coil without ballst resistor?

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mopower440

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On my 440 dart, i switched out the stock mopar ECU box for the GM 4 pin module and have it hidden inside the old mopar ECU box to make it look original, but am using the GM coil also. No longer need the ballast resistor which i like. I dont care for the look of the square GM coil though and want to find a cylindrical shaped coil that looks somewhat like the original one that the mopar ignition used but i need one that will work with the GM module and does NOT need a ballast resistor. Anyone know of coils that dont need the ballsat resistor but look like the old original coils?
Thanks!
 
mopower440 said:
On my 440 dart, i switched out the stock mopar ECU box for the GM 4 pin module and have it hidden inside the old mopar ECU box to make it look original, but am using the GM coil also. No longer need the ballast resistor which i like. I dont care for the look of the square GM coil though and want to find a cylindrical shaped coil that looks somewhat like the original one that the mopar ignition used but i need one that will work with the GM module and does NOT need a ballast resistor. Anyone know of coils that dont need the ballsat resistor but look like the old original coils?
Thanks!
Click to expand...
A non resistor coil at any parts store?..
 
Actually (my car is STILL apart) I used, as an experiment, the stock Mopar coil with GM HEI. It worked fine, and gives a hotter spark than with Mopar ECU. Be aware that some coils (according to internet wisdom) cannot be operated horizontally as the windings "will be out of the water". (Even though some coils WERE mounted horizontally "back when" including Ferds and some Mopars
 
Pertronix ignitor lll is a cylindrical oil filled coil. .32 ohm primary coil, 45,000 volts output. Should work just fine. Designed for electronic ignition setups when ditching the ballast.

If looking to keep it appearing stock, hollow out the ballast resistor and turn it into a 12V jumper by removing the potting compound from the back, removing the resistor wire inside, then solder in a jumper wire across the 2 contacts, fill up with 5 minute epoxy, bolt back on the firewall , and plug it in.
 
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moparmat2000 said:
Pertronix ignitor lll is a cylindrical oil filled coil. .32 ohm primary coil, 45,000 volts output. Should work just fine. Designed for electronic ignition setups when ditching the ballast.

If looking to keep it appearing stock, hollow out the ballast resistor and turn it into a 12V jumper by removing the potting compound from the back, removing the resistor wire inside, then solder in a jumper wire across the 2 contacts, fill up with 5 minute epoxy, bolt back on the firewall , and plug it in.
Click to expand...

Already did that so i could keep the ballast in place, now just needing a more stock looking coil instead of the big square one.
 
I have some coils if needed. Just scored a really good High volt one NORS that does not need a ballast.
12 Volt Internally Resisted Ignition Coil

  • 3.0 Ohm
  • “Hot” Rated up to 55,000 Volts
  • Does Not Need A Ballast Resistor
  • Can Be Wired Directly To 12 Volts
  • Premium Quality
EB40-1-Web.jpg
 
I agree with halifax. Have been doing the 3.0 ohm coil with ballast removed for years with zero trouble.
 
That coil is great I run one with a petronix set up no issues so far.
 
Tell you what I have been looking into ballast resistors a bit more. Holy crap there are a ton of different ohm ratings.
 
Let me rephrase this question, it also has to put out the same kind of power that the GM coil does..
 
Since you are mismatching components, that might be a difficult task. The DC resistance has little to do with the coil performance, especially with more modern coils which use better core material and so on.

Frankly, without someone rounding up a bunch of coils and testing them, I'm not sure anyone can guarantee you an answer
 
67Dart273 said:
Since you are mismatching components, that might be a difficult task. The DC resistance has little to do with the coil performance, especially with more modern coils which use better core material and so on.

Frankly, without someone rounding up a bunch of coils and testing them, I'm not sure anyone can guarantee you an answer
Click to expand...

Wonder if the cylindrical shaped coils from petronix or any of the performance companies would have the same power? Did any of the later mopars use a round coil that had the power of the GM coils? I do want to get the coil that looks more original but doesnt use a ballast, but also want to be able to have the output that the GM coil has
 
That's it I don't know. I doubt, unless someone has tested a number of coils that anyone really does. There never was an "old look" coil that was designed "for" the GM HEI There was a reason the older Mallory and Accel coils were huge---to put up with the large amounts of power fed to them. More modern coil design allows somewhat smaller.

the other thing is "you might be over thinking." How much HP does this engine produce, what fuel and compression, and what makes you think you need something "this special." As I pointed out earlier, a stock Mopar coil driven by a GM module, no ballast, puts out considerably more spark than the Mopar ECU. It "just might be" that most any cylindrical PERFORMANCE coil will "do ya" in good shape.
 
