When the engine starts, and idles, the transmission pump rapidly fills and pressurizes the converter.
The impeller is driven by the engine and turns at crankshaft speed.
With the selector lever in the Neutral or Park position, the turbine also rotates, carried around by momentum of the fluid.
When a drive position is selected, the turbine shaft is locked to the transmission output shaft through the transmission gearing, and the turbine comes to a halt.
Centrifugal force throws fluid between the impeller vanes outwards, around the back of the guide ring in a forward direction. This is due to the shape of the casing and the curvature of the vanes.
With the engine idling and the vehicle stationary, little torque is transferred from impeller to turbine, as the fluid flow is too gentle.
When the engine accelerates, higher impeller speed discharges the fluid across and against the turbine vanes with greater force.
Fluid exits the impeller at high velocity and enters the turbine at its outer edge.
This exerts a turning effort against the back of the turbine vanes, which absorbs energy in the fluid, causing the turbine to rotate, and transferring the drive to the transmission.
The fluid, still at high velocity, now flows between the turbine vanes, leaving the turbine in a direction opposite to impeller rotation.
This is due to the curvature of the turbine vanes.
Unchecked, this would oppose impeller rotation and reduce turning effort.
To defeat this, the stator re-directs the fluid. It re-enters the impeller in the same direction as impeller rotation.
The fluid strikes the forward face of the stator blades with a backward force, which locks the stator on the one-way clutch.
The stationary stator and the angle of the blades change the direction of the fluid flowing between them.
The fluid re-enters the impeller at high velocity, in the same direction as impeller rotation.
It strikes the back of the impeller vanes with considerable force, giving up energy to assist the engine in turning the impeller.
This provides torque multiplication.
