Odometer inaccuracy

[Jesse B]

Has anyone else checked the accuracy of the odometer on their D4? I became suspicious of mine after consistently worse fuel consumption figures than others were quoting. So I checked both trip meters and the overall odo figure against a known correct set of roadside distance markers over distances varying between 70 km and 280 km - all proved to be under-reading by 3.3%! While this does not sound a lot it does mean that instead of the 35000 km its showing I've actually done over 36100 km!

Obviously there are a few implications here, in addition to fuel consumption - servicing (and resale ;)) etc. It brings my consumption on a long recent trip down from about 11.45 to a tick over 11, which feels better, but I wonder if my bus is alone here? Tyres remain standard size at this point, and speedo is actually the other way - it over-reads by about 5% (110 real shows about 115 on the clock).

[mowog]

Based on GPS speeds mine is about the same as yours. Even my 2 Mini's are about the same.

[Colin Pedersen]

Hi Jesse B

The odometer (speedo) is designed that way out of the factory, I had this confirmed by the dealer. The decision process is; to have an accurate speedo reading taking into account wear on the types (which can be up to 20mm off the circumference from new to warn) and to not get sued by drivers for having an speedo that posts a speed over the rated limit, the manufacturers will up the speedo reading 2-5% above the "actual" road speed you are traveling. Its better to post faster speedo speed than the actual road speed.

This can be confirmed with a GPS which will show a far more accurate road speed than the Speedo. In fact, I jumped into my onboard GPS's diagnostics (press the top of the middle of the screen for 5 seconds and enter 753 as the code if you have one) and it shows the accurate GPS road speed.

At speedo speed 50kph I was traveling 48kph, 80 was 77 and 100 was closer to 96. This explains why cursing at 119 on the Highway the radar guys wave at me, I was really only doing about 114km!

This will of course have an affect on the odometer and mileage calculations, you will have actually traveled less than your odometer has reported.

Col.

[wardy1]

Hi Jesse B

The odometer (speedo) is designed that way out of the factory, I had this confirmed by the dealer. The decision process is; to have an accurate speedo reading taking into account wear on the types (which can be up to 20mm off the circumference from new to warn) and to not get sued by drivers for having an speedo that posts a speed over the rated limit, the manufacturers will up the speedo reading 2-5% above the "actual" road speed you are traveling. Its better to post faster speedo speed than the actual road speed.

This can be confirmed with a GPS which will show a far more accurate road speed than the Speedo. In fact, I jumped into my onboard GPS's diagnostics (press the top of the middle of the screen for 5 seconds and enter 753 as the code if you have one) and it shows the accurate GPS road speed.

At speedo speed 50kph I was traveling 48kph, 80 was 77 and 100 was closer to 96. This explains why cursing at 119 on the Highway the radar guys wave at me, I was really only doing about 114km!

This will of course have an affect on the odometer and mileage calculations, you will have actually traveled less than your odometer has reported.

Col.

Lucky you're not in Victoria! You'd be pinged anyway, anything more than 3km over and you're done.

[roamer]

Hi Jesse B

This can be confirmed with a GPS which will show a far more accurate road speed than the Speedo. Col.

Just make sure your are on a flat road with the GPS or readings will be incorrect
Cheers Ken

[Jesse B]

This will of course have an affect on the odometer and mileage calculations, you will have actually traveled less than your odometer has reported.

Col.

Thanks Col - but this is not actually the case with my D4. Like yours, mine shows a higher than real speed on the speedo, which I am not fussed about. But instead of having traveled less km than my odo has reported I have actually done more!

I checked this by setting a trip meter to zero alongside a roadside marker plate saying "Perth 160 km". I also made a note of what was showing on the overall km count. Then when I reached the "Perth 60 km" plate I checked both - they were registering 96.7 km traveled, but I'd actually done 100 km. So, while the speedo is high the odo is low - hence my original statement that instead of having done 35000 km from new I now find I've done 36125 km - a fairly significant difference.

Just to be sure that it was not this particular set of roadside plates that were wrong I checked against two further sets, one being a distance of 80 km and the other 90 km - exactly the same percentage under-read!

[Tombie]

Those signs aren't always spaced correctly.
Often they are out 5-7kms

Don't complain, reading lower is better for your resale!!!

[gghaggis]

Hi Jesse,

If you have a separate GPS unit, measure against that on a long straight level road. Or calc a travel distance using Google Maps and drive it.

Cheers,

Gordon

[DanW]

Hi Jesse,

Or calc a travel distance using Google Maps and drive it.


