MSD Coil replacement

ramcharger said
Well, according to ohms law a resistor will limit both current and voltage. I agree that there is a self defeating property built in to the mopar style ballast resistor. I have put a Blaster 2 on with a Mopar ecu and that ballast got way freaking hot, far too hot to touch in fact and of course the resistance increased.

Wow. There goes all the extra ignition power...

Agreed. Something interesting I came across in an engineering study of the MSD 6AL2 is that they (MSD) calculates the spark energy in mj at 1500 rpm adding the energy of all the sparks vs just a single discharge. I'm guessing that all manufacturerers do the same. Seems a bit disingeniuos as high rpm spark is what we, as hot rodders, are most concerned with. I you are interested, PM me with your e-mail and I'll send you the .pdf It's too big too load up here.

That is a bit disingenuous, though there are probably a lot of guys who seldom take their MSD equipped ignitions out of the multi spark range. :) Sending PM now.

My educated guess in regards to the CDI performing so much better in a high performance engine at high rpm lies with the ability to provide a major whack to primary coil without having to wait for the coil to saturate. At higher rpm the longer spark duration is not necessary due to the minimized time of the compression cycle. I also believe that that "whack" can provide the coil with enough voltage to jump the gap at very high cylinder pressures where an inductive ignition just doesn't have the time to pull it off. Make sense?

That's definitely a big part of it, capacitors charge faster than coils. CDI ignitions evidently have the voltage at the plugs build faster too. Getting the same amount of spark energy you'd squeeze out of an MSD box at high RPM with an inductive system would require multiple coils like on newer OEM applications.

ramcharger said
I agree with you here. I think Don at 4 Seconds Flat has built a new box with upgraded transistors and circuitry and I've heard good things about his products but I have no personal experience with them. I do want to get my MP distributor phased by him as my distributor shows signs of being way off.

Sounds like an interesting project. There's a lot of new developments with transistors and other parts out there that could be stuffed in the classic Mopar box; some of the new ignition transistors can handle 20 amps of current.