The Triumph Dolomite Club - Discussion Forum

Late last night Jeroen and I had a deal. My side of it was to stay in the club so I will comment again.

I certainly seem to have caused a good debate.

Jon, I was under the impression that the Lucas 105 gold sport coil is 3 ohm, this came from a suppliers site giving it that rating. However now its posted here that the coil is 1.5ohm and the auto electrician working on the car says the same. While he was testing it, it started to fail and was at that stage very hot.

I was thinking could it be because these coils are a brand name and have been made by different companies (plus the possibility of copies) so we are getting varying specs. The 105 coil supplied to me was an Intermotor which I was advised was the original branded Lucas coil now supplied by Moss as more reliable than the Chinese made one. Could the original one be 1.5 and the new one now 3?

I hope from all of this we may be able to come up with a definitive answer and recommendations that can list which coils are suited to each application i.e. ballasted, un ballasted, points, electronic taking into account the manufacturer as it seems now that can bring in a variance.

Someone cleverer than me may then be able to make it a sticky and possibly keep it up to date so its easy to find for others needing to ask the same questions again.

I've had lumenitions since the 70s (Optronic - the expensive one!) and ALWAYS, on the advice of the Lumenition rep who visited the firm I was working at when I bought my first one, fitted ballasted ignition coils, even when it meant converting TO ballasted ignition as on my GT6 where I had to fit a separate ballast resistor and swap the starter solenoid for a ballasted type too. The rep said the solenoid was not really needed since it would start fine without it but then, as now, I'm a bit belt and braces.

Steve

Nowadays with the (much cheaper) Accuspark systems I always run full fat 12v and do away with a ballast if fitted ex works.
Like a lot of others I am deeply suspicious of all modern coils, they never seem to last long! I have a number of preloved ones liberated from old Astras, MkII Cavs and points equipped Polos, mostly original Bosch products. They seem much more reliable.

But surely when cranking the engine your coil is unballasted due to the 12v feed direct from the starter motor?

That's what I thought and there is a wiki about converting ballasted to unballasted.

As in more topics facts and personal idea's are mixed up and mentioned together. This does become an never ending story this way as there are 20+ of these open end coil discussions here. Fit what you like to fit I would say. My ever last coil contribution here.

Jeroen

Jeroen, you have a everlast coil.

AlanH wrote:

But surely when cranking the engine your coil is unballasted due to the 12v feed direct from the starter motor?

That's what I thought and there is a wiki about converting ballasted to unballasted.

When cranking with a ballasted system, the extra feed from the starter supplies voltage to the coil. This voltage will be reduced due to the starter "robbing " some of the volts. If you put a multimeter across the battery terminals whilst cranking you will see a reduced voltage- maybe 9-10 volts. This enables enough voltage to fire up a ballasted coil no problem and in the short time it operates like this there is no problem supplying too much V to the coil.
When converting to 12v coils, the cranking voltage will be less than 12v so "may " cause a weak spark and hence bad starting/

HTH

Tony

Elsewhere Jeroen explains why a ballasted system is superior in terms of coil rise time and hence sparking at higher rpm.

This will matter to Sprint racers who regularly see 6000 rpm or more.

Most road users dont get into that territory.

The problem is of course compounded on multi cyl cars and on a Rover V8 you would start loosing sparks at 4000 rpm.
My v8 is on a unipart GCL110, which is probably a painted bosch and has a non discharging Sparkright switch and points. With an SD1 box I dont think it ever goes above 4000....

Jonners