Coil - resistor compatibility question.

[Airmonger]

Hey group. I have researched the information I'm looking for and haven't had much luck finding and answer.
My scenario is as follows;
I purchased an electronic ignition on (God forbid) Ebay from a seller that calls himself mopar_rick. Seemed to know his set up in a email exchange.
The text that follows describes the distributor.
*An OEM-spec distributor with a street-performance advance curve, complete with a high dielectric, brass-terminal cap and adjustable vacuum advance. Uses all stock OEM tune-up parts. IMPORTANT: real "heavy weight" Mopar/Chrysler design -- no spark scatter. Not the Accel "guts" (downsized GM HEI crap design) that were used in MP distributors from 2000 - 2013 and caused no end of problems*
Happy with the quality of the distributor. It included a new ▪︎must use this one▪︎ resistor block.
Prior to this purchase, I had purchased a Petronix high energy coil with a built in 1.5 ohm resister.
My question is, would the coil be compatible with this ignition set up or would I be essentially doubling up on resistance due to the use of these pieces.
Any response from individuals that have dealt with this first hand would be greatly appreciated.
Thanks another folks.

 

[Bewy]

I would be surprised if the coil has a 'built in' resister. The res generates heat & needs air flow around it to cool it.
You should contact Pert to see if the coil is compatible with Mopar Elec ign, as these igns are current limited to a greater extent than HEI & the coil might overload the Mopar ECU.

 

[S'cuder]

Send Rick an email and ask him.
His address is on the link in this page.
Rick Ehrenberg's Mopars

 

[Syleng1]

Plenty of coils come with built in resistors. MDS for one (coil ends in 111 if memory serves right.) No idea how the darn thing does not overheat, but they don’t. It is all in the windings I guess. I don’t know Rick but people speak well of him.
Shoot an email- best way to know.

 

[Bewy]

I suspect the OP has bought the Pert canister coil which has a 1.5 ohm primary resistance; I believe he is confusing this resistance with a non-existent 'internal' resistor.
I have never heard of a canister or E core coil that has a built-in resistor.

 

[abodyjoe]

this dist from ricks-mopars ??

ForMOPAR 273 340 360 318 HiPo Electronic Ignition Kit Plymouth Dodge NOS Tan Cap | eBay

IMPORTANT: real "heavy weight" Mopar/Chrysler design --no spark scatter. Not the Accel "guts" (downsized GM HEI crap design) that were used in MP distributors from 2000 - 2013 and caused no end of problems.

www.ebay.com

 

[Airmonger]

Send Rick an email and ask him.
His address is on the link in this page.
Rick Ehrenberg's Mopars

He leans towards running the resister regardless. Not much more info from him.

 

[Mike69cuda]

How about a picture of what you have?

 

[67Dart273]

I lean towards matching resistance to the coil. In years past, such as the big 'ol rectangular Mallory coil, you not only ran the stocker, but also put a special Mallory resistor in series.

This may get complicated, because it's possible that some coil combinations may cause excessive load on the Mopar ECU box, but that does not seem to be a big problem.

Another issue, tho, in today's parts, are good quality Mopar boxes -- when you need one. Many? Most? you find have a FAKE transistor for looks on the top of the box. The real one (smaller, less heat sink) is buried inside the chineseoationized box

When I had my car together, I did something for two summers that at least one member on here claims you cannot do---I ran a GM HEI 4 pin module with a factory coil and NO resistor.

 

[Mike69cuda]

If you have what is in the picture in post 6, you basically have a stock Mopar electronic ignition. With a 1.5 ohm coil, you should use the stock ballast resistor.

The real issue with matching coils, ballast resistors, and ecu’s is current, which is not easily measured without sophisticated equipment. The current varies with time, so a dc current meter will not give the right answer.

As I recall, the stock Mopar ecu is designed to drive about 5 amps (or close to that). That means, at ~14v, you need about 3 ohms to get a 5 amp current.

If your coil is 1.5 ohms, you need about a 1.5 ohm resistor for a total of three ohms.

If you had an 3 ohm coil, you could probably get by without a ballast resistor. (Maybe)

The thing to keep in mind is that ignitions are designed as a “system” and if you start changing parts, you better follow manufacturer recommendations or you are on your own.

Also keep in mind that cheap meters are not very accurate at measuring low resistances, like 1 ohm.

 

[Bewy]

^^^^ Very good advice.

 

[67Dart273]

^^But the coil/ ballast combo changes with every spark cycle. RPM and dwell time changes the relationship. I don't think you can make those assumptions as to current, but yet you actually (correctly) said that you need sophisticated equipment.

You are right, tho, it is a very loaded question.

It also seems to me, that just as I mentioned, modern ECUs are not what they used to be, at least in the aftermarket, and who knows if MP were in their later years, either?

 

[Airmonger]

I suspect the OP has bought the Pert canister coil which has a 1.5 ohm primary resistance; I believe he is confusing this resistance with a non-existent 'internal' resistor.
I have never heard of a canister or E core coil that has a built-in resistor.

It has to do with windings configurations. According to Pertronix, the coils were available in either a 1.5 or 3.0 to suit either BP distributors or HEI.
I order the 1.5 when still running the stock distributor, until the bushings/bearing started letting the internals flop around like a decked mackerel.
I may end up going back to the stock set up just for simplicity. Even worn out it still worked reasonably well.

If you have what is in the picture in post 6, you basically have a stock Mopar electronic ignition. With a 1.5 ohm coil, you should use the stock ballast resistor.

The real issue with matching coils, ballast resistors, and ecu’s is current, which is not easily measured without sophisticated equipment. The current varies with time, so a dc current meter will not give the right answer.

As I recall, the stock Mopar ecu is designed to drive about 5 amps (or close to that). That means, at ~14v, you need about 3 ohms to get a 5 amp current.

If your coil is 1.5 ohms, you need about a 1.5 ohm resistor for a total of three ohms.

If you had an 3 ohm coil, you could probably get by without a ballast resistor. (Maybe)

The thing to keep in mind is that ignitions are designed as a “system” and if you start changing parts, you better follow manufacturer recommendations or you are on your own.

Also keep in mind that cheap meters are not very accurate at measuring low resistances, like 1 ohm.

Thank you. That is a better perspective of the information I have accumulated.

 

[RustyRatRod]

Go to the auto parts store and order a Standard Blue Streak UC-12X. It's the heavy duty stock coil for all our Mopars that use electronic ignition with a ballast resistor. This is beyond simple. Just use the stock part.