GPS Speed display in RNS510?

[gregozedobe]

Fuel economy is based on distance travelled and fuel consumed not speed. Generally the odometers on cars are accurate (way more accurate than the speedos) so your fuel economy readings should not be affected by a speedo that is optimistic.

True, but the fuel consumption reading on the MFD is (usually) also optimistic, and can be adjusted too (separately). But to be fair, Skoda readings seem to be a lot more accurate than VWs.

[dazag]

Fuel economy is based on distance travelled and fuel consumed not speed. Generally the odometers on cars are accurate (way more accurate than the speedos) so your fuel economy readings should not be affected by a speedo that is optimistic.

Strange, I thought you're odometer is tied to your speedo. So if I sit on 110km/h on the freeway for an hour, my odometer should read that I've traveled 110km over that hour. So what you're saying is I can sit on 110km/h but my odometer will be reading the speed different to be more accurate?? I don't think so, unless they receieve different speed signals?
Or you saying the fuel Economy readout should be accurate knowing that the Speedo is out a little it compensates??

What's the deal with the VAGCOM, please explain??

[Swallowtail]

The car gets the speed and has that internally. That can be seen through the Air con display. The odometer is driven from that. Then a variable is introduced for the speedo, so that it will never under-read. That is called the distance impulse. It is modifiable within a certain range using VAGCOM - www.ross-tech.com.

[Gav23]

Are all German cars speedo's this far out, or just VW's? I can't imagine I'd be impressed if I spent $150K on a Merc and it's speedo was out 10%! If Falcadore's and Hyundai's can have speedo's accurate within 2km (well the ones I've driven anyway), why can't VW?

Taking 10% off isn't difficult, but it is an unnecassary distraction to your driving, especially in busy city traffic.

[Graybags]

The speedo being out isnt a fault, just tweeked to indicate slower speed to stop people being fined, just that they are overly cautious in their tweeking.

[gregozedobe]

IIRC the story is that manufacturers are covering themselves for the scenario when an owner fits tyres that are nominally the same size as std but actually have a larger rolling diameter, so the speedo now reads slow. If the speedo was accurate before, they could now be driving along with the speedo indicating right on the spped limit, but their car is actually travelling 3kmh over so they get booked, blame the manufacturer and then sue the manufacturer for causing it. (if in doubt - blame lawyers and the legal system )

[Gav23]

If getting sued for speeding because of driving tyres other than the standard ones that come on the vehicle, why don't they just put a clause or warning in the owner's manual instead? And if getting sued is such a great concern, why doesn't every other car manufacturer have such a massive gap in odometer speed and actual speed?

[BlackSuperb]

I believe the NSW RTA limits for a calibrated speedo is a maximum of 9% over read and 0% under read.

Anything above or below those limits and you need to renew/recalibrate your speedo.

[K1W1]

Speedo calibration is covered by Australian Design Rules not state based road transport authorities. If that is what the NSW RTA are saying then it will be an Australian Standard.

I actually thought they were moving to a +5% allowable error, the previous one was +10%.

Edit:

A quick Google just found this ADR (click for link). I'm not sure whether it's the current standard but if you want to read through on about page 10 you will find this;
"5.3. The speed indicated shall not be less than the true speed of the vehicle. At the test speeds specified in paragraph 5.2.5. above, there shall be the following relationship
between the speed displayed (V1 ) and the true speed (V2).
0 ≤ (V1 - V2) ≤ 0.1 V2 + 4 km/h"

along with a detailed list of the test procedure requirements.

[Maverick]

Speedo calibration is covered by Australian Design Rules not state based road transport authorities. If that is what the NSW RTA are saying then it will be an Australian Standard.

The ADR is based on UNECE 39/00 (Rev 1).

I actually thought they were moving to a +5% allowable error, the previous one was +10%.

It used to be +/- 10%. Victoria and NSW IIRC "overrode" this and only allowed a car to be ~3% under despite cars being allowed under the ADR to be 10% under hence the 3kph leeway in Victoria for speed cameras.

A quick Google just found this ADR (click for link). I'm not sure whether it's the current standard but if you want to read through on about page 10 you will find this;
"5.3. The speed indicated shall not be less than the true speed of the vehicle. At the test speeds specified in paragraph 5.2.5. above, there shall be the following relationship
between the speed displayed (V1 ) and the true speed (V2).
0 ≤ (V1 - V2) ≤ 0.1 V2 + 4 km/h"

along with a detailed list of the test procedure requirements.

That is the current standard.

I have some info here including how to adjust it using Vagcom/VCDS - Volkswagen Speedometer Error Correction.

[Graybags]

Excuse my ignorance but how do you access VAGCOM? Do you need a cable? Laptop?
-Gt

[Swallowtail]

Excuse my ignorance but how do you access VAGCOM? Do you need a cable? Laptop?
-Gt

It's a combination of software and a special cable - www.ross-tech.com will enlighten you...

[K1W1]

It used to be +/- 10%. Victoria and NSW IIRC "overrode" this and only allowed a car to be ~3% under despite cars being allowed under the ADR to be 10% under hence the 3kph leeway in Victoria for speed cameras.

That's not quite correct.
The ADR is still the ADR and vehicles must comply with the ADR.
What Vic and NSW did was to stop accepting the ADR as a defence for speeding so you can be happily driving in one of those states with your speedo showing exactly 100kph but if you are actually travelling at 105kph because your speedo is (legally) reading slow you will get booked and you have no defence.
Also in Victoria at least the allowance is 3kph not 3%. If you are doing 53 in a 50 zone you are okay, 54 and it costs you $146.00, if you are doing 103 in a 100 zone okay but 104 costs you $146.00

[Maverick]

That's not quite correct.
The ADR is still the ADR and vehicles must comply with the ADR.
What Vic and NSW did was to stop accepting the ADR as a defence for speeding so you can be happily driving in one of those states with your speedo showing exactly 100kph but if you are actually travelling at 105kph because your speedo is (legally) reading slow you will get booked and you have no defence.
Also in Victoria at least the allowance is 3kph not 3%. If you are doing 53 in a 50 zone you are okay, 54 and it costs you $146.00, if you are doing 103 in a 100 zone okay but 104 costs you $146.00

Except you do have a defence, if you have you car tested to show that it's reading within the ADR's this is a valid defence. What you can't do is show up in court and claim your speedo can be + or - 10% and expect it to be accepted.