Impreza L Sport Wagon F4-2.2L SOHC (1999)
Torque Converter: Description and Operation
A: Construction And Function
This system causes the impeller and turbine to be coupled directly without the aid of oil when the engine rpm reaches a certain level. This direct
coupling eliminates torque converter clutch slip and thus leads to a reduction in engine rpm, which in turn results in less fuel consumption and less
noise.
The single plate type lock-up clutch is used, and the transition hydraulic oil pressure is controlled for reducing the lock-up shock of the clutch thereby
achieving smooth lock-up operation.
The lock-up clutch is fitted with torsional dampers which are adopted for reducing the vibration and noise in the driving system.
B: Lock-Up Operation
The Transmission Control Module (TCM) sends output signal to the duty solenoid B (lock-up). Since the duty solenoid B (lock-up) operates in
proportion to the duty ratio, the amount of ATF drained from there is increased, thus lock-up duty pressure being reduced.
As a result, the lock-up control valve moves downward, which connects the torque converter regulator valve and the lock-up control valve apply port
to each other.