Can you spot the changes I've made to the Prius profile in the attached image (I included the original to make it easier). What else would I have changed ? - Well, cut about an inch off the maximum height to reduce drag and compensate for the aerodynamic cost of half an inch extra height above the rear passengers (I'm no really a fan of the peculiar absence of a level roof section). Moved the rear seat down and forward by an inch or so, again for more headroom. Improved rear visiblity. Rounded the front corners. Then, I almost certainly would have given it a more traditional dash design, with softer materials. Added telescopic adjustment of the steering wheel and a nicer design of same. What would you have changed, if you could ?
I'm not good at these kind of games (spot the difference) but the two pictures look the same to me. I bet that cutting an inch off the height would actually increase drag. It's all about the shape, not merely the cross section. Now, if you reduced every dimension proportionally, you'd probably reduce the drag by a tiny amount, but then you'd have a smaller car.
correct, the roof is uneven on purpose, allows flow to stay attached longer and straightens it out both reduce the effects of separation
What I changed Perhaps a little less, but otherwise correct. I think it actually looks better. I'm aware that reducing the height while preserving the slope angle would increase the cW very slightly (although I believe there are lower cars that actually achieve a better cW), but the reduced frontal area should easily compensate and probably allow for a slightly steeper rear slope for more headroom. If not, rear width could be reduced by about an inch. Admittedly I don't have a wind tunnel to prove it, but this is a compromise that every car designer deals with, and few choose a slope angle as low as the Prius.
