Porsche 915 VSS wiring HELP!

[Queefchief]

I’m trying to mate a Porsche 915 transaxle to a Honda k20 engine and would like to use the stock Porsche 915 speed sensor with my standalone ECU. The Honda uses a 3 wire but my standalone allows me to run alternate speed sensors as well.

So which wire from the Porsche VSS is the signal wire and which is the ground?

Or with this being a reed switch would I need to wire a different way?

I essentially just need the signal wire to be ran to the ecu and want to retain the stock Porsche sensor.

Please help!!!

Thank you

[dap930]

Which ECU are you using? For MS3X/MS3Pro, the VSS input is looking for a grounded input. So, one of the two wires going to the VDO speedometer from the reed switch goes to ground. The other wire goes to the speedometer circuit board, which is the wire you want to tee into for VSS input. When the reed switch is not made, the circuit is high (12vdc) and when the reed switch makes, the circuit is pulled low. Porsche 915 transmission provides 8 pulses per wheel revolution.

[Queefchief]

Hondata kpro v4 is the ecu I’m using. It only requires the VSS input as the computer will output all single for gauges, will be using the AiM MXS dreads.

So I’m assuming I’d ground the brown wire and use the green as my signal to the ecu and that should work ok

[DRACO A5OG]

Yes, brown is ground green is signal.

Pulses are via magnets ( positive and negative positioned alternatively ) in the diff.

Love to see your engine swap or is it gear box swap?

[tcar]

With Porsche, Brown is always Earth (Ground).
The color is the clue.

[Queefchief]

Sounds good guys I’ll give it a go!


Thank you

[merlinfe]

IMHO,

The new generation of GPS speed sensors work better and are much more accurate than anything driven by the car. They can also be much easier to wire in.

Good luck,

- Steve

Link to GPS Speed Sensor in 911: Speedometer correction!

[Queefchief]

I totally agree with the GPS. That was the game plan but the Honda ecu reads and adjust fuel trim levels among other things that’s needed with the stock VSS. I got it wired up and working properly!!

Thanks for the help everyone