One of the main factors that affects automobile fuel economy and emissions is aerodynamic drag. In a recent test between four fuel-efficient cars, the Tesla Model S beat them all.
Automobile design changes drastically, depending on which ear you look at. Do you recall the sexy curves of the 1930s and 1940s, the jet-inspired designs of the 1950s and 1960s, and the boxy designs of the 1970s and 1980s? Who could ever forget the sickening, at least to me, bubble car era of the 1990s? Part of the changes have been due to stylistic choices on the part of the automaker, which encourages all the others to copy, but part of it has been improving aerodynamics and fuel economy, especially since the mid-1970s.
Lots of research and development has gone into different ways of reducing drag, and, fortunately, not every car looks the same to achieve its aerodynamic goals. Case in point: Toyota Prius and Tesla Model S. The Toyota Prius hybrid electric vehicle’s unconventional box-fish-inspired design results in a surprisingly low Cd (coefficient of drag), just 0.26 Cd in a recent test. The Tesla Model S, on the other hand, of a somewhat more conventional sedan design, and ≈1,750 lb heavier, achieved a 0.24 Cd in the same test.
The Tesla Model S actually has the same CdA (drag area equals cross-sectional area multiplied by coefficient of drag) of the smaller Toyota Prius, just 6.2 ft2, an impressive feat for such a large vehicle. One need not mention the fact that the Hummer H3 monstrosity has a CdA of some 26.5 ft2! Just for comparison, the 270-mpg Volkswagen XL1 has just a CdA of just 3.0 ft2. Still, how does the Tesla Model S pull it off? Part of it has to do with the active suspension, which lowers the car, while cruising, by nearly an inch. Smooth surfaces under the car, air deflectors by the wheels, and a closed “grille” area all help to reduce turbulence and ease the car’s passage through the air.
Image © Car & Driver
