It's sort of like an organ transplant for cars.

Transonic Combustion, which has been relatively secretive until now, has created a fuel injection system that will let diesel engines run on regular gasoline. Diesel engines get better mileage than regular gas engines, explained CEO Mike Cheiky in an interview. However, diesels typically emit more particulates. Gas is also far more readily available than diesel in the U.S. Insert Transonic's components into a diesel engine and you get the best of both worlds.

Transonic Combustion

Additionally, the company's fuel injection system dramatically increases the internal compression in an engine, which in turn increases efficiency and mileage, he said. A standard 2.3-liter diesel engine that gets 50 miles per gallon can get 100 miles per gallon when retrofitted with Transonic's components.

"This gives us a clean-burning engine at very high compression," he said.

The Camarillo, Calif.-based company has already retrofitted a couple of engines with its injection system and is currently building up a car around one of its engines to test how it works. The car tests, hopefully, can begin this summer.

The principles behind Transonic's technology can be traced back to Nicholas Leonard Sadi Carnot, an 18th-century French engineer, according to Cheiky. Carnot studied the output of heat engines and determined formulas for achieving maximum theoretical efficiency.

In a compression engine, efficiency is dominated by the compression ratio, or the ratio of the volume inside a cylinder when the piston is down and the volume when the piston is up.

"The higher compression ratio, the higher efficiency," said Cheiky. "That is fundamentally why diesels are more efficient than gas engines."

Ultimately, the company will approach car manufacturers about adopting its technology. First, however, Transonic wants to extensively test it. Car companies are notoriously conservative so there's no shortage of testing that can be accomplished.

Cheiky wouldn't say much more about the technology--there's a lot more that he's not disclosing--but that's more than in the past. Transonic popped up on the radar last May when Venrock Partners, Rustic Canyon Partners, and Khosla Ventures announced investments in the company. (At the time, Transonic has single cylinder prototypes.) Details were scarce. Later in 2007, Transonic said it had set a goal of making an engine that can get 100 miles per gallon. The company said the engine could run on any type of fuel but didn't get into specifics on how it worked. More details might come out in the second or third quarter, he added.

One vague clue Cheiky gave me was that some of the technology in Transonic's device can be traced in part to his work in fuel cells and batteries. Cheiky helped start battery company Zinc Matrix Power. (He has 45 patents to his name. Some are in the cellular industry.)

Transonic isn't the only company citing historical sources. EcoMotors, another Khosla company, is working on an opposed cylinder/opposed piston motor that it says could make 100 mpg cars real. The engine design was tried in the 1930s, but it never caught on because of manufacturing costs.