Torque converter

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Fig 1: Identifying Torque Converter

Courtesy of VOLVO CARS OF NORTH AMERICA.

The torque converter functions as an hydraulic automatic clutch. When the engine is idling the pump effect is too weak to drive the turbine and the vehicle will not move. As the engine speed (RPM) rises it successively starts to drive in a gradual way. At higher engine speeds (RPM) the power transfer to the turbine can be up to 95%. The torque converter functions as an hydraulic clutch.

Thanks to a third, smaller wheel, the stator wheel, the torque converter also reinforces the engine torque at low engine speeds.

The rotating impellers and the oil in the torque converter "slip" slightly and create a slight loss of power, which increases fuel consumption slightly.