The volume of space through which the piston moves from TDC to TDC is called cylinder displacement; if the engine has several cylinders, the sum of the operating volumes of all cylinders is called engine displacement. It is usually expressed in L. Engine displacement is one of the most important structural parameters, it can represent the size of the engine more than the cylinder diameter and number of cylinders, many of the engine indicators are closely related to the exhaust.
A large engine usually emits a large amount of energy per unit of time (that is, the chemical energy of the fuel is converted into mechanical energy) , that is, a good“Power”, it's as if a teenage boy is more efficient at manual labor than a healthy adult. So those suvs, sports cars are usually relatively large displacement.