Boost Control System

Boost Control System:

BOOST PRESSURE CONTROL
^ Two bypass devices are used for automatically limiting turbocharger boost: compressor bypass valve and wastegate.

^ The compressor bypass valve responds to high intake vacuum during deceleration, opening to relieve high intake vacuum during deceleration, high pressure inlet air, and the accompanying noise.

^ The wastegate and its controls limit boost to 8.7 psi by regulating exhaust gas bypass flow around the turbine. This regulation initiates with the Electronic Control Assembly (ECA) and its sensors, which monitor engine speed, inlet air flow, and engine knock. The ECA controls the wastegate actuator and the wastegate valve.

^ Since the amount of boost varies directly with engine speed and load, within the control limits of the system, more boost is generated as speed and/or load increase.

BOOST CONTROL SOLENOID
^ Under low to medium speed and load, the ECA allows full boost if available, and opens the wastegate solenoid valve fully, thus venting boost pressure to the compressor inlet and leaving insufficient pressure to move the actuator. As a result, the wastegate remains closed and full boost is available.

^ As load and speed increase, boost pressure reaches its limit and the ECA will gradually close off the venting of boost pressure to the compressor inlet. This increases the pressure to overcome the actuator spring, so the actuator begins to push the wastegate open. This action continues until the solenoid valve is closed and the wastegate is fully open.

OVERBOOST PROTECTION
When engine speed and load increase to an overboost condition, a warning chime is activated by the vane airflow meter through the ECA. Simultaneously, unless the operator reduces speed and/or engine load, the ECA will execute the fuel cut-off operation and stop fuel injection in order to prevent engine damage.