The Gen III has a more extensive rear air foil than the Gen II. By air foil I mean the part of the rear hatch which follows the slope of the upper hatch window and extends out past the lower hatch window. I assume this was done to improve air flow over the car and thereby reduce drag. If a Gen II were modded to emulate the Gen III foil, would mileage improve?
The rear bumpers were creased too to improve the drag and create a flow that pushes the car. Might as well crease them while you're modding the spoiler. Might as well replace the mirrors of the Gen II with the smaller Gen III mirrors while you're at it.
Hi All, The Gen III mirrors are like the Volt mirrors. They are so-called Pedestal-Mounted. The pedestal comes out horizontial underneath, and then up. The Volt engineers indicate this is significant. Apparently (my guess) this frees up airspace between the mirror and the body to allow less disturbance of the double air (air from straight on, and air washing off the windshied sideways). That would be good Gen II hack. The Volt engineers also indicated a 3/4 inch long by 3/8 inch high bump on the rear spoiler helped as well. I have done that to my car with some rigid foam plastic that is taped over for UV protection with outdoor duct tape.
This is a near perfect description of the Gen II Touring hatch "spoiler" which is some 1-1/2 inches longer than the standard spoiler. Yet, the advertised FE/MPGs for the two is identical. It is well documented that the Touring's MPGs is reduced by the slightly wider tires... One step forward, one step back. I would very much like to see an aftermarket kit to adapt the Gen III mirrors to the Gen II -- a complete kit that is; all parts and wiring with installation directions in English. Make it a killer mod with turn signals and folding options as well.
