speters48

Once upon a time, a man bought a fine watch from a jeweler. The watch manufacturer advertised extensively about the quality of its very expensive product.

A few days after the purchase, the man noticed the watch gained one hour and twelve minutes a day, every day. He took the watch to the jeweler for regulation. The jeweler's watch technician told him that many purchasers of that manufacturer's watch were very upset about this bad timekeeping of the watch, but that the manufacturer would not let the jeweler adjust the watch to keep accurate time.

A little research revealed that the watch manufacturer deliberately designed the watch to run fast. When the man contacted the manufacturer, the company said that there was no law that required them to make watches keep accurate time, and that their watch complied with industry standards. Besides, the watch was a prestigious piece of jewelry, so what was the problem.

Your Porsche and mine are equipped with speedometers that deliberately overstate the speed of the car. Porsche will not adjust the software that interprets the linear relationship between the rotation speed of the drive shaft and the speedometer indication. This is about the simplest thing in the car, and Porsche deliberately misrepresents the true speed of the car. They have to manufacture the error into the system, because the error is not linear.

We need to rise up and make Porsche correct our speedometers. Let's start by telling everyone we meet that Porsche speedometers are inaccurate.

Sniffer

I`d guess most speedometers are inaccurate in that they state you`re going faster than you actually are, not just Porsche, I`m not saying its right but thats how it is

Then of course there are other variables like wheel/tire sizes which will affect the accuracy of the speed

In an odd way they're kind of doing everyone a favour for when Chief Wiggum needs to get his monthly speeding ticket quota and you`ve accidentally crept a couple of miles per hour over, you actually haven't so all is well

Food for thought, I think the pros & cons balance each other out on this one......

Wisconsin Joe

Speedometers read high. Water is wet. The sky is blue. That's all vehicles, not just Porsche (although Porsche and BMW are the worst).

http://www.caranddriver.com/features...ometer-scandal

If you read the link, Euro regs say the speedo can indicate up to 10% plus 4 kph high, but never low. Those are regulations, not just "industry standards."

If you want to know how fast you're really going, use a GPS. They take a couple seconds to catch up, but they are usually pretty accurate.

speters48

Wisconsin Joe, this is not Europe. I have owned 18 automobiles, and only two of them have been more than 1 MPH off at 70 MPH. Porsche speedometers are egregiously and deliberately wrong.

MJG911

I run 285/35-22s, the recommended size for 22s and according to my GPS app, the speedo is spot on.

I think its a rule in the US that the speedo can not run low, so they all make them a little high.

j patterson

I find it irritating too. My last three Audi's speedometers were spot on when compared to gps. It is obviously intentional on Porsche's part.

Todd B

It's always been this way. When I had a 993, it was the worst. All of our vehicles are off, 3 different brands.

8202632

Are you doing a lot of competition driving with your cayenne where you need spot on accuracy? Mine seems to be within 1 mph judging by my passport 9500ix and other speed radar signs. I'd be more worried about the accuracy of other things like tire pressure, oil temp, etc.

Just saying...

bigbuzuki

1st world problems.

jmh981

My 981 is off by 2 kph at 80 kph, according to GPS. That's pretty much the same as most of my other cars.....

ect8

I participated in RSD Rally at Porsche Parade at French Lick this past June and this topic was discussed at length. The main speaker going over the rally and required training beforehand has been teaching the course for over twenty years. He is also responsible for traveling to the next parade site and setting up course over the next 12 months for the next parade.
ok, enough of the background...National PCA made it quite clear as to why Porsche does this intentionally on all models. Basically, the penalty for murder is less in Germany than for speeding. We are not talking about the Autobahn. We are talking about going over posted speed limits; they have zero tolerance for such violations with severe fines.
Most Porsche owners in the Motherland as well as here in the colonies do not have a problem with this. We are talking about what 3 to 4 mph? Rally people have not had any problems adjusting accordingly. We just view this as it is; a super conservative auto manufacturer that is trying to keep its customers out of hot water and avoid unnecessary speeding tickets. Most of us are spirited drivers and are really thankful for the help. I hope this helps shed a little more light on the issue. regards,

dryadsdad

We discussed this when it comes to German bikes too. The reason given is the TUV (DOT of Germany) which demands that no matter what combo wheel or tire put on, the speedo cannot EVER read low. So to assure this, the speedos are calibrated high.

Blame the German government - not Porsche.

docwyte

All my German cars did this, including my KTM motorcycle plus my Subaru STI. Huge fines for the company if it's found that their speedo's read low, so they all make sure they read high.

The speedo in my E46 M3 was off by almost 10mph at speeds over 80mph...

AGARubberDuck

So does this mean my cayenne with 160K miles on the odo. potentially has only 144K miles on the chassis? (Figuring it is tracking speed/distance 10% over)
This also means our 36K mile warranties are potentially used up at 32,400 actual miles.

docwyte

Nope, odometer is correct, no fudge factor there