*Editor's note: In the June issue of Wired, contributing editor Charles C. Mann argues the U.S. auto industry must encourage and incorporate outside innovation in order to survive. In this series of blog posts, he examines two companies, far outside Detroit, that are working to create the kind of breakthroughs the American auto industry desperately needs.
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Because gasoline has historically been inexpensive, U.S. consumers have had little reason to buy fuel-efficient automobiles, giving manufacturers little reason to make them. As a result, today’s cars are amazingly wasteful. Less than 20 percent of the energy in the gas consumed by typical passenger vehicles is used to power the wheels. Most of the rest is lost as heat or sent into the air as pollutants.
To San Diego inventor and entrepreneur Mike Cheiky, the conclusion was obvious: To make cars more fuel-efficient, figure out how to increase that percentage. If Cheiky could create an internal combustion engine that used just 40 percent of gasoline’s potential energy, he would effectively double gas mileage. The goal didn’t sound impossible. After all, many electric engines operate at more than 80 percent efficiency.
Cheiky founded Transonic Combustion in 2006 to tackle the problem. His solution: Manufacture a new kind of fuel injector.
Hypothetically, automobile engines would function most efficiently if all the fuel in the cylinder exploded instantly, just as the piston reaches its highest point. In the real world, of course, that doesn’t happen. Not all the gas gets burned, for one thing. And the explosion is stretched over time, so that some of it continues as the piston is moving down the cylinder — the expanding gasses end up chasing the retreating piston, instead of striking it solidly. Ordinary fuel-injection systems like the one pictured improve efficiency by squirting a carefully calibrated mix of fuel and air into the cylinder just as the piston rises to meet it.
Transonic’s fuel injection system goes another step: It shoots the fuel-air mixture into the engine in what is called a “supercritical” state. Usually liquids heated above a certain critical temperature become gases; gases compressed above a certain critical pressure become liquids. Substances that are simultaneously heated above the critical temperature and compressed above the critical pressure go into a supercritical state—neither liquid nor gaseous. Transonic’s system heats and compresses the fuel-air mixture until it is supercritical, then injects it into the cylinder.
Supercritical substances have unusual physical properties. According to Transonic, gasoline becomes much more explosive. Typical fuel injectors blast about 15 times as much air as fuel into the cylinder. Transonic injectors have been able to function at ratios of 100:1 or even 200:1, a huge potential improvement that would require much less gas. And because supercritical combustion is more complete, Transonic president Brian Ahlborn notes, there will be fewer leftover pollutants released into the air.
Transonic is still learning how to commercialize its technology, which works with gasoline, diesel fuel and ethanol and ultimately could be added onto existing car engines without extensive modification. Ahlborn stresses that the company, which has backing from Khosla Ventures, Rustic Canyon and Venrock, still has much work to do.
“But we’re pretty excited about what we’re seeing,” he says. “There’s a lot of room to make standard internal-combustion engines a whole lot better.
You can read Charles C. Mann's piece, "Beyond Detroit: On the Road to Recovery, Let the Little Guys Drive," here.
Photo: Flickr / peteSwede
