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 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.

 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

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