Speedo Help

[gazzman1]

ok so i dont no what is going on I got my stagea not that long ago its all stock and has 16"wheels on it but my speedo it out it is right at about 50 then it starts going 10ks out @110 im doing 100 135 im doing 120 so on and so on any help would be good

[wolverine]

Designed and normal.

[Blek]

Grammar

But yes, this is normal. It sucks, I know.

[gazzman1]

so how do i fix it

[scotty nm35]

The ecu knows the correct speed, but the dash displays it incorrectly on purpose. Putting larger rims and tyres on it will help a fair bit.

You can also use your gps speedo app, or buy an ecu reader that displays speed, like the Greddy touch or the HKS OBlink.

[gazzman1]

that would be good if i had a obd2 port as i have a consult port

[scotty nm35]

Consult port works with the Greddy informeter and many other units. But hey, giving up is much easier.

[coparts41]

Ringwood speedo`s have an interface that is programmable . Wires into the speedo trigger circuit and can be adjusted via GPS and a bit of playing around . Although price does include them setting it up.

[Commsman]

Interesting to see them get it working on an M35. Does it inferface with our CAN? (I bet it doesn't).

The speed signal can be intercepted at the TCU where it comes from the gearbox (It's about 149Hz at 20km/h if anyone's interested). After that it's transported by the CAN bus. If the VSS is changed, it could affect other things as the ECU won't know the true speed. At the very least the trip info/fuel consumption would be out, & we'd probably lose some top speed as the cut out would come in earlier (not that it's a huge deal unless at the track).

[scotty nm35]

No, the speed signal is independent of the driveline, as a few of us have changed diff ratios with no change to the speedo reading. At a guess it comes from the wheel speed sensors, and the ABS computer is something I wouldn't recommend playing with.

[Commsman]

Oops, sorry - I forgot about that. Thanks for the correction, Scotty

So my post should read; "The speed signal can be intercepted at the TCU where it comes from the wheel sensor/s"

But other than my gaff with where the sig comes from, it doesn't change the difficulty of rectifying the issue without interfering with other car functions (the point I was trying to emphasise). Like getting our ECUs programmed locally, I bet we won't see a suitable speedo correction solution, lol.