Does anyone know the official accelaration time from 0 to 165 mph or non official good times? What (besides drag) influences the acceleration at top end - say between 135 and 165 mph? It seems like my s4 takes somewhat longer in the end to reacht top speed. Btw I drive a lot in Germany..thank god for the autobahn..

Thanks

 

It is nearly all drag at the high speeds because the horsepower needed goes up by the square not as a straight line . It might take three times as much power to go 200 mph than it does to go 150 mph. as you reach the maximum speed there is so much work being done pushing through the air that there is little left to increase the speed. Then at some point there is nothing left and the car goes no faster.

 

Here's your horsepower loss for a 928 at speed.

.34(drag coefficient) x 29.1 (Front area in sqft) x Speed squared (mph)
15,0000

or

Cd * A * (V3)
------------------------------------
150,000
where:

Cd = drag Coefficient
A = frontal area in sq. ft.
V = Velocity (speed) in MPH


Punch in your speed squared and you get horsepower loss do to speed. Great for converting GT teck numbers to a more realistic number.

Ie if an OB shows 178hp @ 5400rpm @ 70mph. It really has 200.5hp.
22.6HP loss at 70mph
@140mph the loss is 180hp!

The hp loss goes up by 8 every time you double speed. (Velocity cubed)
Not exact science as wind direction etc can make big changes.

Drag for S4 is closer to .30

That does not include road friction or transmition loss. With most of the available horsepower being use to maintain speed, not much is left for acceleration.

 

ok thanks for your replies...that must mean that there's nothing I can do to make my shark reach top speed faster...

 

There are ways... but they involve power adders like turbos, superchargers, or nitrous.

 

nitros / super / turbo charger

 

Beat-cha!

 

Or a Kamm tail.

 

Without busting up the engine or my wallet...think I will go for an x-pipe first and see if that stills the hunger...

 

It probably wont!