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!!!

 

Mine is off, but not that much.

 

Mine is accurate I suppose. At least with .9 mph. Since the hud and gage shoe different readings. pointer and digital readout.

 

Digital gauges are specified +/- one count, analog gauges are specified to be within 3% of full scale. That translates to a maximum error of+/- 1 MPH for the HUD and +/- 6 MPH for the analog speedometer due to the different display types. Of course speed calibration, which is a function of tire rolling diameter, diff gearing, and the software calibration of the count taken by the tailshaft revolution counter could be off, making both readouts inaccurate. But they are both driven by the same source, so if they are off because of that, they'll both be off by the same amount.

 

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.

 

Mine ususally reads the same, but sometime there is a 1 mph difference. I would assume the digital readout would be more accurate than the analog if in doubt.

 

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.

 

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

 

Mine are pretty close.

 

I also have the same 1 mph experience. I also would guess the HUD is the more accurate.

 

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.

 

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

 

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.

 

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.

 

Don't forget that anything 99.001 - 99.999 MPH still reads as 99 on the HUD.

 

Same here.

 

Same here!

 

I am a horrible owner I don't even think about stuff like this.

 

No HUD, so no problem here.

My speedo does match my GPS, so my bet is the speedo is correct.