Twin Plug 3.2 Motor?

[911TT33]

Hi all,

Is there a HOWTO on wiring two MSD 6AL's for a twin plug setup for the 3.2 Carrera motor which uses the BOSCH Motronic DME?

Can the trigger signal from the Motronic unit be wired to the two MSD units in parallel, or do I need to also buy an Andial Signal Splitter device?

Thanks for your advice.

[Jeff Alton]

You need a splitter, either one home made or the Andial unit.

If you search there was thread a couple of years ago where a fellow built his own splitter.

Cheers

[911TT33]

Hmmm... may as well get a M&W Pro14R ignition unit which takes the Motronic trigger signal and drives two ignition coils. It's got a wiring diagram for a 964/993 twin distributor setup.

Neater than installing a splitter + dual MSD's + dual coils

[Jeff Alton]

I am not familiar with that particular M&W part, but they do make excellent products!

[JP911]

Curious why you would want to use the MSDs AND the Motronic for ignition? Not even sure it's possible.

[911TT33]

Originally Posted by JP911

Curious why you would want to use the MSDs AND the Motronic for ignition? Not even sure it's possible.

The Motronic DME triggers the aftermarket ignition system (MSD/Crane/M&W), which then fires aftermarket MSD/Crane coils.

I need the hotter spark because my motor is turbocharged and the OEM ignition system just isn't hot/strong enough under heavy load.

[jcc911]

I need the hotter spark because my motor is turbocharged and the OEM ignition system just isn't hot/strong enough under heavy load.

I have been Following this thread as I am interested in the same thing. How were able to determine this? As I may have the same issue.

Thanks

[911TT33]

jcc911, if you are experiencing engine hesitation under boost and you have ruled out any vacuum leaks, then it's most likely ignition (e.g. the spark being blown out under load) and you need a stronger spark. This is a very common problem with aftermarket turbo conversions depending on what boost levels you run.

[jcc911]

No, no hesitation. Only lag. Running a 7200 with 993 HEs so I should, in theory, spool quick but that is not the case. Some have said it is ignition related, so I thought maybe I was blowing out the spark but I am only running 0.5 bar.
Thanks.

[JP911]

Originally Posted by 911TT33

The Motronic DME triggers the aftermarket ignition system (MSD/Crane/M&W), which then fires aftermarket MSD/Crane coils.

I need the hotter spark because my motor is turbocharged and the OEM ignition system just isn't hot/strong enough under heavy load.

Very interesting. Thanks for the explanation. I've seen twin plug setups for CDI ignition and for Motronic, but never the two combined. Certainly seems to make sense given the need for hotter spark. Good luck!

[Brando]

911TT33, I have the wiring diagram for MOTRONIC with MSD systems in my profile. You only need 1 MSD box but 2 coils (one for each distributor). Run a splitter from the Small Orange wire and Small Black wire to the Yellow & Black of each coil.

[Jeff Alton]

I have not seen that diagram or application before, not alll togeher suprising.....

Have you run that or has anyone??

[Brando]

Jeff,
I made that because others had asked me how to do it. I also thought about sending it to Mallory to include just for us 80's Motronic cars (BMWs and others have Bosch Motronic). I followed that same setup for my 3.2 Carrera. Been almost a year, no issues, runs strong.

[911TT33]

Thanks for the info, Brando. I heard that firing two coils in parallel from the single MSD isn't recommended as the resulting spark energy will be halved.

The general consensus is to run two MSD's and one coil per MSD for maximum spark energy

So, I *think* the recommended way is:

Motronic => ANDIAL Splitter => Two MSD 6AL's => Two MSD Coils => Twin Distributor

Can someone please confirm?

The M&W Pro14R ignition unit apparently replaces the Andial Splitter and two MSD's like this:

Motronic => M&W Pro14R => Two MSD Coils = Twin Distributor

Seems like the M&W solution offers a neater solution.

[Brando]

Mallory (Not the company named MSD) supports the idea that you can run efficiently 2 coils without loss. With their coil (P/N 3440) you will not see diminished spark. The Mallory Hyfire VIA/L MSD system is an all-digital, micro-processor controlled unit. I've run one box on single-plug and twin-plug setups before with no loss.

[BURN-BROS]

You can run one analog MSD with two coils with no problems, but I am not sure about the digital 6AL. Has anyone tried it yet?

[LJ851]

Why couldn't you just use a twin tower coil triggered by motronic or a single MSD ?

Rotary engines use these and have large spark requirements and many sparks per revolution. (Stout Coil !)

Am i missing something?