New CDI conversion observations

[DonE]

Originally Posted by sjf911

Wouldn't it still be better to run this in a wasted spark mode? You are in effect splitting the 115 mJ between two plugs firing under load whereas under wasted spark, only one plug fires under load and the other "wastes" but uses little of the energy.

In the wasted spark config, 65mj is split between two different cylinders, one on compression and one on exhaust stroke. Under compression, lighting a fuel mixture is more difficult, so the cylinder without compression gets more energy (path of least resistance). To counter this, you must use wires and plugs that are resistor types - thereby reducing energy even more, but ensuring an even spark as much as possible.

Using CDI, I am using all 115mj of energy in one cylinder. That's nearly twice the energy in each cylinder, IF you assume all the wasted spark energy is going into one cylinder - but it's not - it's shared between two.

One more thing. I can gap my plugs out to .032 and use Iridium - its a big hot spark. With wasted spark, the maximum gap was .024 before it misfired.

The Link ECU has an ignition test function where you can test each channel - just pull a plug, turn the car on and test the channel. With the wasted spark, the plugs would sizzle with each test fire. Pull a plug using CDI and test the channel, you'll get a sharp crack you can easily hear in the cockpit.

I always wanted a G50/50 tranny for this car because 4 gears doesn't do well on technical tracks. Now I want to hit a track with the new spark (and presumed increase in torque) and see if it made as big a difference as I feel on the street.

I hope to dyno this config in a couple of weeks. I just found out that a local shop in Peachtree City has a dyno. Unfortunately its a dynojet but it should give me a reference point.

[DonE]

Originally Posted by vmisquez

Thanks for Sharing Don. I'd prefer to run two Pro16B-S3 wired in parallel and use 12 CNP modules. I do not know if my Autronic SM4 will support this setup up though, I need to check.

You seem satisfied with the energy delivered by this setup and I may concider your setup as a possible solution but I do like the clean install and short wires of CNP

I'm also using twin plug, 76.6 mm stroke crank and 98 mm pistons. I plan on using an IA 993 GT2 EVO grind 563/564 beacuse I already purchased them sigh...

I know the newer grinds deliver more linear power. I just want to get this car back on the road.

thanks again for sharing and I alway look foward to reading your posts.

Neil and I talked about running a parallel system too, but I didn't want to spend an additional $850 for another CDI unit. We were going to split the ECU channels and since the CDI just needs a small 5v trigger signal, it was possible. I would bet your system could do the same. With the parallel system, we would have been looking at nearly 250mj of energy per cylinder using the M&W unit. Let us know how it works out.

[David]

Don, thanks for the explanation.

Now I just need to figure out how to get the extra three ignition signals from my ECU to the engine since I've already used all 47 pins on the bulkhead connector. I guess I'll have to give up on my dream of having NOS injection

[WERK I]

Don,
Is the M&W 6 channel CDI system a multi-spark at lower revs like other CDI systems?
Thanks,

[David]

I don't believe any of the M&W CDI's are multi spark. They are of such high quality and power that I don't think it would add much over what it already does.

I just wish they had a 6 channel available when I built my engine. Unfortunately they didn't so I'm running a 4 channel M&W with 3 channels split to make 6.

Even if someone is still using a distributer, I recommend using a single channel M&W CDI vs other options if they don't mind the additional cost over Bosch, Permatune, or MSD. I think a single channel M&W CDI is about $600 but you can make a harness to connect the M&W straight into the 6 pin connector on the stock Porsche harness.

[DonE]

Originally Posted by WERK-I

Don,
Is the M&W 6 channel CDI system a multi-spark at lower revs like other CDI systems?
Thanks,

No, its a single spark.

[TimT]

Don,

Before this conversion your car was batch fire/waste spark?

The reason I ask is when I was setting up the LinkPlus Gen 1 EFI on my car six or seven years ago.. I was tempted to go the CDI or COP route but getting the car on track won over any more development...

Did you change the trigger that you are using? did you add a CAS (cam angle sensor) to define sync and home events?

I looked at the schematics for the M&W Pro 16 S3 and it appears you only need 3 ignition channels to fire the coils...Sounds like since you are still using the 2 output coils it is still waste spark not true sequential? or am I missing something?

