STEAM AND ELECTRICITY were used to power cars until early this century, but neither power source was ideal. Electric cars had to stop frequently to recharge their heavy batteries, and steam cars gave smooth power delivery but were too complicated for the average driver to use. A rival power source, the internal combustion engine, was invented in 1860 by Etienne Lenoir. This engine converted the force of a controlled explosion into rotary motion, to turn the wheels of a vehicle. Early
variations on this basic model included sleeve valves, separately cast cylinders, and the two-stroke combustion cycle. Today, many internal combustion engines, including the Wankel rotary and diesels, use the four-stroke cycle, first demonstrated by Nikolaus Otto in 1876. The Otto cycle, often described as “suck, squeeze, bang, blow,” has proved the best method of ensuring that the engine turns over smoothly and that exhaust emissions are controllable.
