Range Rover Sport. Manual — part 78

Counter balance

12

Pulley attachment flange

The hydraulic pump is driven at approximately 1.7 times crankshaft speed by the auxiliary drive belt. The pump is a radial
piston type which delivers fluid at high pressures.

The radial pump has eight pistons located in bores in a cylinder housing. A balanced central shaft, which is driven by a
pulley and the auxiliary drive belt, has a cam which operates the pistons as the shaft rotates.

As the cam lobe reaches each piston, the piston is pushed outward, moving the fluid above the piston. The pressure created
by the fluid flow from the bore opens a spring loaded discharge valve. When the valve opens, the now pressurised fluid
flows, via the silencer volume area of the cylinder housing, to the outlet port. The silencer volume assists with damping out
operating noise from the pump. When the piston reaches its full stroke, the flow reduces and the discharge valve closes
under spring pressure.

As the cam lobe moves away from the piston, a spring pushes the piston down the bore, creating a vacuum above the
piston. As the piston moves down the bore, ports in the piston are exposed and connect with the fluid inlet port. The
vacuum draws fluid into the piston filling the piston and the chamber above it. As the piston is again pushed upwards, the
ports in the piston are closed off by the bore and the pressurized fluid opens the discharge valve and flows to the outlet
port.

The above sequence is applied to each of the eight pistons for every revolution of the shaft and cam. When the engine is
running the sequence occurs rapidly creating a constant flow of fluid. The fluid flow varies with engine speed and the
rotational speed of the shaft. The pressure applied to the actuators, created by the flow from the pump, is controlled by the
pressure control valve in the valve block.

The pump has a displacement of 6cm

3

/rev and an operational pressure of 165 bar (2248 lbf/in

2

). The pump output flow

ranges from 6.5 l/min (1.7 US Gallons/min) at idle to 10 l/min (2.64 US Gallons/min) at 1000 rev/min and above.

DYNAMIC RESPONSE VALVE BLOCK

The valve block is located below the right hand sill of the body and is secured with three bolts and rubber bushes to captive
nuts located in the chassis. The rubber bushes isolate the valve block preventing hydraulic noise from transmitting through
the body.

Description

1

Nut (3 off)

2

O ring (3 off)

3

Directional control valve coils (DCV1 and DCV2)

4

O ring (3 off)

5

DCV1

6

Pressure transducer

7

Mounting bush (6 off)

8

Washer (7 off)

9

Bolt (3 off)

10

Nut

O ring

12

High pressure filter

13

O ring

14

Pipe connections

15

Stud (3 off)

16

Pressure control valve

17

O ring

18

Pressure control valve coil

19

DCV2

20

Spacer (3 off)

21

Captive nut (3 off) (chassis mounting)

The valve block directs hydraulic pressure to the actuators via solenoid operated directional control valves. A solenoid
operated pressure control valve regulates the required pressure to the actuators. The three solenoid valves are controlled
by signals received from the dynamic response control module. A pressure transducer monitors the pressure generated by
the Pressure Control Valve (PCV). A serviceable high pressure filter is installed into the underside of the valve block and
filters the hydraulic fluid before it reaches the control valves. The filter must be changed at the intervals defined on the
vehicle service schedule.

The two Directional Control Valves (DCV's) are fitted to ports in the top face of the valve block. The DCV's are screwed into
the valve block and are sealed with O rings. Each DCV has a solenoid for electrical operation of the valve. The solenoid is
sealed to the DCV with two O rings and secured with a threaded nut. The nut, coil and O rings are serviceable parts. The
DCV's are non-serviceable and failure of a DCV requires replacement of the valve block assembly.

The PCV is fitted to a port in the rear facing end of the valve block. The PCV is screwed into the valve block and is sealed
with O rings. The PCV has coil for electrical operation which is sealed to the PCV with two O rings and secured with a
threaded nut. The nut, coil and O rings are serviceable items. The PCV is non-serviceable and failure of the PCV requires
replacement of the valve block assembly.

The pressure transducer is located in the forward facing end of the valve block and is sealed with an O ring. The pressure
transducer measures the hydraulic pressure and returns a signal to the Dynamic Response control module.

A high pressure filter locates in a port on the lower face of the valve block. The gauze and fibre filter is sealed in the port
with O rings and is secured with a threaded cap which is also sealed with an O ring. A threaded hole in the lower face of the
filter allows a bolt to be fitted to remove the filter from the port. If a system hydraulic component is replaced, the filter must
also be replaced.

Four ports are located on the forward facing end of the valve block and two ports on the opposite end. Each port is fitted
with a seal pack which contains two O rings and backing rings. The pipes locate and seal in the seal packs and are secured
to the valve block with studs and nuts.

ACTUATORS AND STABILIZER BARS

Two stabilizer bars with integral hydraulic actuators are used for the Dynamic Response system. The actuators apply a
hydraulically generated force or rotational torque to the stabilizer bar to oppose lateral forces caused by the vehicle
cornering.

Actuator Sectional View

Air bleed ports

2

Piston

3

Ball screw

4

Stabilizer bar

Each actuator has a piston which is attached to the inner part of a rotor linear ball screw, which is splined to half of the
stabilizer bar. The outer part of the ball screw is crimped and welded into a housing which is attached to the other half of the
stabilizer bar. As pressure is applied to one side of the piston or the other, the ball screw converts the linear force applied to
the piston into a rotational torque between the two halves of the stabilizer bar.

Front Actuator and Stabilizer Bar