2003 A4 3.0 Speed limiting in ECU

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Please don't chastise me. But in the name of science I took my A4 out on an empty highway near me yesterday. After some test runs up and down this road to nowhere, looking for speed traps. I tested to see
if it was indeed programmed not to exceed 130MPH. At 135MPH I felt my question had been answered. At that point I asked myself, "What are Y rated tires good till?" At that point I let of the gas and two mile later I was back down to 75MPH, it felt like it could have gone faser, and the car felt great.
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You must have been tempted.....
snipped-for-privacy@anywhere.org wrote: At 135MPH I felt my

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On Mon, 11 Apr 2005 15:13:18 -0400, Jules
back.

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Actually, Y-rated tires are good up to 186 mph.
http://www.tirerack.com/tires/tiretech/general/speed.jsp
Cheers,
Pete
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On Mon, 11 Apr 2005 17:52:39 GMT, snipped-for-privacy@anywhere.org wrote:

At an indicated 135mph, I'd expect you to be doing less than 130mph. Does that climate control hack that shows you the speed in KM work on a 2003 A4? It might be worth seeing what that says. Of course, looking down at the climate control screen whilst doing 130mph might not be the smartest course of action!
andyt
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On Mon, 11 Apr 2005 19:46:50 GMT, Andy Turner

ECU would be using the same number as the speedometer, does this mean I have to run the test again? ;)
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There's error in the speedo so what you observed is not entirely out of place. I'm sure the ECU is using an electronic measurement of speed from some sensor that's no doubt more accurate than the speedometer.
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Charlie Giannetto wrote:

Why would it? Which additional sensor would there be? And even more, what sense would that make?
Regards
Wolfgang
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Wolfgang Pawlinetz wrote:

It makes legal cover-your-ass sense, at least in the US.
-- Mike Smith
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Mike Smith wrote:

Well, I'm not doubting that it makes sense to have a speedo which is showing a little more than the actual speed. It's the law here as well.
But I'm wondering where the ECU/Air Conditioning display should get different info from.
IMO it's just the same information shown on another display.
Regards
Wolfgang
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The speedo shows a little less than the actual speed.
Both the speedo and the Air Con display get the speed from the same place (usually the ABS Sensor) but the speedo is calibrated to show a little less.
Richard
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Richard Goulding wrote:

It should be vice versa, no? At least here in Europe that is. The speedo shows a higher speed than the actual one.
Regards
Wolfgang
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In the uk speedos always read a higher amount than the actual amount.
That is,
Speedo speed = 30mph, Actual Speed = 27mph.
Richard
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"Richard Goulding" wrote

IME, the speedo shows a little MORE.
Cheers,
Pete
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Richard
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I actually like this 'feature', as I tend to drive around about 10 mph higher than the posted speed limits, which generally the police will let you have - so in the case of the Audi, an indicated 10 mph over is really more like 7 mph over, which is better for the driver's license....
Dan D Central NJ USA
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snipped-for-privacy@anywhere.org wrote:

Audis and VWs are designed to show a higher than actual speed on the speedo. The ECU knows the real speed (to within the accuracy permitted by variations in tire size due to wear, etc.) and there's a trick you can do with the Climatronic to get it to show the true speed. (On the Passat, it's fan-down, temp-down, and Econ all at the same time, then use temp-up to reach option 16 - don't know if it's the same on an A4.) I recently did this on my Passat and found that the difference was about 3-4 MPH at 50.
-- Mike Smith
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Mike Smith wrote:

Interesting, I'll try that as well.
Regards
Wolfgang
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On Tue, 12 Apr 2005, Mike Smith wrote:

I have checked the speedo in both my A4 (2002) and Passat (1995) by timing the interval between mile markers on the highway at a constant speed (65mph). Both were within 1mph of the calculated result.
Steve
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Andy Turner wrote:

Indeed, prob. < 120mph. If you can, borrow a GPS unit which will give you a more accurate "actual" speed. My GPS unit tells me that when I'm doing 70mph, it's actually 65. The differential gets greater the faster you go (compared to say 30 mph).
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