Really? I've always found Google Maps to be pretty inaccurate themselves. Not just on actual road routes but on distances as well. whereis.com seems a bit better but they also seem not to be able to keep up with infrastructure changes making the actual distance different from that indicated on the website.

From what I can tell all new cars over the last 5 years come from the factory with low reading speedo's. I read "Wheels" regularly and they use "Actual speed at 100km/hr..." as a test point and nearly all of them are actually 96 or 97km/hr

[mowog]

This can be confirmed with a GPS which will show a far more accurate road speed than the Speedo. In fact, I jumped into my onboard GPS's diagnostics (press the top of the middle of the screen for 5 seconds and enter 753 as the code if you have one) and it shows the accurate GPS road speed.


Col.

The code wont work for me. I can get the screen for the pin but it does nothing?

Are there any other codes?

[gghaggis]

The code wont work for me. I can get the screen for the pin but it does nothing?

Are there any other codes?

There are two "hidden" screens - which one are you accessing?

Cheers,

Gordon

[gghaggis]

Really? I've always found Google Maps to be pretty inaccurate themselves. Not just on actual road routes but on distances as well. whereis.com seems a bit better but they also seem not to be able to keep up with infrastructure changes making the actual distance different from that indicated on the website.


Google maps should be pretty accurate on established routes. For instance, it logs Perth CBD to Kalgoorlie as 594km. So does Travel Around Australia (which uses Whereis), and the WA traveller's portal list it as 596km.

Not much difference between them. So if you specify exact start and end points (eg an intersection) on established roads, I'd be confident that the distance reported would be more accurate than the average car's odometer.

I guess it depends what you're using as a reference to gauge the various GPS/mapping providers' accuracies? Short of getting a survey map and a good digital map wheel, what standard do you use to determine the accuracy of Whereis vs Google?

Cheers,

Gordon

[Graeme]

..This explains why cursing at 119 on the Highway the radar guys wave at me...
They were trying to get you to stop cursing at 119 kph!

[mowog]

There are two "hidden" screens - which one are you accessing?

Cheers,

Gordon

I am trying to access the GPS screen as discussed above.

Would good to know what the other screen is and its pin.

[Bushwanderer]

SNIP I read "Wheels" regularly and they use "Actual speed at 100km/hr..." as a test point and nearly all of them are actually 96 or 97km/hr

Hi Dan,
That actually means that the speedo is reading high, as you would expect.

What it is saying is that for a speed of 100km/h indicated on the speedo, the actual speeds were 96 or 97km/h.

Best Wishes,
Peter

[Jesse B]

Hi Jesse,

If you have a separate GPS unit, measure against that on a long straight level road. Or calc a travel distance using Google Maps and drive it.

Cheers,

Gordon

Will do - when I get back from the east. But I repeat - this is a WELL known highway (to me at least) - I've driven it hundreds of times in the last 40 years, and know the distance markers that I used to be pretty accurate, so don't expect much to change. However, will run this cross-check in 10 days when I return.

Also - for all those kind folk who have noted that almost all cars nowadays have speedos that read above real speeds - thanks, but my interest is in distance traveled, not speeds. And no - I'm not complaining! - it's just good to know the real situation, and I wondered if my D4 is "unique" in this behaviour.

[gghaggis]

And no - I'm not complaining! - it's just good to know the real situation, and I wondered if my D4 is "unique" in this behaviour.

Hmm - now you've got me intrigued - I might have to try a test run myself!

Cheers,

Gordon

[vnx205]

..... ..... .....

I wondered if my D4 is "unique" in this behaviour.

No, my 1973 Series III LWB did the same thing. :p It read 100 km for 107 km actually travelled when the retreads were new and 106 km travelled when they were worn.

However that was almost certainly because I think it had the speedo from a SWB fitted, so it was calibrated for 650 or 700x16 tyres, not 750x16 and so both the speedometer and odometer were out. At an indicated 90kph, I was actually doing 100kph.

That doesn't have much to do with your situation. It just amuses me that the latest Land Rover isn't much better than my old Series III, which I always suspected was built up from odd bits, especially as when I bought it in 1983, the motor was from an early 60's Land Rover.

[isuzurover]

No, my 1973 Series III LWB did the same thing. :p It read 100 km for 107 km actually travelled when the retreads were new and 106 km travelled when they were worn.

However that was almost certainly because I think it had the speedo from a SWB fitted, so it was calibrated for 650 or 700x16 tyres, not 750x16 and so both the speedometer and odometer were out. At an indicated 90kph, I was actually doing 100kph.

