CORE ASSEM. 8S3637 - Caterpillar

Illustration 1 g03780988
In-line engines
(1) Exhaust bypass
(2) Linkage
(3) Electrohydraulic actuator
Illustration 2 g03780989
Vee engines
(1) Exhaust bypass
(2) Linkage
(3) Electrohydraulic actuator Electrohydraulic actuator (3) for exhaust bypass (1) receives an electronic command signal from the Electronic Control Module (ECM). The command signal is a Pulse Width Modulated signal (PWM). The signal causes electrohydraulic actuator (3) to move linkage (2) in order to operate the exhaust bypass.When the ECM requests a leaner air/fuel ratio, the actuator moves the exhaust bypass toward the closed position. This directs more of the exhaust gas to the turbocharger turbine wheel. The additional exhaust gas increases the rpm of the turbine wheel and of the compressor wheel. A greater quantity of air is compressed for combustion. This increases the amount of air in the air/fuel mixture.When the ECM requests a richer air/fuel ratio, the actuator opens the plate of the exhaust bypass. This diverts some of the exhaust gas directly to the exhaust elbow instead of through the turbocharger. The reduction of exhaust gas to the turbine wheel reduces the rpm of the turbine wheel and of the compressor wheel. Less inlet air is compressed for combustion. This reduces the amount of air in the air/fuel mixture.