Auto components lighten up to improve mileage
— -- Automakers are putting cars on a diet in a bid for better gas mileage.
They are finding ways to shave pounds from car bodies — from the hood to the back bumper — often by substituting plastic, composites and aluminum for steel.
When they use steel, it is often a higher-quality grade that delivers more strength and less weight.
Every 120-pound reduction can yield a 1% gain in gas mileage, says Bill Grabowski, director of body core engineering for Chrysler. Best of all, if engineers can make the body lighter, other components, such as brakes, suspension and the engine, can be lighter, too. And the vehicle won't need as much gas-guzzling horsepower to push it around.
Driving drastic weight-loss plans: the prospect of tougher government-mandated fuel-economy standards. Facing that possibility, "We will focus on almost nothing but ways to improve our fuel economy for the next five years," Grabowski says.
But it won't be easy. Even as engineers are trying to find ways to eliminate excess weight, government and consumers are demanding new features that add pounds. Some offer safety, such as side-impact protection and protection from roof crushing. Others are luxury touches such as glass roofs or rear-seat entertainment systems. A glass roof alone can add up to 200 pounds.
Says General Motors gm Vice Chairman Bob Lutz: "It's weight, weight, weight going in."
The result is a balancing act. Ford Motor F, for instance, added 64 pounds of features to its remodeled Ford Focus subcompact but found ways to take out 104 pounds from other places.
Ford replaced steel with aluminum in the brakes (7.5 pounds), redesigned the rear seat (10.7 pounds) and changed the carpeting in the trunk (3 pounds). Using aluminum wheels instead of steel saved 22 pounds on Focus.
Due to those and other changes, Focus will be up to 5% more fuel efficient than the old version.
Taking the heft out:
•Lighter materials. The Infiniti EX35, which goes on sale in December, has a plastic rear hatch and aluminum bumper supports, suspension components, hood and wheels. Infiniti parent Nissan says the goal was to make the luxury sedan weigh about 60 pounds less than comparable BMW and Lexus models.
Some high-temperature plastics can be used for engine parts such as valve covers.
•Stronger steel. The new Honda hmc Accord sedan increases its use of the highest-strength steel to 42% of the body, up from 13% in the old version. The steel has twice the tensile strength of the regular stuff. But because the new model is bigger, the sedan still weighs 92 pounds more than the previous generation. Chrysler's Grabowski says greater use of high-strength steel can cut 100 pounds out of a vehicle's body weight.
And David Cole of the Center for Automotive Research says high-strength steel gives automakers their best chance to make cars lighter. "It's tough to work with, but they are figuring it out," he says.
•Taking out parts. In some cases, automakers are jettisoning components altogether. Some automakers are switching to tires that can keep running even when they go flat so vehicles don't have to carry 20-pound mini-spare tires. Those lightweight spares, in turn, replaced the even heavier full-size spares that cars used to carry.
•Weight-reducing computer design. Chrysler's new design computer can model automotive structures the same way that nature molds bodies. Just like the hollow bones of a bird that make it lighter for flight, the program figures out where the points of highest strain are on a car's body and puts the weight there. "It indicates where to put the strongest structures," Grabowski says.
Weight reduction isn't always about better gas mileage. Sometimes, it's about better performance. Mercedes-Benz's CLK Black Series deletes the sunroof and the back seat and adds carbon-fiber fenders to save weight. But given that gas savings aren't usually top of mind for owners of limited-edition $136,000 sports cars, the primary goal was to lighten the car for greater speed.