67Dart273 said:
That's it I don't know. I doubt, unless someone has tested a number of coils that anyone really does. There never was an "old look" coil that was designed "for" the GM HEI There was a reason the older Mallory and Accel coils were huge---to put up with the large amounts of power fed to them. More modern coil design allows somewhat smaller.

the other thing is "you might be over thinking." How much HP does this engine produce, what fuel and compression, and what makes you think you need something "this special." As I pointed out earlier, a stock Mopar coil driven by a GM module, no ballast, puts out considerably more spark than the Mopar ECU. It "just might be" that most any cylindrical PERFORMANCE coil will "do ya" in good shape.
Click to expand...

I must have missed that..you say you can run the GM module with no ballast with a stock old mopar coil without hurting it, AND it does put out better spark still? I always thought the ballast had to be used with the stock coil..? but then again, i also remember hearing that the ballast was for the ECU and not the coil, but not sure which is correct..
 
Didn’t GM and Ford run with out a resistor back in the 60s and 70s? What about the coil that was designed for the Gold Box? Kim
 
I did this just as an experiment. The GM HEI does "manage" dwell and current and that might be what makes the difference. I cannot of course guarantee this as this WAS just one car, one coil. But I also had a GM HEI module on a Toyota 22R engine I'd installed in a dozer. Same deal, the coil was there --likely stock Toyota--so I ran with it. The old girl is gone now.

20adv8j-jpg.jpg
 
oldkimmer said:
Didn’t GM and Ford run with out a resistor back in the 60s and 70s? What about the coil that was designed for the Gold Box? Kim
Click to expand...
So far as I know GM pre HEI and Ford both had a resistor wire in the harness.
 
67Dart273 said:
... As I pointed out earlier, a stock Mopar coil driven by a GM module, no ballast, puts out considerably more spark than the Mopar ECU. It "just might be" that most any cylindrical PERFORMANCE coil will "do ya" in good shape.
Click to expand...
The ECU just tells the coil when to fire. The coil produces the voltage. The #8202 MSD coil I mentioned above puts out 45,000 Volts/140 mA. According to several sources (Google it) an OEM G.M. HEI coil puts our 40,000 volts.
 
A GM HEI module had both active dwell control and current limit, a ballast is not typically required. Current limit may differ, 5.5A stock, after market performance up to 7.5A. The active dwell adjusts coil charge to start, a few milliseconds prior to spark event. This greatly reduces heat dissipated (wasted) in coil. Points and Mopar ignition box need ballast to limit current, otherwise coils will overheat.

Using a 3.0 Ohm coil may reduce spark energy at higher RPM on a V8.

A scope and 0.1 Ohm 10W resistor can be used in series with ignition coil primary, to measure current by measuring voltage on resistor. One amp per 0.1 V. Viewing waveform will show current ramp as coil charges, current limit , and ignition event. Average voltage times ten, will be average coil primary current. Typical V8 points ignition draws about 3 to 5A, and can coils live at that. There are cheap lcd scopes for around $30.
 
Coil and ballast resistor choice is really all about the current draw the particular ecm is designed for. Coil current is hard to measure, so most folks talk about voltage. Voltage is easy to measure, but doesn’t tell you much. This leads to a lot of confusion when swapping parts around.

Let’s talk about the current on a stock Mopar electronic ignition. Instead of trying to measure something (current is pulsing, so it is hard to measure) let’s do a little simple Ohms law calculations.

There are different ballast resistors, but I believe 1.2 ohms is a common value used with Mopar ECMs. It is in series with the coil, which is about 1.5 ohms. This presents a 2.7 ohm load to to the ECM (1.2 + 1.5 = 2.7).

Let’s assume the ECM supply voltage is 13V. Using ohms law, the current in the coil (and ballast resistor) is 13V / 2.7 ohms = 4.8 amps. All these things have tolerances, so it would appear that the Mopar ECM is designed to operate at about 5 amps.

The stock coil and ballast resistor provide about a 5 amp load to the ECM, so everything is good until you start switching parts.

if you substitute a 3 ohm coil, now you have a total resistance of 4.2 ohms, and the current goes down. Usually this will reduce your spark. This is a situation where removing the ballast resistor makes sense. That would get your current back up around the 5 amps the ECM is designed for.

If you substitute a 0.7 ohm coil, now you have a total resistance of 1.9 ohms which drives the current up. Now your current is about 7 amps. Can the ECM handle it without burning up? I don’t know, but I suspect this is one reason why ECMs fail. Here is a situation where a larger ballast resistor would work.

The above calculations are “nominal” in value, intended to show how ECM, coil and ballast resistor compatibility works.

For aftermarket ignition systems, all the same calculations apply. If you know amps or ohms the unit will drive, then you can figure out what to do.

As also stated above there are lots of other factors that will affect how hot you spark is. Two coils that have the same resistance and pull the same current could have very different outputs due to other factors. I have not considered that here.

My point in this long winded explanation is that if you understand the basics of how to match ECMs with coils and ballast resistors, you will be able to get your system operating within its design limits and have good performance and durability. You can have really expensive and high performance ignition components, but if they are not properly matched, you may not get what you paid for, and you may even lower your performance.
 
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