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Discussion Starter #1
I have the factory rims and common tires ( forget at the moment ) so I believe my gauge is correct. Torque via the ECU not GPS says 5 to 10 (-) MPH. My guess is that torque is just wrong but wanted to ask if this is common. It's not that it lags behind its just 5 to 10 MPH off when driving at a constant speed.
 

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The speedometer has an 8%-fast fudge factor in it. The odometer should be accurate provided your tire sizes are stock. TADTS

A lot of people tested this a lot when the car first came out, because they were worried that if the registered speed was always 8% over the GPS speed, they'd be getting scammed out of 8% of their warranties. It turns out the car knows how fast you're going, sets the odometer correctly, and is just lying to you.

The fudge is set in the cluster itself on the '05-'07 - the CANbus sends it the accurate speed in kph and it displays 8% higher. The '08 has two separate speed fields in the CAN frame, I think for MPH/KPH swapping on the ECU side rather than cluster side. But I think the cluster still fudges above the speed you send it anyway.
 

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I use my Traqmate as a speedometer when it's not a short trip. The nice thing is the stock speedo reads fast so no tickets from the error unlike another car I had...
 

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Did you consider a search? Really, c'mon.
 

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Discussion Starter #6
^^ What the hell crawled up that guys tail pipe?

I use my Traqmate as a speedometer when it's not a short trip. The nice thing is the stock speedo reads fast so no tickets from the error unlike another car I had...
Makes good sense.

Thx for the clarification, I though maybe that was the issue.
 

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No need to be impolite.

But, look at this way:

This site has been around since roughly 2004.

What are the odds that you or anyone would be the very first to ask this question?

Close to none.


It is tedious (and boring) to read the same questions over and over again. You see that, right?


--

BTW, almost all cars have optimistic speedometers. C&D did an article about the topic a few years back.
 

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Discussion Starter #9 (Edited)
glb, first off I figured it was related to torque so obviously the search hits did pull up. I tried google, but now I see its not torque related.
Second yes I know what you are saying but there are two things even worse.
1) Someone that thinks the topic in question was a duplicate and could have been answer by a search. If I had reason to suspect its was the car, the yea I would have seen that.
2) those annoying people that say do a search... because of them when you do a search you get nothing hits that say "do a search". ( not saying that is you as the info was already provided )

So if having to "read the same questions over and over again" is worthy of a degrading comment, then take the effort to link to the answer and keep the forums clean. because both not searching and commenting and posting nothing more the "do a search" are really the same thing, yielding the same result a dead pointless thread.
 

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Discussion Starter #11 (Edited)
I have not done much testing with it but at 50 MPH on speedometer ECU says 43-ish. I could change to digital to get exact I guess. Though yes it changes at low and higher speeds.
 

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It's related to legal issues across the pond if I remember correctly. Basically, they have to build in enough padding so the speedometer can be guaranteed to never read low. Hence why it is scaled up for the speed and not for the distance.
 

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Error is normally a percentage, not a fixed mph.
 

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Discussion Starter #15
I'm new yes, but also have that one book marked.
 

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My car after 40 miles or so the Speedometer reads lower than the speed you are going.
Odometer is correct. To know your speed I just use a multiplication factor on my tachometer. I feel some resister is heating up but since the dealership is not driving the car 40 t0 50 miles to have it act up they have no idea what the problem is. I have an 05 Elise.
 

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Discussion Starter #17
For me its like the speedometer is reads lower until 45 or so, then crosses over and starts to read higher. Though it is very hard to tell while driver so I may be wrong but it sure seems that way. I's ask my wife to take readings for me but someone may get the wrong idea...
 
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