“You can see the cylinder sleeve moving for the intake stroke,” he yelled over the din. Mostly what I could see was oil bubbling in the tiny window, hidden behind the spinning bands driving the camshafts. On the other side of the block was a bigger belt, joining the engine’s two crankshafts and spinning at 4,000rpm, the current test speed. The safety glasses I was issued on entering the test room would be little help if the belt snapped.

This was the engine test cell at Pinnacle Engines in San Carlos, Calif., a soundproofed room containing the most recent prototype of this innovative new engine design. The engine sat on a test stand, hooked up to sensors monitoring every aspect of its operation, from torque output to emissions.

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