You need to understand how a MSD or CD or Capacitor discharge system works:
The capacitor in the box takes the 14V from the battery and converts it to 400-440V. When triggered the 440V is fired at the coil, the coil then converts it to 10,000 to 40,000 volts or whatever it takes to force the electrical charge to jump from the electrode to the ground strap on the spark plug.
If you reduce the Voltage by way of a ballast resistor you'll only get 6V to the box and everything is cut in 1/2. When under full load this low voltage will cause a misfire.
Now bear in mind that with any ignition system whether it's a CD or ECU it will only build enough voltage to jump that spark so it doesn't matter if you run a ballast as long as you never build high cylinder pressure and dense fuel loads within the combustion chamber (which create high resistance) to resist the output of the coil.
For example, at light cruise a mild street motor with a plug gap of .035 may only need 10-12KV to jump, the wider the plug gap the higher voltage required so if you gap them at say .050 it may take 25,000V to jump.
Now a car with about 13:1 compression at WOT and 7000 RPM with a gap of .045 will take 34,000V to jump with Cylinder pressure at around 3000PSI (We test with nitrogen Tank)
A simple way to explain a ECU or stock Mopar Electronic system…the ECU has a dwell or recharge time built into it, so between each signal sent by the pick-up coil in your distributor the coil receives a re-charge, when triggered by the transistor in the ECU the coil releases the voltage stored and fires the plug. Each type of coil has a very specific job to do, one is basically and inverter and one is a storage unit, they can be interchanged but will not work to there potential when used on a system they aren’t designed for.
So here's where all the advertising is sort of misleading..... "80,000V Ignition"...why? If we already know that most of the cars owned by people on this site will only require a maximum of 34-38KV then why do we need a 80KV system? Truth is You Don't, it doesn’t matter what the system is capable of, that spark will jump when the voltage gets strong enough to jump to the ground strap, excessive opening up of plug gaps only over loads the coil and shortens it’s life.
There's a lot more to all this then I have time to explain in a quick reply but I will close by saying IMO and after many years of testing ECU type Ignition on various engines most cars that run MSD or any other CD ignition is just plain overkill. It's all about resistance within the combustion chamber and how much voltage it takes to get that spark to jump and too get it hot enough to ignite the fuel.
With today’s high quality fuels that contain more additives and alky than gasoline a wider plug gap and an ignition system capable of producing a hotter spark is important but a CD ignition is seldom necessary to achieve that. I know of several cars that run 10 flats in the ¼ mile with an ECU and good coil. Of course these are not Mopar ECU’s and coils and they don’t run at 6V with a 1.2 ohm ballast. It’s all about the recharge time and of course more voltage in = More voltage out.
So the answer to your question is “No, you do not run a ballast resistor with any CD Ignition System”