That doesn't have much to do with your situation. It just amuses me that the latest Land Rover isn't much better than my old Series III, which I always suspected was built up from odd bits, especially as when I bought it in 1983, the motor was from an early 60's Land Rover.

In series vehicles (and others with mechanical speedo drives), the ODO reading is directly related to the speedo reading - as they are both driven by the same cable. IME 110/defender speedos under-read on standard tyres but are spot on if you fit 33's.

The D3/4/RR(?) is a different kettle of fish. As it has an inbuilt GPS(?) and a billion sensors there is not necessarily a correlation between the speedo reading and the ODO reading (though there could be?). Jesse - I assume you have standard wheels? (sorry if you have mentioned and I missed it). Maybe this is yet another software glitch???

[gghaggis]

I assume you have standard wheels? (sorry if you have mentioned and I missed it). Maybe this is yet another software glitch???

Jesse - not quite a "glitch", but that reminds me - have you re-calibrated the SatNav (there's a function in the Nav setup). You need a decent straight road to get it spot on. I think this would also reset the trip computers.

Cheers,

Gordon

[vnx205]

In series vehicles (and others with mechanical speedo drives), the ODO reading is directly related to the speedo reading - as they are both driven by the same cable. IME 110/defender speedos under-read on standard tyres but are spot on if you fit 33's.

The D3/4/RR(?) is a different kettle of fish. As it has an inbuilt GPS(?) and a billion sensors there is not necessarily a correlation between the speedo reading and the ODO reading (though there could be?). Jesse - I assume you have standard wheels? (sorry if you have mentioned and I missed it). Maybe this is yet another software glitch???

A squillion sensors and they still can't get it right. :D:D:D

If it uses a GPS to measure speed and distance, wouldn't that make the size of the tyres irrelevant?

[roamer]

A squillion sensors and they still can't get it right. :D:D:D

If it uses a GPS to measure speed and distance, wouldn't that make the size of the tyres irrelevant?

Exactly right, but the on board GPS hidden screen for speed aleast on mine is 5kph slower than the speedo, so speedo must get signal from another source. Problem seems to be that odometer reading is also out.
I think there is an adjustment to recalibrate for new tyres, maybe it thinks your wearing the tyres out faster than you are.
I'll compare mine, but I'm in QLD and on most flat roads at the moment would be in knots.
Cheers Ken

[101RRS]

Most modern cars take their speedo input from the ABS rings on one of the driveshafts.

Garry

[Colin Pedersen]

The code wont work for me. I can get the screen for the pin but it does nothing?

Are there any other codes?

Sorry, the code works for a D3, not sure about a D4. the D3 was more of a pattern than a code you may need to try some trial and error hoping its is still a 3 digit number! You might be able to google it somewhere?

[AGRO]

Each measurement system has inaccuracies even GPS.

All odometer and speedo values will be correct again when the GPS Sytem don't work anymore, the battery dies and people begin to look at the real world, street signs and road maps again.

The reliance of the modern world on the "TRUTH" that comes off and out of a black box GPS computer never ceases to amaze me - whilst working they are great but switch them off or break them and how do you know where you are.

At best its a useful tool and aid to get you through the real world rather than the other way around. 100% reliance on them would be not be wise.

I love those KM Markers on some highways that enable you to check your odometer and speed. Even the 10km markers along main highways and can be used to verify odometers and speedos and bring your attention into the real world rather than a screen a few cms in size on the dash board. This has the added advantage of focusing attention on the road rather than on a menu on navigation unit.

In the remote back blocks and off road your awarenes of position relative to real topography and a papermap is more important than where a computer thinks you are on a matrix of excited electrons on a miniture screen.
:):):):):wasntme:

[Jesse B]

Jesse - not quite a "glitch", but that reminds me - have you re-calibrated the SatNav (there's a function in the Nav setup). You need a decent straight road to get it spot on. I think this would also reset the trip computers.
Gordon

Gordon - have not done a recalibration, but will do so when I'm re-united with the bus in a week or so. Given that I've suddenly found I've done more km than thought I need to get it in for a service too - so will see what the dealers dudes have to say about it too.

And yes, I do have standard size tyres (255x55/19) tho not standard manufacturer as I'm running Pirelli Scorpions - not that this should make any difference.

[allisong]

http://www.aulro.com/afvb/d3-d4-rrs/111697-d4-speedo-v-gps-4.html#post1847705