Speedometer accuracy

[indydave]

Mine's a 2001 S, and its speedometer is off by a constant 3-4 mph at all speeds above about 20mph.

The odometer is accurate. Odometers have to be accurate as a too-optimistic odometer will run out the warranty more quickly. One of the Japanese automakers (Toyota, I think) lost a class-action suit over this odometer issue.

I used my Garmin GPS this past weekend to check the accuracy of the odometer too. It's off by a little.

For a 300 mile trip on the odometer, the GPS read about 297.5 miles.

[Cloudsurfer]

My speedo is 4MPH higher than GPS indicated speed consistently. I've also found this to roughly the same error in the odometer, when comparing trip figures from the cluster to trip legs from my GPS.

Patrick

[schnellman]

I thought it was a joke when I read that your HVAC controls could be used as a diagnostic tool, and to tell you your true speed. But, I tried it on my '98 and was truly amazed to find it was true. I checked the speed at 60, 70 and 80 mph indicated on the speedometer and sure enough, when I converted the kph shown on the HVAC I was always exactly 10% slower than the speedometer indicated. Can't say as I appreciate Porsche lying to us about the speed of our cars, but it's good to know.
Thanks, guys.

[Bladecutter]

Originally Posted by schnellman

I thought it was a joke when I read that your HVAC controls could be used as a diagnostic tool, and to tell you your true speed. But, I tried it on my '98 and was truly amazed to find it was true.

Exactly how do you do this?
I would like to check.

BC.

[rick3000]

http://www.cb-racing.com/boxster_AC.html