Industry looks to “lightweighting” to meet new fuel economy and emissions standards
Like the drivers behind their steering wheels, vehicles have been adding extra pounds—a 20 percent weight gain overall in the past 20 years. And it’s not just big luxury cars, SUVs and pickups.
For example, the lovable little 1990 Honda Civic has become a somewhat porky 2010 Civic with its slightly more than 16 percent weight increase—a 2,262 pound curb weight versus 2,630 lbs. Even the automotive darling of nearly every greenie on the planet, the Toyota Prius, isn’t immune to adding a little flab; the newest edition is 152 lbs. heftier than the model it replaced.
While overweight drivers can choose to shed weight or not, automakers don’t have a choice for their cars and trucks. Recent government regulations to increase fuel economy and reduce emissions is forcing the industry to use weight-saving materials as part of the solution to meet the mandates.
Advances in combustion engine technology, the increase in hybrid offerings and the advent of electric powertrains certainly go a long way in the quest to comply with the new fuel and emissions standards but they can only go so far.
Enter “lightweighting,” the auto industry term for reducing weight. As automakers chase every mile per gallon in order to meet the new fuel economy requirements, reducing vehicle weight is beginning to take on importance. Ford has said that lightweighting will be a major part of its efforts to improve fuel efficiency, accounting for as much as 50 percent of the automaker’s fuel mileage gains.
Engineers use a general principal for improving vehicle mileage: reduce vehicle weight by 10 percent and fuel economy improves six percent. A major target for the industry is a vehicle’s largest structure, the “body-in-white.” BIW is the body sheet metal including the hood, rear deck and doors, but without the drivetrain, chassis, window glass, interior, etc.
Steel and Aluminum
Steel, because of its strength, has been the mainstay for BIW dating back to Henry Ford’s time. Today, advanced high-strength steels are so strong—even though they are a thinner material—they provide the same strength as regular steel in a vehicle, reducing vehicle weight by up to 30 percent. That strength is important when it comes to meeting government safety regulations such as the roof crush standard, which calls for the ability to handle 1.5 times the curb weight of the vehicle, and a forthcoming standard that will require handling three times curb weight.
United States Fuel Efficiency Standards
- Current: 25.5 mpg (cars & trucks)
- By 2016: 34.1 mpg
- By 2025: Between 47 and 62 mpg
Europe CO2 Emission Standards
- Current: 160 grams per kilometer (Equivalent to about 38 mpg)
- By 2012: 120 grams per kilometer(Equivalent to about 50 mpg)
- By 2025: 70 grams per kilometer (Equivalent to about 80 mpg)
While the use of advanced high-strength steels result in vehicles that are safer than ever in severe crashes, those same ultra-strong steels are making it difficult to extract survivors from badly crushed vehicles. Traditional cutting tools like the “Jaws of Life” cannot shear through the new steels. Rescue workers either have to use new tools that cost about $5,000 each or learn new techniques.
Use of aluminum to reduce vehicle weight goes back decades. Between 1975 and 1995, as the U.S. auto industry sought to raise the fuel efficiency of gasoline cars by 50 percent to meet government fuel economy regulations, one technique was to replace heavy cast iron engines with lightweight aluminum engines. The metal has come a long way since then and carmakers are utilizing it in a variety of body applications: Acura estimates that the aluminum hood on the 2010 ZDX saved 15 lbs. compared with steel, while BMW says the aluminum doors on the 5 Series sedan results in a weight save of approximately 50 lbs. compared with steel doors.
Nearly 50 years after development, carbon fiber-reinforced plastics remain a niche material in the auto industry. But recent developments point the way to expanded use: In a joint venture with Seattle-based SGL Automotive Carbon Fibers LLC, BMW is constructing a factory in Moses Lake, Washington to produce the composite, and Italy’s supercar manufacturer, Lamborghini, recently opened a laboratory at the University of Washington to study the use of the super-strong, ultra-light material in future vehicles.
Yet, at around $10.00 per pound compared to less than a $1.00 per pound for high-strength steels, it would seem that the use of carbon fiber would be limited to concept cars and exotics in the $500,000 range. However, European carbon dioxide emission standards that could limit fleets to a minuscule 70 grams per kilometer (equivalent to about 80 mpg) might be impossible to reach without carbon fiber.
Of course there are other areas in a vehicle to that are going through weight loss programs, although their reductions are measured in ounces rather than pounds. Plastic is becoming more prevalent under the hood as metal engine components are being replaced by lighter weight thermoplastic. And inside, heavy sound insulating materials—from 55 lbs. for a small vehicle, to as high as 135 lbs. on a luxury sedan—are being swapped for lighter sound absorbing products.
The Department of Energy’s national labs are working with the auto industry to develop materials and manufacturing technologies that, if implemented in high volume, could reduce the average weight of vehicle structure and subsystems by 50 percent. If the Obama administration’s notice of intent, filed earlier this month, that could push fuel mileage standards to as high as 62 mpg by 2025, that 50 percent weight reduction will become an absolute necessity.