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Wasted spark for 944
https://forums.tipec.net/viewtopic.php?f=25&t=10513		 Page 1 of 1
Author:  barks944 [ Wed Feb 23, 2011 10:21 am ]
Post subject:  Wasted spark for 944
I am implementing a wasted spark ignition system for the 944 and I am looking at options for what the best way to achieve this would be. The DME will have a dedicated ouput for each channel of wasted spark. This will be a 5V/Gnd digital output or could even be a12V/GND digital output. These outputs wont have significant current carrying capacity so wont be able to drive a coil directly. There are a multitude of ways that this could be implemented. One that looks ok is:

Combined amplifier coil pack e.g: http://www.efi-parts.co.uk/index.php?productID=121

But it doesn't look like a particularily high quailty bit of kit. There must be plenty of OEM systems that could do something similar. Ive also looked at Coil On Plug but I read some of the nissan boys have a lot of trouble with them due to the heat issues. Any suggestions on good options in terms of conceptual design or for appropriate bits of hardware would be appreciated.

Cheers

Tom
Author:  DaveM [ Wed Feb 23, 2011 12:53 pm ]
Post subject:  Re: Wasted spark for 944
That one has BERU on it so I would think it would be pretty good. If not there's a few out there but I think the Bosch ones from a ford could be a good option. The amplifiers are seperate though.

http://www.mattlewismotorsportonline.co ... ductid=152

I would also think that a modern coil on plug would be reliable, if you can convert an OEM system. The ones that first started appeared on engines about 10-15 years ago did start to break down after about 5 years but I believe the modern ones are very reliable. You could also get seperate units for each plug so if one did go, you'd only need to relpace one and not all 4.
Author:  barks944 [ Wed Feb 23, 2011 2:06 pm ]
Post subject:  Re: Wasted spark for 944
Thanks for that, I might give that Beru one a go then. Not much too loose at £45.
Author:  DaveM [ Thu Feb 24, 2011 12:18 pm ]
Post subject:  Re: Wasted spark for 944
And another £10 for the 4 pin plug!
Author:  JW590 [ Thu Feb 24, 2011 8:07 pm ]
Post subject:  Re: Wasted spark for 944
I didn't even know what it meant, so I read it up on the internet, however I still don't understand the purpose of it.

Can somebody explain it in lay-man's terms? What does it do and what's the benefit?

Not too technical please.
Author:  DaveM [ Thu Feb 24, 2011 9:17 pm ]
Post subject:  Re: Wasted spark for 944
I think the advantage is not the second wasted spark but that it gets rid of the rotor arm and dissy cap. As the name suggests the spark in the cylinder on it's exhaust stroke is a waste. However if you get rid of the cap you get rid of the small gap to the rotor arm and several connections in the ignition path, you get a stronger spark. It is also alot easier to control exactly when the plug is fired with an aftermarket (or home made) ECU.

I think the the better system technically is seperate coils for each plug but this is more expensive as it needs a more complex controller and obviously twice as many coils, but it gives the coils longer to recover between each spark so gives you a stronger spark again, especially at high revs.

Now don't take that as gospel but that's how I understand it.
Author:  djaychela [ Thu Feb 24, 2011 10:11 pm ]
Post subject:  Re: Wasted spark for 944
That's pretty much it, Dave. Plus better reliability due to the lack of rotor arm/cap, as well as stronger initial spark.
Author:  Brett928S2 [ Fri Feb 25, 2011 12:31 am ]
Post subject:  Re: Wasted spark for 944
Hi :)

To be honest this sort of thing makes me laugh...

To get petrol to burn, you NEED a spark....

Now engines are not fussy about what sort of spark generally, and Porsche did a very good job of getting that spark into the cylinders at the correct time...

For a normal engine thats more than perfectly adequate...you can spend hundreds of pounds fitting any fancy system you like but all you will get is a spark in the right place at the right time (hopefully) ..NO power increase at all, NO more economy at all...

Even for someone like me that does weird things in the cylinders with my Nitrous, including changing the combustion temperatures and timing at various points, I use the standard spark created by the normal 928 twin dizzies and coils , nothing special...apart from running 2 heat ranges colder (BP8ES rather than BP6ES)

The only reason I run different heat range plugs is to ensure that I get a NORMAL spark at the strange temperatures that Nitrous causes.....not a better spark, not a stronger spark, just a normal one....

Modern engines that were designed for waste spark systems are totally different from ours and are a different generation of engine...these new engines will fairly easily do 40 to 50 to the gallon.... and take my word no matter what you do to the spark in your 80s or 90s Porsche engine, that just aint happening...not ever :)

All the best Brett :)
Author:  DaveM [ Fri Feb 25, 2011 12:40 pm ]
Post subject:  Re: Wasted spark for 944
I think for the most part you're right Brett, but I believe it does make a difference on highly modified turbo charged cars. Again please excuse me if I get this wrong as my understanding comes from reading suppliers websites and forums. The more boost you have the more fuel you have to dump in to avoid detonation. There comes a point, usually at high revs, were there is so much fuel that it effectively starts to drown the spark and you have to start reducing the spark plug gap to maintain it. The wasted spark coils tend to be alot more powerful than normal coils and the ignition system doesn't have as many loses. Running Nitrous is a bit different as you are replacing the air with something more combustable and the extra fuel isn't enough to drown the spark.
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