[Mk2] [Generic] Matching Speedo and speed sensor

[Hutchie]

I have an import rev 2 turbo track car that now has a rev3 NA engine and JDM gearbox. It has UK clocks (I assume - as the speedo is in Mph).

The problem is that the speedo massively under reads - not too much of an issue for track use but just a tad frustrating.

Does anyone know how I can get the right speed sensor/speedo combination to get reasonably accurate speedo readings?

Many thanks in advance

[gtschris.com]

I have an import rev 2 turbo track car that now has a rev3 NA engine and JDM gearbox. It has UK clocks (I assume - as the speedo is in Mph).

The problem is that the speedo massively under reads - not too much of an issue for track use but just a tad frustrating.

Does anyone know how I can get the right speed sensor/speedo combination to get reasonably accurate speedo readings?

Many thanks in advance

is the speedo a 0-160 or 0-180 ?

how much is it under reading by.... so an example at 70mph actual whats your indicated speed?

[toxo]

I had one that underread a lot. I took the needle off and put it back reading what it should do using a satnav on a private road :/

[gtschris.com]

I had one that underread a lot. I took the needle off and put it back reading what it should do using a satnav on a private road :/

Yes, a tried and tested method! takes a bit of practice and a co-driver shouting out sat nav speeds pretty helpful.....

[Hutchie]

Thanks Guys,
Maybe I'm over-thinking this, I know the final drive ratio is different in the JDM boxes, so I was thinking you need an appropriate speedo to match the sensor, but then I guess A JDM speedo is in kilometres not MPH, hence my confussion/concern because there may not be an MPH speedo for a Jap box.

But then maybe the sensor is matched to the gear ratios so a constant signal is being sent to the speedo?
Maybe I just have a dodgy speedo or the wrong speedo type
- not sure what the max speed on it is.
I'll look at it again tonight.
Thanks again for your thoughts

[Super_red]

I had one that underread a lot. I took the needle off and put it back reading what it should do using a satnav on a private road :/

Do all speed sensors give out the same number of pulses per revolution of the wheels? If not then this method is only good for the correct speedo that is under/over reading. If the wrong speedo and speed sensor are used together the amount of discrepancy will vary with speed so this method would only get one key speed 100% (maybe 60 as then 70 will only be a small % out and most speeds under will under read).

[toxo]

In this particular case it was one which had previously read correctly and had the needle removed, so it was fine! You're right, this method will only work when the speedo is the same number of mph (not speed %) out across the range.

[Hutchie]

Ok, so I've looked at the speedo and it only goes from 0 - 110
I'm guessing they might be the wrong one given that gtschris was asking if its a 160 or 180?
Any one know what is usual for a rev3 na?
Cheers.

[gtschris.com]

Ok, so I've looked at the speedo and it only goes from 0 - 110
I'm guessing they might be the wrong one given that gtschris was asking if its a 160 or 180?
Any one know what is usual for a rev3 na?
Cheers.

So what you have there is a 0-180 speedo that someone has stuck a 0-110mph face on top - this is a cowboy conversion

MR2 Turbo and Glimited (JDM) have 0-180 kilometer speedos
MR2 NA UK spec 3SGE have 0-160 MPH speedos

I would recommend you install a 0-180 speedo head with converison chip so it reads correct in MPH and takes off your 112mph speed limit.

Or cheaper option, as pre previous posted, do the pull needle off and stick back on whilst driving trick, its obv not been calibrated properly when the clock face was initially installed.

We can help with parts, all instock.... [email protected]

[Hutchie]

Just to help me understand - the speed sensor should always send 4 pulses per revolution of the wheel - right?
So if the sensor is picking up a signal from one of the output shafts they should all be pretty much the same regardless of MPH or KPH otherwise the sensors would probably be different depending on the final drive?
So if there are just 4 pulses per wheel rotation, the speedo itself must do the trickery to convert this to the appropriate reading?
So if this is the case wouldn't any MPH speedo give the correct reading?
I understand that the speedo then outputs it's speed to other things such as the ECU, but why wouldn't the 110 that I've got read correctly and wouldn't a 160 just work?
Sorry to labour the point - just trying to understand!
Many thanks.

[Ryan6926]

I apologise for jumping in on this but I have the same issue as in I have a G limited Rev 2 which also has 110 clocks yet my Speedo over reads by 10mph through the entire speed range.

Would it be possible to just change the entire unit to UK clocks? I don't mind the limiter still being there but if I buy some UK clocks would the Speedo then read properly in mph?

[Ryan6926]

I apologise for jumping in on this but I have the same issue as in I have a G limited Rev 2 which also has 110 clocks yet my Speedo over reads by 10mph through the entire speed range.

Would it be possible to just change the entire unit to UK clocks? I don't mind the limiter still being there but if I buy some UK clocks would the Speedo then read properly in mph?