Speedo Accuracy??!!

[rskardon]

Its worth bearing in mind that GPS is only accurate on a perfectly flat road. Think about it in extreme terms if you drove your car off a cliff you may be doing 100mph but as its straight down and not along the gps would register 0mph, obviously that is extreme but a GPS will typically measure movement along the horizontal plane only.

That said i do believe the speedo is a bit inaccurate, as with most cars i have owned it reads high, this makes sense as it allows the cars fuel economy to appear better than it is. Also i would think that car companies would leave themselves open to being sued if the speedo read low, as you would argue that the car reading is at the speed limit.

Cheers,

R

[RedRobin]

^^^^
Interesting point about GPS reading horizontally and one to remember when next hurtling off Beachy Head!
 
Still much more accurate than the VW oem speedo though I expect.

[Poppa Dom]

If people are finding that there speedometer is quite a lot different than GPS verified speed, don't forget that you can make adjustments using VCDS. This is in the instrument cluster. Changing the last digit of the long coding (Distance impulse number) is used to fine tune/calibrate the speedo. There is a VW TSB that states that this should be set as 7. You'll have to use a bit of trial and error with your own settings, playing with values between 1-7. Just make sure you verify the change with GPS.

[RedRobin]

^^^^
Excellent info, Dom!

I've got so used to my GSP big digital display in my sightline that I rarely look at the VW speedo now but more at the rev counter.

[stealthwolf]

...you can make adjustments using VCDS...

Thanks for that! Hmmm....I need to do some midnight runs to ensure the speedo is correct. Is there an ideal speed to hold the car at and use as a benchmark?

[Poppa Dom]

Erm - 70mph?  In an ideal world you want to calibrate at a speed where the readings between true gps speed and speedo start to diverge.