Cylinder

(See also Engine Displacement, Engine Size) In a reciprocating engine, a cylinder is the chamber in which combustion of fuel occurs and the piston moves, ultimately delivering power to the wheels. Common engine configurations include 4, 6, and 8 cylinders. Generally, the more cylinders a vehicle has, the greater the amount of engine power it has. However, more cylinders often result in less fuel efficiency. (DOE4)

A pressure vessel designed for pressures higher than 40 psi and having a circular cross section. It does not include a portable tank, multi-unit car tank, cargo tank, or tank car. (49CFR171)