wrong speed displaed on speedometer GTZ 1992

[ranausaurus]

Hi all, I bought a GTZ 1992 1 month ago and there is a huge difference between the real vehicle speed and the displayed.
when I made 120kph real by GPS it showed 135-140kph but the computer is the good one, the cluster gauge, tire size, transmission too.
can it be the VSS ?


thank you

[themixer]

more than likely the cluster itself, using a obd 1 scan tool you would be able to see the VSS speed

[ranausaurus]

ah ok I will see it, thank you

[Bapsu]

20kph difference between wheels and gauge is quite normal... just get used to it.

[woody90gtz]

You can adjust it in the tune if needed.

[ranausaurus]

I'm planning to get parts from moates to adjust the road speed constant but 13-15% of difference in stock, is quite high.

[3X00-Modified]

Is it a constant % off? If so then it could be just the needle has moved and isn't pointing to real zero.

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[Rettax3]

Is it a constant % off? If so then it could be just the needle has moved and isn't pointing to real zero.

???
If it is a constant %, that is a ratio problem -reluctor-ring tooth count, mismatched gauge, ECM, something like that. A constant kph off would be a misaligned needle...
Moates is likely the best route to go to fix it. Although a Dakota Digital SGI-5 (I think they are up to a -5E now, I've used the -5C models before) lets you reprogram the VSS ratio (and even signal types, like sine-wave to square or vice-versa) and is a reliable, quality part. Usually costs around $50 U.S.

[3X00-Modified]

That's what I meant, a constant amount, not %... I don't know why I put that in there.