News

Supersize The Automobile

Some people may interpret Tata Motors' small Nano car as a sign of a new green esthetic that favors small cars. The presumption is that the Western style of supersized, muscle-bound, gas-guzzling, climate-harming cars may shrink to more sensible sizes, inspired by Tata's Gandhian frugality. Although the Nano gets good gas mileage—20 kilometers to the liter, by Tata's reckoning—it could do that without being small. Weight (not size) accounts for three fourths of the energy needed to move a car. Light but strong materials can therefore make a car very efficient without having to make it small or costly.

These two attributes—light and small—sometimes get confused for one another. In 1997, the U.S. National Highway Traffic Safety Administration issued a report purportedly showing that light cars are less safe for all road users than heavy ones. Though widely cited, the report rested on a false assumption—that size and weight are equivalent. They're not. In 2002, Dynamic Research Inc. took the same data but separated the effects of size and weight. This revealed that, weight being equal, size protects passengers; size being equal, more weight kills more people.

The way to save lives and oil and money, all at the same time, is to make cars relatively big, which is comfortable and protective, without making them heavy, which is hostile and inefficient. Achieving lightness only by making cars smaller, without improving their materials and design, degrades safety because passengers have less "crush space" to protect them. (Of course, makers of light and relatively small cars like Honda are already masters of crashworthiness.) Achieving lightness through improved design and lighter and strong materials can improve safety at any size. How do Formula One drivers generally walk away from seemingly devastating high-speed crashes? Mainly because their cars are made of ultralight carbon-fiber composites that can absorb six to 12 times more crash energy per kilogram than steel.

The heavier the car, the more fuel it needs to make it go, and the more carbon it emits. The typical car today wastes 94 percent of its fuel energy in its engine's losses and idling, its transmission, and its tires and air resistance. Only 6 percent of the fuel energy accelerates the car. In turn, the driver is only one twentieth of the total mass; the rest is the steel car itself. A mere three tenths of 1 percent of fuel energy goes into moving the driver. After 120 years of engineering effort, that's not a gratifying result.

Good design and advanced materials can help us out of this trap. Using a good hybrid engine roughly doubles a typical car's efficiency. We can then redouble efficiency by using advanced materials to halve the weight, and better tires and sleeker aerodynamics. As the car becomes lighter and more slippery, the hybrid engine can shrink by a half or a third, lowering costs. Moreover, the higher costs of advanced materials can be offset by simpler manufacturing processes: for example, in 2000 my team designed an ultrasafe carbon-fiber SUV that needed 10 to 20 times fewer body parts and no body shop (the parts snapped precisely together without jigs, robots or welders). It didn't require a paint shop because color can be molded into the composite. The car yielded 72 percent fuel savings, repaying the $2,511 extra retail cost in one or two years. Replacing pure gasoline with cellulosic-ethanol E85 (85 percent ethanol, 15 percent gasoline) would push that gas savings per kilometer to 93 percent. And we haven't yet counted plug-in hybrid, battery-electric or fuel-cell cars, all of which become attractive as light cars.

Carmakers have begun to notice. At the Los Angeles Auto Show in November, Ford announced that from 2012 to 2020 it will trim 250 to 750 pounds out of each car it makes. In January, Nissan announced an average 15 percent weight cut by 2015. Mazda has already begun making lighter cars. Making lightweight cars is a wonderful opportunity for the U.S. motor industry to rebound. Using advanced materials and design doesn't require a huge upfront investment—just a big cultural change. Automakers everywhere should follow the lead of Boeing, which made its 787 Dreamliner 50 percent out of carbon-fiber composites, a bold step that leapfrogged its sales and market position over Airbus. Ford in 2006 hired the head of Boeing Commercial Airplanes as its CEO; he's now in Detroit intent on transformation.

Lightweight cars can be made of light metals, ultralight steel or advanced composites. The market will sort out which materials win. But Japanese automakers have shown every intention of jumping over metal solutions to even lighter carbon fiber. Toyota's 1/X concept car, shown at the Tokyo Motor Show in October, is one third the weight of a Prius and uses half the fuel, yet has the same interior volume. Its tiny half-liter engine tucks under the rear seat. It's a plug-in hybrid, yet weighs just 420 kilograms. The day before Toyota announced it, Toray, the world's biggest maker of carbon fiber, announced a ¥30 billion factory in Nagoya to mass-produce carbon-fiber auto parts for Toyota, Nissan and others. That's a clear signal of strategic intent. Weight, as Henry Ford said, is advantageous only for steamrollers.