What ballast resistor do you use for the aftermarket electronic ignition system?

[Kern Dog]

First off....YES, I did do a search of this. The info that I'm seeking wasn't clearly listed.
For years, various vendors offered a factory appearing electronic ignition conversion kit for these cars. It featured a distributor, a 2 pin ballast resistor, a 4 pin ECM and a small wire harness with the plug for the ECM.
What happens when you need to replace the ballast resistor? What is the OHM rating of that 2 pin ballast resistor?
Looking at a troubleshooting book that I got from @halifaxhops it shows the stock 4 pin dual ballast resistors and states .5 ohms. Is it fair to say that the 2 pin ballast resistors should also be .5 ?

I had a ballast that reads:

I bought one that the NAPA guy claims is correct for a 1970 Charger with a 318 and points ignition:

Where do I find a .5 ballast resistor?

 

[toolmanmike]

First off, who should you PM when you have a question like this? Only 1 guy, Halifaxhops.

 

[S'cuder]

That 0.7 could be cold resistance. Hot is probably closer to 0.5.
But, here are some available from the man himself.

[FOR SALE] - Points ballast resistors

 

[lemondana]

I like to use the 5 pin ECU so I use the dual ballast resistors.

 

[halifaxhops]

Really depends on which ecu you use. Ballast should be measured hot they drop down a bit when hot. .5 is points standard usually.

 

[halifaxhops]

great explanation here


FYI.....on the ORIGIONAL issue of the MOPAR ECU's system (approximately 1973 +/-) used the four pin ballast resistor. The resistor had two sections: one section was 0.5 ohms, used to control the coil primary current and the other section of the ballast resistor was 5.0 ohms, which applied a constant voltage to the internal components of the ECU. The wiring was "keyed" to insure correct connections. The external switching transistor switched the coil current on/off to create the spark controlled by internal components of the ECU. These internal components controlled the DWELL function (ON time of the switching transistor to charge the coil's primary winding and to determine when the spark event occured to begin the next recharge event) and to turn OFF the switching transistor to create the spark.
Later editions of MOPAR ECU redesigned the circuitry of the ECU to eliminate the need for the separate 5.0 ohm section of the ballast resistor, using just the 0.5 ohm resistor to control the coil primary current. .....ITS JUST THAT SIMPLE......
BOB RENTON

 

[Kern Dog]

That is simple to someone that is familiar with electronics. It isn't so simple to someone that has more experience with mechanical things like engine rebuilding, suspension-brake-steering systems, interior restoration and general automotive repair.
I appreciate the effort but sometimes engineers write and talk as if those on this end speak the same engineer language. Not all of us do.

 

[halifaxhops]

OK I will try. Not a engineer but a ex avionics guy.

Basically the lower the ohm value the hotter the ecu gets and you will get more RPM's out of a ecu. Great example are chrome ecu's. Alot of cars run them and they are a good unit on the street you should run say .8-1.0-ohm ballast and you will get lower rpms out of it, so the heat does not build up. When racing they recommend a .25 ohm to get the max output RPM's of around 10K but they are also turned off and cooled down between runs. If you use that on the street, I will give the ecu a hour on average before it fails. Most of the new Mopar "authorized" kits with the Chinese ecu come with a 1 ohm ballast. But they seem to overheat due to the fake transistor cove and the newer style one is buried in the potting on the back so no place for the heat to escape to hence more failures. That help?

Here is a simple way to think of amperage.
A 1/4" straw and water will let the water (amps) flow a good amount (think amps)
a 1/8 straw will restrict the amount of water (amps) to the unit so less amps.

You reverse this for how ohms work .25 ohms would be the 1/4" straw less restriction more voltage, the 1/8 straw would be say the 1 ohm ballast so more restriction less amps.

That help anyone?

 

[Kern Dog]

Thank you, Ray. That helps a lot. I'm going to copy and paste this to post in my thread at FBBO.

 

[Bewy]

If you want an accurate reading of the BR resistance, you should buy a special low-ohms meter.
The standard DVMs are not very accurate at low ohms.