Originally Posted by xcel
___Basjoos, the Prius is already pretty darn slick with a Cd of 0.26. The HP numbers needed at 50 mph with that low a Cd are miniscule so aero-modding would help only at higher speeds where SHM may not be as productive?
Even though the Prius starts out will a fairly good Cd, there is still a lot of room for improvement, particularly if you want to try to get 70mpg @ 70mph. For example, I've looked at my Dad's Prius II and noticed it exhausts its hot radiator air under the car just like with any other car and its underpanelling is still very rough with lots of corrugations, gaps and seams, so there is lots of air turbulence under the car. My car has a totally smooth underpanel, exhausts its radiator air through the front wheel wells and the extended low-pointed rounded nose allows mostly laminar air flow under the car with the turbulence coming off the back of each front wheel confined to a channel between the two side skirts I have on each side of the car. And there are many other areas where the Prius aero could be improved as well, even if you don't go as far as installing a boattail. I had a recent discussion at the Gassavers website of possible Prius aero improvements with a Charleston area Prius owner who showed an interest in aero modding his new Prius to improve his mileage.