Permatune CDI fried - MSD equivalent is 6AL?

[billjam]

As it says, my Permatune CDI (6 wire version) in my 930 is fried. I can get MSD units locally but supplier isn't very helpful.
I presume an MSD 6AL will do the job and looking at the wiring diagrams on MSD's website, this one seems to be the one that applies.



I haven't seen the unit yet, but it seems that I'll need to splice a few wires to hook it up ... correct?
Also, does the original tach wire go straight to the tach output terminal on the MSD?

[Bob Kontak]

I recently saw a thread where one poster linked to another thread where you can install the MSD 6AL without any splicing. I will find it an post it here.

I spliced plenty when installing mine. My six pin connector to the old Perma-tomb (which replaced the older Perma-tomb which replaced the Bosch) has one wire into it. That is it.

Make sure you are anal-retentive when fixing the ground wire. I installed the MSD under the drivers seat and ran a big fat ground wire to the transmission lug ground.

I ran the tach output direct to the tach but it did not work on my 81 SC. I had to install a tach adapter.

Summit Racing has the 6AL and Blaster coil, etc. Pelican does as well.

All told, I have had the 6AL in my car for eight years and have had zero problems.

[billjam]

Bob, I was wondering why you mounted your unit under the seat so I looked up the dimensions ... 8" x 4" x 2.25"
There's no way that will go in the back corner of my car without a lot of reorganising of what is already there.
I'm interested in the wiring info if you find it first.

[Bob Kontak]

Installing an MSD-6AL on my '83 3.0L

See link several posts in

[Bob Kontak]

My father lives in Charlotte, North Carolina. We visited Penske's NASCAR shop in nearby Mooresville. They mounted twin MSD's on the cars dashboard and they go 190 MPH. I figured a few extra feet of wire would not be a problem if they can do it.

Glad to help you out in any way.

[Perma-Tune]

Hi All,

Why not send your Perma-Tune to us for a check up, it is free. Give us a call at (631) 909-1011 for the address and instructions.

Like we always say, the coil should be replaced with the ignition box. If you did not do this, I recommend that you start with the coil. The only coil that can be used on the turbo is the factory coil. (Use GERMAN only, not the Brazilian coil!) Our coil is too long and will not fit under the intercooler.

I noticed that Bob talked about the ground wire, this is an issue on the air cooled Porsche. This being a turbo, another thing you should consider is checking the speed relay and the run on relay. It could be there is nothing wrong with your Perma-Tune, either of these relays could cause the ignition to not function.

If you do wire in the MSD, be certain that you wire in the run on and speed relays. If you follow the instructions you have posted, both of these relays would be out of the circuit. This would cause the engine to backfire through the turbo when shutting off the engine. Worse yet, if the engine goes into an over boost condition, there would be no way to shut it down. Either condition could wind up costing you big money.

Best regards,

Lonnie

[billjam]

Lonnie,
Thanks for the offer to check the unit, but I am in Australia so it's time-consuming and expensive to fly these parts around the planet.
I am reasonably confident that the unit is faulty but I'll check the relays you mentioned.

The results of my testing are in this thread on the Turbo forum.

It's good to see suppliers keeping an eye on our favourite web forums.

[billjam]

Originally Posted by Perma-Tune

Hi All,

I noticed that Bob talked about the ground wire, this is an issue on the air cooled Porsche. This being a turbo, another thing you should consider is checking the speed relay and the run on relay. It could be there is nothing wrong with your Perma-Tune, either of these relays could cause the ignition to not function.

If you do wire in the MSD, be certain that you wire in the run on and speed relays. If you follow the instructions you have posted, both of these relays would be out of the circuit. This would cause the engine to backfire through the turbo when shutting off the engine. Worse yet, if the engine goes into an over boost condition, there would be no way to shut it down. Either condition could wind up costing you big money.

Best regards,

Lonnie

I've been thinking about what you wrote here with regard to by-passing the two relays. That obviously sounds like something to be avoided!
But surely if I connect a new CDI (regardless of brand) using the original 6-pin plug, this shouldn't be an issue?

