Macster

Not necessarily.

Very early in my 02 Boxster's ownership I took a 200 mile drive after having reset the car's trip odometer to zero and at the same time the odometer flipped over a new mile. Simultaneous with this I reset my Garmin GPS's trip to zero.

After 200 miles the car's trip odometer and the Garmin's distance traveled differed by just 0.2 of a mile.

I can't remember now which was ahead of the other, but the difference was so small that in 50K miles (warranty miles) the error would amount to just 50 miles.

Now some cars (not Porsche though) have an odometer error that not only results in the car gaining miles faster than actual but this also affects miles penalties for leased cars.

Sincerely,

Macster.

buddy911t

interesting info. Thanks! I was under the impression it was higher than just 4-5. On one of those cable shows they hit 206 in a GT3 RS but had to adjust the reading back to 198 mph.

Targatoo

So, the odometer is not connected to the speedometer? Is that possible?

nick49

You can!

This was a big topic on the boards when the Boxsters first came out in '97 or '98. The dealer can reprogram your speedo to be accurate. My friends at the dealer did this to my wife's '99 Boxster 9 years ago. I have checked it with my GPS and it's dead on.

I never had my 996s recalibrated, I may have my Turbo done if it ever goes to the dealer.

logray

With a 99' 996 I've been told "sorry can't do that" by a dealer when I asked them to calibrate it.

Do you have a link?

Thundertub

The "analog" speedo, the digital speedo, the odometer, and the trip odometer are all electronically operated. Unlike the early days in cars, there is no actual mechanical connection. The pick-up sends its signal to the computer, and the computer decides what signal(s) to send to the various displays. They can in fact be programmed to work together or seperately at different ratios. It is all done by computer and programs and coding.
Thus, it is entirely possible to to have an "error" programmed into the digital speedo readout, but not the "analog" gauge (there is nothing analog about it but the moving needle). A program is created for each readout. So "flashing" the computer to correct the imbedded errors is only possible if you are a real major computer geek who knows how to work through the actual programming to find the codes to correct, and what the codes should actually be. Think about the levels you would have to work through. Nobody who does this would take the time to do it for such little reward.
And the small size of the "analog" speedo makes it impossible to really see those details of speed, which is easily seen by watching the digital readout. Then there are also external factors like paralax error...

Also, 4 mph error does not equate to 4% error. Depends on your current speed. 4 mph at 50 mph equates to 8% error. And the trip odometer and non-resettable odometer can have a totally different factor or even no error factor vs the speedo's.

As for GPS accuracy, the military depends on the pinpoint accuracy of the same satellite-based transmitters as your hand-held Garmin...
And sea-level navigation through treacherous inlets such as those found in the Carribean Islands is now far less dangerous because of those same transmitters.
And the WAAS scrambling and error programming of a decade ago has long since been turned off or cancelled out by the programming in newer GPS's.

logray

I have the latest version of a PST2 and there are no speedometer calibrations possible within the unit. I have also flashed my DME with the map that comes with the final version of PST2 software version #24 (reported by several posts to be one of the "software" fixes available at the dealer to calibrate the speedometer).

I've heard the "rumor" about correcting the speed readout before, but have not seen any evidence it can be actually done.

I do not believe there is a speedometer calibration function within PIWIS either, but could be wrong.

Perhaps it is model year dependent and what type of instrument cluster version one has, but at least on the 1999 car I would be hard pressed to find evidence it is possible to adjust the speedo without doing modifications outside of what is "sanctioned" or "available" by the dealer/Porsche.

OZ951

Using a motorsports datalogger/precision GPS I noticed at 30mph the error is 3mph, 4mph at about 40-70 and then 5mph above that. UK 99 C2 new tyres.

This is consistent with the local radar units that show you your speed as you approach them.

Macster

Based on my observation/confirmation at least with my Boxster while the speedo reads optimistic the odometer does not have the same optimism so I would have to say the speed display and the speed displayed on the dash and the odometer and distance traveled are not connected, not directly. I see no reason why Porsche would do this for the Boxster and not for every other car it makes.

Sincerely,

Macster.

speters48

Porsche has deliberately built overstatement into the speedo. They are very sensitive about this, and will NOT allow their dealers to correct it. We need to start a campaign to embarrass the company into behaving responsibly.

Atrox

Bunch of great free speedometer apps for iPhone or android. Mine reads 4 over 02 996 turbo.

JayG

Both my Targa and my Boxster read 3 mph fast

IIRC, it has something to do with German law and liability that a speedo must not read slower than true speed so they make them read a little fast just in case.

My VW's also read 3-4 mph fast

Triple Black

Mine is a constant 5 kph over.

Water Hound

Mine is always 4 percent high

Macster

Doesn't bother me any. As soon as I confirmed to my satisfaction there was no error with the odometer which would or could affect the mileage and result in less warranty coverage I just adapted to the fact that my Boxster's speedo read between 4 and 5 miles optimistic.

I can't recall now if my 2008 Cayman S's odometer was optimistic but my 2003 Turbo's odometer is just 2mph optimistic.

Also, it could be worse. My '96 Mustang GT odometer would stick and after over 15 miles of driving would gain only a few miles. (The trip odometer worked ok.) I brought the car to the dealer and the stupid dealer checked the speedo and because it read ok deemed the odometer ok as well. I found out much later there was a recall on this the lube IIRC used in the speedo gearing dried and caused the odometer counter to not turn properly.

But the car was still under warranty and the "error" was in my favor so I said to heck with the stupid dealer and lived with the problem. But that was my last Ford.