who was responsible for inventing the first working four-stroke engine?
The earliest internal combustion engine used a system that came to be known as the four-stroke cycle. In engineering circles it is called the Otto Cycle since it was invented by Karl Otto. A four-stroke engine needs to have valves, and a mechanism for opening and closing them at the correct time, and it produces power only once every two rotations of the crank. A well built two-stroke halves the number of components and doubles the power.