Breakerless Transistorised vs. Points and Coils

[TJ 450]

I am picking up my 280S from my Dad's house tonight where it has been hibernating for a while.

Whilst it is on my mind, I'll say that I have converted to the transistorised ignition system so that I can use the tachometer from the K-Jet car. It all functions fine and dandy, however I have some questions about the differing coil setup.

The basic kettering ignition system on the 280 includes a black coil with one ballast resistor. The k-jet cars feature the blue coil with 2-stages of ballast resistors. The K-Jet version coil is designed to run at a lower voltage as required if I remember correctly (6v/12v?). The black coil only runs at the single voltage.

Is there any harm in simply using the black coil as is, as it working with no issues whatsoever? I have done an exhaustive search on this matter and found nothing.

Tim

[koan]

What's the value of black coil ballast resistor?

Think K-Jet coils are designed to run on 4 volts.

Possibility is insufficient current buildup to saturate the coil at high RPM due to lower volts.

As long at it fires OK at full throttle and and high rpm it's OK.

[Big_Richard]

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[TJ 450]

The value of the resistor is 1,8 ohms if I remember correctly. I think I'll have to do some more road testing when the weather clears up, but it seems fine at the moment.

Tim

[koan]

would there be any more strain on the switching transistor with the coil running at a different voltage than its used to ?

I think the switching transistor will have less voltage across it and less current to sink.

[TJ 450]

I drove it tonight, there were no issues other than a slight hesitation under load. I doubt it is related though.

Tim

[Tony66_au]

Resistance coils run at 8 volts warm and some initially run at 12 volts while cranking and then revert to 8 volts when running.

2 resistors usually feed the coil (One resistor) and the 2nd resistor feeds the electronic ign module.

Although running an 8 volt coil at 12-14 volts wont kill it right away it will get hot and break down over time, Run an electronic ign module at 12 volts and the switching transistors will fry fairly rapidly.

The last vehicle I found a 6 volt coil on was my old VW Microbus and a mates 30's Chev pickup.

[Tony66_au]

BTW I believe that K jet cars are touchy about which coil used because of the electronic ign module so id ensure the coil is specced for the car.

[Tony66_au]

would there be any more strain on the switching transistor with the coil running at a different voltage than its used to ?

Ding ding ding!  Give the man a Kewpie doll!

Got it in one MT, yes it will damage the ign module and fry the trannies.

[TJ 450]

There's no sign of any excess heat dissipation however. I'll see how it goes.

Tim

[Tony66_au]

There is wiggle room Tim because ceramic resistors are quite crude and their value changes with heat and age although usually downward voltage wise as the resistance increases.

Some vehicles have a 12 volt "Hotwire" that juices the coil only at battery voltage while cranking because of hard start conditions but the CDI units normally are not as tolerant.

With a breaker "Points" trigger and no CDI system the other issue with running a non resistance or 12 volt coil is that they tend to chew out points much faster and other associated components.

[Big_Richard]

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[TJ 450]

Fair enough, I wouldn't want it to go when I'm out in the sticks. I'll look at one of the spare wiring harnesses to see what's required.

Tim

[Big_Richard]

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