Torque Converters Explained
A torque converter is a fluid-coupling device that also acts as a torque multiplier during initial acceleration.
1) Impeller Pump – The impeller pump is the outside half of the converter on the transmission side of the weld line. Inside the impeller pump is a series of longitudinal fins that drive the fluid around the outside diameter into the turbine because this component is welded to the cover, which is bolted to the flexplate. The size of the torque converter (and pump) and the number and shape of the fins all affect the characteristics of the converter. If long torque converter life is an objective, it is extremely important that the fins of the impeller pump are adequately reinforced against fatigue and the outside housing does not distort under stress.
2) Stator – The stator can be described as the “brain” of the torque converter, although it is not the sole determiner of converter function and characteristics. The stator, which changes fluid flow between the turbine and pump, is what makes a torque converter a torque converter (multiplier) and not strictly a fluid coupler. With the stator removed a converter will retain none of its torque multiplying effect.
FOR THE STATOR TO FUNCTION PROPERLY,
THE SPRAG MUST WORK AS DESIGNED:
- It must hold the stator perfectly still (locked in place) while the converter is in stall mode (slow relative turbine speed to the impeller pump speed).
- It must allow the stator to spin with the rest of the converter after the turbine speed approaches the pump speed. This allows for more efficient and less restrictive fluid flow. The sprag is a one-way mechanical clutch set between two races that fits inside the stator while the inner race splines onto the stator support of the transmission.
3) Turbine – The turbine rides within the cover and is attached to the drivetrain via a spline fit to the input shaft of the transmission. When the turbine moves, the car moves.
4) Cover – The cover (also referred to as the front) is the outside half of the housing toward the engine side from the weld line. The cover serves to attach the converter to the flexplate (engine) and contains the fluid. While the cover is not actively involved in the characteristics of performance, it is important that the cover remain rigid under stress (torsional and thrust stress as well as the tremendous hydraulic pressure generated by the torque converter internally).