Gps speedometer conversation
 

I have an 7/31 915 Transmission from a 74 with Mechanical speedometer output...my car is it 86 with electric speedometer has anyone successfully added A GPS modulator? ... I installed a intellitronix gps speedometer sending unit from Summit that the Chevy guys use and for some reason I can't make it work even though the pulse rate is correct.
Any ideas?

How do you have the Intellitronix unit wired to the speedo?

I'm not sure what your "mechanical speedometer output" is, except from an earlier trans that uses a cable drive to spin the speedometer. Doesn't your 915 use #6 below to feed the speedometer?
http://forums.pelicanparts.com/uploa...1435433877.jpg

Have you tried contacting Intellitronix Corp.?

I'm sure they'll help you get your GPS Modulator working. I've seen this setup on an old MG locally and it worked perfectly.
I'm actually considering one for my 78SC because I have a speedo from an 89 that I'm going to install.

I tried contacting intellitronix and haven't gotten a response, hopefully soon.
Cmonref, the transmission is from a 74 the car is an 86 so is the issue of mating mechanical output with electronic speedo.

HMMMMM.... I have a late electronic speedo going into my '71 914-6. The Six has the gear driven speedo cable. I understand VDO has a converter that the cable screws into that converts the revolutions to electronic signal for the electronic speedo. I have not however confirmed that all of that will work. Hartmut at Palo Alto Speedo, who is restoring and converting my gauges, gave me that info.

Any updates?

Did Kevin ever get this to work. This might solve an issue I am having.

I was never able to get this to work, sorry for the super long delay in response. Was anyone else ever able to get it to function correctly?

Sub'd

The Porsche electronic speedometer receives 8 pulses per revolution of the rear tire from the magnet plate in the transmission. The circumference of the rear tire is about 6.6 ft. So, over 1 mile that is approximately 6400 pulses. So, the GPS interface unit would have to transmit close to that number of pulses. Just my thought.

I have a mechanical speedo that I will be removing from my project car, had a 915 with mechanical drive. going to a 930 4sp with elec sensor.

I was looking into this for my car, and found this thread. It appears the Intelletrinix does not work as it is not adjustable to mimmic the 6,400 PPM we need. So I kept searching and found this from Autometer. It appears to be infinitely adjustable. I read the instructions on line. It appears you use an adjustments button to adjust it to read dead on 80mph (which in your driveway of couse through a setting mode). It then memorizes the setting for that and you are all set. I may have to give this a try.

Autometer GPS Speedo Sensor

I had to convert my mechanical speedometer 915 transmission to an electric sending unit when I installed it into my 914-6 conversion car. I was able to install the factory magnet ring on the ring gear and got a differential side cover that held the factory sensor to make my speedomter work.

I'd wonder if anyone could install gps speedometer guts into a VDO shell to provide accuracy and the matching appearance desired?

Well that is kind of the ideal of this, it feeds the stock speedo a signal it understands, and can be calibrated to make the stock speedo accurate. I have the same sensor setup you are talking about on my 915. it does not work. It could be the tranny doesn't have the internal parts to make it work. This system could al be buried under the dash,....save the GPS antenna. That needs a clear shot to the sky. You could burry it under your dash pad probably (thats what I may try to do). It comes with a 16' cabler the antenna so you could also put it under the rear deck int eh passenger compartment.