Pics of the R36

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Originally Posted by R36 Dreamer

In "D" and showing 6 on the MFD

In your figures using numbers as indicated on the speedo or actual speed?

When I use my GPS, at speedo indicated 125km/h I am only travelling around 117 according to the GPS.

At GPS indicated 125, the speedo is nearer 135km/h.

I know the speedos in most VW's are out by about 10%, and the GPS is dead accurate (once a constant speed is maintained),
This has been confirmed by roadside speed indicators (at roadworks sites etc.), as well as by setting the cruise on a flat road, resetting the MFD, and getting an average speed from the trip computer.

Funny that the cars electronics know the exact speed, but cant make the speedo show it!!.

This problem was also the case with my MkV GTI, and my brothers 2.0FSI Golf.

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I have calculated the gear ratio, final drive, tyre circumference and engine rpm, and get - from memory - about 49km/h per 1000rpm, which tallies quite closely to the speedo.

The speedo in the Passat is about 5-6% out, not 10% as far as I know.

I would say that road side speed indicators are not so accurate.

As for calculating the speed by measuring the distance and then dividing by the time taken, this will be more accurate as the speedo needle requires a certain amount of "slippage" in order to show speed. It has to "slip", otherwise it would wind off the clock. The odometer is different in that it is "hard wired" to the gearbox in that there is a sensor that counts revolutions - no "slippage" - and then calculates distance by using the tyre diameter x revolutions.

I therefore find it strange that your speedo would indicate 124kmh at 3,000rpm when my Passat, with the same gearbox and theoretically the same final drive, indicates at around the 100kmh mark and 2,000rpm! If I was indicating 3,000rpm in my Passat, I would be travelling at an indicated 150kmh, which *maybe* about 141kmh if you take into account the "error".

Quote:

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Originally Posted by Lance B

I have calculated the gear ratio, final drive, tyre circumference and engine rpm, and get - from memory - about 49km/h per 1000rpm, which tallies quite closely to the speedo.

The speedo in the Passat is about 5-6% out, not 10% as far as I know.

I would say that road side speed indicators are not so accurate.

As for calculating the speed by measuring the distance and then dividing by the time taken, this will be more accurate as the speedo needle requires a certain amount of "slippage" in order to show speed. It has to "slip", otherwise it would wind off the clock. The odometer is different in that it is "hard wired" to the gearbox in that there is a sensor that counts revolutions - no "slippage" - and then calculates distance by using the tyre diameter x revolutions.

I therefore find it strange that your speedo would indicate 124kmh at 3,000rpm when my Passat, with the same gearbox and theoretically the same final drive, indicates at around the 100kmh mark and 2,000rpm! If I was indicating 3,000rpm in my Passat, I would be travelling at an indicated 150kmh, which *maybe* about 141kmh if you take into account the "error".

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I respectfully disagree - I only know what my car does, and the amount it (and the GTI before it) was out in the speedo dept - cannot speak for your car.

I can't remember... is your car one with or without the reversing camera?

I ask because I got a call from Volkswagen today, saying they hadn't found an acceptable retrofit option but will instead give me $1500 to make the problem go away. Proper Bluetooth will be doable in the second week of October (the week after I leave for four months!)...

On the F3 you can do a 5km distance check of your odometer / speedo. I have timed the 5km run doing a constant 'indicated' speed and then worked out my 'true' speed.

After indicating 120km/hr over 5km, my 'true' speed was 116km/hr.

Most cars under read like this, for the obvious liabilty / arse covering reasons, i presume.

VW don't seem to be overly out here.

Hey Lance,

Dreamer's "GPS" speed of 124km/hr is probably more like 128km/hr on the dial, so a smidge over 3000rpm in 6th is about right i reckon.