What kind of signal does the speedo use from the tranny to the gauge? Is it a digital signal (on/off)? I want to feed the signal to my ECU to measure speed and gear selection for boost control.

Thx

 

Geoffrey told me he uses a pickup on the axle shaft bolts.

 

Don, hope this helps.

Note, it is for the 915 from the 3.2 carrera though. It appears it is on - off.

http://www.porscheclubgbforum.com/tm.asp?m=216390

 

Thank you

 

It is a mag sensor, so it produces a sine wave.

 

How would you test for that Geoffrey ? I mean how would/could you test the sender ?

TIA

 

There is a connection in the tunnel under the plate where the coupler is. Use an ohm meter connected to the two wires coming from the sensor. Drive the car or just turn the rear wheels and you should get a reading that moves from continuity to infinite ohms.

 

How sensitive do you need to set the meter to, the X setting ?

TIA

 

The best way is to use an oscilloscope which will show the waveform and you can determine if the wave is a rising or falling wave as well as the number of teeth (I believe there are 6 but cannot remember). A mag wave will be an analog wave, not an on/off digital wave.

 

My meter auto ranges, but you need to be able to read 0 ohms to infinate ohms. Basically,if you get a reading that flucuates then you can safely assume the sensor is working. Now, if you are trying to check for speedometer accuracy or want to know anything more in depth like how the waveform looks then you need to do what Geoffrey suggests with a scope. For general purposes though, that is not neccessary.

 

Thanks guys.

In my 915 there are magnets, but like Geoffrey said 5 or maybe 6, I cannot remember either.

I know they are magnets as they collect the swarf...