Automakers Look to Improve Fuel Economy Through Aerodynamics
WARREN, Mich. November 18, 2005; Dee-Ann Durbin writing for the AP reported that with higher prices at the pump hurting sport utility vehicle sales, automakers are looking to squeeze out every ounce of fuel economy possible, including designing vehicles that flow through the air as efficiently as birds or airplanes.
Automakers are redesigning grilles and roof racks, angling side mirrors so air flows around them better and lifting underbody components such as exhaust pipes so they won't produce drag.
"Aerodynamics is extremely important and becoming more important by the day with the price of fuel," said Steve Wegryn, Ford Motor Corp.'s manager of North American aerodynamics. "We are being pressed harder and harder to come up with new and better ways to address the coefficient of drag on our vehicles."
Drag caused by wind can dramatically effect a vehicle's fuel economy. According to General Motors Corp., aerodynamic drag accounts for 23 percent of the energy consumed in the average vehicle. Only engine friction is a larger contributor, at 27 percent. Tire resistance, vehicle weight and energy used by the transmission are smaller factors.
An air dam on the front of Ford's new Lincoln Zephyr sedan saves about one-tenth of a mile per gallon of gas because it prevents air from going under the car, said Wegryn.
GM says its 2007 Chevrolet Tahoe reduces aerodynamic drag by 8 percent, which improves its fuel economy by 3 percent. The new four-wheel-drive Tahoe will get 20.3 miles per gallon, compared to 18.2 with the 2004 model, GM said.
Aerodynamics engineers often work side by side with vehicle designers at the beginning stages of a vehicle's development. At GM, engineers will start aerodynamic testing on a clay model one-third the size of the actual vehicle, so changes are easier to make. Eventually, the full-size model will be tested in the company's massive wind tunnel in the Detroit suburb of Warren.
GM's 25-year-old wind tunnel is powered by a fan that is 43 feet in diameter. The fan has six blades made of polished spruce that weigh one ton each. They can rotate at a speed of 415 miles per hour.
The testing area, which is separate from the fan, is 18 feet high, 34 feet wide and 70 feet long, large enough that it was used to test the Stars & Stripes sailboat before the America's Cup race. The maximum wind speed in the testing section is around 120 miles per hour.
Automakers say testing in a wind tunnel also allows them to figure out ways to reduce wind noise in the vehicle. Toyota Motor Corp. spokeswoman Cindy Mahalak said Toyota did noise-reduction tests for its 2005 Toyota Avalon sedan in a U.S. wind tunnel and conducted separate aerodynamic tests at a wind tunnel in Japan.
Sometimes, design can win out over fuel economy. Designers may insist that the vehicle has a high back or a trunk design that doesn't optimize aerodynamics. Automakers say they have to make trade-offs.
"How do you maintain the style but also do in a way that lets you cut through the wind?" Ford spokesman Said Deep said. "Everybody can make a jelly bean, but how do you make a car with personality?"
General Motors Corp.,
