32 replies to this topic

[gaspen]

Hello

 

I bought a GEU930MS distributor from MiniSpares for my 850 but I am confused with the coil.

 

MS suggests to use a 3 ohm coil for it. Even written on its box to use it with MSC105.  

 

In the other hand I read on this forum and on another sources too that unit with variable dwell I should use 1.5 ohm coils. 

 

My actual dizzy has a white dot on it but I am not sure that it means "low energy" . I guess this type of module does not have a "high energy" variant, sure?

 

What is your advice ?

 

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[shera12]

Hi, I’d go with what MiniSpares recommends, using the 3 ohm coil with the GEU930MS. The white dot usually just indicates the module type, not high or low energy. Using a 1.5 ohm coil could overload the module if it’s not designed for it. If you want extra reassurance, maybe check MiniSpares or the module datasheet to confirm compatibility.

[Ethel]

If you have a 3 ohm coil I'd certainly try that first. Worst case, you'll get weak sparks.

[68+86auto]

That looks like one I'd use a 3 ohm coil with. The dwell is most likely fixed on that one.

[Lplus]

If you do what Minispares say and it fails they can't complain you didn't follow fitting instructions.

[ACDodd]

Follow the suppliers instructions. Fixed dwell needs a 3ohm coil. A variable dwell unit will run much better with a 1.5ohm coil, but ONLY if rated for it.

Running a 3 ohm coil on variable dwell reduces the spark power at lower rpm, and therefore you actually have less power than running points!

It's the basics of this that people need to underStand if they give advice on forums.

You would have been better off to fit one of these along with a 0.8 ohm coil, 3 ohm coils have no place in any a-series nowadays,

https://www.minispar...-276-cam-profil

Ac

Edited by ACDodd, 15 December 2025 - 01:18 PM.

[gaspen]

 Fixed dwell needs a 3ohm coil. A variable dwell unit will run much better with a 1.5ohm coil, but ONLY if rated for it.

 

I totally understand this. But : this actual dizzy equipped with a PowerSpark module, see the picture

 

In PowerSpark's catalog I can't find only one module for 25D for -ve earth.  This one Powerspark Electronic Ignition Kit for Lucas 25D & DM2

 

Are these units the same or not ?

 

Additionally I've tested this dizzy on my distributor machine and it has variable dwell.

 

I accept if I have to use a 3 ohm coil but I'm confused at the moment 

 

You would have been better off to fit one of these along with a 0.8 ohm coil, 3 ohm coils have no place in any a-series nowadays,

 

I will be use this car with a C40 dynamo, capable of 22A load. The 0.8 ohm coil will charge it ~17A, sure ?

 

 

 

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Edited by gaspen, 15 December 2025 - 01:51 PM.

[gaspen]

Hi, I’d go with what MiniSpares recommends, using the 3 ohm coil with the GEU930MS. The white dot usually just indicates the module type, not high or low energy. Using a 1.5 ohm coil could overload the module if it’s not designed for it. If you want extra reassurance, maybe check MiniSpares or the module datasheet to confirm compatibility.

 

Where can I find a datasheet of this module ?

[ACDodd]

As you have now identified it's I variable dwell and powerspark, I can confirm it will run perfectly with a 1.5 ohm coil, no lower.

Ac

[gaspen]

As you have now identified it's I variable dwell and powerspark, I can confirm it will run perfectly with a 1.5 ohm coil, no lower.

Ac

 

Thank you very much AC and sorry that I did not write in the first post 

[gaspen]

One more question : where would you set the static or strobe timing for this dizzy ? My guess is static TDC / 3-4 degrees at 1000 maximum

 

Unfortunately MS won't share this information nor the theoretical curve.

 

My test shows on the black graph (blue and orange is 41026 factory data)

 

 Képernyőkép 2026-01-07 085429.jpg   21.89K   0 downloads

Edited by gaspen, 07 January 2026 - 07:57 AM.

[Lplus]

One more question : where would you set the static or strobe timing for this dizzy ? My guess is static TDC / 3-4 degrees at 1000 maximum

 

Unfortunately MS won't share this information nor the theoretical curve.

 

My test shows on the black graph (blue and orange is 41026 factory data)

 

Képernyőkép 2026-01-07 085429.jpg

Seems reasonable to provide the same level of advance at high revs, since the static timing of the 41026 was tdc.

[ACDodd]

Is your graph showing dizzy advance or crankshaft advance?

Timing is set at full advance figure, if your engine needs 28degrees to achieve max power, then time it at 28degrees at 5000rpm. The lost motion in the engine and the advance curve shape will determine where the static advance ends up.
Basically you don't time an engine at idle.

Ac

[shera12]

Stick with the 3 ohm coil MiniSpares recommends the GEU930MS is designed for it. The white dot isn’t “low energy,” and there’s no high-energy version, so you should be fine.

[gaspen]

Is your graph showing dizzy advance or crankshaft advance?

 

These are crank values. I measured it on my distributor machine and mutiplied by 2 for the graph. The engine is restored but remained a standard 850, the car is still in the paintshop but I would like to prepare myself 

 

Timing is set at full advance figure, if your engine needs 28degrees to achieve max power, then time it at 28degrees at 5000rpm. The lost motion in the engine and the advance curve shape will determine where the static advance ends up.
Basically you don't time an engine at idle.

 

I know this but I will need a basic setup for the 1st start. 

 

Theoretically : if the engine is happy with 28 d's max advance, but the dizzy produces 30 d's it should be adjusted to 2 d's static ATDC ?

 

In practice I should limit the max advance by 2 d's at least ?