I am looking at making an even more painless VSS solution for retrofits. I am speficically targeting 16197427, but I can do one for the previous generation as well.

My plans are simple- to use a custom housing and a photo interrupter that will use a miniature in-line wheel on the speedo cable. This way you can change your VSS characteristics by changing your wheel. No more bolting rings below the vehicle.

I also might be able to add a gear information if a tach signal is provided. I'm looking for the signal charateristics for these pins. is is +/- 1v? 12v? etc?

 

It is a simple open collector pull down.

RBob.

 

Oh that is awesome, So if I understand you correctly, then I can just use a transistor and short it to ground directly from the photo interrupter?

Tach is the same way?

 

Basically yes. The ECM side has a 5.1K pull up to IGN+, then into a buffer (inverter) with some filtering/protection. The optical/magnetic buffer boxes (4-0ut/DRAC/optical), just pull that line down and release it to form the square wave input.

There is a capacitor on the output of the buffer box to help protect the transistor.

Not sure about a tach signal, as there isn't one. There is the DRP input to the ECM, and the EST output (5V square wave). But I don't like messing with those as they are important to the proper running of the engine.

RBob.

 

Oh ok, I'll take the EST then and compare it to the speedo and calculate the gear. Then I can express that as pins so I can get highway mode in addition to DFCO.