dwccfp

I have a hand held GPS and have used it with my other cars and have used the speed function to see if my speedo was accurate. The hand held GPS is extremely accurate. I decided to test it on my 2002 C4S ( I have only had the car for 5 months now) The indicated speed in the car is 5 miles per hour faster than the GPS. Is there a fix for this? One would assume that I am putting more mileage on the car than acutal.

1999Porsche911

It is programmed that way but the odometer is accurate.

kevinrubin

Are you suggesting the speedo is intentionally set 5 mph faster from the factory? Why? To prevent speading tickets (meaning you are actually traveling 5 mph slower than you expect)?

1999Porsche911

Yup, that is what I am saying, although speed difference varies with actual speed of car.

dwccfp

I guess I am going to have to test the actual distance on the highway when mileage markers are set. Any other ideas???If you are in South Orange County CA area and want to test your 996, I'll hitch a ride and we can test your actual speedo.

kevinrubin

The difference would be exaggerated at higher speeds, but seems odd that they would do this intentionally. I thought my speedo issue was due to change in wheel/tire profile...very interesting.

1999Porsche911

Hook your scanner up and look at the speed sensor or use the Climate Control display to see the unadjusted speed of your car.

grahamtwatson

I think all car manufacturers do this to some degree. If the speedo was *ever* reading slow and someone got a ticket from that fact and could prove it, they'd probably be open to a lawsuit, especially in America. So it's easier to err on the side of caution.

Does the Porsche GPS system have a speed readout? It would be interesting to compare readings on the THREE speed displays if so...

bnewport

Same on my 99 996. At 60 on the digital tach, my G2Extreme logger has me at 56.4 mph. It's around 5 too high. Never trust the speedo on the track.

MagnusB

How do you get the speed displayed on the CC unit?

washington dc porsche

Mine registers 2-2.5 mph faster than my GPS at all speeds.

missmy993

I did same thing on '99 C4, GPS speed was around 3 mph more than digital display in the car. This was true from 30 mph-75 mph.

washington dc porsche

Funny thing for me was while I had my car set on cruise at 73 testing the speedo to find out exactly what speed my GPS would display I was pulled over and ticketed for doing 80 in a 65.

LVDell

dc....that's a cop just being a *****.

washington dc porsche

Thing is he didn't seem to be as much a ***** as I initially thought when we talked after court.