New CDI conversion observations
 

I just finished converting my wasted spark EFI car to a sequential CDI spark. The conversion was easy as I only had to run three more channels (already had three for the wasted spark) to the CDI and reverse wire the Bosch coil packs. The CDI is a six channel M&W model. The coil packs are dual post, three-coil packs to give me 12 plugs. The dual posts for each coil takes care of the upper and lower plug for each cylinder.

A cool feature to the ECU I use allows me to test each ignition channel so I can confirm each cylinder is getting a spark. When finished confirming power to each cylinder, all that was left to do was to set the timing in the ECU for full sequential injection and ignition. I also re-gapped the plugs from .025 to .032. When the timing was set and locked, the car fired right up. I had to run the motor for 20 min at 2000 rpm to run-in the new cams (Performance Developments improved GTII). After that was done, I confirmed the timing was set and went for a ride.

Wholly crap.

First gear used to be a blur - its now a faster blur. Second gear pulls as hard and nearly as quick as first. It never did this before. Granted, this is also a function of the cam, but wholly crap. Not paying too much attention, I came to a stop sign to turn right and left it in second as I made the rolling turn. I hit the throttle and the tires actually broke loose! In second.... From there, I had a ***** eatin' grin for the rest of the drive. Of course, someone pulled out in front of me in a ricer (not dangerous) about a mile from my house, and all I did was press the pedal and I felt the smoothest scary acceleration I've felt in a long time. By the time I got back in my lane the Honda was a speck in my mirror. Very cool.

I have some fine tuning to do now that it seems to be running OK. The AFR's are very lean now - for example, idle was ~14.5 but now its closer to 16.5. Cruise was ~13.8 and now its almost 15. In general, the AFR's are much leaner than before. The idle is now dead solid. No random spikes or movement of RPMs and its smooth. Once set, it just sits there smooth and quiet. Neil Harvey said I should open the gaps to .035 and see how it goes.

All in all, I have to say I am really impressed with the transformation. The car feels completely different in the way that it starts, idles and accelerates. This is something I would HIGHLY recommend to anyone considering an EFI conversion or someone who has an EFI wasted spark system.

Great write up. You can never have too much power!

Damn it!!! Something else to spend money on!!! So, It was that noticable?? Should I do it before getting the car running, since I still have a bit to go?? ( a couple of months).....

Interesting!

I've been contemplating replacing my 4 channel M&W CDI with the new 6 channel M&W, but I hadn't considered using each twin lead coil for its own cylinder. What's the advantage of doing this over waste spark? My non-electrical background thinking is that two coils split over two cylinders would have more spark than one coil on one cylinder since the the waste spark cylinder would be a weak spark.

Ok, I'll bite.

What ECU are you using?

What is the model number of the M&W CDI unit?

What Bosch coil packs are you using?

Great work and thanks.

Jim
1980 930
1995 993

Yes, its that noticable. Make the change before finishing the car.

Don- post up some pictures of the beast

There is a reason why many F1 teams use CDI. It gives short but mighty powerful spark. AFR is probably off the whack due to new cams which changed VE table, so you might need new tuning session (or at least do some open-road AFR adjustments).

I'm glad to hear that engine is getting even better. You had impressive setup even before.

I use a LINK G2 ECU, able to fire up to 8 ignition and fuel injection channels to 15,000 rpm.

The M&W unit is the Pro16B-S3. It only needs 6 ignition inputs, 12v power, 12v switched power, ground, 6 coil outputs, coil grounds and shielding. It can supply the tach and can run off a separate trigger.

The coils are Bosch 3x2, part number 0 221 503 002.

Rgds

Now that I am a believer, I am told its the spark energy (heat) that beats inductive or wasted spark. Now I have 115mj of spark energy at each plug rather than 65mj over 2 plugs (wasted spark). I can also use a rare earth metal (iridium) plug that can (NGK BR9EIS) to take advantage of the extra spark power and larger gap. I also fire each coil every other cycle, giving each coil pack one cycle to recover. In other words, coil pack 1 fires cylinder 1, coil pack 2 fires cylinder 6 then coil pack 1 fires plug 2 and so on.

Starts are quicker and I gained throttle response. Very cool
Rgds

To clarify, you had six dual post coils in your previous configuration... waste spark..

Now you are using those same six coils with CD sequential ignition?

Here is a shot of the engine compartment. The CDI is mounted on the firewall, about 12 inches back and out of the elements, at the upper left of the engine compartment.


http://forums.pelicanparts.com/uploa...1242873422.jpg

Here is a pic of the coil packs mounted in the car. These are the same coil packs I used with the wasted spark, except I had to reverse the wiring. In wasted spark, a 12v source was provided to a common bus in the coil pack and each coil was fired by grounding it's pin. With the CDI, I grounded the common bus and fire each coil with the output from the CDI to the individual pin.


http://forums.pelicanparts.com/uploa...1242876010.jpg

Cool stuff. Thanks for the update and the component info.

Jim

One more comment.

In first gear, boost comes in nearly 300 rpm faster. In second gear, boost comes in nearly 500 rpm quicker. The cams and the CDI combo are pretty impressive.

That looks awsome, are the coil packs/system hard to wire up?

Wiring is straight-forward. Draw a diagram from the ECU to the CDI to the coils to the plugs and follow your map.

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.

This is my thinking too, but I barely passed the two electrical engineering classes I was required to take and I don't understand electrical systems very well.

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.