Quote:
Originally Posted by whatmaycome14
Somewhere along the lines, I heard that the Lexus SC430 convertable had the same Cd when the top was down as when it was up. I've always thought this was quite impressive.
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Actually, I wouldn't be surprised if this happened in a lot of convertibles. The convertible top tends to have an awkward shape (since it needs to fold) and this could push the airflow over the top so that it doesn't reattach to the rear. I'm no aero expert, maybe someone else can chime in on this but I suspect it's more important to have surfaces following the airflow where the car is tapering. Afterall, a 2 door pickup truck has a very long bed but they have pretty crap drag coefficient.
In my own car, top down with wind screen up it's actually very civilized in the cabin, and sticking my hand into the air I can kind of feel the air moving at full velocity just a few inches above the wind deflector. I wouldn't be surprised if the drag were the same with top down, and I wouldn't be surprised if the drag were lower in a Z4 or Boxster with top down, seeing how short and low their tails are.