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944 Wasted Spark Installation

barks944

New member
I have just installed a VW Audi wasted spark coil pack system to my 944 Lux to replace the coil and distributor. Will in future fit a more advanced type of ignition system like coil near or coil on plug but this was a simple place to start. This uses a modified version of the standard DME which among other things has extra outputs for wasted spark. Just a quick video to show the installation and the engine up and running. I've just driven it home and it feels very good, nice and smooth :).

http://www.youtube.com/watch?v=P4_y33HC6cE&feature=youtube_gdata

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Barks,

would you be kind enough to:

- refresh my understanding of "wasted spark"

- and also the benefits - especially in a 951 application.

keep up the good work

thx
George

944t
 
Wasted spark is a term for firing the spark plugs in pairs on a 4 cylinder (maybe others too) engine. With a 4 cylinder each pair (1,4 and 2,3) of cylinders shares its compression and exhaust stroke. So what you can do is have two coils each which generate a spark on one pair of plugs. One of these sparks occurs during the exhaust stroke and one in the compression stroke its respective pair of cylinders. Hence one spark is wasted during the exhaust stroke. The benefit is you can ditch the distributor. You just need outputs to drive two coils which the 944's DME does not have by default. Once you have these outputs you can fit any modern ignition system which can give a much stronger spark than the coil/dizzy setup of the 944 which we were previously stuck with. This means a better burn of the fuel air mixture.
 
You just need outputs to drive two coils which the 944's DME does not have by default.

I have wondered why Porsche didn't use newer Motronic versions on these cars. 8V models use practically first generation Motronic system. 16V ones have more advanced system, with 60-2 triggering. All models have dizzy, which is odd. Take for example time period BMW E30 318IS with 16V engine. It has coil pack and no dizzy at all. Wonder why Porsche didn't choose that setup.
What i am looking for is a COP solution, should be quite straightforward to do after coil back.... Tom, how about that?
 
Sure, only thing to note is that the dme outputs are low current so you need amplifiers. They are cheap. This coil pack has them built in.
 

ORIGINAL: os951

I have wondered why Porsche didn't use newer Motronic versions on these cars. 8V models use practically first generation Motronic system. 16V ones have more advanced system, with 60-2 triggering. All models have dizzy, which is odd. Take for example time period BMW E30 318IS with 16V engine. It has coil pack and no dizzy at all. Wonder why Porsche didn't choose that setup.

They certainly seemed to want to make it hard to tune. You have this nice 8v head then they use a cam, throttle, AFM and intake that all is about at its flow limit at just a bit above stock HP. Then the dme is hard to tune and the AFM is junk and the ignition system is old skool. Yet the bottom end and drive train is good for a million hp. Supercharger 4tw :).
 

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