prof

Posting in the 2nd Gen section, as that's my application, but mods - feel free to move this to the engine management section if that's more appropriate.

Couple of questions on the stock Ignition setup.

The leading coil drives both leading plugs, so it's wasted spark. If you have a Multispark ignition, how many degrees of rotation from the initial firing point are you allowed to fire mulitsparks before the plug is in the 'wrong' chamber.

It might help if I explain this a little - when the coil fires, one rotor face is up against the plugs and this is the main spark event, but there is also a wasted spark event in the exhaust cycle on the other rotor. Looking at the way these things rotate around, there doesn't seem to be much rotation before the plug carrying the wasted spark is actually in the chamber doing the 'compression' cycle, and so you wouldn't want to fire it.

So if I have a unit that's doing multiple sparks, how many sparks or how much time (would be a better quesion) would I have before that other plug is in the wrong cycle and shouldn't be fired ?

The 2nd question is kind of related to the first:

Is multispark a bit of a waste of time on the leading ignition, and better kept for the trailing's, as these will follow the leading in any case, and the same effect could I guess be achieved by firing the trailing plug multiple times, and that would also avoid the 'wrong firing' scenario I described above ?

The other option would appear to be the replacement of the one leading coil pack with two coils, and with some additional logic, use the ignition select signal and fire them alternately like the trailings.

tweaked

iTrader: (4)

I use an MSD 6AL on the leading coils. I love it. as soon as I installed it, my idle was smoother and low RPM was stronger. I also noticed better MPG.
As for spark duration, You have to think of it in degrees of crank rotation. The MSD produces a spark for 20 degrees of crank rotation. I don't have one on the trailing coils, but I konw of people who have. They have not mentioned any problems with the spark firing in the next rotor face.
Since the leading coils are what initially fires the fuel mixture, I would say install it there first. Then if you want, install them on the trailing coils. I know that as far as the MSD 6AL is concerned, you need two for the trailing cols and one for the leading. Since I haven't installed anything on the trailing coils, I can't speak for the effectiveness. But if you want to only buy one box, and you want to see some results from it, then install it on the leading coil.

Also, don't try to rework the leading coils so that they fire only when needed. a wasted spark is no big deal, it won't hurt anything, and the coils are designed well enough that it will be charged for the next event. And the work and trouble to get it to work right will be more aggravation than it's worth. I doubt someone could get it to work with out a new engine management system.

arghx

iTrader: (3)

I ran MSD on the leading for both my turbo and nonturbo FC, but the boxes are huge and require a lot of wires if you want to do the trailing ignition. I just ended up installing the HKS Twin Power (which has CDI) on the turbo car, as it does leading and trailing and is way smaller and simpler than the MSD.

If you are nonturbo you definitely don't need anything more than an amplifier on the leading. I noticed a leaner idle when I went with the MSD on that car. You're not going to find a ton of detailed information about multispark systems because it is proprietary data.