by Jim Anderson in the January 2002 RootesReview:

The Economist magazine had an interesting article recently (Dec. 8, 2002) on the physics and economics of automotive aerodynamics. It seems that open-wheeled Fl and CART racers have the approximate aerodynamic quality of a barn door – twice as much drag (because of the exposed fat tires) as the average family sedan or sports car where the tires are mostly concealed by bodywork .

With engines approaching 900 horsepower, much of that racing horsepower is used to create massive amounts of downforce, to make the 1500-lb cars stick to the ground. But all those flaps and spoilers create a lot of drag, especially at higher speeds. So the super-engines are basically there to overcome the air resistance of the wings and things that force the cars to hug the ground.

The idea is to smooth out the airflow underneath the car and slow the airflow down on the top of the car, making it adhere to the road better. Much the same is true of high speed road cars. The head of BMW recently estimated that the front air dam on a car such as the M3 or M6 creates a downforce of several hundred pounds at autobahn speeds, and thus the need for stronger engines to overcome the air resistance – not to increase the maximum speed, because that could be achieved by a cleaner shape.

This raises a corollary Sunbeam question: In cars such as a non-racing Tiger with fairly good aerodynamic qualities, what is the point of replacing the standard small-block Ford with a larger and much more powerful engine? Well, acceleration of course, but the advantages become increasingly marginal and expensive as the power curve goes up. Top speed? For a non-racing Tiger that is usually a non-issue.

Which leaves several possibilities: the sheer engineering challenge, bragging rights, or the Mallory-Everest principle – because it’s there.

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