Do SPOILERS Really Work???
filed in 1988 Supra
Question: The rear spoiler that mounts on 1983 and newer Firebirds produced a measurable reduction in drag coefficient by smoothing the airflow over the rear of the car. That would be something that would affect CAFE numbers at highway speeds.
I have a 1988 Dodge Lancer Shelby with spoiler mounted above the rear window at the tail of the roof, like the Supra. I ran coast down time tests from 110 mph with and without the spoiler and was not able to discern any difference. It is still on the car, however, because my wife likes its looks.
Answer: I thought that thing that hung over the window of a Supra was a sun shade. Could the one on the Lancer also be a sun shade and not a spoiler?
Anyway, someone earlier mentioned the reduced lift on a 911 at 100 mph (from 130 to 10 pounds, I think, implying the wing added down force of 120 pounds). Note that the down force generated by a wing/spoiler of a particular design is a cubic function of its velocity through the air. So, at a more realistic 50 mph, the added downforce would be 15 pounds. At 65 mph, it would be around 33 pounds. So, at legal speeds, the wing would do very little. Of course, the lift created by the car would be similarly small as well. The real function of these wings is for driving at extremely high speeds, which we can’t legally do in the US. So my opinion would be that wings are, for the most part, useless at providing down force in “normal” driving.
Chin spoilers, on the other hand, have been shown to be effective at keeping air from getting under the car. This can effectively help prevent lift at high speeds. They may or may not directly contribute to down force or drag, since the air that is deflected away from under the car will not have a chance to drag on underbody components. So a well designed chin spoiler could reduce net drag, while also reducing net lift.
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