Terms & Technologies

Atkinson-Cycle Engine (Hybrid Vehicles)


The original Atkinson-cycle engine improved fuel efficiency by reducing the volume of air and fuel introduced on the intake stroke and compressed on the compression stroke. This smaller intake charge would then burn more efficiently during ignition, while still providing adequate torque on the power stroke. Honda engineers used the flexibility of the i-VTEC® system to simulate the original Atkinson-cycle principles, with operating efficiency that goes far beyond a traditional internal-combustion engine. Specifically, one of the i-VTEC cams delays the closing of its assigned intake valve until much later than usual on the compression stroke. The resulting smaller volume of air/fuel mixture then burns more completely and efficiently during the power stroke. However, the other intake cam is timed more like a conventional engine’s for greater power output.