This looks very promising for our use.

The coils can be mounted on a heat sink from the looks
of them. That looks like a huge advantage to me.
I'll have to get one to look at it and test it.

Paul Lamar

I just talked to MSD and they said the dwell time
is 4 to 4.5 ms which is an improvement on the 5 ms LS2.
Also the bottom is flat so it can be mounted on a heat
sink with two bolts rather than the RX8 coil which only
has one hold down bolt and would require an additional
clamp.

These points seem minor but believe me they
are important. The LS2 cannot be mounted on a heat
sink but it has a very small heat sink on it and
we are attempting to fire it twice as often as it
as it is designed to do and or see's in a 7500 RPM V8.
That means it is drawing twice the current and generating
twice the heat. The V8 cylinder fires every other rev rather
than every rev as in a one rotor.

The icing on the cake is these MSD coils have CD built
in and fire multiple times at low RPM.

Paul Lamar

Paul, The MSD coil looks like a nice part but the price at
performance parts.com <http://parts.com is $92.95 each or $699.95
for a set of eight and the dwell time is still twice as long as
the RX8coils.I am not up to speed on the electronic circuitry
but a recentpost said you had eight RX8 coils on hand for testing
and then laterthat you were down to two. I was wondering if it
the test rig which isfailing the coils. Possibly not firing the
plug under compression isencouraging multiple sparks because the
spark energy needed is lowerjust firing in air. If the intent is
for developing multiple sparkignition then testing that should be
distinguished from standard systemsapplication. I have been under
the impression that Mazda coils cooled bya blast tube are a
reliable component and that if one were to fail it isunlikely
that the remaining three would fail on the same flight. Thecoils
with an outside air blast tube would be significantly cooler than
 the underhood temperature when installed in the car.

Have you tested a Ford waste spark coil which has no internal
electronics since that function is in the driver (EDIS) module.
It might be interesting to see how it stacks up with the
secondary forthe secong plug grounded firing only one plug. These
coils are reportedto work up to 8300 RPM firing once per
revolution (due to the wastespark). If the coils are usable they
might be tested with the EDISmodule driving them first with waste
spark then with the second pluglead grounded.

george grimes

If you own a $15,000 LS7 what is another $800 for coils? :)
I am sure there is a huge retail markup. I notice Ebay has a
lot of MSD stuff much cheaper.

The dwell on the RX8 is 2.5 to 3 ms while the MSD is 4 to 4.5.
Not double.

Yes there is no question the test rig was failing the RX8 coils.

They don't like an out in the open spark anywhere around them
They continually re-trigger and the dwell becomes infinite.
Then they soon over heat lickity split and fail permanently.


The waste spark is problematic on the trailing coils
of a rotary but will work on the leading coils. The 2nd gen
RX7 engine was waste spark on the leading coils. I have not
bothered to test the Ford stuff as I must be sure it is
a long term solution and not based on obsolete parts if
possible. The coil on plug seems to be the long term
solution for the future.

Paul Lamar

Umm, Paul, would a simple coil check, almost possibly part of a
preflight be to simply swap the plug leads between leading and trailing
plugs and run the engine up. Won't a failed coil  then reveal
itself? I guess it could be an in car test as well:)

John Evans

I think Tracy has something like that in his installation schematics.
I am still doing a heat sink mounting that will make the
coils more reliable. Silly Mazda mounted the coils on the hot
engine block with a steel plate. Merely making that plate out of
SS instead will reduce the heat transfer from block to coils.

Paul Lamar


I was wondering how MSD managed to get a complete multi spark ignition
system in just the coil.

"The history of the capacitor discharge ignition system can be traced back to
the 1890's when it is believed that Nikola Tesla was the first to propose such
an ignition system. In United States patent #609250 first filed February 17,
1897."

I was fascinated by the new MSD coil that combines a multi-strike capacitor
discharge system in the same package as the inductance coil.

Where does the 500 volts come from to charge the capacitor?
Normally a very expensive switching power supply is required.
How do you squeeze a large 1 mfd, 500 volt cap into such a small coil
package?

Can anybody figure this out for me?

Paul Lamar

See attached.
C. Smith

Those are resisters not caps Craig :)
Did you send the wrong file?

Paul Lamar