Some of the start-up engine companies say they could ultimately get orders from makers of power generators or boat engines.

WSJ: How to Make Better Car Engines

Makers are the new power of the economic engine.

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Meanwhile, auto makers are proving there's still plenty of potential in the gas-powered engine to meet customer's fuel-efficiency demands.

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Some of the proposed alternatives to traditional engine design offer fuel savings that aren't that much greater than auto makers believe they can achieve through improvements to the designs they know.

WSJ: How to Make Better Car Engines