stroke

In the context of an internal combustion engine, the term stroke has the following related meanings: A phase of the engine's cycle (e.g. compression stroke, exhaust stroke), during which the piston travels from top to bottom or vice versa. The type of power cycle used by a piston engine (e.g. two-stroke engine, four-stroke engine). "Stroke length", the distance travelled by the piston during each cycle. The stroke length, along with bore diameter, determines the engine's displacement. Phases in the power cycle Commonly used engine phases or strokes (i.e. those used in a four-stroke engine) are described below. Other types of engines can have very different phases. Induction-intake stroke The induction stroke is the first phase in a four-stroke (e.g. Otto cycle or Diesel cycle) engine. It involves the downward movement of the piston, creating a partial vacuum that draws an air-fuel mixture (or air alone, in the case of a direct injection engine) into the combustion chamber. The mixture enters the cylinder through an intake valve at the top of the cylinder.