Joe2000C4Cab

He said top up. Also, maybe he pushed his 911 off a really big cliff to get to 180mph? J/K...

Qualnhick

I don´t know why are you soo admired, my car has manual transmition and has been upgraded by superchips. But even if it was stock, if you look at Porsche manual it reads like this:

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2004 Porsche Cayenne Turbo
2003 Porsche 996 C2 Cabrio
1999 Jaguar Xk8 Cabrio

yvesatlanta

1 mile = 1.61 km => 290 km/h = 180 mph
Usually speedometers lie.
I remember taking my Yamaha R1 to 196mph, while my GPS read-out was 176mph.

care4era

i took my C4 to 250km last friday on a trip back from Poland. Steady as a rock, i guess the 4 feels more stable at high speeds, like you are on rails.

Riad

At that speed it really doesn't matter.

washington dc porsche

I think GPS's are wrong since they can be up to 10 feet off. Non the less my speedo vs GPS differences have been no more than 1.5 mph at low and very high speeds.

ayaz

i too find my 02 cab a bit unstable at 250+
i have the identical setup as you.

Nicolaasdb

I think all cars get a little more unstable at high speeds! That is why F1 cars have the huge wings and and special bottom under car to create stability.

I drove my P up to 145MPH before I lowered it and it was a little scarry...now after lowering it feel much better......a couple of years ago I had a 928s.....and this P was solid as a rock..I worked in Germany a lot and 270-280 KMH was like driving 100KMH that stable..I think that weight distribution is also a large factor!

996Pilot

------ trust the GPS speed. The up to "30 feet" off (10 meters) is due to alot of factors. The speed is calculated relative to the timing which is set using Cesium clocks (accuracy of 2 nanoseconds per day or one second in 1,400,000 years). I'd go with the GPS speed to "calibrate" the on-board speedometer.

JMHO

Dan

GoodSpeed Sweden

The C4 is heavier in the front and therefore quite stable at high speed.
I have tried 280 Km/t = 174 Mph with mine and it was quite steady. A turbo front spoiler will probably do the rest.