The Green Book, produced by the American Council for an Energy-Efficient Economy (ACEEE), says that in evaluating plug-in hybrids, it considers both the emissions from the gas engine and from the power plants that feed the grid.

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Because peak power arrives at different rpm for the gas engine and the electric traction motor, peak system horsepower nets out to be an even 200 hp at 5, 600 rpm, which is the rated redline.

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The difference between turbocharging and supercharging is simple: a turbocharger boosts engine air pressure by using exhaust gas to power a turbine that pushes more air into the combustion chamber.

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Cummins is leading global manufacturer of diesel and natural gas engines, engine-related component products, and electric power generation systems.

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PowerBox Concept hybrid, for example, shown at the L.A. show, looks a lot like a standard sports utility vehicle (SUV) but combines a supercharged V-6 engine that runs on compressed natural gas and an electric motor that provides added power for acceleration and passing.

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The rocket engine power plant runs at a 35% thermal efficiency, versus 55% for conventional gas-fired plants.

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