By its very principle, a reciprocating piston engine develops its torque cyclically. Some rotating mass is essential to accumulate temporarily kinetic energy and the return in order to stabilize the rotation. Unless the engine has a large number of cylinders, a flywheel is screwed necessarily the end of the crankshaft to increase the rotating mass. On manual transmission car or robot, one side of this wheel is used to support the clutch while its periphery is set with a crown wheel for engagement of the pinion electric starter. But there should be a very heavy flywheel to eliminate any perceptible trace of torsional vibrations in the driveline. However, a rotating mass deteriorates the transient response to changes in engine speed and crankshaft submit to additional torsional and flexural.

The conventional way to limit the propagation of torsional vibrations in the transmission so far has been to insert a damper spring in the hub of the disc clutch. However, this solution adds a rotating mass, not linked to the crankshaft but primary shaft gear, and therefore to synchronize during gearshift. In addition, it allows only one race depreciation of less than 30 °, which is insufficient, particularly when operating at low speed diesel engines. The situation is improved on virtually all diesel and some gasoline engines by mounting a dual-mass flywheel, which means not only having a mass attached to the primary crankshaft, but also a mass attached to the secondary transmission. These two coaxial masses are connected by springs that allow up to 120 ° of relative motion, or more.