Another pointless question

[Marcellus]

During yesterdays drive home (8 hours coast to home) at one point my iPod batteries had run out and I couldn't find the charger so being unable to have any "fun" driving I found ways to amuse myself.

One of the questions I came up with and wasted a good half hour thinking around was;

"It is generally accepted that a speedo over-reads, by as much as 10/12% in our X Trail when compared to a GPS speedo.....does that mean that the mileage is also over reading by the same amount?"


SO over to the Petrolhead Nirvana massive!!!

[Ben-san]

Hmm. Ponderous indeed. :)

It may depend on the manufacturer... I'm guessing older cars with mechanical odometers might clock up by spinning cables so theoretically, it would over read in line with what the speedo is saying.

BUT, aren't digital odometers linked to the ECU to prevent clocking?

[Marcellus]

but you're still converting wheel rotation into two readings...one is the speed the other is the distance!!

[Ireland]

Marcellus, I reckon you are spot on.

If you have cruise control set to 120kmph and you watch it for a set time, say 15 mins, you'll find you have done 30kms so the speed and the distance readings correspond.

I obviously was bored on a drive one day and tried it.

This was ages ago ..... but I reckoned nobody would be interested so I never bothered posting it anywhere. :D

I'm glad you posted it.

Now I don't feel as daft any more.

;)

:D

[Marcellus]

oooo my trip got a lot worse than that...I too timed and measured every 15 minutes to see average speeds........other great time wastes included;

> playing "name that tune" by text with katie
> betting with myself whether I could get trucks and cars that I passed to wave or not (me on the right side of a car versus the rest of the drivers on the left...you can get very close)
> the % of men versus women who waved!!
> could I eat a pringle without chewing
> how many pringles I could have in my mouth at once without breaking any
>

[Ireland]

Oh ....

After reading that I feel almost sane.

;)

:D

:D

[Ben-san]

> could I eat a pringle without chewing


That's pure genius.

Note to self: buy pringles on the next long journey!

[Marcellus]

ben - make sure they're "hot and Spicy" flavour...adds another dimension....at one point I had tears!!

I also can now say that the very top speed of the landy is 95mph (indicated)....that was down a long long hill with a following wind draughting a Caenne!!

[harry_430]

Right, so a relatively sensible question about over reading speedo's.....
i think there might be a parallel to the mens swimming manufacturer. do you think they over read as well?

Personally i believe that the speedo and the mileage over read, so most cars have dont between 5 and 10% less than they read. but then as all cars are afflicted with this it is not hugely relevant.

as for the crips i suggest hedgehog flavour as that is likely to start the debate on how people know whether the taste is as accurate as the speedo (this time i think i do mean the mens trunks)

[bruce fielding]

"It is generally accepted that a speedo over-reads, by as much as 10/12% in our X Trail when compared to a GPS speedo.....does that mean that the mileage is also over reading by the same amount?"


Yes.

Next question...

[Marcellus]

Yes.

Next question...

Should I have Emmental or Rocquefort in my baguette for lunch today?



on the initial topic...is that really so?
> you using the rotation of the wheel as the measuring device and then (and this is possibly the important bit) converting that to a needle/dial display for speed whereas for distance your just using the measure and displaying it electronically digitally.

Isn't it the coversion to the need/dial display where the error occurs?

[Harsh]

have some cheddar you tart.

HTH

[Marcellus]

ch ch ch cheddar!!

(the french don't do ch ch ch cheddar)

[tinman]

"It is generally accepted that a speedo over-reads, by as much as 10/12% in our X Trail when compared to a GPS speedo.....does that mean that the mileage is also over reading by the same amount?"


haha, depends on the car. my old Rover 827 would show 36mph as 30 (kinda found out 3 miles after buying it and going through a speed camera). However, at 50mph it would be bang on. At 60mph it would show 56. At 70 it would show 60, at 80 maybe 71, at 85 it would 77, and 90 it would be 85, and by 100 it would be 100. It would then be accurate all the way to the end after that. Had it at just over 140 in Italy. Rude not to.

[S B - Nigel]

In my Midget on the new drive cable the recon speedo the speed needle, tripometer and odometer appear to be out by different amounts but none by much and all are more accurate than my wife's brand new (well 6 months old) car's digital readouts

When I had my Griff it's speedo inaccuracy wasn't linear with the speed

So I would guess the mechanical drives can mean a difference in accuracy between speedo and odo/trip

Well I've made that as clear as mud :rolleyes:

[Harsh]

In my Midget on the new drive cable the recon speedo the speed needle, tripometer and odometer appear to be out by different amounts but none by much and all are more accurate than my wife's brand new (well 6 months old) car's digital readouts

When I had my Griff it's speedo inaccuracy wasn't linear with the speed

So I would guess the mechanical drives can mean a difference in accuracy between speedo and odo/trip

Well I've made that as clear as mud :rolleyes:

i'm glad we got that sorted out :confused:

do you know professor stanley unwin by any chance?

[Redex R]

of course the speedo overeads officer...now I'm off for some Pork scratchings :)

[S B - Nigel]

i'm glad we got that sorted out :confused:

do you know professor stanley unwin by any chance?

Unwin - you're showing your age there Harsh! ;)

My explanation made sense . . . . . . before I wrote it down

Any other technical explanations you want simplifying just let me - don't phone as my voice mail is completely full with questions left by that nuisance, Hawkins :D