Ballasted Coil

CastleMGBV8 · Post by **CastleMGBV8** » Wed Sep 19, 2007 8:41 am

Can anyone tell me if the original coil from a SD1 would have been ballasted or not? The coil on my car gets quite warm and is currently fed with a unballasted supply. The coil came from the donor car and being over 20 years old probably needs replacing, but don't want to buy the wrong one again as I bought a Lucas sports coil some time ago and found out that they don't work with the DLM8 distributor.

Kevin.

Post by **katanaman** » Wed Sep 19, 2007 10:43 am

to my knowledge the SD1 being electronic should use a 12v coil.

CastleMGBV8 · Post by **CastleMGBV8** » Wed Sep 19, 2007 2:47 pm

Thanks Marki,

That was my understanding, but saw a post the other day referring to a ballasted coil on an injection engine.

Kevin.

Post by **katanaman** » Wed Sep 19, 2007 4:02 pm

might have been running a mallory or something.

Pocket rocket · Post by **Pocket rocket** » Wed Sep 19, 2007 5:27 pm

The 35DE8 (Opus) distributor uses a ballasted coil

Paul B · Post by **Paul B** » Wed Sep 19, 2007 9:45 pm

katanaman wrote:to my knowledge the SD1 being electronic should use a 12v coil.

My '84 SD1 uses a 12 volt coil, no ballast, from the factory.

CastleMGBV8 · Post by **CastleMGBV8** » Thu Sep 20, 2007 1:03 am

Thanks guys thats clear then, any recommendations on 12V coils.

Kevin

ChrisJC · Post by **ChrisJC** » Thu Sep 20, 2007 7:09 am

My advice would be to get the right coil for your distributor from somebody like Rimmers (or at least somebody that knows their V8's).

I burned out 4 aftermarket coils from my local motor factors, to the point where I used to carry a spare! Once I fitted the right one, it's lasted 12 years!

My distributor has the amplifier on the side - DLM8??

Chris.

russell_ram · Post by **russell_ram** » Thu Sep 20, 2007 7:24 am

My view is that if the distributor has the small black amplifier on the side then it's definately 12V. However, if the 'amplifier' is under the coil in an aluminium case then it's most likely a low voltage coil because the big alumium amplifier box also contains a ballast resistor.

Russ

ramon alban · Post by **ramon alban** » Thu Sep 20, 2007 10:10 am

russell_ram wrote:My view is that if the distributor has the small black amplifier on the side then it's definately 12V. However, if the 'amplifier' is under the coil in an aluminium case then it's most likely a low voltage coil because the big alumium amplifier box also contains a ballast resistor.

Russ

Russ, I'm not sure this is correct because of confused terminology here.

In the ealier systems Rover erroniously described the 6.8 kohm resistor in the line to pin 1 of the ECU a "ballast resistor". It appeared on some of their circuit diagrams and system descriptions labeled that way.

That misnamed resistor IS (as you say) contained within the aluminium case behind the coil but the cct diagrams show it to be inline with the pickup point that feeds the ECU, pin 1, but with the later amplifier on the dizzy the resistor was connected floating inline adjacent to the AFM.

I think this has caused a lot of confusion over the years because that term is more correctly (and universally) applied to a resistor in series with the coil to reduce its normal running voltage to 8-9 volts after cranking has finished at 12 volts.

Hence when the word "ballast" appeared in the Rover Efi descriptions it led to confusion.

With the standard Rover electronic distributor amplifier, early or late, I believe all the coils were 12 volt and ran without a series ballast resistor.

I am fairly confident about this because I acquired a couple of early ignition systems and interchanged the coils on two cars with the later systems without any coil overheating problems.

There is a bit more about this confused terminology here:

http://www.vintagemodelairplane.com/pag ... ger01.html

Paul B · Post by **Paul B** » Thu Sep 20, 2007 12:36 pm

russell_ram wrote:My view is that if the distributor has the small black amplifier on the side then it's definately 12V. However, if the 'amplifier' is under the coil in an aluminium case then it's most likely a low voltage coil because the big alumium amplifier box also contains a ballast resistor.

Russ

I think not, as mine has no ballast resistor in. There is some sort of diode and a capacitor device, I believe, for cutting electrical interference, but no ballast resistor.

CastleMGBV8 · Post by **CastleMGBV8** » Thu Sep 20, 2007 6:55 pm

Thanks again I think that it's definitely a 12V then, having read quite a bit of tech info theres quite a bit of confusion re coils and differing resistances.

The sports coil 12V 1.5 ohm I bought some time ago definitely doesn't work with the DLM8 it seems to need 3 OHM + the specified coil is the Lucas DLB198 or there is a cheap Intermotor one which is said to be compatable dont think it's worth trying to save a fiver and have the car break down 100 miles from home. I always thought a coil was a coil as long as you had the right voltage, seems nothing is that simple.

Oh I did see a recommendation on this board for the Bosch Blue coil but there seem to be numerous different types of Blue coil.

Kevin.