perryinva

Discovered something interesting yesterday..let me know if this is old news. According to my GPS my 996 speedo, digital & analog are showing 4 to 5 mph higher than it really is. Interestingly, this is exactly the same amout that BMW's read high. Now here's the interesting part. If I hook up my Autoenginuity software to the OBDII port, it shows the CORRECT speed reported to the DME!. So When my rear spoiler goes up at 75mph per the speedo, the DME knows damn well it's really 71mph. Anyone else able to verify the same thing? Does Porsche (and BMW) really think that we can't handle the REAL speed? I had always thought that the higher reading was built in so that variations in production would never yield a speedo that reads lower than actual...but apparanty, that's not the case!

spaceman_spiff

I have noticed a 5 mph difference (no matter the speed - legal of course) between my speedometers and those roadside radars that display your speed.

htny

https://rennlist.com/forums/showthre...ht=speedometer

Wellardmac

I'm yet to drive a car that doesn't do this.

perryinva

AHHH, that only took 4 minutes!!! What the hell are we all doing on our PC's at 9:30 on a Sat night...we're all a bunch of losers......oh, wait...that's right..I mean married... I guess it is exactly as I originally assumed, intentional for legal reasons ( I wonder why the US makers have no problem getting it right though...) the accurate odometer point is what I over looked, of course. They would HAVE to know what it really is, or else they could be reporting 10% or more mileage than was really being racked up..thanks, guys.

Wellardmac

...nailed that one. I'm exhausted from chasing the kid all day.

tooloud10

+1

Patrick

Not one of the Ford products that I have owned has ever differed from GPS by more than one mph.

Jon996

I think you are almost right--I had heard that in Germany, the speedometer had to be either right on or read lower than actual, so the statistical approach is to make them all read low. Mine reads 2 MPH lower than actual.

On the bright side, probably reduces the number of tickets we all get a little. . .

dresler

I hate it. I always go 4 mph faster, knowing it is low.

tooloud10

My F250's speedometer reads especially low...an indicated 70 mph is actually 65 mph. No modifications to the vehicle...

Wellardmac

Yup, Ford does it too.

We've owned a Mercury Mountaineer and a Sable and both did it.

lanny

me too- but none of my other cars have I ever noticed it in

ArneeA

Just drive 5mph faster!

Wellardmac

Yup, that's my philosophy.

I know that I can do 72mph in PA before they'll pull me over, so that translates into 77mph on the speedo.

Additionally, I know that they'll haul my *** off to jail for 78mph, so I'm really good until 83mph.