Flywheel：A 4-cylinder engine produces a power stroke every half crankshaftrevolution，an 8-cylinder, every quarter revolution. This means that a V8 will be smotherrunning than a 4. To keep the combustion pulses from generating a vibration, a flywheelis attached to the back of the crankshaft. The flywheel is a disk that is about 12 to 15inches in diameter. On a standard transmission car, the flywheel is a heavy iron disk thatdoubles as part of the clutch system. On automatic-equipped vehicles，the flywheel is astamped steel plate that mounts the heavy torque converter. The flywheel uses inertia tosmooth out the normal engine pulses.

    Balance Shafts: Some engines have an inherent rocking motion that produces anannoying vibration while running. To combat this, engineers employ one or more balanceshafts. A balance shaft is a heavy shaft that runs through the engine parallel to thecrankshaft. This shaft has large weights that， while spinning，offset the rocking motion ofthe engine by creating an opposite rocking motion of their own.