Ballast wire or not with electronic ignition

[Pete 21]

Hi- I’m running my Mk2 with electronic ignition using a bosch red coil, served directly from the fuel cut off- i.e. not via ballast.
I’m doing this based on the instructions for the electronic ignition (the straight forward distributor base plate points replacement type) but am I actually potentially cooking my coil.
I know ballast question has often come up repeatedly but would appreciate clarification on whether should be direct 12v or drop down to 6v when running electronic please.

[trunt]

Is the coil a ballast type coil or a 12v coil? That determines whether you still need the ballast.

My view is that the ballast was a 70’s answer to boost a weak ignition, electronic ignition with the right coil provides a “boosted” ignition all of the time.

[Goldstar]

Pertronix does a 12v coil which I had on my mk1 - worked fine without the ballast. Mk2 a bit more involved but also possible. If you have a 6v coil you will want the ballast.

[Wheelz]

If you are using this one you need a ballast or you will soon cook the coil!

[Pete 21]

Many thanks for your replies guys. I am using the bosch red so based on the comment in the article I need to do a bit of re-wiring or face imminent failure!
I noticed in the spec wheelz kindly provided that it refers to the ballast dropping the voltage down to 9v (rather than 6v)? Hopefully running at 6 will not mean a weak spark.

[Wheelz]

I noticed in the spec wheelz kindly provided that it refers to the ballast dropping the voltage down to 9v (rather than 6v)? Hopefully running at 6 will not mean a weak spark.

The voltage depends on the value of the ballast. Their note says: " For use with ballast systems 1.4-1.8 ohm." The Stag ballast is about 1.4 ohms so it is within their range.

[DJT]

My Bosch Red coil died suddenly at just over 12 months old. It was the one in the link in post 4 above, running ballasted. I now run Pertronix ignition matched to an unballasted Flamethrower coil powered by a 12v supply direct from the ignition controlled fuse. Starts and runs fine. 5,600 miles since installed in Feb 2022.

[jbuckl]

I had a Bosch red coil running ballasted. It failed after about 3 years.

Replaced with a viper dry resin coil , still ballasted.

Fire up is very quick.

Keep the ballast system.

Its easy to renew the ballast wire if necessary & also provide a new supply for the igniter too.

Junction to use is an external ‘ wort’ in the loom , just behind the speedo.

piggy backing the inertia switch is very convenient, but not a good place electrically…. Best left to power the pump only.

piggy backing at the inertia switch can lead to poor pump feed & or poor ignitor feed.

[Pete 21]

So…I switched my coil feed back to the original ballasted wire…and now I’m getting a slight ‘roughness’ on load. I appreciate there can be many reasons for a slight misfire but any thoughts on why it should have happened when switching from 12v to 6v coil feed would be appreciated. As a reminder, I have Bosch red coil (that I’m pretty sure is 6v).

[richardthestag]

The mk2 ballast wire Pink/white on my stag failed and caused roughness which got worse over a period of time. cold start was perfect but after a few miles a misfire started to develop under load. The failure eventually escalated until the engine would just stall and not restart for 30 mins. then it was back to perfect running again. after swapping all manner of stuff over weeks and failing to find the root cause the pink/white wire failed completely and the car started to misfire from cold start rather than 5 miles from home.

I initially went down the mk1 route with the ballast white block, feed taken from one of the white wires on the back of the fuseboard and the ballast block output to the +ive on the ballasted coil. The white/yellow wire to the coil +ive was still doing its stuff and I was still running a piranha / newtronic EI, feed taken from the output / pump side of the inertia switch. logic was that in event of the unthinkable both pump and ignition would cut, thus instantly stalling the engine rather than waiting for carb float chambers to empty.

Then the piranha optic started to hang up on the baseplate so I went for an expensive but cheap and nasty rebuilt unit complete with the powershart module. this instantly fixed to failure to proceed and allowed to be to get much further from home before it also failed. cooked apparently. If these powershart modules last more than 50 miles there is a good chance you have an ok unit. Location of distributor and engine bay heat does the delicate electronics no favours though. Anyway this remains my only recovery of shame in nearly 30 years of ownership.

Now the car is running a pertronix ignitor and flamethrower. the pickup and performance from just adding these two was money well spent. smooth and reliable again.

[Paul Kelley]

As an adjunct for those using standard Lumenition (Mk17) it requires 6v coil and ballast.