Engine Vibration

Great efforts are continually being made to improve comfort for car drivers and passengers. Two areas that have been addressed are engine vibration and noise level, both of which are a result of the basic design of the engine. Through combustion, during which chemical energy is converted into mechanical energy, gas forces are generated that act on the piston crown. The reciprocating motion of the pistons and connecting rods, combined with the rotation of the crankshaft, generate inertial forces that act on the engine block and cause it to vibrate in various ways. At low engine speeds, these gas forces are greater than the inertial forces but at high engine speeds, the inertial forces are greater than the gas forces. The most significant forces arise periodically once or twice per crankshaft revolution. They are known as first-order and second-order forces respectively. The first-order inertial forces are completely cancelled out since the crankshaft is balanced and the two piston pairs, 1-4 and 2-3, reverse their direction simultaneously when they reach top dead centre and bottom dead centre.