Does anyone know the difference (-if there is one-) between a Volvo 240 (Bosch) electronic ignition and a capacitive discharge type?
Dave Barton

Hi Dave,
Bacially, the inductive stock ignition uses only the coil for generating high voltage. It uses only the induction/transformer effect of the coil for this and is triggered by the magnetic pickup in the distributor. A CD ignition uses an internal oscillator to generate and to charge capacitors up with much higher voltage than the normal 12v. When triggered the capacitor discharge current through the coil makes the induction/transformer process of the coil start with a higher voltage. This gives much higher power and the rise time is better because the oscillator is higher frequency than the motor can run rpms. It's best to have a coil that is designed to handle the high voltage discharge,
because you don't want to saturate the stock coil or overheat it from higher input voltage. From what I've learned about CD the input to the coil is usually around 450 volts.

The other issue I know about with MSD units is they don't source a powerful enough rpm signal to drive the k-jetronic fuel pump relay. If you aren't using k-jet then you are fine but if you need to supply that fuel pump relay you'll have to add an amplifier or a dummy coil to help amplify the signal. Happy rolling!

Dave 82 242ti 279k mi.

Great answers everyone. That helps a lot.

I have an MSD 6A sitting on the self that I want to try out along with a Nology high energy coil I just purchased (which I now realize requires a CD ignition to function properly).

Dave,
You mention the need for an amplifier for the signal to the fuel pump relay. MSD sells a Tach Adapter... do you know if that is an item that can be used to cure this issue or does that do something different? (I have heard of the dummy coil trick, but I don't particularly like the idea).
Thanks,
Dave Barton

DLOT wrote:
....The other issue I know about with MSD units is they don't source a powerful enough rpm signal to drive the k-jetronic fuel pump relay. If you aren't using k-jet then you are fine but if you need to supply that fuel pump relay you'll have to add an amplifier or a dummy coil to help amplify the signal. Happy rolling!

I believe that the tach driver is what you want. If I remember correctly it is part number 8910. It is basically a small coil to provide more current to drive the relay better.

Dave 82 242ti 279k mi.

Thank you,
I ordered the MSD 8910 Tach Adapter from Summit Racing this afternoon. It was $25, in stock and being sent out today.
Don't you wish all Volvo projects went this well? I do.
Dave Barton

Your welcome Dave,
I have learned alot from you. I'm glad I was able to provide a small amount of knowledge to help you. Thank you for sharing so much of your knowledge and experience with all us Volvo folks.

Dave 82 242ti

I have a complete Jacobs ign that I would like to get rid of. Holler if you would be interested.

dick

The Volvo ignition is inductive. It is powerful enough and works fine even for higher boost. If you wanted dramatically higher rpm usage, it might not "recharge" in time. A CD ignition would then be better, as they have faster rise time. I assume you are referring just to amplifiers, the little add on boxes made by Crane, MSD, and others. I think the low end of those companies is an inductive model, but the "6" series are CD. Fancier versions include boost retard features, which I have used and like.

Philip Bradley

I have a an MSD 6 series that I had on a Ford V8. Do you know if this can be adapted for use on my 93 245?

A capacitive discharge system produces a burst of sparks of longer duration than the original (normal) type coils. Normally a coil produces a single spark as the magnetic field collapses, as the points open or the electronic equivalent, a transistor turns off (goes from very low resistance to very high resistance). A CD system still gets a trigger the same way (hall device or equivalent) but creates a series of multiple sparks with the benefit that it triggers more even burning of fuel. In theory.
With the Volvo system, you wouldn't replace the ignition computer really- you'd replace the coil and I suppose the power stage. It might take a bit of creative wiring but I'm sure that one of these could be fitted and made to work for any Volvo except a 960 (you'd need 6 of them!)

You'd still keep the computer with its advance curves and other programming.
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Rob Bareiss, New London CT ::: 86 244DL, 87 244DL, 88 744GLE, 91 244: 808K total