I promise I'll keep this real short.
I like driving my English car with the windows rolled up. It makes it
a little quieter, and also a little warmer. I can't tell if people think
I'm wierd because I have my windows rolled up, or because I own a British
car. And I don't even care.
As far as aerodynamics is concerned, the reason a BGT goes faster than
a roadster is because the air doesn't have to go thru as many violent
vortices and pressure differences as it goes over the car. Weight has
nothing to do with top speed. The only factors that affect top speed are
rolling resistance, air resistance, horsepower, and of course, speed limit
signs.
Air resistance doesn't increase linearly as speed increases. Depending
on the shape of the vehicle, a good approximation can be obtained from the
square of the velocity. From this, a given car at 60mph has 4 times the
aerodynamic resistance as it does at 30mph.
I do notice a difference on the freeway when I put the top up on the
Spitfire. I don't know where the break-even point is, but I'm sure it
would be different for different cars, as you say.
Happy motoring,
Greg Meboe MEBOE@wsuvm1.csc.wsu.edu
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