Spoiler, No-spoiler or Airfoil - MIT video

[DIMS]

Sports Car Aerodynamics: Spoiler Alert! - YouTube

http://www.youtube.com/watch?v=TKH1DyV9vNU

[redpoint5]

I learned some things from the video, but the conclusion should be qualified.

The narrator concludes that an airfoil reduces both lift and drag to the degree that a car would win a drag race against the same car without an airfoil. Then he mentions that F1 cars generate so much downforce with an airfoil that it exceeds the weight of the vehicle. However, in F1 they have the DRS (Drag Reduction System) that can be activated that moves the rear wing, decreases downforce, and increases speed.

So there appears to be a balance between downforce and drag that has to be achieved, otherwise an airfoil will not always be more efficient.

I would think the Prius would include an airfoil if it would improve the drag profile of the car.

[shovel]

I'm a little disappointed in MIT, for continuing to propagate incorrect lift theory

But then, I get asked idiotic questions every single day by "highly educated" people.

[Arragonis]

Originally Posted by redpoint5

I would think the Prius would include an airfoil if it would improve the drag profile of the car.

No, because it would get in the way of the shopping.

[aerohead]

I couldn't get the audio portion,but I think I'm okay with what they presented in the context of the 1/18-scale models they depicted.
Any separation which occurs 'over' any portion of the body will induce lift,which is induced drag,which increases overall drag.
A carefully 'tuned' airfoil of just the right size,and angle of attack,can mitigate the lift do to separation,reduce the overall drag,which would win the drag race if long enough.
It would be on a case-specific basis,so whatever you saw on a Carrera,you wouldn't want to put on a Lancer,or anything else.
PS Merely lofting the roof-line up to the ideal pathway would kill the lift right there.