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Packing on the pounds can be a big problem, whether you’re an athlete or an automobile.
Over the last two decades, cars have been getting bigger and heavier, in part due to customer demand, but also to meet federal safety standards. The problem is that “mass is the enemy of efficiency,” says Dave Leone, the chief engineer at Cadillac. A heavier car delivers lower mileage, is more sluggish and has less nimble performance.
Driven by customer demand, and tough new fuel economy standards, automotive engineers are putting the industry newest models on a diet. In some cases, they’re shaving as much as 700 to 800 pounds off vehicles like the new 2015 Ford F-150 pickup and the 2016 Cadillac CT6 sedan unveiled at this month’s New York Auto Show.
The new Caddy is the same size as a full-size BMW 7-Series, but it weighs barely as much as the German maker’s smaller 5-Series sedan. The new Cadillac CT6 flagship weighs less than its own midsize luxury sedan, the CTS.
“Lightweighting” has become one of the big buzzwords in today’s global auto industry as maker’s race to trim the fat from their vehicles. They need to meet the tough new Corporate Average Fuel Economy, or CAFE, standards that will jump to 54.5 mpg by 2025. The good news for consumers is that lighter vehicles not only get better mileage but also tend to deliver better performance.
To trim mass, automotive engineers have been turning to new, lightweight materials, such as aluminum. The completely redesigned Ford F-150 pickup, for example, averages about 700 pounds lighter than the older truck thanks to its “aluminum-intensive” body.
BMW took things even further with the debut of its battery-based sub-brand, BMW i. Both of its two new models, the i3 electric city car and i8 plug-in sports car, make extensive use of carbon fiber. That super-light, super-strong composite is also super-expensive, until now limiting its use to the likes of Formula 1 race cars and exotic vehicles from a Ferrari or Lamborghini.
Steel has long dominated the auto industry and its suppliers aren’t about to fade off into the sunset. They’ve been developing new, ultra-strong versions of steel that can be made thinner and much lighter for a given application.
That’s why the 2016 Cadillac CT6 will use a mix of aluminum, steel and other materials, notes the brand’s global president, Johan de Nysschen.
The goal, stresses the South African-born executive, was to come up with “the right materials for the right parts and components.”
Japanese maker Mazda underscores what auto engineers like to call a “systems approach.” By reducing the weight of a vehicle’s body and chassis they are cutting the size of suspension components, downsizing the engines used in new vehicles, even trimming a gram out of every lug nut. In the end, models like the latest Mazda CX-5 are adding several miles a gallon.
“Lightweighting is only part of the solution,” but it's a critical part, says David Cole, director-emeritus of the Center for Automotive Research in Ann Arbor, Michigan.
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Keeping costs down
Part of the challenge, adds Dr. Cole, is keeping costs from running out of control. Aluminum is significantly more expensive than steel per pound, though an automaker needs less of it. The cost of carbon fiber is even more astronomical.
BMW has been working with a partner on developing new production methods that have begun driving down the cost of what is more formally known as carbon fiber-reinforced composites, or CFRPs. Together, they recently announced plans to expand a pilot facility in Washington State that will soon become the world’s largest producer of the advanced material.
Part of the challenge with new materials is that they often require very different production and assembly processes. Ford has spent over $1 billion retooling the two plants – near Detroit and Kansas City – that produce the F-150.
Safety is another issue. The basic laws of physics suggest that if two otherwise identical vehicles collide, the lighter one will sustain the greater damage. No matter what you do, a Smart Fortwo will come out the loser in a battle with an 18-wheeler.
That said, while new materials such as aluminum and CFRP may be lighter than steel, they’re usually a lot stronger, pound-for-pound. Engineers also have learned a lot about how to absorb and control crash forces, directing them away from the passenger compartment, even as advanced safety systems such as airbags make it possible to survive what once would have been a fatal collision.
How much lighter might tomorrow’s cars get? Over the last two years, it’s seemed like every new model has been shedding at least 100 pounds or more.
The DeltaWing concept could take things even further. Based on an experimental design that has been running on the endurance racing series, it blends advanced aerodynamics with super-light materials that could trim the weight of a conventional 4-seat sedan by half.
Under development by a Georgia-based start-up, it needs just a 1.4-liter, 138-hp engine to give V-6 performance – and is forecast to yield 74 mpg on the highway and 54 mpg combined. It hopes to have the concept in production before the end of the decade.