Techart Porsche Cayenne Turbo closes in on 200 mph at Nardo — Autoblog

This article tells how Techart have made a Porsche Cayenne Turbo reach almost 200mph.  On the face of it this sounds really clever but it is nothing of the sort.  It is merely basic Physics at work.
The maximum speed of a car occurs when the power available equals the power required to overcome the rolling resistance (the friction of the tyres and moving bits in the engine) plus the drag of the car travelling through the air.  The drag in turn has two parts: skin friction and form drag due to the size of the front of the car and the overall shape.  In aeroplanes there is a third type called "lift induced drag" which hardly matters here because the prospect of a 200 mph Cayenne lifting off is too terrifying to contemplate.  So to make a car go fast you need it to have lots of power, a small frontal area and a slippery shape.
For a Cayenne there is not much you can do about its frontal area or shape so the only way to make it go faster is by giving it more power - hence the 680 bhp of this one.  So theoretically one might imagine that doubling the power would double the speed so a Techart Cayene with 1,360 bhp might do 400 mph.  But it doesn't work like that because drag also increases with speed and not directly. It is a squared relationship so at 400 mph the Cayenne would need four times the power required at 200 mph or a whopping 2,720 bhp!!!    I suppose you could build a 2,720 bhp Cayenne but it would be like an AA Fuel Dragster.  It would need to run on nitromethanol and  would only last 10 seconds before either running out of fuel or exploding!
So you can see how silly this sort of thing is because it depends on only producing more power.  And for what?  Such a car offers nothing remotely useable over the highly capable standard Cayenne.  I suppose Jezza and the Hamster might be able to persuade little boys that it's wonderful but not me.

Techart Porsche Cayenne Turbo closes in on 200 mph at Nardo — Autoblog