A **flywheel** provides mass for rotational inertia to keep the engine in motion

A flywheel serves four main purposes (in most vehicles):

  • It provides mass for rotational inertia to keep the engine in motion
  • It is specifically weighted to provide balance for the crankshaft
  • It provides a means to get the engine started (starter ring)
  • It provides a connection for power transfer between the engine and transmission (along with the clutch it also provides a means to interrupt the power flow)

Another such item, like unto a flywheel is a flexplate. This is a thin plate which connects the engine to a torque converter in automatic transmissions. While it provides the starting, connection, and balance of a flywheel, it alone does not have enough mass to provide the rotational inertia. In this case, the torque converter provides this for the engine.