Hydraulic Unit

To control braking system pressure, brake hydraulic unit has a 3-way valve which permits 3 separate brake pressure conditions. Pressure build-up, pressure retention and pressure drop are the 3 pressure phases that adapt to vehicle braking requirements. Control procedures are as follows:

• As soon as wheel lock-up is indicated, brake fluid pressure is reduced. If wheel still tends to lock, pressure will be further reduced until wheel acceleration or slip limit is detected. Pressure is then raised and control phases repeated. These pressure changes occur in milliseconds.
• The return delivery pump returns brake fluid from wheel brake cylinder, while dropping pressure to appropriate brake circuit. Pump is a 2-piston pump design so circuits of a dual brake circuit system remain separated.
• Two relays are located under hydraulic control unit cover: an engine relay and a valve relay. The engine relay is the larger relay.