jimculp

We're not getting spark on cyl #1 and we're running out of ideas.

jimculp

Let me explain my problem a little further.

I'm running an Autronic SM4 ECU with twin CDI ignition boxes firing two plugs per cylinder. We're using a Multiplexer which allows the 4 ignition ouputs of the ECU to fire the 12 plugs.

The motor runs really well on only 5 cylinders, unfortunately it will not fire on cylinder #1. We've checked the wiring half a dozen times. We've switched our the coil and that doesn't affect anything. We have shipped back the ECU and CDI's and they check out fine. The Autronic supplier is stumped, and we're stumped. Any suggestions would be appreciated.

125shifter

Can you sketch out the wiring, I'm not seeing it. What CDI & coils?

jimculp

The ECU has 4 outputs that go to two 500R Autronic CDI boxes through the multiplexer.

I don't know exactly what kind of double ended coils they are- could be Autronic- they came with the "kit". I'm trying to scan the wiring diagram now.

jimculp

Here's the pin diagram- don't know if this helps matters? Still trying to get a hold of the wiring diagram.

Geoffrey

Why do you need the multiplexor? Since the R500 accepts low level inputs, you wire the three ignition outputs of the SM4 to 3 of the four inputs of the R500. Since you have 2 R500s, the each ECU ignition output is split, one to each R500. The double ended coils sould fire IGN 1 - 1&4, IGN 2 - 3&6, and IGN 3 - 2&5. The remaning R500 ignition is simply not use and if I recall correctly, it needs to be grounded or something like that. Since you have dual plugs, the setup is mirrored on the other R500. The R500 is a very old CDI system and there are other better alternatives.

I can't really tell for sure, but it sounds like you are trying to use a wasted spark system to fire the system sequentially and you cannot do that with a wasted spark system. You cannot run the top and bottom plug off the same wasted spark coil and expect it to perform properly, with enough ignition engergy and system reliability.

If you want to run your ignition system sequentially, you need an ECU with 6 ignition outputs like a MoTeC M600 and direct coil per plug or coil on plug systems.

I also seem to recall that the Autronic ignition system is wired one cylinder behind, but since the Autronic documentation is so poor, you may have missed that.

jimculp

After everything was wired we found out that we only needed one CDI unless we wanted sequential ignition as Ray Hall says. The dealer Speed lab suggested this setup, so we went with it.

But since everything is in place and wired (seemingly overly complex), we would like to get it running as is. Do you think the multiplexer could be the issue Geoffrey? Thanks for the tip though- we might re-wire your way.

Geoffrey

I have no idea since the system is wired incorrectly in the first place. Save yourself pain and use the technology as it was designed.

jimculp

Are you referring to no multiplexer, or just one CDI?

Geoffrey

I was referring to wiring them wasted spark rather than sequential. The "Right" way would be no multiplexor and two CDI Controllers, however, I know it will work with just a single CDI controller. This would be wasted spark, not sequential.

jimculp

Thanks Geoffrey.

125shifter

For reference: My M600 ECU sends three ignition signals to three of the four inputs on an M&W Pro-14 four channel CDI. Then three CDI outputs go to the coils where each output is split into two to drive a pair of wasted spark coils. So three signals go to 12 spark plugs.

jimculp

Thanks 125.

So each coil is pushing 4 plugs? My Autronic rep didn't feel comfortable with each coil doing that b/c he felt that with forced induction it would be dividing the coils power too much if that makes sense. That's why he was pushing for the two CDI's following a Multiplexer.

My guy at Speed Lab never considered a setup like Geoffrey is suggesting, so he is now working on a pin diagram for that type of setup.

jimculp

Do you mind taking a look at this revised pin diagram?

Before we so the re-wire, I'd appreciate a second set of eyes to see if it looks right.

125shifter

I couldn't find the SM4 diagram on their site. Are you firing in the 1,3,2 order as far as the 3 outputs go? Are you using 12 single coils or 6 waste spark?