Full-Lock Unloader System; Power Steering Speed Sensor 1 7 - 1 - Honda Prelude 1993 Service Manual

The 4-way valve shifts the direction of fluid flow when
the steering wheel is turned right or left.
However, when the wheel is turned to the right or left
lock at parking speed, the edge of the pinion holder
rides up on the end of the rack, moving the pin in the op-
posite direction which pulls the 4-way valve back to
nsutral.
This keeps pump pressure from building up (which
could cause idl€ speed to drop), and improves steering
leel by increasing resistance at left and right lock.
Control in "assist" position
4-way valve moves back to "neutral" position
System Description
Full-lock Unloader System Power Steering Speed Sensor
The power steering speed sensor is a trochoid-rotor,
hydraulic pump combined with a relief valve and a one-
way valve. lt is driven by the speedometer gear shatt
which in turn is driven by a helical gear on the
differential.
INNER ROTOR
OUTER ROTOR
ONE-WAY VALVE
SPEEDOMETER GEAR
The power steering speed sensor turns only when the
car is moving. controlling the gain control valve.
The constant pressure is generated by the pressure
conlrol valve.
This pressure is used as a relerence pressure for the
response to the car's speed. Bv introducing this
pressure to the power steering speed sensor through
the sensor oritice, the pressure downstream of the
orifice is changed according to the speed of the car.
PRESSURE CONTROL VALVE
FEEO SIDE ORIFICE
To power steering speed sensor
Pressure in response
to vehicle speed
17-12