LINK-PIN END-RH 3P3043 - Caterpillar

Illustration 1 g00926843
Flow of the compressed air/fuel mixture during activation of the compressor bypass group (50 Hz arrangement)
(1) Actuator for the bypass valve
(2) Bypass valve
(3) Throttle
(4) Throttle actuator
(5) Fuel metering valve The master Electronic Control Module (ECM) monitors the engine speed. The ECM responds to a rapid increase in the engine speed by sending a command signal to actuator (1). This causes the actuator to move a shaft that is connected to a plate inside bypass valve (2). The bypass valve opens.The bypass valve is connected before throttle (3). Tubing is connected from the bypass valve to the inlet for the turbocharger compressor. When the bypass valve is opened, the compressed air/fuel mixture is diverted through the tubing away from the throttle. This reduces the back pressure that is caused by excessive pressure in the air inlet system.Note: The bypass valve for the 60 Hz arrangement is connected to two sets of tubing: one set of tubing is connected to the inlet for the right turbocharger and the other set of tubing is connected to the inlet for the left turbocharger.Additionally, the ECM sends two other command signals. A command to throttle actuator (4) opens the throttle in order to reduce the resistance that contributes to back pressure. A command to fuel metering valve (5) reduces the fuel supply in order to reduce the engine speed and the turbocharger's speed.The combined effect of these actions reduces the opportunity for a turbocharger surge.The ECM determines a time period that is required for opening of the bypass valve. After the time period has expired, the ECM sends a command signal to actuator (1) in order to close the bypass valve. Normal operation resumes.The compressor bypass group is also operated during engine shutdown. This reduces the opportunity for a turbocharger surge during engine shutdown. Additionally, any air/fuel mixture that may have been trapped in the tubing is purged.Active BypassThe compressor bypass valve is commanded to a wide range of positions if the engine is equipped with an Auxiliary Sensing Module (ASM). This is called active bypass. The ASM uses inputs from the manifold air pressure sensor and the boost pressure sensor in order to determine the pressure drop across the throttle plate. The ASM determines the amount of active bypass that is required in order to maintain the desired pressure drop across the throttle plate. The ASM transfers the information to the master ECM via the Cat Data Link. The master ECM sends a command to the actuator for the bypass valve in order for the bypass valve to move to the desired position.