Does anyone know how cg for a car is determined? Is car during testing in the windtunnel placed on a treadmill running at the speed of the airflow to account for the effect of the rotating tires or it's completely stationary?
How does 08 impreza frontal area compare to 07?
snipped-for-privacy@gmail.com wrote in news:1176698113.722333.63190 @q75g2000hsh.googlegroups.com:
Not sure how Cd is calculated/determined but I do know that windtunnel time is typically not done with the wheels turning. I personally have always seen this to be a serious shortcoming in windtunnel testing. F1 cars sometimes use a moving "road" surface during testing but this is EXTREMELY expensive and, for the typical passenger car manufacturer, not worth the cost.
As a former bicycle racer, I know that spinning wheels have a profound effect on the aerodynamic drag of a vehicle. Witness the "smoothie" wheel covers of the Bonneville racers and the disc wheels on racing bicycles. Now, look at the wheels on any street car. Do you see any real aerodynamic considerations? I don't. Wheels could be designed so that they help pull air out from under the vehicle, thus improving downforce/stability at high speeds, as well as improved engine and brake cooling and potentially lower drag. As far as I know, the only aftermarket wheel ever made with this in mind was the Enkei 81 (or maybe it was the 82). I'm not sure Enkei even makes that wheel any more. I thought it looked really nice though...like a thick fan.
~Sh0ck~
See the wheels of the 1993 Ford Probe GT.
Blair
it looks like these could have helped to suck the air out of the wheel wells rapidly and is a much cheaper solution than igniting the air into the wheel wells thru ducting.
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