First of all, what the heck is the Atkinson Cycle and why should we care? Naturally, it's a bit complicated, but basically in a modern Atkinson Cycle engine, the intake valve is held open longer than normal to allow a reverse flow of intake air into the intake manifold and allowing for a smaller compression ratio than the expansion ratio, making the engine more efficient with a slight reduction in overall power. Consult the all-knowing Wiki for more on that.

Most hybrid vehicles' gas-powered engines use an Atkinson Cycle, including the Toyota Prius and GM's 2-Mode Hybrid trucks and SUVs. According to the reliable Lyle Dennis of, the Chevy Volt will not use an Atkinson Cycle engine, instead relying on the standard Otto Cycle. For what it's worth, we also know that the Volt's 1.4-liter four cylinder engine will be controlled and monitored by all manner of electronic gadgetry, and we're sure the automaker has done its homework on making it as efficient as possible.


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