Odometer/Speedometer Accuracy
 

I bought my 8 in Ft. Liquordale and drove it back 450 miles to Tallahassee, following my wife in her Honda Odyssey. During the trip back we compared speeds by our cell phones and I was showing consistently 3-4 MPH LESS on my speedometer than she was on the Odyssey. When we got home we checked the mileage on both odometers and there was only 0.2 miles difference for the entire 450 mile trip. Does that make sense? I always thought that the speedometer and odometer would register the same error rate.

Also, has anyone else checked the accuracy of the RX8 odometer and speedometer?

What type of MPH display does an Odessy have? Could it be a dial and so subject to parallax error in reading by your wife?

Re: Odometer/Speedometer Accuracy
 

No, the error can and almost always is different for speedos and odos.

I and quite a few others have checked our RX-8s with GPS units, and at around 70 mph, the RX-8 speedo indicates only about 2 mph high - ie, for an indicated 70 mph, true speed is 68 mph. I'd suggest that it's most likely that your Odyssey has a higher error on it's speedo.

Regards,
Gordon

Spin9K, the Odyssey has an analog, and I was about to say you probably had the answer. My wife was driving that Odyssey MUCH slower than I wanted to go with the 8, and I kept complaining, so the thought occured to me she might have been going slower than she said.

Gord, thanks, that really answers it for me. I am used to cars with a 5% or more error and just was surprised that there was no corresponding odometer difference. The Odyssey must be accurate on the odometer but 5 or so MPH low on the speedo at highway speeds.

At 80 on the speedo my GPS was registering around 78, so it's pretty accurate (according to GPS anyhow). I think 82/83 on the dial was right around 80 as measured by the GPS. I seem to recall the error being a little less the slower I went, which makes sense I suppose.

Cheers,

I concur with Gord. Using GPS as the standard, my 8's speedo registers about 3% high... so at GPS 68mph the car's speedo reads 70mph. The % error remains consistent throughout the speed range (well, at least up to about 80mph... I'm too sure I'll get a ticket if I go faster around here).

Afterthought: Please, NO ONE post a pic of yourself in your speedo. Thank you. ;)

Well, I think a good way to check out your speedo is:

- take the highway
- run at 60mph flat, use cruise control to keep speed stable
- use a stopwatch, and mesure exactly 1 minute
- verify that the trip milage went up exactly one mile after 1 minute.

Nice thing about this is that you don't need a gps to test it out. Of course this assumes that the odo is more precice than the speedo.

Only a matter of time....
 

Jeez, what took so long? :D You guys are worse than high school kids. Of course, lots of you ARE high school kids...

RX-8 speedo

I did something verysimilar. I just ran on the interstate and measured time between mile markers. At 60 mph it's suppost to be 60 seconrds. My test on original tires and snow tires both came up to 61 and some change. Close enough for me.

I got a kick out of the complaints of the digital speedo when the car came out. The analogue speedo on my 3rd gen RX-7 is terrible. And it's inaccuracy varies all over the place with speed (using a Garmin GPS III+ as a standard). The car has a Apex'i Power FC in it which reads out speed (trans. has a "digital" output for speed - pulses). The reading on it is pretty close, and consistant. So it's the cheap analogue gauge that's the problem.

Only good thing about the analogue gauge is boasting value - kids often ask "can you really go 280 Km/Hr?" when they look in the car. :)

I passed a MPH display on the side of the road today that our police department has setup at various spots around town to try and reduce speeding. I was going a steady 72 mph according to the 8 but the MPH display picked me up as going 69 mph. There were no other cars around me so it couldn't have been another car. Your guess is as good as mine as to which MPH was correct.