C4 questions - crosswinds and mpg

mikfinch · Mar 2, 2005

Took my new (to me) '99 C4 out for a blat last weekend. It was quite windy but not what you would call gale force. I was surprised how much my C4 was affected by crosswinds at motorway speeds and I was wondering whether all 911's do this (light at the front?) or whether there's something wrong with the geometry of my car. If this is a charateristic of the car at UK speeds, how does it feel at really high speeds in really high winds?
The other slight dissapointment is that I cant get more than 20mpg according to trip computer even on a longish run and using BP Ultimate. Is this about right for a C4? Road test reports suggest that standard C2's should do 22-25mpg . Is this a result of the 4WD system?

Rotorhead · Mar 2, 2005

911s can be susceptible to cross winds, but there is also a sensitivity through the steering that can give the impression that the car is moving around.

The C4 is slightly heavier than the C2 and there is also likely to be some power loss between the fly wheel and the final drive, but a C4 should average c.25mg in normal use. A C2 might be 26 - 27 mpg. The car should also run perfectly well on 95 Ron unleaded.

philippe · Mar 3, 2005

My C4 3.4 does average 24 mpg that is not driving really hard. I was also out at the weekend in rural Norfolk where the winds can be strong and i think were but the car felt totaly stable even at high speeds. it sounds like your geometry is out which will also effect your MPG if it is bad.

Phil

Guest · Mar 3, 2005

You'd expect a 911 to be slightly sensitive to crosswinds because (goes into physics mode) the centre of pressure (roughly in the centre of the car) is in front of the centre of mass (just in front of the rear wheels), so that a wind will actually have a turning effect on the car. The steering does feel 'alive' in comparison with a front engined, front wheel drive car but that's why we like it right? If you want a motorway cruiser then buy a big beemer.

I get about 23-24 mpg out of my C4.

John Ware · Mar 3, 2005

Ditto the above regarding crosswinds.

For mpg, on long fast runs (mostly motorways, A roads), the computer gives 27mpg+. I can't remember the average speed but I tend to sit at 90 ish on the motorways and whatever I can get away with elsewhere [

]. When I've stuck to speed limits, I've seen 31mpg at 70mph over distances. A different way to get your kicks if you're not in rush.....

Normal day to day mixed driving I get 24-25mpg, confirmed by how often I have to fill the tank.

I don't track it but I would expect to see 15mpg ish or less.

garyw · Mar 3, 2005

996TT, not really noticed cross winds blowing the car about, sure I can feel them but nothing to concern me.
On a motorway run I can usually return at least 24mpg+

garyw

garyandjanet · Mar 3, 2005

pn a run our C4 does 26 mph just driving in to town and about 19 mph.

Cross winds have made a diffence to the car when pushing it on a m/way (100 +)

But not big deal [

]

Guest · Mar 3, 2005

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I am a newbie with a Millenium C4 and I am getting 25.1 mpg according to the OBC. Thats from daily driving usual mix of roads, lightish right foot but no nose to tail - thank god!

Last weekend also noticed the (apparent) instability in strong winds/crosswinds on the motorway, it felt like the car was "squirming" on the tires - that said it was much better than my last car, an M3 on 19" wheels which could be very unstable in the worst conditions.

I still wouldnt change the 911 for anything else!

Ess_Three · Mar 4, 2005

ORIGINAL: John Ware

For mpg, on long fast runs (mostly motorways, A roads), the computer gives 27mpg+. I can't remember the average speed but I tend to sit at 90 ish on the motorways and whatever I can get away with elsewhere []. When I've stuck to speed limits, I've seen 31mpg at 70mph over distances. A different way to get your kicks if you're not in rush.....

Normal day to day mixed driving I get 24-25mpg, confirmed by how often I have to fill the tank.

Hmm...
Do these engines get noticably better on fuel, as they get a few miles under their belt?

I'm lucky to get my C4S to return better than 20 (20.1/20.2 on the trip) for open road driving.
In traffic, it drops to about 14.

I've only done 1600 ish miles...so I'm hoping the engine it still tight.

garyw · Mar 4, 2005

Yes, nearly all engines have better economy as the engine parts bed in correctly..When I first had mine it was returning around 19mpg on a run, now in the 24+.

garyw