MK5 Golf GTI

All Things Mk5 => Mk5 General Area => Topic started by: berttie21 on September 08, 2009, 10:08:07 pm

Title: Speedo Accuracy??!!
Post by: berttie21 on September 08, 2009, 10:08:07 pm
I installed a fiscon bluetooth kit today and the MFD now shows the current speed. however this is quite different from the speedo when travelling above 50mph.

MFD = 48mph   Speedo = 54mph
MFD = 70mph   Speedo = 81mph
MFD = 80mph   Speedo = 93mph

I had a friend follow me in s ford focus and at 80mph in the focus the speed was reading about 95mph.

is this common with all speedo's of somthing common with vw of GTI's?

Also does anyone know where the fiscon pulls the speed data from compared to the speedo?

Cheers
Title: Re: Speedo Accuracy??!!
Post by: Top Cat on September 08, 2009, 10:09:57 pm
All speedo's are like this. You can play with the air-con settings and get the true accurate speed reading up on their.  :happy2:
Title: Re: Speedo Accuracy??!!
Post by: keith on September 08, 2009, 10:13:56 pm
Aye my sat nav is always dif from the dash, lower speeds are more accurate but higher exagurate on the speedo.
Title: Re: Speedo Accuracy??!!
Post by: Janner_Sy on September 08, 2009, 10:14:52 pm
mine isnt that bad. according to my tom tom when it shows 70mph, my speedo is over reading about 3mph. @100mph on the tom tom my speedo is about 5mph out until about 145mph when it goes a little wayward
Title: Re: Speedo Accuracy??!!
Post by: Poppa Dom on September 08, 2009, 10:18:20 pm
mine isnt that bad. according to my tom tom when it shows 70mph, my speedo is over reading about 3mph. @100mph on the tom tom my speedo is about 5mph out until about 145mph when it goes a little wayward
Of course, this was on the autobahn or private road/track :)

Title: Re: Speedo Accuracy??!!
Post by: Top Cat on September 08, 2009, 10:19:21 pm
mine isnt that bad. according to my tom tom when it shows 70mph, my speedo is over reading about 3mph. @100mph on the tom tom my speedo is about 5mph out until about 145mph when it goes a little wayward
Of course, this was on the autobahn or private road/track :)



It actually was the jammy sod lives or did right the ring.  :fighting2: :rolleye:
Title: Re: Speedo Accuracy??!!
Post by: Janner_Sy on September 08, 2009, 10:23:46 pm
was/did is exactly right there. removals collecting my furniture tomorrow. mentioned a ring trip today to her and got the look of death. I might wear the trousers, but i dont rule the roost. :ashamed:

@domT   i wouldnt dream of driving over the speed limit in the UK, that would be illegal, and im an honest, law abiding, hardworking, citizen.....who hasnt been caught yet
Title: Re: Speedo Accuracy??!!
Post by: Hurdy on September 08, 2009, 10:57:58 pm
I ignore my speedo....it tells me lies :fighting2:

I concentrate on the GPS speedo on the head unit as I know it is accurate to 0.1mph :happy2:
Title: Re: Speedo Accuracy??!!
Post by: WhiteHartMart on September 08, 2009, 11:11:23 pm
Yep - compared to my Sat Nav the speedo was about 4 - 5 mph or so out at Motorway speeds.

Can you get an accurate speed display on the RNS510 at all??
Title: Re: Speedo Accuracy??!!
Post by: RedRobin on September 08, 2009, 11:22:35 pm

All speedo's are like this. You can play with the air-con settings and get the true accurate speed reading up on their.  :happy2:


....But not exactly the ideal position for watching your speed.
Title: Re: Speedo Accuracy??!!
Post by: Andy on September 08, 2009, 11:24:26 pm
read some where speedo's are 10% out
Title: Re: Speedo Accuracy??!!
Post by: RedRobin on September 08, 2009, 11:31:40 pm
....

VW speedo accuracy tested against GPS Road Angel: 100 on speedo = 87mph

VW speedo accuracy tested against GPS Pgo Alert: 100 on speedo = 87mph

(https://www.mk5golfgti.co.uk/forum/proxy.php?request=http%3A%2F%2Fdaz.co%2Fmedia%2Fb308%2FRedRobin_05%2FPogoAlert1.jpg&hash=0725314f294c151c78b8fb41c52ccb13704ed27c)

I hardly ever look at the VW speedo now.
Title: Re: Speedo Accuracy??!!
Post by: RedRobin on September 08, 2009, 11:32:51 pm

read some where speedo's are 10% out


....Speedo's are allowed to be 10% out apparently.

VW volunteered to change mine as it's more than 10% out but they said they couldn't guarantee a new one would be more accurate than under 10%, so I said thankyou but no thankyou.
Title: Re: Speedo Accuracy??!!
Post by: Andy on September 08, 2009, 11:44:34 pm
slightly of topic-the digi dash & speedo in the vauxhall astra gte was ony 2% out :laugh:
Title: Re: Speedo Accuracy??!!
Post by: pitch3110 on September 10, 2009, 08:59:28 pm
I have noticed this.

My A4 is pretty spot on with TomTom on board.

Wifey's ED30 is a mile out
Title: Re: Speedo Accuracy??!!
Post by: rskardon on September 11, 2009, 04:00:29 pm
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
Title: Re: Speedo Accuracy??!!
Post by: RedRobin on September 11, 2009, 04:27:59 pm
^^^^
Interesting point about GPS reading horizontally and one to remember when next hurtling off Beachy Head! :laugh:
 
Still much more accurate than the VW oem speedo though I expect.
Title: Re: Speedo Accuracy??!!
Post by: Poppa Dom on September 11, 2009, 04:54:01 pm
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.
Title: Re: Speedo Accuracy??!!
Post by: RedRobin on September 11, 2009, 06:06:21 pm
^^^^
Excellent info, Dom! :drinking:

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.
Title: Re: Speedo Accuracy??!!
Post by: stealthwolf on September 11, 2009, 10:57:14 pm
...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?
Title: Re: Speedo Accuracy??!!
Post by: Poppa Dom on September 11, 2009, 11:39:35 pm
Erm - 70mph?  :laugh: In an ideal world you want to calibrate at a speed where the readings between true gps speed and speedo start to diverge.