Polo 9n3 gti speedo signal source !

[Alex Mckenzie]

A little advice please
I’m installing the bxj and 02r into a mk2 golf,
But not sure where the Speedo gets the signal, dose it come from the abs rings or gearbox and where is the sensor located

I see on plug at gear mech. And one at the back of the 02r,

Just trying to work out what Speedo to use.
Internet search doesn’t give anything definitive, but suggests the signal is from the ABS ring.

Thanks


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[sambb]

If I pull the ABS fuse in the fuse panel the speedo stops working. pretty sure that points to the abs rings being the speedo signal. From memory there is a plug on the box but I think thats only a reverse monitor for the reverse light. There is another black socket on top that is not used on the 02R. I think that probably was a speedo signal on earlier cars perhaps but isnt used in the Polo gti 9n3

[simon k]

The speed does come from the ABS wheel sensors - there is a speedo drive gear on the differential and a fitting on the back of the gearbox/diff housing that would be for a mechanical speedo drive - but the pinion isn't fitted. There should be a speed signal (VSS) output from the ECU that you could tap into, but if you really want a mechanical drive then I think you could take the speedo drive gear from an earlier 02A/02J type gearbox put it down that blocked off fitting and it'd probably work... I don't think you'd need to split the gearbox to do it, depends what you find when you remove that fitting.

You might find that you can get a speedo drive pinion out of a new Beetle or early 2000's Golf, it'll be something like this -> Original VW Speedometer Pinion - 02A409197 | eBay

This is the type of gear that is fitted to the differential. I took mine off with a hammer and chisel -> Speedo Drive Gear, 02A 02J – Cascade German Parts

[JTop]

Earliest 02r boxes came with it, I had a mechanic doing a roadworthy complain to me about that it's not plugged in, and I had to explain that my speedo works without that speed sensor. HWY box with that, not sure because now own another two of those and they don't have them...

Sam is right, ABS system relates the wheel speed giving the speedo reading. I found that 215 size tyres give the accurate match for the readout compared to the 205's which are a tad off. Which are larger than the "recommended" size VW recommends on the Polo

Simon is pretty much spot on with those part, just need the exterior plug/sensor for that too, mine went off the box 90degree and could be turned in any direction. I ended up taping it up to protect it if ever needed. Car's being taken apart so if nobody has taken that, still in Bentleigh VIC.

[Alex Mckenzie]

Thanks all.

My concern is the number of teeth on the ring.
I’m using mk3 vr6 hubs which from what I can tell is half the teeth of the polo tone ring.
This would mean I’d be in jail as I’d be doing 200kph while the Speedo read 100kph.

I’ve since found I can modify with vag com
By adjusting the distance impulse .

I’ve not played with vag com so really have no clue if this is correct. But in any case can’t let this stop the build, I’ll worry about that when I get to.

Thanks again for all your advice


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[sambb]

hey mate just something to consider.
The Polos ME7.5 ECU has an ABS wheel speed sensing system where what looks like the soft dust shield on the Polo's wheel bearing actually has magnetic strips in it and the sensor looking at them needs a voltage applied to it. Apparently its called 'magneto resistive' and is an 'active' sensor. Our ABS module expects to see highs and lows between 1.9 -0.6v.
The older 'passive' system thats found on a Mk4 golf or Audi S3 is different in that it has a steel chopper disc on the wheel bearing and the sensor that looks at it is magnetic, basically a reluctor system that produces a sine wave/Hz.
So if you're using Polo hubs/shafts with the BJX's Bosch ME7.5 then you are good but if you were going to use different hubs you might not be able to get a speed signal off the wheels and may be forced into going for a gearbox speedo cable.

[Alex Mckenzie]

Thanks, that’s the thing I was afraid of.
I can fit the polo rear hubs, but the fronts... that will be a interesting challenge.
Going mechanical might be my only option
Thanks


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[sambb]

Dont know much about Golf 2's but I have seen them done using TT wishbones. If you could do that I'd be willing to bet that its ball joint would fit our hubs ball joint receiver. For instance we fit Audi TT RS ball joints to our stock wishbones for roll centre correction and that ball joint pin angle fits aok. So TT arms, polo driveshafts, polo hubs......you'd only then have to get a compatible tie rod end and make sure the strut tube fits our hubs receiver.
If you need any measurements off the polo hub let me know as I have some spares in the garage.

[Alex Mckenzie]

Now that sounds like a option worth looking at, from what I’ve seen based on what you’ve suggested, sound like I’ll need some bc coil overs.
Thanks for the info


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