other revolution. So 7500
RPM in a Corvette engine the plugs are only firing
3550 times a minute. A rotary fires the plug every
revolution. One reason they get so much power
for the small size of the engine.

I therefore conclude the RX8 coils are our best bet
long term. Mazda had trouble with the early versions.
Some early coils over heated and died killing the engine by
washing off the apex seal oil with raw unburnt fuel.
Poor Mazda had to increase the RX8 engine warranty to
100,000 miles or eight years.

I must say I am not surprised because Mazda was out
there on the bleeding edge with a 9000 RPM
red line and a rotary to boot. Law of unintended
consequences.

Mazda finally identified the problem and improved
the coil (we think) about 2006 to 2007.

Here is a heat sink that should add a bit of long term
reliability.

If you  are running a 2.85:1 gear box I recommend RX8 coils.


Paul Lamar

Hi Paul,
Been reading the problems with overheating,and trying to find suitable
coils, having to build heat sinks etc. etc.

Coils seem to be a bit of a hurdle....

not sure if it's possible but what about 2 coils per plug, and splice the
lead and alternate them firing, so that way the only have to do half the work,

might need extra pickups to time them... if you using magnets for timing.


Just thinking out loud...

Regards Keith


That is a pretty good idea. As I vaguely recall there used to be some sort
of high voltage splitter on the market. I am not sure how it worked or
even what it did and why it was needed.

Another possibility is a high voltage diode.

Of course a capacitor discharge system does not have the same heating
and timing problems as the inductive coil system does. It does  not
need to have any sustained current flowing through the coil. The coil is
just used as a pulse transformer.

I think Victor suggested using the falling edge of Tracy's ignition
pulse to trigger the CD system. I think that could be taken a step
further and build a device that would oscillate 4 or 5 cycles
after it saw Tracy's ignition negative going edge. In effect
build a multi spark CD system at high RPM. It would take a high
power, 500 volt power supply to recharge the capacitor multiple
times. Usually it only takes a couple hundred micro seconds to charge
a one micro farad capacitor in a 500 volt CD system. The current
consumption is the area under the voltage curves. So for the same
spark voltage the coil heat could be near half. See the attached
charts.

At 8000 RPM one only has 7.5 milliseconds for 360 degrees of E-shaft
rotation to fire. .008 seconds. 7.5/36 is  200 micro seconds per 10 degrees.
So if we fire the cap every 20 degrees five times. We could fire at
20 degrees BTDC, at TDC, 20 degrees ATDC, 40 degrees ATDC and
60 dgrees ATDC. The total expansion stroke in a rotary is 270 degrees.

Due to Tracy's timing system, and a fixed oscillator frequency in the
device, at lower RPM's the degree range would shrink back towards
20 degrees BTDC.

I am sure Victor could design this device.

Adding a heat sink for the RX8 would be easier :)

Paul Lamar


So Paul, just trying to connect the dots. These RX-8 type coils are the best
choice for my 13b regardless of the system I end up using for ignition?
Not wanting to spend any more money on necessary stuff.
C. Smith

Based on the info I have so far I think so.
Advanced Auto Parts in your neck of the woods have them
for $21 each which  is pretty cheap.


Paul Lamar