The Atkinson Differential Engine

In 1882, to get around the patents of the day, James Atkinson developed the Atkinson Differential Engine. In the design the four strokes of the power cycle -- intake, compression, combustion and exhaust -- were all accomplished during a single rotation of the crank shaft. The fellow in the video above does a good job demonstrating how that is achieved.

While his original design was never widely used, the Atkinson cycle can allow for a longer power to compression stroke which improves fuel efficiency. For that reason the Atkinson cycle is used in modern rotary engines, which are coupled with electric drive trains, in many production hybrids today. 

The Wikipedia article on the Atkinson cycle lists vehicles currently using such rotary engines. It also has a detailed animation that shows how the modern rotary engines achieve the Atkinson cycle.