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Wales
by Joske Vermeule, September 1
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Forums39
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Jun 14th, 2026
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Joined: Dec 2014
Posts: 216
L - Learner Plates On
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OP
L - Learner Plates On
Joined: Dec 2014
Posts: 216 |
Hello,
the speedo of my 3.7 Roadster shows close to 20% too high speeds compared to my GPS. Even my smartphone-GPS confirmes that it shows too much. After some internet research I think that the car software was fed with wrong informations about gearing, rear axle ratio or tire size at the factory. Can a normal dealer correct that with his equipment or do I have to visit a tuner which offers speedo correction? Have you ever heard of such an issue?
Ex-Roadster 3.7, now P6
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Joined: Apr 2012
Posts: 5,013 Likes: 32
Charter Member
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Charter Member
Joined: Apr 2012
Posts: 5,013 Likes: 32 |
My 3.7 speedo gives a pretty accurate reading on GPS - I used sat nav on a recent long journey and the two measurements were reasonably aligned.
+8 4.8
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Joined: May 2014
Posts: 5,442 Likes: 133
Black Rat Charter Member
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Black Rat Charter Member
Joined: May 2014
Posts: 5,442 Likes: 133 |
Go to this website http://www.caigauge.com you can reprogram your own. When you get to the website go Q&A Smiths electronic speedo. It is quite easy to get to programming mode but then some careful measuring is involved.
Keith
2013 narrow bodied + 4 Ruby.
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Joined: Dec 2013
Posts: 1,075 Likes: 1
Has a lot to Say!
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Has a lot to Say!
Joined: Dec 2013
Posts: 1,075 Likes: 1 |
Is your car still under warranty?
John
Silver 2005 S1 Roadster V6 - Henrietta
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Joined: May 2011
Posts: 4,896
Drive on the Wild Side Part of the Furniture
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Drive on the Wild Side Part of the Furniture
Joined: May 2011
Posts: 4,896 |
Go to this website http://www.caigauge.com you can reprogram your own. When you get to the website go Q&A Smiths electronic speedo. It is quite easy to get to programming mode but then some careful measuring is involved. The 3.7 Raodster has VDO gauges not Smiths, I'm not sure that they can be calibrated accept through the ECU. I have the same issue, when Speed reads 70 mph, car is actually doing just under 60mph. Be careful with GPS readings, speed reading on my iPhone was 5 mph lower than that on Neilm's using the same software. Going to try re-install and recheck.
Adrian
Buggered Off, to a modern none leaky car, heart's still ticking
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Joined: Jun 2007
Posts: 859 Likes: 1
Talk Morgan Regular
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Talk Morgan Regular
Joined: Jun 2007
Posts: 859 Likes: 1 |
Now I know why Adrian's car reaches 60 in 4.5 seconds, its actually only 45 mph. Always thought my 3L roadster was quicker. 
Honda S2000
Lexus UX 250h
Toyota Auris Hybrid
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Joined: Dec 2014
Posts: 216
L - Learner Plates On
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OP
L - Learner Plates On
Joined: Dec 2014
Posts: 216 |
NeilM,
the positive thing about it is, that my roadster now has 20% more km. And since it is often complained about that our cars are not driven enough, this is a good thing..
To all, thanks for your feedback. Adrian S is right, this can only be corrected trough the engine control unit. The 3.7 uses the instrument cluster of the Mustang.
I've advertisements of tuners, which can reprogramm the unit if you change tire sizes or the rear axle ratio. So it can be adjusted. I guess I'll do the obvious and visit the dealer. He didn't give me the impression so far, that he can fix that. So the next step then is a local Mustang tuner which can. For some cash. And yes, the car is still under warranty.
Last edited by beltempo; 28/12/14 10:40 AM.
Ex-Roadster 3.7, now P6
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Joined: Feb 2012
Posts: 112
L - Learner Plates On
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L - Learner Plates On
Joined: Feb 2012
Posts: 112 |
Hi Neilda,
I have a Roadster 3.7 in build at the factory and and im wondering why your speedo is ok and others arnt.One thing springs to mind is wheel diameter and tyre size.
Mine is having 16"x7" wheels and whatever tyres they are fitting at the moment.Can you please tell me what size your wheels and tyres are?
regards David
,,BSA Goldstar,Honda CB1100R. Jaguar FTypeS Porsche Cayman S
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Joined: Apr 2014
Posts: 3,550 Likes: 5
Talk Morgan Addict
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Talk Morgan Addict
Joined: Apr 2014
Posts: 3,550 Likes: 5 |
I think the 3.7 build speedo issue is a kmph issue and not mph I think the new Plus 4 has the same issues?
Mark - No Longer driving Archie the Old English Sheep Mog........... 2010 Roadster 3.0 V6 (S3) 
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Joined: Jul 2007
Posts: 28,911 Likes: 354
Salty Sea Dog Member of the Inner Circle
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Salty Sea Dog Member of the Inner Circle
Joined: Jul 2007
Posts: 28,911 Likes: 354 |
Graham (G4FUJ)
Sold L44FOR 4/4 Giallo Fly
'11 MINI Countryman Cooper D All4
'90 LR 90 SW
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