I want to see the most AERODYNAMIC Yaris --- Photoshop!

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Originally Posted by XYaris

Not all spoilers create downforce. In fact many do not. Since the goal here seems to be manipulating the flow of air behind the car, like the cone shape discussed above, maybe an attachment at the mid trunk level could do that in the right way. I wish I had a wind tunnel.

ok well generally speaking, they are used to create down-force, then. (I've actually never seen one that wasn't but that doesn't mean they don't exist) I believe that any thing intruding into the air flow, will increase drag. The trick is of course to figure out a positive cumulative effect. Vortex generators increase drag locally by interfering with the flow of air where they stick into the air stream, but if the turbulence allows a smaller vacuum pocket behind the car and better over all drag then it's worth the trade-off.