Importance

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Abstract

The fuel efficiency of an internal combustion reciprocating piston engine may be increased through selective secondary expansion of exhaust gas in the engine cylinders in order to recover exhaust gas energy which is otherwise wasted by cylinder blow-down at the end of the power stroke. Exhaust valve cam switching, intake valve deactivation, multiple exhaust valves, a specialized exhaust manifold arrangement and an exhaust gas diverter valve can be configured to enable a reciprocating engine to selectively operate in efficient eight stroke cycle compound mode when moderate engine power is demanded, then revert to conventional four stroke cycle non-compound mode operation when high engine power is demanded, without stopping the engine. For a road vehicle application, the benefit is substantially reduced highway cruising fuel consumption, while incurring minimal impact on engine weight, minimal impact on engine manufacturing cost, and no adverse impact on vehicle acceleration performance, hill climbing performance or trailer towing performance.

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First Claim