[Lorenfb]

"But surely if I connect a new CDI (regardless of brand) using the original 6-pin plug, this shouldn't be an issue?"

Yes, that's right. So what happened to the original Bosch unit which is very reliable
compared to the mentioned other units? Try and find a Bosch unit either used for
$150 - $200 or a rebuilt for $300 - $400. Then your Porsche remains stock and
not Mickey Mouse with a Chevy type engine mod. Additionally, there's no benefit
to using the MSD as some claim.

[billjam]

Loren,
Sounds like a good plan, however I don't have the original unit and a quick check on eBay didn't turn up any OE units at all.
A local Porsche workshop offered me a used unit for $1000!

At that price, I'm happy to try my luck with another PermaTune or go MSD.

[Lorenfb]

Just checked under "Porsche Bosch ignition" on eBay and there're 3 (6 pin) units for sale
that're compatible with your car for under $400 and on the 1st page.

[Perma-Tune]

Hi Bill,

Yes, as you said, using the 6 pin harness of the car to wire in the ignition box will insure that the relays are in the circuit. Just be careful to get the distributor pickup wires right or you will throw off the rotor phasing.

I looked at your other thread. The only thing I see wrong in your troubleshooting is that you assume 12 Volt power is present at the coil primary.

That is how most ordinary cars are wired. Except for the super cars that we make ignition for.

On your car, there is never 12 Volts on the coil primary, the primary is connected only to the ignition module on one end of the coil primary wire and the other end is connected to ground. The module steps up the 12 Volts to 400 Volts (Perma-Tune output) and fires this power through the coil primary to ground. This is called capacitive discharge ignition, or CD for short.

DANGER: This type of ignition can deliver a deadly blow from both coil windings so beware! Never connect a 12 Volt test light to the coil primary, it may not be designed to hold a 400 Volt discharge which would knock you across the room.

Your trouble shooting procedure is also incomplete. You did not follow up on why the Perma-Tune shows no 12 Volt power to the tachometer circuit and why the uF reading is wrong. If you ignore these two thing you may wind up burning out your next ignition box too, be it Perma-Tune, Bosch or MSD.

Here is the check for the tach circuit:
Connect your Ohm meter to pin 2 of the ignition harness connector and the other lead of your meter to ground. You should see open circuit or high resistance. If you see low resistance, unplug the signal (~) wire of the tachometer and try it again. If the resistance is high now, then the tach is shorted. If it is still low resistance, unplug the speed relay. If now the resistance is high the speed relay is shorted, if it is still low resistance, then there is a short in the wiring between the ignition box and the front of the car.

I have seen the wiring short on the turbo cars inside the tunnel at least a couple of dozen times over my 40 years with these cars. This is so difficult to repair that I just run a new wire under the car from point to point.

Here is the check for the uF reading:
Perform the ground circuit check as defined on our web site........
Perma Tune High Performance Ignition Systems
Once you are sure that the grounds and tach circuit are OK, then you can put a new box on the car and start it up. Put your Volt meter on the fuse block and on the ground in the engine compartment. Set your meter to the lowest AC Volt setting. Turn on as much electrical load as possible (high beams, wipers, radio .....) and rev the engine up to about 2200 RPM. The Volt meter should show no more than .3 Volts AC. More than that indicates a defective alternator rectifier.

I think you will get a much better price on a new Perma-Tune from Zims than what you find on the internet and they ship worldwide:
1-800-356-2964
Zim's Autotechnik

Best regards,

Lonnie

P.S. There is a reason that there are two MSD boxes mounted inside the cockpit of all NASCAR race cars. (hint: they are not dual plug engines) This is so that when one fails, the driver can switch to the backup.

[billjam]

Lonnie,
Thanks for your input, I'm sure others will find it useful as well.
I am traveling this week but will carry out all your suggested checks when I get back home on the weekend.