The stator’s one-way clutch plays an important role in multiplying torque. The fluid circulating between the impeller and the turbine is called vortex flow. This flow exists only when there is a difference in rotational speed between the impeller and turbine.

The greatest speed difference between these two components occurs when a vehicle first accelerates from a stop. At this point, the impeller is spinning, but the turbine is not. Because of the great difference in speed, vortex flow and torque multiplication are at maximum. The vortex flow passing through the stator blades tries to turn the stator counterclockwise. When this happens, the clutch rollers move down the ramps and lock the stator to its support.

As the vehicle accelerates, the turbine gradually gains speed in relation to the impeller. Eventually, the turbine speeds up to the point where the fluid begins to flow in one direction (clockwise).

As centrifugal force reduces vortex flow, torque multiplication is also reduced. Finally, when the turbine’s speed reaches about 90 percent of the impeller’s speed, the torque converter reaches “coupling” phase. In this phase, the torque converter simply transmits engine torque through the fluid coupling to the transmission input shaft.

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