Hey guys I have been thinking about this for a while and I finally had a chance to experiment. I found out that it works exactly as planned.



What you need for this mod is a single MSD 6AL box and a second gen leading coil.



What I did was connect the MSD to the leading pickup (no ignitor) and then the output from the MSD straight to the second gen leading coil. I then ran the two outputs from the second gen coil to the L and T inputs on the distributor cap. I removed the leads from the trailing ignitor. I then connected the outputs on the distributor cap to their respective spark plugs.



The result is leading and trailing fire at the same time and we all know that on an N/A no timing split can help produce more power. There is also no wasted spark when running off the distributor cap. This also gives you the benefit of firing all 4 plugs with a bit more authority than if you strictly ran a single MSD for leading.



For some reason running my setup this way made my bridgeport idle a lot smoother than running dual second gen leading coils with individual MSD boxes. I'll try this out for a while and see if I discover anything else.



The reason I posted this is because I know some people may not be able to afford 2 MSD boxes and coils.



I hope this helps and if so post up your results.

 

Well if you already have 2 MSD's and 2 second gen leading coils run them direct fire straight from the coils to the plugs. Just grab the signal from the leading output on the distributor for the 2 MSD's works wonders. I know there are guys that do this with the CAS and MSD's but haven't figured that one out yet.

 

thats a neat idea. you could also do this with the stock coils, and just wire it like you would with an msd+2 msd coils

 

I'm not a fan of using both ends of a double-post coil for the same rotor, even with an MSD. No OEM in the world does it for their twin plug designs, and for good reason. There's just not enough spark energy available from one coil to reliably fire two sparks under chamber pressure, and with an MSD it may work but I would monitor coil temperatures to make sure it's not overheating.



It sounds as if you're trying to avoid a waste-spark system. There's really no downside to it, especially on a rotary. As j9fd3s said, it would be easier and probably more reliable to just use the coils that Mazda put in the car. I'd like to add to that and point out that it's just one more coil away from going straight from coil to plug for the leading side.

 

Anyone got a simple write-up to do no-split for the 2nd gen?

 

http://www.savefile.com/files2.php?fid=2596048



Take a look closely at the firewall on this car you will notice a set of 2nd gen coils and it is setup like the picture I posted previously. This car is making well over 300rwhp PPort on alcohol and everyone knows how hard it is to ignite alcohol. You better have serious spark or else the spark will be snuffed out.

 

In that case, the MSD is indeed a wonderful, wonderful device.



Is that a drag-only car or does it see street or road course type use? (Do the coils have opportunity to overheat)

 

Well I had 1 MSD running 2 plugs on the same rotor for months. Dual MSD direct fire. No split, no wasted spark. Thats how we made 225 HP. No signs of overheating at all.



The car is a daily driven Bridgeport and I have not sensed any type of overheating. Even after driving for an hour straight averaging 95 MPH.



Sorry I could not go longer but I had to stop for gas. lol.

 

The MSD can drive two coil primaries with no problem. The MSD can light both ends of a lost spark coil and still arc to your watch band, and leave you sitting in the grass trying to remember your name.



If you have Stents (as I do) or a pace maker, the MSD and similar systems can kill you. Unhook the plus side of the battery while playing with it. Depending on model, the MSD runs the 12Volt coils at 350 or 400 volts. And, at low speeds, it restrikes the coil 40 times.



So, coils with built in resistors tend to fail of heat stroke. More modern epoxied coils usually work OK, but just the same, MSD has a list of those that do work, and a list of those that don't.



Only the trailing plugs need to be distributed.



On my Pport I ran a single relutor on the front pulley with a pickup on each side of the engine. One pickup for each housing, 180 degrees apart driving an MSD for each Oldsmobile double ended coil. Worked fine.





Lynn E. Hanover

 

if i end up putting the haltech on my 91 (its been reliable! and gets good mileage!) i'm gonna run the msd on the leading with 2 msd coils, same setup as the 1st gen and it seems like it works great.



i'm also a fan of the rx8 plugs, but with better ignition, maybe you can run anything?