The Incredible Shrinking Engine

A new engine design could significantly improve fuel efficiency for cars and SUVs, at a fraction of the cost of today's hybrid technology.

At MIT's Sloan Automotive Laboratory, Daniel Cohn (pictured above) stands behind an engine equipped with test instruments (in yellow) and an injection system that sprays fuel directly into the engine's combustion chambers.
Credit: Porter Gifford

The following article appears in the March/April 2007 issue of Technology Review.
For Daniel Cohn, a senior research scientist at MIT's Plasma Science and Fusion Center, the ­century-­old internal-combustion engine is still a source of inspiration. As he strides past the machinery and test equipment in the MIT Sloan Automotive Laboratory, his usually reserved demeanor drops away. "An engine this size," he says, pointing out an ordinary-looking 2.4-liter midsize gasoline engine, "would be a rocket with our technology."
By way of explaining that technology, he shows off a turbocharger that could be bolted to the 2.4-liter engine; the engine, he adds, uses direct fuel injection rather than the port injection currently found in most cars. Both turbocharging and direct injection are preëxisting technologies, and neither looks particularly impressive. Indeed, used separately, they would lead to only marginal improvements in the performance of an internal-­combustion engine. But by combining them, and augmenting them with a novel way to use a small amount of ethanol, Cohn and his colleagues have created a design that they believe could triple the power of a test engine, an advance that could allow automakers to convert small engines designed for economy cars into muscular engines with more than enough power for SUVs or sports cars. By extracting better performance from smaller, more efficient engines, the technology could lead to vehicles whose fuel economy rivals that of hybrids, which use both an electric motor and a gasoline engine. And that fuel efficiency could come at a fraction of the cost.