rmag

Which is more accurate ... the speedo, or info from a data logger which uses GPS (G2xtreme)? Was at the track last weekend and glanced "quickly" down at the speedo at the end of the straight once. It read 154MPH. Looked at my data logger info, it didn't have a number over 147MPH (not sure which lap I checked the speedo on).

NNH

FWIW, my 996's speedo overreads by a consistent 4mph vs both GPS and radar gun once over 120 or so, so I'd believe the GPS.

ltc

Maybe a class action lawsuit, following the Honda/Acura one, would get everyone extended warranty periods for the inaccuracy:
http://www.engadget.com/2007/02/19/h...ed-odometers/2

rodneyr

GPS is more accurate. This is a common issue with at least BMW and Porsches that the speedo is overly optimistic -- I have seen the same 4mph difference.

Bill911

I was testing my G2x the other day and found that my speedo was reading about 2.5 to 3 Mph higher than the GPS in the GT3 and the Cayenne speedo was reading about .5 Mph higher.