Durametric Speed Precision

[Tool Pants]

A PST2 can also display the speed. It is said this is accurate while the speedometer reads high.

[rdancd816]

When I do a speed check using my GPS the indicated speed on the speedometer is always about 4MPH faster than what the GPS claims. I have also run the car with my wife pacing and her speedo is also about 4-5 MPH slower. I have heard this is common with Porsche vehicles. Maybe the Autobahn set is trying to keep our speeding tickets down! ??

[OldBlevins]

Yeah, I've found that when my speedo reads 70 mph, I'm really only going about 67. Interestingly enough, my odometer is very accurate.

[efahl]

We just drove our "new" '97 Boxster 3.4 from California to Michigan across I-80 and to while away the hours I timed mile markers when I wasn't driving. Anyhoo, we tuned the cruise to give 45 second miles (+/-0.2 s timing 10 mile sections at a shot; hey, it's a long drive!) with the speedo indicating 83 most of the time and flashed 84 occasionally. The odometer showed a similar error, reading about 4% high.

Eric

My GPS shows the Boxster is off (faster than actual) by about 2 MPH. My Ford Explorer is off by about 3 MPH.