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Post by peylix on Apr 10, 2023 21:05:28 GMT
So I'm looking to swap the speedo faceplates from my MK7 GTI to the MK7 R. Not changing the cluster itself, or messing with the immo or anything. Just the paper faceplates on my original cluster. I enjoy the look of the white rings from the R faces. However the Golf R face has a higher top speed and after 120mph, the increments change.
I would like to code my GTI cluster like an R cluster. So it will read speed properly.
I've also seen examples of this actually being done. So I know it IS doable. I just do not know how. I don't know if this can be done through long coding via OBDeleven/VCDS or if this is something that needs to be done via a dealership (though when asked, they said they won't touch it). I've been told so many different things, and no one has been able to give a clear answer.
It's starting to drive me crazy.
I appreciate any help.
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Post by dv52 (Australia) on Apr 11, 2023 21:53:28 GMT
peylix : Hi - interesting problem!! I'm not sure that your project is possible - can you provide references for your claim "I've also seen examples of this actually being done"? Just thinking out-loud, modifying the behavior of the speedo alone sounds tricky because by definition "speed" = distance traveled divided by time. So the formula involves using the odometer reading - which on modern cars is sacrosanct and there are lots of protection protocols against playing with this number. You are correct about the long-code string on the hex17 module having software switches that can modify the speedo reading. These switches are on Byte 3, Bit 0-2 - but they are intended to apply when installing tires with different wheel diameters. However, as has been discovered by those that have tried to change the factory values, it's only possible to change the tire diameter in one direction. I suspect that the protection protocols against odometer changes (i.e. stopping a reduction in the odometer reading) are binding when playing with these software switches.
As for the different non-linearity of the speedo scale on a Golf R dial - clearly the reading behavior over the full-scale is determined by the firmware in the hex 17 module. I would think that for a particular module, the needle response is fixed by this software. If you change the "paper faceplate" only - I would be very surprised if the software designers for the dataset in the module contemplated this modification. And even if the software designers did make this accommodation, I'm not at all confident that you could find the correct memory addresses within the module firmware to activate the sub-routine for the Golf R needle response.
Don
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