hesperus

I had my VBox GPS on my car (997 GT3) recently, and while driving at normal speeds, i noticed that the speedo was consistently over-reading by between 6-10kph versus the VBox.

Now I realize most cars' stock speedos are on the optimistic side. However, I thought that Porsche were more accurate than other cars, and that the inaccuracy showed up more at higher speeds.

Anyone else observe this? Or is my car just out of whack?

(oh, and the VBox is brand new and based on the calibration certificate, its pretty accurate)

Hank Cohn

I have one of the Garmin units and my car's speedometer consistently indicated 2 mph (~3 kph) faster than the speed indicated on the gps.

Hank

GoFastKindaGuy

Vs my NAVMAN GPS, my 996tt speedo reads 4mpn high (My Audi RS6 is spot on.)

Hank Cohn

I was not aware of Navman until your post. It looks very interesting!

Hank

LVDell

I did this very test a couple weeks back. At 55mph I was about 2-3 mph slow and at 100mph I was about 5 mph slow (ie, speedo says 100 and GPS stated 95).