High pressure pump
|Type||Five piston volumetric|
|Operating speed||Half engine speed|
|Output (per pump cycle)||4 cc|
|Cut-out pressure||170 ± 5 bar|
|Cut-in pressure||145 ± 5 bar|
|Capacity||0.40 litre (0.70 pint)|
|Calibration pressure||62 + 2 bar – 32 bar|
|Slide valve return spring calibration pressures:|
|Isolation pressure (min)||80 bar|
|Suspension supply pressure (min)||100 bar|
Torque wrench settings Nm lbf ft
|Hydraulic pipe unions:|
|3.5 and 4.5 mm diameter pipes||8 to 9 6 to 7|
|6.0 mm diameter pipes||9 to 11 7 to 8|
The hydropneumatic suspension and the braking system are both pressurised by a common hydraulic system.
Fluid is drawn from a reservoir which is mounted on the right-hand wing valance and delivered under pressure to a pressure regulator which is mounted on the front of the engine. The system is pressurised by a belt-driven pump, which is mounted on the gearbox and driven by the camshaft pulley.
From the pressure regulator, fluid passes to the security valve which has pipe connections running to the compensator control valve and the front and rear suspension height corrector units.
Fluid from the suspension height corrector units (one at the front and one at the rear) flows to the suspension unit cylinders. From the suspension cylinders the low pressure return fluid is returned through pipelines to the hydraulic reservoir.
The height correctors maintain the hydropneumatic suspension at the manually selected height by admitting fluid to, and releasing fluid from, the suspension cylinders according to the movement of the front and rear anti-roll bars to which they are connected.
Four height positions can be selected by the manual height control within the vehicle. They are as follows:
- Lever set at second setting position from the front – Normal driving position.
- Lever set at most forward setting position – Minimum height setting for use during repair and overhaul procedures on the vehicle. Should not be used for normal driving.
- Lever set at third setting position from the front – Raises vehicle ride height to intermediate setting. For use when traversing rough road conditions.
- Lever set at fourth setting position (ie. lever moved fully back) – Raises vehicle to maximum height setting. Primary use is to assist when changing roadwheels. Should not be selected when driving except under exceptional conditions such as negotiating undulating surfaces, then only for short distances and at very low speeds.
Hydraulic pressure for the braking system is supplied from the compensator control valve with separate front and rear circuits. The front circuit is supplied direct from the compensator control valve, whilst the rear brake circuits operate in conjunction with the hydraulic circuits to the rear suspension. This arrangement results in the braking effort being biased in favour of the front brakes and at the same time regulates the braking effort on the rear wheels according to the load on the rear suspension. The heavier the load, the greater the pressure in the rear suspension, thus more braking effort.
Hydraulic pressure is released from the system by slackening the bleed screw on the pressure regulator. This allows the pressure fluid to bleed off to the reservoir.
On power steering models, a flow distributor is fitted between the HP pump and the pressure regulator unit. The purpose of the flow distributor is to control the hydraulic pressure between the steering circuit and the suspension/brake circuits.
Further details of the system are available in the Downloads section which features pages from the Technical Manuals.