Speedo calibration for engineering purposes / aftermarket speedo question

[GOT-20V]

hi,

Current speedo in the Ke70 reads around 10km/hr slower now that is has a BT 20v in place. For a engineer cert. this needs to be fixed.

How does one calibrate a speedo, is there such a place that can do this?

It crossed my mind to just redo the whole dash with aftermarket guages, but would i have the same problem?

Sort of a virgin to fiddling with the guages as all my cars i have just left the dash standard as i like factory magic, but i'm sure other people have had this problem with conversions etc..

any answers/ideas will be appreciated

[70XIN]

I don't know why the engine would have caused the speedo reading. Either you changed wheels (rolling diameter) or diff ratio.

But anyway, if you're unable to get a 'lenient' engineer certificate, then you can but speedo adjusters. They're pretty basic and kinda overpriced for what they are, but they do the job and there's not much else you can do about it (other than changing diff ratio or wheel size).

[GOT-20V]

Yes sorry, diff ratio is 4.3 so that would be changing the reading. But the wheels are only 14 x 7 so i'm not sure if they make any impact?

Thanks for the links, yet to do some research but i would be using the mechanical ratio box yeah?

Your right the electrical ratio box isn't cheap at $895! EDIT: just found a cheaper version perhaps :

[jakel]

how would that work? you would have mechanical speedo with gears. Otherwise you could just double sided tape a GPS to the dash mine has some thing where it has just a speedo on the screen and its just a cheap garmin one.

[70XIN]

GOT-20V, you just have a T50 with a mechanical speedo yeah? All you need is the corrector box. Second link, halfway down the page - $120

[Sam-Q]

if you source the gear(s) out of the jap spec T50 that should bring it back

[GOT-20V]

Does the mechanical corrector box have some adjustment on it, so you can either adjust your speedo from up or down? I understand how the electronical one works, if you were smart enough it seems you could wire it all up to the ecu as well.

Is that true, if a jdm T50 was used it would all be in order?

[jakel]

or maybe a jdm dash cluster?

[Skylar]

Not JDM. You need the original speedo drive gear that was fitted to a car with a 4.3 diff. There's part numbers floating around on the internet of the right gear to buy.

[Oly AE86]

Mechanical corrector box has no adjustment. You tell the guys that sell them your indicated speed at a measured 100km/h (via GPS etc) and then they match up a gearset that suits. Takes about 5 mins to install and you are done

If you change diff ratios again eg. 4.77, you simply remove the box and re-measure your indicated speed, then get another one made up, selling the original one marked 4:3