to it) has to travel in the top 180° of crankshaft rotation is greater than in the bottom 180°. Greater distance in the same time equates to higher velocity and higher acceleration, so that the inertial force through top dead centre can be as much as double that through bottom dead centre. The non-sinusoidal motion of the piston can be described in mathematical equations.

In a car, for example, such an engine with cylinders larger than about 500 cc/30 cuin (depending on a variety of factors)