This looks very promising for our use.

The $15,000 GM LS7 V8 is a high RPM racing version with Titanium rods.

Apparently the GM part number "??" is one step up from
the LS2 coils. Hopefully the  dwell time will be more like
the RX8 coil coil 3 ms dwell time.

The coils can be mounted on a heat sink from the looks
of them. That looks like a huge advantage to me.
The LS2 has a small heat sink but it would be better
if it could be mounted on a heat sink which it cannot.

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 RX8
coils.
   I am not up to speed on the electronic circuitry but a recent
post said you had  eight RX8 coils on hand for testing and then later
that you were down to two.  I was wondering if it the test rig which is
failing the coils. Possibly not firing the plug under compression is
encouraging multiple sparks because the spark energy needed is lower
just firing in air. If the intent is for  developing multiple spark
ignition then testing that should be distinguished from standard systems
application. I have been under the impression that Mazda coils cooled by
a blast tube are a reliable component and that if one were to fail it is
unlikely that the remaining three would fail on the same flight. The
coils 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 for
the secong plug grounded firing only one plug. These coils are reported
to work up to 8300 RPM firing once per revolution (due to the waste
spark). If the coils are usable they might be tested with the EDIS
module driving them first with waste spark then with the second plug
lead 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 as 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.

I just got another 3 out of my RX8 and all were discolored.

I am working on a heat sink solution for cheap RX8 coils
if you don't want to use the MSD versions. Either will work
on the heat sink.  A small 1 inch square 12 volt fan
is optional on the heat sink.

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