This is the car that should have become the second-generation Honda Insight in 2007.
Honda IMAS
It's a small two-seater, and aside from concept car shenanigans, it's very much like the first-gen Insight. The drag coefficient is 0.20, which would probably translate to a production car with a drag coefficient slightly lower than the Insight's 0.25.
The rear glass on the IMAS is interesting. It curves in from both sides more sharply than on the Insight, and the curvature begins in the doors. The shape of the roofline is sharper than that of the Insight, and much sharper than the streamlining template, which I think demonstrates there are 3D streamlined shapes with lower drag and lower fineness ratios than 2D streamlined bodies. These shapes may be beyond the reach of DIYers, though.
One of my complaints about the Insight is how little cargo space there is, and how much the IMA system and >600mi gas tank intrude into it. The IMAS has a cargo floor about 6" lower than the Insight's. Good, but I bet they did this by deleting the spare tire and stuffing the IMA box into the spare tire well. That's hardly a solution that could have been put into prodcution.
The grille opening of the IMAS suggests the car has (or more likely, could have) a split radiator, located between the bumper and the front wheel wells. That would be expensive and fragile, but if it reduces drag, so be it.
They're claiming 94mpg (on what cycle?) in concept-car form. Nice, and I wonder what it could do with a boat-tail.
Additional material:
http://robson.m3rlin.org/cars/wp-con...ncept-2003.jpg
Honda Worldwide | Tokyo 2003