Auto Tech: 2010 Ford Fusion Hybrid powertrain

2010 Ford Fusion Hybrid. Click image to enlarge

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By Jim Kerr; photos by Jil McIntosh

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2010 Ford Fusion Hybrid

Toyota and Lexus have been the big players in what is still seen as a niche market, with Honda second in line, but with every introduction there is new technology that does things better, faster and more economically. Now Ford has introduced the newest hybrid on the market – the 2010 Ford Fusion.

The Fusion is available in hybrid and non-hybrid models. The gasoline engine in the hybrid model shares the same 2.5-litre displacement as the four-cylinder engine in the regular models but there are significant internal changes. While both use variable cam timing and electronic throttle control, the hybrid engine uses the Atkinson cycle principle to optimize fuel economy. The Atkinson cycle delays the closing of the intake valve during the engine’s compression stroke. As the piston is starting its upward travel, there is no restriction because some of the air in the cylinder is pushed back into the intake port. Then the valve closes. By reducing this restriction, less energy is wasted on the compression stroke.

The Atkinson cycle unfortunately also reduces low-end torque. One way of compensating for that is to increase the compression ratio so that the air remaining in the cylinders has more pressure when combustion occurs. The Fusion Hybrid has a compression ratio of 12.3 to 1 compared to the 9.7:1 compression ratio of the regular Fusion engine. Even with this high compression ratio, the engine can still operate on regular fuel.

Another method of compensating for the lower torque produced by the Atkinson cycle is to assist the engine with electric motors. Electric motors are great at producing high torque at low rpm, so combined with the gasoline engine they can provide excellent drivability.

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