Engineers at the Mercedes-Benz Technology Center and DaimlerChrysler Research constructed a model of the tropical boxfish and discovered the low drag coefficient of 0.06 when they put it in the wind tunnel at Stuttgart. Measuring a quarter-scale clay car that loosely resembled the boxfish yielded a drag coefficient of 0.095. Engineers went on to design and build the bionic car, which turns in a Cd of 0.19.
By comparison, the Partnership for the next generation of Vehicles' best coefficient of drag was about 0.16. PNGV participants Ford, GM, and Chrysler produced three very expensive 80-mpg cars for the government in the late 1990s.
According to DaimlerChrysler, the new car gets around 70 mpg in a combined city-highway cycle, it seats four with luggage, and, by spraying an aqueous urea into the exhaust, spews 80 percent fewer nitrous oxides out the tailpipe than a conventional diesel engine would. The company calls the emissions technology selective catalytic reduction.
Company engineers also discovered nature's unusual construction method: the boxfish wears a skin composed of many "hexagonal, bony plates" that weigh very little but manage to protect the animal from injury. The engineers have applied bone-formation principles in producing the exterior door panels to achieve a 40 percent weight reduction without diminishing strength.