Q for those running EFI and electronic speedo...

[Cobra Dude]

If you're using Fuel Injection AND an electronic speedometer... what are you doing about VSS (Vehicle Speed Sensor) signal?

[ The VSS is important for idle and shift management (IAB control), so I don't want to start a debate on why it is or is not necessary. ]

On a Mustang T-5, the VSS is physically connected to the speedo cable on the tranny. When using an elec. speedo, there is a special (speed) sensor that replaces the cable in the transmission, so the VSS can't fit there.

Would love to hear how any of you have solved this.

The folks at USI (United speedometer & Instrument, from whom I bought all my VDO gauges/sensors) tell me that the computer wants 8 pulses per rotation (ppr), but mine is 16 ppr. Not sure if actual ppr amount is important for non-cruise-control perhaps the computer just needs to know if the vehicle is moving or stopped for IAB management???

Only thoughts I have to far is...
(1) Use the regular VSS with a piece of a speedo cable into a custom "box" that will let me attach the elec speedo sensor.
(2) Use the elec sensor and tap off the signal wire for the computer. Obviously this means figure out signal levels from sensor and for computer and building a custom circuit for this.
(3) Get a mechanical speedo -- nope! (Good reasons).

I'm sure this has to be a common problem. Help, please!

Cheers,
-Neil.