Speed difference?
Thread Starter
Instructor
Joined: Apr 2006
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Speed difference?
My HUD and my speed odometer are off by 3 or 4 miles per hour. Which would be more accurate? The HUD is always the lower of the two. My car is all stock with only 6,000 miles and I noticed this discrepancy from the first day I got it. Thanks for all reply's!!!
Race Director
Joined: Oct 2004
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Originally Posted by C6 Vet
My HUD and my speed odometer are off by 3 or 4 miles per hour. Which would be more accurate? The HUD is always the lower of the two. My car is all stock with only 6,000 miles and I noticed this discrepancy from the first day I got it. Thanks for all reply's!!!
Racer
Joined: Jan 2006
Posts: 365
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From: Randolph NJ
Originally Posted by Indy-hp
My HUD is 1 mph lower than the speedometer. I'm not sure which is correct, but tend to think the digital HUD should be more accurate than the analog gauge.
Mine is the same.
Le Mans Master
Joined: Sep 2005
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From: Central Florida. Black Sheep Squadron Member. 465 rwhp & 477 rwtq
Cruise-In VIII Veteran
St. Jude Donor '07
Mine is fairly accurate, only at 69 and above I see a difference of 1 mph difference. The HUD is one 1 mph at 69 or above.
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Melting Slicks
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Originally Posted by C6 Vet
My HUD and my speed odometer are off by 3 or 4 miles per hour. Which would be more accurate? The HUD is always the lower of the two. My car is all stock with only 6,000 miles and I noticed this discrepancy from the first day I got it. Thanks for all reply's!!!
Since I own a stripper (I love saying that
), I can't directly answer your question, but hopefully it won't be hijacking your thread to give my own recent observations as to speedo accuracy on my own C6:1. My own analog speedo is about 1-2 MPH optimistic @ 70 MPH, as compared to a WAAS GPS, checked over very long distances, several times.
2. I don't have a HUD, but setting the cruise gives your set point in digital fashion on the DIC as you adjust it. Interestingly, for my car this was within 0.4 MPH of the WAAS GPS -- e.g., setting at 70 MPH indicated on DIC yielded 69.6 MPH on GPS, repeated on many trials, over different set points ranging from ~55 MPH to uh well, um... speeds that are higher than that.
3. I did not run across a 'measured mile' check section or I would have also timed it manually, however, I am confident in the accuracy of the GPS - both intrinsicly [1], and also since I had a chance to match it to one of those remote radar trailers in a construction zone. It has pretty god specs [2].
4. So it seems the car has very accurate information in it somewhere, but the analog gauge appears slightly biased to keep you on the safe side.
[1] Accuracy of WAAS-enabled GPS for the determination of position and speed over ground.
http://www.ncbi.nlm.nih.gov/entrez/q...&dopt=Abstract
[2] DGPS (WAAS) accuracy: +/- 0.05 meter/sec steady state
70 MPH = 31.2928 meter/sec, Speed Error = +/- 0.15978%
http://www.garmin.com/products/iQueM5/spec.html
Last edited by TrackNoob; Jun 25, 2006 at 11:43 AM.
Burning Brakes
Joined: Dec 2004
Posts: 793
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From: Wheaton Illinois
Originally Posted by Indy-hp
My HUD is 1 mph lower than the speedometer. I'm not sure which is correct, but tend to think the digital HUD should be more accurate than the analog gauge.
Burning Brakes
Joined: Mar 2006
Posts: 757
Likes: 2
From: Lake Worth Florida
Originally Posted by Wingrider
I also have the same 1 mph experience. I also would guess the HUD is the more accurate.
A good test: set the cruise control to, say 50mph. The DIC will say "cruise set at 50 mph". Then check out the HUD. 51 mph.
Burning Brakes
Joined: Nov 2004
Posts: 1,161
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From: North Carolina
St. Jude Donor '06-'07-'08
Originally Posted by tv_dir
Mine is also 1 mph off, with the HUD being 1 mph faster.
A good test: set the cruise control to, say 50mph. The DIC will say "cruise set at 50 mph". Then check out the HUD. 51 mph.
A good test: set the cruise control to, say 50mph. The DIC will say "cruise set at 50 mph". Then check out the HUD. 51 mph.
Mine is about 1 mph off but in the opposite direction
...Set cruise to 50. DIC says "Cruise set at 50". Hud reads 49.
Pretty close though.
Anothercrisis
Race Director
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From: Virginia Bch VA
Cruise-In VI Veteran
Cruise-In VII Veteran
St. Jude Donor '06
He always had 3 watches. One was 2 hrs fast, another 2 hrs slow, and the third stopped at 2 o'clock. He always added the time on watch 1, to watch 2, and then divided by 2.
That should work.
Last edited by JFTaylor; Jun 28, 2006 at 11:15 AM.
Team Owner
Joined: May 2004
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From: McKinney TX
St. Jude Donor '21-'22-'23-'24
The C6 has a speedometer? I didn't know that. Learn something new every day. 
I probably don't look at my speedometer more than once a week. Glad to know the hud is probably more accurate, because if the speedo and hud were different by more than 1-2 mph, I'd be worried about it.
I probably don't look at my speedometer more than once a week. Glad to know the hud is probably more accurate, because if the speedo and hud were different by more than 1-2 mph, I'd be worried about it.
Team Owner
Joined: Oct 2004
Posts: 27,420
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From: San Clemente CA
Originally Posted by Indy-hp
My HUD is 1 mph lower than the speedometer. I'm not sure which is correct, but tend to think the digital HUD should be more accurate than the analog gauge.
Same here.
Burning Brakes
Joined: Aug 2005
Posts: 967
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From: / California
Originally Posted by Indy-hp
My HUD is 1 mph lower than the speedometer. I'm not sure which is correct, but tend to think the digital HUD should be more accurate than the analog gauge.
Same here!
I don't even think about stuff like this.
