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Hi guys,

 

Well, I know there's at least half a dozen threads around here about speedometer errors -- many Porsche models have them. Case in point, my 2014 Cayenne Turbo S does show a speed that is 6% over the real speed; it's been established all Cayennes do that from factory, meaning it's clearly on purpose. I guess Porsche is trying to keep those insurance rates from exploding from speeding tickets.

 

However many don't -- case in point, my 997.2 Turbo S is 100% accurate.

 

So I decided to start a thread on the Macan's speedometer error, for those who are wondering if this model inherited the Cayenne's problem or if, given its positioning as a "sports car", Porsche decided to go with the real speed, like in the 997.2.

 

The news is -- they went with the Cayenne strategy. My Macan does show a 6% error too.

 

My extremely friendly dealer did try whatever they could to correct the issue, but, it seems to be built in to the programming of the speedometer display (analog and digitial) at least in the Macan, there's nowhere in PIWIS you can correct it. The only input in the PIWIS that is related to this is the tire size, but my Macan did have the correct tire size in, and even if we tweaked it a bit (essentially lying about the tire size in PIWIS), it wouldn't compensate for the 6% error.

 

Note that the mileage counter is 100% precise -- so there's no negative implication on mileage measurements. This is particularly obvious in a test I did recently where, bu using the Cruise Control, I went for 30 minutes at a steady speed that was displayed in the speedometer as 70mph (and in my GPS as 66mph), but the onboard computer, when calculating the average based on miles/time, correctly showed my average speed as 66mph.

 

They did put in a call to Porsche, I'll keep you guys posted on what the results are. I doubt they will tell the dealer how to fix it (I doubt there's a way other than flashing the on board computer) but I'm curious to see what they say.

 

If you guys can share your experiences in this thread, it would be great -- there might be an off chance somebody will find a way to correct this...

 

 

 

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BMW has done this for years, there's even a formula they use to determine whether the error is within their acceptable range (and it's a pretty WIDE range, in excess of 10% IIRC). They claim it's because of European penelties they face if a car ever displays slower than what it's actually going and that includes if the car has aftermarket/oversize wheels.

 

My 993 is spot on, the '10 Cayenne was off by 1 - 2%, I have yet to measure the Macan but will do so promptly.

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I just did a quick GPS comparison with the displayed speed in my '16 Macan Turbo..... Mine reads +3MPH vs GPS.  Same as the OP.

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Being a shop, we obviously see both a lot of different cars as well as makes.  Finding a car (or truck) with a correct reading speedometer is the exception rather than the rule.  Most are off 3-5 MPH high.

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My 2015 Macan S is a bit closer at 4.2% fast.  An cruise at 124 kph results in an actual GPS speed of 119 kph.   The indicated fuel consumption was 9.8 L/100km  - actual measured was 9.9 L/100km.  So fuel consumption was reasonably accurate at 1% error probably the error inherent anyway in measuring by usage from full tank to full tank.  

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2003 C4S, about 3 mph higher than Tomtom gps.

I'm only here because I may need to switch from my 6-speed to a PDK, and I'm considering a Macan rather than another Carrera.

Cheers to all, 

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My 2014 911 is accurate, within 1 mph, high. My 2016 Ford is also within 1 mph. My old 987 and993 were less accurate, within 2-3 mph. All at highway speeds.

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