I think I'm going to call Neil tomorrow and order one of these..

[DonE]

Originally Posted by TimT

Don,

Before this conversion your car was batch fire/waste spark?

It was wasted spark using 2 three channel ignitors to the same coils.

Did you change the trigger that you are using? did you add a CAS (cam angle sensor) to define sync and home events?

I am using the same triggers - one for the crank and the other for the cam position. Both are Honeywell hall effect sensors. It's pretty easy to determine the angle and set the offset.

I looked at the schematics for the M&W Pro 16 S3 and it appears you only need 3 ignition channels to fire the coils...Sounds like since you are still using the 2 output coils it is still waste spark not true sequential? or am I missing something?

I think I'm going to call Neil tomorrow and order one of these..

In wasted spark, you only need three channels. For sequential, you need all six. I am using two 3x2 coil packs which gives me 6 coils with dual outputs (12 plug wires). Each coil fires the upper and lower plugs. If I could afford another CDI, I would run them parallel and power 12 individual high output coils. That would cost another $1400+.

[m42racer]

Just caught this thread. It's been awhile, but I has two of the single CDI units on my 930. The difference was huge. Before I had Electromotive on the car. Although back then there was not so many choices, the M&W system made the car come alive. For quite sometime i thought the car was as good as it could be. I soon found out just how much performnace I was losing.

I have not had the need for the multi channel units, but if they are as good as the single units, you made a great choice.

Someone posted if they have multi spark. The single unit did I know for sure. It was wired so it gave the multi spark on starting and idle and as soon as the boost came in it when to high power, which doubled the output. I cannot remember exactly how it was wired to do this, but thro EFI systems, switching is easy. Even on CIS engines without EFI, I think a simple boost switch would work.

Don, I would love to know how the car feels under acceleration and how the throttle response is compared to before. That was my biggest gain. Compared to how the CDI made the car respond, the Electromotive seemed really lazy and soft and mushy. You have stated its better, but can you quantify how myuch better yours is. In my case I would say it was greater than 50% better. It made a new car out of mine.

Have a great drive.

[DonE]

I spent most of the morning driving the car and fine tuning the fuel maps. A couple of very noticeable things:

Idle - what a huge difference. Using the same map, the idle is now nailed. I mean, the idle doesn't move more than a couple rpm and the engine is dead solid. Its now a toss-up between my Acura and the 930 on which idles smoother.

Another big improvement is throttle response, and I don't mean just off idle. While adjusting the fuel table today, I had to pass a car was slowing me down. So, while behind them I noticed the TPS showing 7.5% at 50mph in 3rd gear. I pressed the pedal slightly and the car just flat pulled - I looked at the TPS and it showed 15%. It was pulling as if I had pressed the throttle halfway to the floor. Very very cool.

And the biggest improvement is something that is the hardest to explain. In fact, I called Neil today on his cell phone just to talk about it. When I get into boost and the car takes off, it is the smoothest acceleration I've ever felt in this car. I've driven a lot of newer P-cars at the track and always liked how smooth they were. Prior to the change, I would explain the acceleration as contained violence - raw power. Now, the power is so smooth and refined. Under WOT now, the power is deceiving - I used to gauge the power/speed by the feeling of the car. Can't do that now. I looked down on a WOT pull for a data log and wholly crap - 120. Did not feel that one coming.

Anyway, the car is very different and I am really enjoying it all over again.

[m42racer]

Way cool.

[m42racer]

Hey Don,

Your comments about how smooth the car is, tells me you have done a good job in the mapping. Great job. And how good the EFI system you have is.

[SCHNELE]

I wish we could get Geoffrey in on this discussion, FYI I used to run the M&W setup but I now use the DENSO coil near plug setup from motec and the ECU controls the spark which allows for a little over boosting while still operating safely.

[m42racer]

SCHNELE,

Are the Denso Coils the CDI type or do they have Igniters built in?

[SCHNELE]

The igniters are built in.

[TurboKraft]

DonE,
I completely agree with your evaluation. We use the same coils and M&W CDIs, and they work extremely well. We think they are the best CDIs made and now use them exclusively.
Looking forward to your dynos. Hope you can keep traction on that Dynojet with that monster!