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Speedometer Question

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Old Oct 22, 2001 | 10:48 AM
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From: Winston-Salem
Default Speedometer Question

I called American Honda today to ask about variance in the speedometer. They told me that the speedometer could only read above the actual speed you are going and never below.

I think this is BS myself as it seems like there is a lag when accelerating. Anyone ever tested the S2000 against a radar gun especially during periods of rapid acceleration?

Thanks,
Dean
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Old Oct 22, 2001 | 11:16 AM
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Testing with my GPS unit seems to back up their claim. The GPS will read 100 mph and the speedo indicates my speed to 103 mph. Faster than I am really going. For the record: It's a known issue about the speedo's error. My testing revealed a 2.7% error factor from 50mph on up. Even in reverse!!

Mark
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Old Oct 22, 2001 | 11:25 AM
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thank you for that bit of information...now i will speed 3 miles over the speed limit =)
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Old Oct 22, 2001 | 11:30 AM
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Testing with my GPS unit seems to back up their claim
Lips2000:

Thanks for the idea. I do have a portable GPS at the house. I can check the speed with it.

However I did notice in my previous car that there appeared to be a little lag on the GPS speed calculation although I will do some testing to see.

Dean
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Old Oct 22, 2001 | 11:47 AM
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Why should we assume that tracking with a gps would be a good indicator of actual speed? According to the Garmin website, and I have a consumer quality Garmin, relative positional accuracy for their units is +/- 15 meters or 49 feet. This alone could account for the difference between speedometer and gps reading.
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Old Oct 22, 2001 | 11:57 AM
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Also, my pet peeve with the speedo is that it is doing a sampling or averaging algorithm, so it doesn't update continuously. At the track, accelerating hard down a straight, it will read 82, 86, 89, 92, etc. Are you saying that I am never going as fast as the speedo says, even though it is averaging the speed over some time period?

Tanq
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Old Oct 22, 2001 | 11:59 AM
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so when a cop busts out w/that pointless question of,
"do you know how fast you were going?" right after he asks, "do you know why i pulled you over?"
should i answer,
A)"to get a better look at the car!"

B)"no sir, my speedometer is a bit off, you tell me!"

C)"60 if my speedo. read 63?"
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Old Oct 22, 2001 | 12:15 PM
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Originally posted by scooby2
Why should we assume that tracking with a gps would be a good indicator of actual speed? According to the Garmin website, and I have a consumer quality Garmin, relative positional accuracy for their units is +/- 15 meters or 49 feet. This alone could account for the difference between speedometer and gps reading.
You are correct, with respect to pinpointing your position, but if I am moving, the error plays less of a factor (assuming that the current position moves relative to the last known position). Basically, assume the error as a constant in both distance and direction. You would, then, get an accurate speed reading. Does this make sense to anyone with better verbal skills? Hope so...

Mark
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Old Oct 22, 2001 | 12:16 PM
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[QUOTE]Originally posted by dean29
[B]
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Old Oct 22, 2001 | 12:21 PM
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[QUOTE]Originally posted by Tanqueray
[B]Also,
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