Torque/power transmission increase/direct, function

W25.40-1040-01

Lockup clutch open

When the vehicle is stationary and the engine is idling, the lockup clutch in the torque converter is always open.

If the engine speed drops during normal driving conditions, the lockup clutch opens from an engine speed of approx. 950 rpm.

If kickdown is actuated, the lockup clutch opens at approx. 1,100 to 1,150 rpm to achieve a greater pulling power for a short time.

L Stator

P Impeller

T Turbine wheel

Arrow Power transmission

W25.40-1041-01

Lockup clutch closed

When driving at engine speeds over 950 rpm and when kickdown is not actuated, the lockup clutch is always closed.

When the lockup clutch is closed, the speed ratio of the impeller (P) to turbine wheel (T) is 1:1.

L Stator

P Impeller

T Turbine wheel

Arrow Power transmission

The torque converter consists of an impeller (P), turbine wheel (T) and stator (L) which form a sealed system.

The torque converter is driven directly by the engine and converts the mechanical energy of the engine into hydrodynamic energy.

The ratio between the turbine torque and impeller torque is the conversion (increase in torque).

The greater the difference in speed between the impeller (P) and turbine wheel (T), the greater the increase in torque. The maximum conversion occurs when the turbine wheel (T) is stationary.

The conversion decreases as the turbine speed (input speed) increases. For an approx. 80 % speed adaptation between turbine wheel (T) and impeller (P) a torque increase no longer takes place.

The torque converter is now bridged by the converter lockup clutch and the drive torque corresponds to the engine torque.

The torque converter is bridged by the lockup clutch closing automatically at a specified turbine/engine speed ratio of 0.8.

The input is now applied directly to the manual transmission without increasing the torque and without slip.