Alan,

I think I now know why Porsche developed the "digital speed signal". Here's why...

With the magnetic differential speed sensor/sender, when the vehicle is at rest, the signal may be +12V or 0V, depending on the position of the magnets relative to the sensor.

With the digital speed signal, when the vehicle is at rest, the signal will alway be at 0V.

So it might be that the GTS dynamic kickdown relay won't work with the magnetic speed sensor signal on pre-89' cars, be cause the circuit does not expect to see 12V with the car at rest.

 

Has anyone installed a dynamic shift relay in a pre-digital dash car, yet?


I'd like to try putting the relay in my '86.5 (using a 951 TPS), if the speedo thing is not a problem.

 

Mike - did you ever get that installed?

 

Sorry, was out of town on business.

I have not finished this yet. I did install the newer TPS and ran the wiring, but have not yet tied it into the cruise control box or relay board. I have the relay sitting in the drawer as well.

The reason this went on the back burner was because of the WP failure last year. Also, when I changed over to the 91 transmission with the 2.54 gearing and had the stall increased on the TC, this car kicks down alot more than before. It is already acting like it has this dynamic kickdown. It is weird. I am concerned that I might not be able to tell a difference when I do get it hooked up. We shall see.

 

Currently in the final stages of completing this with Paul Anderson in the UK on MY88 928. Has anyone actually completed this job on a '88 car with the speed signal from the diff speed sensor of cruise control?

Some specific details and photos of where to get this signal on a MY88 928 would be most helpful.

Thanks
Steve

 

Bizman keep me updated on your project, us 88 fellas need to stick together

1988 s4 Auto ROW black/black West Australia

 

As soon as we get this fitted & working we will let everyone know.
Hope someone can help us get this signal issue sorted out for the MY88 year.

Thanks
Steve

 

I have not done it - but the cruise control speed signal is Pin 11 on the cruise module - a Blue/Red wire.

Not sure if thats directly compatible with the Speedo-A signal from the DigiDash - but its all you have, it is at least close enough that either of these signals can be used to drive the same cruise speed control module between years - so worth a try... I suspect it will work fine.

Alan