Displacement: refers to the sum of the cylinder volumes traveled by the piston in the engine cylinder from the top to the bottom. Simply put, if the engine cylinder is a cup, the displacement is the volume of the cup. Now both engines are composed of several cylinders, so the displacement is equal to the sum of the volumes of these cylinders. Horsepower: Horsepower is one of the units of power. When we pay attention to the horsepower of a car, we are actually asking the maximum power of the engine of the car.