340mopar said:
The ballast resistor is function of the module or points not the coil. For example on a Mopar ignition you use a different ballast resistor for either the orange box and chrome box(1 ohm) or the gold box (.25 ohm) this has nothing to do with the coil. When I was a GM guy in the early 80's I used an external Accel Super Coil on my HEI without a ballast resistor for 2 years with no failure (was a daily driver with weekend racing). In a breaker point application the ballast resistor protects the points from burning. I had a '55 Chevrolet pickup that kept burning points. It turned out the previous owner had the ballast resistor wired wrong (he had the start and run wires reversed).
Now I would not convert to an HEI on my Mopar for the reason of eliminating the ballast resistor, It is probaby the most trouble free part of the Mopar igntion system.
Nope! Everything to do with the coil!
Start with a points system: The condensor (or capacitor if you prefer) across the points is what keeps them from burning. As the points open all current flow is shunted through the condensor until it's charged up. By the time that happens the points are open far enough that the gap is two wide for an arc. It's the arcing that will burn points. Can't comment on your 55, but rest assured the reason the ballast was designed into the system was not to protect the points from burning.
A little explanation on what a ballast does: As current flows through a ballast it heats up (I'm sure we have all burned our fingers on one) as it heats up the resistance goes up. As resistance goes up current flow is reduced.
Why is this important in an ignition system?
A little explanation on how the coil works will hopefully clear that up:
When current flows through the primary windings of a coil it creates a magnetic field. This field will envelope the secondary windings. If you abruptly stop the current flow (points open or ecu switches off) the magnetic field collapses resulting in a voltage potential on the secondary windings. Once this potential builds up to a level that can jump the plug gap you have a spark.
Sounds simple and it is but the hitch is it takes time for this magnetic field to build up (refered to as saturation) which means as the rpms of the engine increase the time gets shorter for this to happen. So, just when the engine needs a hotter spark to ignite the mixture the ignition system is getting weaker.
What to do? Well you can increase the voltage (for constant resistance a voltage increase will increase current flow) so I can get adequate spark at high rpm but I run the risk of over heating the coil at low rpms (an espeically in a points system where the engine is not running the ignition is on and the points are closed). Here's where the ballast comes in. You can design a coil that with full battery votage will make a nice hot spark to help the car start easier (by pass the ballast), have a ballast that limits current flow at low rpms by getting hot and increasing it's resistance and as rpm's increase the resistance goes down (the ballast runs cooler at high rpm's because the time current is flowing between each spark is less) allowing more current flow and a hotter spark when it's needed.
As far as your Accel Super coil story, I have known lots of people that have bypassed the ballast in mopar igntions and got away with it for a long time. From an engineering design standpoint you are over stressing the coil and greatly increasing the probability of a failure. Go look at the specs for the coil and you will see that when used in an "inductive" ignition system (which all igntions but capacitive discharge like an MSD are) it requires a ballast, not only when used in a mopar system.
BTW, how did you use an external coil with a GM HEI? The HEI system has the coil integrated into the cap and the secondary makes direct contact with the rotor, with an external coil you would need a cap that would accomodate a coil wire. Did they ever sell caps like that?
As for the orange and chrome requiring a 1 ohm and the gold a .25 ohm that's easy. The Orange and Chrome are intend for both street and strip use and the Gold is a race only item that is used for short periods of time where the coil does not have time to over heat.
Just a comment about points and electronic and high performance modules. The reason you get a significant boost going from points to electronic is the elimination of the condensor and the faster electronic switching in an ecu. The amount of voltage potential that can be created is also a function of how abruptly the current flow can be stopped and an electronic switch (ecu) is faster. The high performance modules use better components that switch faster and have some extra circuitry to jockey around the dwell time (i.e., amount of time the current flows) to extend the rpm range. They have no impact at low rpm's.
