"i", the mitsubishi concept car, has somes interesting solution for a lower drag.
between these, it is present, an atypical underbody panel.
between the chassis and the panels, an interstice is present.
Mitsubishi declares that the hot engine air flow, between the interstice with minimal drag becouse, this system reduce the rear vacuum.
you can read the source:
http://www.mitsubishi-motors.com/cor...004/16E_07.pdf