I'm contemplating what can be done to improve aero at the rear of the car.
The rear undertray extending past the bumper is the best I can come up with for the underside.
Not much can be done with the sides, especially since the rear of the fender curves in so sharply that there is no way to get flow to reattach past the rear wheels (those little vertical strakes are worthless, I realize).
Perhaps I will try wheel covers in the summer, but that will test my fabrication skills quite a bit.
For now I am toying with some sort of coroplast lip at the rear, either from the
roofline or
trunklid. At the roofline I can keep flow fully attached for another foot or so while reducing the wake profile, but can't extend it further as it would block my sightline from the rearview mirror. Since the flow on the bottom stays attached several inches past the front bumper, the difference between when flow detaches at top and bottom is creating quite a swirl effect, I assume, which is very bad. A lip at the trunklid extending to at least the edge of the undertray can reduce this, but will not prevent flow from separating at the roofline. A full boattail is not an option, as I need my trunk and rear lights, and I'm no basjoos. Here are the two options, with the red dotted line showing the angle from the roofline to the edge of the trunklid lip, which is too steep to keep attached flow between these points, but neither will it break up quite as much as in the wake.
What say you?