UKSaabs

not sure where this belongs but for anyone wanting to get the speed signal into the t5 ecu for live speed /gear position and boost control this is my solution . i dont have any abs rings on my car so had to use the old saab 9k speedo head .

the head is simple enough to get out of the dash unit and comes apart with a few screws

not my bag but seems fairly obvious that the signal from the box gets re jigged in here before going on to other modules



the connections are simple enough
the top two are the black and white from the speed sensor on the gearbox

the other three are black to earth ,red to 12v switched and the green is the output to the ecu .in the car the output splits to the cruise module and the trip computer so signal strength wont be an issue if you use the output to drive an aftermarket speedo


ive wrapped the unit in a bit of foam and tucked it away under my dash as it weighs bugger all
this should work with most gearbox transducers with two wires on them

Hey cool thread!

I have been looking into solutions to the speed signal issue if I t5 my 8 valve. What t5 vehicle did you make this speedo mod up for?

I have the wrong speedo type (my speed signal sends a sine wave) and if I change to a later c900 speedo Iwill have to change my cruise and speedo cable etc ) I was wondering if the gearbox on a 9000 uses an inaccurate sine wave (seeing as it's only 2 wire, my understanding is square require 12v and ground) similar to what my early c900 speed signal .

It would make sense if the 9000 did send a sine wave from gearbox to the speedo unit where it is converted to square wave (speedo unit has 12v and ground right and there is an output to the ECU (pin58?)?

The square wave must be made in the speedo as the ECU obviously only accepts a square wave. My idea is that perhaps I could use a 9000 speedo to convert my sine wave from my stock speed signal to a square wave and send it to the ECU, and do what you did and tuck it up into the dash!

What do you think ?

9000 greabox sensor is just a spinning magnet within a coil...

Sin wave..

wrighar wrote:9000 greabox sensor is just a spinning magnet within a coil...

Sin wave..

that is so good to know, so the speedo definitely converts it to a square wave...

Early speed signals in c900s are sine waves (for the cruise control), I should be able to hopefully splice my cruise wire to the 9000 speedo to get a square wave for the t5 ecu!

interesting, what years of this speedo can be used as such? bc I have a display from a 99 9-3 and I am looking into putting the engine into another vehicle.