Twinspark - 964/993 & Motronic

[911hillclimber]

I'm sure I have read that anything over 100mm bore needs twin plugs to get the best from it all, piston head shape, bore diameter and injection point.
All of this added complexity was one of the reasons I decided to stick at 3.2 for my race Lola Porsche.
The cost did not seem to deliver an effective engine improvement in power or torque.

[hot66]

I’m running the clewett crank fire twin plug system. It’s a great set up and affordable, but obviously doesn’t look period. Ive got comp ratio of around 10.3 from memory,

[fetuhoe]

How about one of these ? Single input with 2 coils as output.

£35.00 each - may be worth a try?

[smallspeed]

Do they fire both at once (effectively wasted spark)?
Might be a useful thing however on a 6cyl engine there might not be much dwell time at higher rpm..

[fetuhoe]

Yes they fire together and I would agree that there may be some issues at very high revs but I think that should be good for 8K.

Must be worth a go at £35.00

[smallspeed]

Do you have a link? Sounds like a useful thing

[Jonny Hart]

Calling Jonny of Classic Retrofit, come in, come in...…………..You can run, but you can't hide....the people want splitters.....

I hear ya but won't be 'til Autumn. I have a plan though...

[DustyM]

Do they fire both at once (effectively wasted spark)?
Might be a useful thing however on a 6cyl engine there might not be much dwell time at higher rpm..

Why wasted Spark? Surely on a twin plug engine you would use one per cylinder, firing both plugs together on each cyl or am I missing something?

[Bruce M]

On a single plug engine they would be wired to a pair of opposite cylinders, firing simultaneously & the one on its exhaust stroke would “waste” the spark. In the twin plug situation both sparks are being used for the same cylinder but it’s exactly the same operation for the coil, one trigger and two sparks.

[Jonny Hart]

That is most likely a wasted spark coil (like a 2CV). If you use it to fire two plugs on the compression stroke you'll get half the energy. Not good.

Wasted spark gets away with it since firing the cylinder on the exhaust stroke requires less energy although it still reduces the compression cylinder spark energy by around a quarter.

[Magnum]

Hi Jonny

For me this is a medium term project - I've just started assembling the components so that timing should work out.

It strikes me that a known, quality "splitter" is missing in the market - there are literally dozens & dozens of threads on Pelican, Rennlist etc. looking for a replacement product for the Andial splitter (which is obviously NLA now that they're gone). I'm not sure whether technology in the last 10-odd years since Andial went has obviated this splitter, but there is certainly no well known or obvious alternative based on the threads.

With your growing brand (focused on innovative quality products on the electrical side of 911 ownership) I think this may fit well?

Cheers

[Jonny Hart]

It is definitely on the cards. I’ve reverse engineered the original Andial
Splitter but I’m afraid that it does not meet the most basic electronics standards.

I’m astounded that such a naive circuit was ever allowed near a car or could be considered for motorsport applications and it doesn’t surprise me that they did not last long.

Shame as it means that a copycat circuit is a non starter. It needs further thought, design and of course testing.