Acura NSX 1997 Service Manual page 392

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Partial Lock-up
Lock-up Control Solenoid Valve A: ON Lock-up Control Solenoid Valve B: OFF
The TCM switches solenoid valve A ON to release modulator pressure in the left cavity of the lock-up shift valve.
Modulator pressure in the right cavity of the lock-up shift valve overcomes the spring force, and the lock-up shift valve is
moved to the left side.
The torque converter pressure is separated into two passages:
Torque Converter Inner Pressure: enters into right side to engage lock-up clutch
Torque Converter Back Pressure: enters into left side to disengage lock-up clutch
Back pressure (F2) is regulated by the lock-up control valve, and the position of the lock-up timing valve B is determined
by throttle B pressure, tension of the valve spring, and pressure regulated by the modulator. Also, the position of the lock-
up control valve is determined by throttle valve B pressure, back pressure of the lock-up control valve, and torque converter
pressure regulated by the check valve. In low speed range, throttle B pressure working on the right side of the lock-up con-
trol valve is low, causing the valve to be moved to the right side. With the lock-up control solenoid valve B kept OFF, mod-
ulator pressure is maintained in the left end of the lock-up control valve; the lock-up control valve is moved slightly to the
left side. This slight movement of the lock-up control valve causes the back pressure to be lowered slightly, resulting in
partial lock-up.
NOTE: When used, "left" or "right" indicates direction on the hydraulic circuit.
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