9000 Hatchback L4-2290cc 2.3L DOHC Turbo EFI (1994)
The control valve functions to control pressure and flow as required by the steering.
One side of the control valve is in direct communication with the delivery pressure (4) from the pump. The pump outlet (5) incorporates a diameter of
restriction from which a connecting passage (1) leads to the other side of the valve, that is fitted with a spring (2). In the inactive position, the valve is
pressed against the outlet side.
A relief valve is incorporated into the control valve (3), that is effected, at high pressure, by the hydraulic pressure on the spring loaded side of the
control valve.
For the valve to operate, a certain amount of fluid must circulate continuously through the valve, although not when the steering is at full lock.
The pump delivers a maximum pressure of approximately. 95 bars and a maximum flow of approximately. 7.5 liters per minute.
Steering, Low Engine Speed
The pressure raised by the pump (shaded portion in the illustration) is reduced slightly by the restriction in the pump outlet. The reduced
pressure is also communicated to the spring loaded side of the control valve, giving rise to a slight pressure difference between the two sides of
the valve. Owing to the low speed of the pump, the hydraulic pressure is insufficient to overcome the force of the spring and actuate the valve.
Steering, High Engine Speed (Pump In Flow Regulation Position)
With increased engine speed the flow of hydraulic fluid increases to the pump. The flow velocity also increases because of the restriction in the
pump outlet. This causes a drop in pressure in the connecting passage and as a result the pressure on the spring loaded side of the control valve
will be lower than that acting on the outlet side of the valve. The valve, therefore, overcomes the force of the spring, opening a port to the
suction side of the pump and allowing internal recirculation of the fluid. A constant flow out of the pump is achieved, independent of
pump/engine speed.
