S80 Speedo tells lies.

marcus.grant · Aug 17th, 2007, 17:37

My TOM TOM SAt Nav has a speed read out that is suppose to be very good. I have use it in 3 Cars and it has always showed the same speedo read outs in the right place to be wrong i.e. 30,40,50, 60,70. each car being different but showing the same results over 6-12 months no matter the weather.
The S80 speedo is very slow. Car-30 Sat-24 Car-70 Sat-64.
Can you tell me the part I need and were it is on a S80 2.9se B6294s
I am sure it is a common problem, just takes a stopwatch or a sat Nav to tell you, or a red face in the car behind.
Mine you the fuel economy is great.
Regards Marcus

Viper_7 · Aug 17th, 2007, 18:03

Sounds about right. Most speedo's specifically record a lower value than actual and can be up to 10% which is what your seeing at the opper end. The lower end does seem to be under reading a bit much though.

This is to protect the manufactures from people claiming against them for people who have been caught speeding etc if they read under rather than over.

You can have it calibrated, but again it will be set under but will be closer to the real figures.

Sat-nav speed readings are only accurate at sea level I belive, so this won't be 'that' accurate either.

Vipes

marcus.grant · Aug 17th, 2007, 18:26

Reading way under the true speed is a little of and understatement here. If I went as fast as the Car would allow, it would read 185mph at this off set.

You can have it calibrated, but again it will be set under but will be closer to the real figures.
How and were Viper? I haven't heard of this I thought it was a sender replacement to be honest.

Sat-nav speed readings are only accurate at sea level.
That Sound right to me, thanks for that reminder of the rules of triangulation with Sea level being Zero datum.

Marcus

Viper_7 · Aug 17th, 2007, 18:40

You could be right it may be a replacement sender - but surely these are calibrated somehow?
there's nothing stopping you changing the wheel/tyre sizes so that the overal radius is different from "normal" and thus the speedo would mis-read and would need to be calibrated. I know people who do this - not specificaly with the S- series though but you'd think it would be possible? As to how - don't know!

I agree with you though especially with the 30mph different that it's out more than it should be.
Is it still within the warranty period - I'd get it in.

Vipes

Aug 17th, 2007, 17:37	#1
marcus.grant Junior Member Last Online: Oct 16th, 2016 06:48 Join Date: Aug 2006 Location: Melksham, Wiltshire.	S80 Speedo tells lies. My TOM TOM SAt Nav has a speed read out that is suppose to be very good. I have use it in 3 Cars and it has always showed the same speedo read outs in the right place to be wrong i.e. 30,40,50, 60,70. each car being different but showing the same results over 6-12 months no matter the weather. The S80 speedo is very slow. Car-30 Sat-24 Car-70 Sat-64. Can you tell me the part I need and were it is on a S80 2.9se B6294s I am sure it is a common problem, just takes a stopwatch or a sat Nav to tell you, or a red face in the car behind. Mine you the fuel economy is great. Regards Marcus

Aug 17th, 2007, 18:03	#2
Viper_7 Premier Member Last Online: Aug 30th, 2013 17:33 Join Date: Apr 2006 Location: York	Sounds about right. Most speedo's specifically record a lower value than actual and can be up to 10% which is what your seeing at the opper end. The lower end does seem to be under reading a bit much though. This is to protect the manufactures from people claiming against them for people who have been caught speeding etc if they read under rather than over. You can have it calibrated, but again it will be set under but will be closer to the real figures. Sat-nav speed readings are only accurate at sea level I belive, so this won't be 'that' accurate either. Vipes __________________ S60 D5 SE 2004 Titanium Grey Winter Pack Mods: Volvo Tax disc holder - increases power output by 5% Child Seat Rear and side Volvo fitted blinds. Tree Sap from May - July. Removed at least 46 cup holders for weight reduction.

Aug 17th, 2007, 18:26	#3
marcus.grant Junior Member Last Online: Oct 16th, 2016 06:48 Join Date: Aug 2006 Location: Melksham, Wiltshire.	The go slow, when it says your gone! Reading way under the true speed is a little of and understatement here. If I went as fast as the Car would allow, it would read 185mph at this off set. You can have it calibrated, but again it will be set under but will be closer to the real figures. How and were Viper? I haven't heard of this I thought it was a sender replacement to be honest. Sat-nav speed readings are only accurate at sea level. That Sound right to me, thanks for that reminder of the rules of triangulation with Sea level being Zero datum. Marcus

Aug 17th, 2007, 18:40	#4
Viper_7 Premier Member Last Online: Aug 30th, 2013 17:33 Join Date: Apr 2006 Location: York	You could be right it may be a replacement sender - but surely these are calibrated somehow? there's nothing stopping you changing the wheel/tyre sizes so that the overal radius is different from "normal" and thus the speedo would mis-read and would need to be calibrated. I know people who do this - not specificaly with the S- series though but you'd think it would be possible? As to how - don't know! I agree with you though especially with the 30mph different that it's out more than it should be. Is it still within the warranty period - I'd get it in. Vipes __________________ S60 D5 SE 2004 Titanium Grey Winter Pack Mods: Volvo Tax disc holder - increases power output by 5% Child Seat Rear and side Volvo fitted blinds. Tree Sap from May - July. Removed at least 46 cup holders for weight reduction. Last edited by Viper_7; Aug 17th, 2007 at 19:11. Reason: XC90??! changes to S-series!

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