Having solved the poor running issue I now have points back in the dissy.
I have noticed a slight loss in ppwer and general respones and driveabilith. It is not much but it feels slightly slugvish compared to the EIM when it was working properly.

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Cheers Dave.

Have you got the dwell/points gap set correctly? Did you reset the base timing?

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Yes. I went through the whole gamut of tuning the ignition and fuel m8xture.

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Cheers Dave.

What condition is the distributor in? a worn bush, shaft or cam will cause dwell variation and timing scatter which wont be present with the electronic module. It could also be worth checking the voltage drop across the points.

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1986 Mayfair (998 auto), 1974 S, 1974 Van, 1972 PMG Van

Too many minis

Does anyone know specifically how the powerspark module changes and controls the dwell and how it improves the performance of the ignition?

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Cheers Dave.

I would guess it has a pre determined dwell curve vs rpm. At lower RPM you need less dwell angle to fully charge the coil, then as RPM rises the dwell angle needs to increase (as the time between firings decreases)

Points by their design have a fixed dwell angle based on the points gap and the shape of the lobe.

If you have a dwell function on a timing light or multimeter you would be able to check the dwell

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I didn't think that these cheap modules changed the dwell at all, I thought they were just fixed.

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1986 Mayfair (998 auto), 1974 S, 1974 Van, 1972 PMG Van

Too many minis

From the powerspark website:

https://simonbbc.com/Powerspark-Electro ... tor-K4--R2

They also make a "high energy" version which is able to run a 1.5 ohm coil

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Thanks Guys
So we can assume that it does not vary the dwell. It maintains the dwell at a set time thus maximising coil saturation current. Unlike points where the coil saturation changes as the points operation speeds up.

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Cheers Dave.

I assume your first sentence means dwell time not dwell angle.

So it is sounding like the powerspark module may change the dwell angle depending on the rpm. I suspect the timing curve may be a bit different with it varying the dwell unless it is predicting when it needs to fire.

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1986 Mayfair (998 auto), 1974 S, 1974 Van, 1972 PMG Van

Too many minis

From this post here he suggested that the dwell needed to charge a GT40 coil is 7ms (and 80% charge takes 5ms).
viewtopic.php?p=941745#p941745

Doing some maths means that you only need 20degrees at 1000rpm to get a fully charged coil.
As the RPM rises you get to a theoretical peak of 90 degrees at approx 4200RPM
However at 90 degrees dwell that's 100% duty cycle for the coil and it would probably overheat
My programmable box suggests a max of 75 degrees dwell - I'm not sure what other systems can cope with
Once the unit reaches peak angle it won't be able to provide enough dwell time to maximise the coil.
Changing to a ballast system can improve the high RPM spark energy, or changing to a high energy module and lower ohm coil.

The powerspark unit would hopefully be able to measure the RPM, calculate the dwell based on the RPM and adjust the dwell while maintaining the spark timing the same

I have thought way too much about dwell time in the last 12 months

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Can you explain what "dwell angle" means.... in the context of a non points ignition?

Cheers, Ian

It’s simply the time the coil is charging as measured in distributor rotation angle (as the angle is the most common way of measuring dwell on a distributor based ignition system. You should be able to measure the dwell angle of an electronic module using a timing light)

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Exactly, my comment was prompted by this statement "I assume your first sentence means dwell time not dwell angle." as I couldn't see the relevance to discussion of EIs... and always happy to learn something new...

Thanks, Ian

My comment was because if it meant angle which is usually what dwell refers to then the other parts of the comment were the wrong way round.

It has already been said but here is a slightly different explanation. The dwell angle is the number of degrees per cylinder that the points are closed/coil charging in one rotation of the distributor. Electronic ignitions work the same way.

The time which this takes depends on both the dwell angle and the RPM. The coil needs around the same amount of time to saturate throughout the rpm range however this occurs in a different amount of time depending on the rpm.

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1986 Mayfair (998 auto), 1974 S, 1974 Van, 1972 PMG Van

Too many minis