Speedo Accuracy

[STV4SYT]

OK< i know the speedo is not th emost accurate in the world, i've beenlearning the car using the Climate Control trick over the weekend. this seems more reasonable to go on, my only concern is that i am within the range of not getting a ticket by driving at 10kmh over the speedo. ie 110 on speedo is 103 actual 9or is it)

The question i have it where do these readings come from?

obviously if there is something in the car, ESP maybe that needs to know real speed as opposed to the displayed speed this makes sense, but how accurate is it really?

[gareth_oau]

[QUOTE=steve_tdi;126962]OK< i know the speedo is not th emost accurate

G'day Steve. Be aware also that yr speedo accuracy will also vary according to the depth of yr tyre tread.

From new to old, yr tread depth can vary up to 10mm. This varies the circumference by around 3.5%.

Form a speeding perspective this is probably good news. you can assume the speedo was calibrated for new tyres, so as you wear the tyres out, yr speedo reads higher than yr actually travelling - for example at 100kph, yr speedo will read 103 so yr safe.

if of course, you change tyres from standard, you need to keep the same overall or rolling diameter, otherwise yr speedo will be wrong.

checkout this website for a calculator

http://www.carmodifier.com/default.asp?Action=tireTechCentreCalculator

[Mischa]

OK< i know the speedo is not th emost accurate in the world, i've beenlearning the car using the Climate Control trick over the weekend. this seems more reasonable to go on, my only concern is that i am within the range of not getting a ticket by driving at 10kmh over the speedo. ie 110 on speedo is 103 actual 9or is it)

The question i have it where do these readings come from?

obviously if there is something in the car, ESP maybe that needs to know real speed as opposed to the displayed speed this makes sense, but how accurate is it really?

how long is a peice of string? lol... there was a LONG thread which evoked some emotional responses about this issue some time ago. i've tested it wiht those radar trailers the rta has set up as well as with a gps and the climate control seems accurate to within 1km/h or so. others also tested with gps and seems to be accurate.

[STV4SYT]

Hi Gareth, im not planning to change the wheels or tyres, merely wondering where the digital readout in the Climate Control (after putting it into diagnostic mode) gets its numbers from and how accurate they are.

[mrx]

Personally, based on my climate control research, I allow 5km/h up to 80, 10km/hr from 80-180, and (untested of course) 15km/hr from 180-300.

ie. travel at 65km/hr on the speedo, if the speed limit is 60.

[STV4SYT]

yep, thats what i found too, jst trying to uncover where the "accurate" speed comes from and how reliable it is before i rely on it too much,

[Logzy]

This is what we need.

http://www.digiprog.com/

or at least to know somehwere that has the unit. Its 12000 Euro so I'm not buying one.!!

Clearly, when looking at this we can see that the speedo can be corrected and on the Golf MK5 its done through the OBDII Diagnostic port.
The unit for sale is a complete unit that does not need a loptop or anything.

It would be good if one of us was a software engineer and could write a program that runs on the laptop. It must be possible.

I'll bet that if the Digipro guys can create a product that corrects this then VAG-COM should be able to do it too.
Its a pity these guys just wont do it though.

[STV4SYT]

This is what we need.

http://www.digiprog.com/

or at least to know somehwere that has the unit. Its 12000 Euro so I'm not buying one.!!

Clearly, when looking at this we can see that the speedo can be corrected and on the Golf MK5 its done through the OBDII Diagnostic port.
The unit for sale is a complete unit that does not need a loptop or anything.

It would be good if one of us was a software engineer and could write a program that runs on the laptop. It must be possible.

I'll bet that if the Digipro guys can create a product that corrects this then VAG-COM should be able to do it too.
Its a pity these guys just wont do it though.

Can get similar thing for motorbikes called speedohealer. mostly used when someone changes the gear ratios. the run at about $250 and are plug and play into the wiring harness.

[Logzy]

Can get similar thing for motorbikes called speedohealer. mostly used when someone changes the gear ratios. the run at about $250 and are plug and play into the wiring harness.

Yeah, You can get similar to the speedohealer and build it yourself from Jaycar electronics for about $50
Read this.

The other unit for 12000 Euro actually reprograms the cluster so you dont need an inline device like the speedohealer.