Which Permatune Box model is this?

[Schulisco]

Hi all.

I purchased this used Permatune 3rd gen 6pin box (from 1989-2004) as a replacement for my broken Permatune 4th gen (potted black box) of my 1981 SC w. 930/16. But it seems that it is not appropriate for the SC.
The type shield says "model GS" ant not "911SC". I guess this is a version for early 911s from 1972-1977 and others like 914 with breaker points (and not the inductive pickup of the 911SC). It's got a 8pin connector with 6pins brought out.
Can't find any further information about the model "GS" and what it does stand for? On the permatune web site they're talking only sth from 911EOS (911E old style). Can anybody confirm this or provide more information?





Thanks, Thomas

[ischmitz]

Without knowing anything about the permatune box you have I am just throwing this out here:

Early 930 Turbos came with Bosch 8-pin CDI boxes - similar to what was used on the 935 where the 8-pin Bosch CDI also had an adjustable rev limiter that cut out fuel and operated a buzzer. Internally the DC/DC converters are very different between the 6-pin and 8-pin versions but they use the same inductive pickup input. And you can run a 6-pin or an 8-pin Bosch CDI on the 930 Turbo or on an SC. They are interchangeable as long as you provide the correct connections to the boxes.

If your box isn't potted internally I'd check if its pinout matches the Bosch 8-pin CDI box for a 930 Turbo. In your picture pin 5 and 6 are missing and these were only used on the 935 Bosch CDI boxes for the buzzer and magnetic fuel shutoff valve. They are not connected in the 930 Turbo version. So the correct 6 pins are on the front connector.

[Schulisco]

Thanks ischmitz. My 3rd gen box isn't potted. I guess the 3rd gen boxes weren't potted at all, Permatune began with the 4th gen and the following generations to pot them.

I asked Permatune by myself, and now I got an answer!! Special thanks to Lonnie!

• The model "GS" stands for "General Service", meaning it is usable on most cars with breaker points distributors.
• The model "911SC" of this 3rd gen box is - as the name says - for the 911 SCs with magnetic/inductive pickup.
• The model "GS" is for 12Volts cars.
• The model "GS6" is for 6Volts cars.

Thomas

[Jonny H]

Originally Posted by ischmitz

Without knowing anything about the permatune box you have I am just throwing this out here:

Early 930 Turbos came with Bosch 8-pin CDI boxes - similar to what was used on the 935 where the 8-pin Bosch CDI also had an adjustable rev limiter that cut out fuel and operated a buzzer. Internally the DC/DC converters are very different between the 6-pin and 8-pin versions but they use the same inductive pickup input. And you can run a 6-pin or an 8-pin Bosch CDI on the 930 Turbo or on an SC. They are interchangeable as long as you provide the correct connections to the boxes.

If your box isn't potted internally I'd check if its pinout matches the Bosch 8-pin CDI box for a 930 Turbo. In your picture pin 5 and 6 are missing and these were only used on the 935 Bosch CDI boxes for the buzzer and magnetic fuel shutoff valve. They are not connected in the 930 Turbo version. So the correct 6 pins are on the front connector.

Not quite 100% interchangeable. It depends:

Yes, the 6 pin box will run the early 930 Turbo engine but the tacho will not work. The early Turbo tacho requires a high voltage pulse which the 6 pin box doesn’t provide.

Going the other way, the 8 pin box will run an SC engine too and the SC tacho will ‘work’ with that high voltage pulse from the 8 pin box. Whether there will be long term damage to the SC tacho driving it with the wrong signal - not sure.

[Schulisco]

Originally Posted by Jonny H

Not quite 100% interchangeable. It depends:

Yes, the 6 pin box will run the early 930 Turbo engine but the tacho will not work. The early Turbo tacho requires a high voltage pulse which the 6 pin box doesn’t provide.

Going the other way, the 8 pin box will run an SC engine too and the SC tacho will ‘work’ with that high voltage pulse from the 8 pin box. Whether there will be long term damage to the SC tacho driving it with the wrong signal - not sure.

I received a confirmation from Permatune, that the GS and 911SC boxes won't differ in the tacho signals. So, beside the breaker points / magnetic pickup, no further differences. You can use the GS box on earlier 911 impact bumper cars originally equipped with the CDI/HKZ.

Thomas

[Jonny H]

Originally Posted by Schulisco

You can use the GS box on earlier 911 impact bumper cars originally equipped with the CDI/HKZ.

Thomas

Yes, except for the early 930 where the tacho requires a 300v pulse…

If that box is compatible with ‘most’ cars it will have a pull to ground to drive the tacho.

[Schulisco]

Just saw that I owe you feedback upon this topic: The Permatune box works fine in conjunction with my 123 tune USB dizzy which is the breaker points version for 911 up to 1977 in my 1981 SC!'
Due to replacing the original Bosch dizzy this is no problem and the box is the perfect fit for this. Tacho works also fine.

Thomas