simple question-Can you run the OEM coil with MSD 6al2 CD box?

[fredmeister]

I know this should be a simple yes or no answer, hoping for a quick response.

Can you run the stock Bosch ignition coil from my 79 930 with the MSD CD boxes, specifically the 6AL2 unit?

I know the MSD coils are listing 70turns to 1 or 100 turns to 1 ratio but I dont know what the stock Bosch unit coil ratio is.
Or if there are other reasons not to run the stock coil with MSD and risk damaging it.

thanks,
Fred

[304065]

Fred,

Nothing in electronics is a simple yes or no. A 0 or 1, maybe.

The reason is, many here will say "I use an MSD High Vibration Blaster II" coil with my stock CDI and it works fine!

But in truth, the HVB blaster II has different specs:

Primary resistance .7 ohms
Secondary resistance 4.5K ohms
Inductance 8mH
Turns ratio 100:1

Compare that to my measured specs for the factory CDI coil 0 221 121 001, primary res 0.2 ohms, inductance 1.8mH.

The MSD coil has too much inductance if you ask me, although you are correct that people report that it works OK. No dyno information, however.

[fredmeister]

Thats alot of info thanks, but not sure if you answered my original question of running the stock coil with an MSD CD box.
Can this be done without causing problems or shortening the life of the original OEM coil or worse damaging the MSD unit?
You mentioned the MSD coil having too much inductance, but MSD will tell me to buy one of their coils with the 6al2 unit, and I am trying to get an opinion free from conflict of interest.

Fred

[Eagledriver]

They are both CDI coils and I used my stock SC coil for 6 years. I replaced it with a MSD coil because I was having ignition problems. It turned out to be a pick-up problem so the coil was fine. I now keep the stock coil as a spare. I have been told that the MSD is hard on the stock coil but it worked fine for me.

-Andy

[304065]

Fred,

Likewise, the MSD box drives a coil with much higher inductance. I suppose this is because of the switching time to very high amperage, there's a lot of time to build up the flux in the coil.

On the other hand, the CDI coil has very little inductance, which means it doesn't store much energy on its own.

There's a big enough difference that I wouldn't interchange them.

AND if you have a factory Bosch coil, it's worth much more to someone with a stock CDI than the price of a new MSD coil. I would go MSD all the way, if you burn out their coil it's easier to replace than the NLA factory black one.

[lindy 911]

Why not just run what is known to work and use the MSD coil with the 6AL? I could understand a stock box with an MSD coil because of budget, but you've already spent the money on the 6AL...

[fredmeister]

Originally Posted by 304065

Fred,

Likewise, the MSD box drives a coil with much higher inductance. I suppose this is because of the switching time to very high amperage, there's a lot of time to build up the flux in the coil.

On the other hand, the CDI coil has very little inductance, which means it doesn't store much energy on its own.

There's a big enough difference that I wouldn't interchange them.

AND if you have a factory Bosch coil, it's worth much more to someone with a stock CDI than the price of a new MSD coil. I would go MSD all the way, if you burn out their coil it's easier to replace than the NLA factory black one.

Thanks man......I will order the whole shebang. Your reasoning is sound.

Fred