72ScampTramp
Scamp Tramp
Chasing some issues in my ignition. I decided to go back in install a ballast. I see there are different ratings how do you choose what you need? All aftermarket msd box, coil and distributor.
How to choose a ballast
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72ScampTramp
Scamp Tramp
Thanks for chiming in Del. I did know that but in the instructions there is one wired in. Just trying to eliminate any issues. May not help just thought it and a power filter couldnt hurt.
67Dart273
Well-Known Member
Let me clear this up. On an MSD, you normally hook the "large" black and red power wires direct to a hot battery source. These are what supplies the "heavy" power. The "small red" is an "enabling" wire or "triggering" wire like a relay wire. The idea is that it really does not matter if there's a ballast in the small red wire or not as there is no real amount of current flow in there.
In some MSD setups, you can wire them up in such a way as to quickly be able to disconnect the MSD box in case of failure and resort to the original ignition. This may be why they show it that way.
In some MSD setups, you can wire them up in such a way as to quickly be able to disconnect the MSD box in case of failure and resort to the original ignition. This may be why they show it that way.
It is, read the note in the lower left corner.
72ScampTramp
Scamp Tramp
Thanks fellas. I did read that part. I figured for as cheap as they are and easy to install it couldnt hurt. Im not even sure what it is going on but I believe the module in the dizzy failed. Just thinking of ways to prevent it.
67Dart273
Well-Known Member
I really don't know. "I have heard" they are not all that reliable. Cannot speak directly. What do the modules cost? I would think that pretty soon you will have paid for a breakerless magnetic distributor!!
72ScampTramp
Scamp Tramp
You are right on that Del they are about $40 a pop for the accel brand and $80 for the Mallory brand.
72ScampTramp
Scamp Tramp
Summit is going to warranty the module which will save me some cash. I think ill try one of those power filters see if that keepts the module alive.
67Dart273
Well-Known Member
There are really two criteria. You have to match the ballast to the coil, and if you are using an ECU.........like a Mopar ECU, then the ECU has to "handle" the coil / resistor combo
This was especially true "back when" you had the "old huge" Mallory big rectangular coils. Those things used the "stock" factory ballast along with the Mallory supplied ballast in series with the factory ballast, and THAT could be a lesson in "how to read" destructions
I actually saw a guy explode one of them once on a 55 Chevy. Installed it, left out one of the ballast resistors, and left the key on while trying to get it to run, and promptly exploded the coil........oil and all......all over the engine bay.
In the case of Mopar stock coils, refer to the specs in the back of the service manuals........there are listings for the coils and ballast resistors. "In the old days" before the Chineseos took over, you could actually look up ballast resistors in the parts books and find out "what they were."
This was especially true "back when" you had the "old huge" Mallory big rectangular coils. Those things used the "stock" factory ballast along with the Mallory supplied ballast in series with the factory ballast, and THAT could be a lesson in "how to read" destructions
I actually saw a guy explode one of them once on a 55 Chevy. Installed it, left out one of the ballast resistors, and left the key on while trying to get it to run, and promptly exploded the coil........oil and all......all over the engine bay.
In the case of Mopar stock coils, refer to the specs in the back of the service manuals........there are listings for the coils and ballast resistors. "In the old days" before the Chineseos took over, you could actually look up ballast resistors in the parts books and find out "what they were."
ir3333
Well-Known Member
i didn't think it was that critical and thought you could actually delete the ballast with electronic ignition with a good quality coil.(but i wouldn't)
Doesn't it just reduce the applied voltage to the coil from 13 to about 9.5 when running?
The book says about 1 ohm for the Mopar Performance ecu.
Doesn't it just reduce the applied voltage to the coil from 13 to about 9.5 when running?
The book says about 1 ohm for the Mopar Performance ecu.
KitCarlson
Well-Known Member
The ballast serves as the pull-up for the ignition module. The MSD needs a trigger that goes high and low, ballast pulls high, ignition module pulls it low. Without it the module tries to pull the 12V to ground, a short circuit and the module blows! A ballast limits the current to a safe value. It would even work with 100 Ohm resistor, but that would not work with an ignition coil, for roadside fix, if MSD CDI fails. The ballast in the MSD CDI circuit, is not in series with the coil, it is in series with the ignition module supply, so no change in performance.
For a standard MOPAR ignition, the ballast limits the coil current to a safe value at low engine speeds. Most ignition coils are rated at 4 to 7A. With that said, few provide the current specification. Failure depends on operating conditions, average current, ambient temperature, coil construction.
If an ignition coil measures 1.2 Ohms, and a 1.4 Ohm ballast is used, the current is limited to I = V/R , 13.8/2.6 = 5.3A. A rule of thumb in the old days, was to match the ballast resistor to the coil resistor, so the coil would see 6V. Modern HEI controls the coil charge time, and has a current limit in the coil drive, to safely limit coil current, so a ballast is not required.
For a standard MOPAR ignition, the ballast limits the coil current to a safe value at low engine speeds. Most ignition coils are rated at 4 to 7A. With that said, few provide the current specification. Failure depends on operating conditions, average current, ambient temperature, coil construction.
If an ignition coil measures 1.2 Ohms, and a 1.4 Ohm ballast is used, the current is limited to I = V/R , 13.8/2.6 = 5.3A. A rule of thumb in the old days, was to match the ballast resistor to the coil resistor, so the coil would see 6V. Modern HEI controls the coil charge time, and has a current limit in the coil drive, to safely limit coil current, so a ballast is not required.
ir3333
Well-Known Member
..doesn't the ballast resistance change..hence the term "ballast"?
and is the coil resistance just the measurement you can take on the bench?
and is the coil resistance just the measurement you can take on the bench?
KitCarlson
Well-Known Member
The resistance increases as the ballast heats up, it is ni-chrome wire. Properly sized for wattage, it should not get hot as in a heating element. Most often resistance measurements are done at 25C, or near room temperature.
Measurements can be done with an Ohmmeter, but only the more expensive ones do an accurate job at low Ohms. Hooking a ballast and coil in series, and measuring the voltage drops for near 50% is a good ball park test.
Measurements can be done with an Ohmmeter, but only the more expensive ones do an accurate job at low Ohms. Hooking a ballast and coil in series, and measuring the voltage drops for near 50% is a good ball park test.
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