Fuel and Emissions System Description - Turbocharger Control System
Fuel and Emissions System Description - Turbocharger Control System
Turbocharger Control System
Refer to the system diagram to see a functional layout of the system.
Turbocharger Boost Sensor
This sensor converts charge air cooler pressure into an electrical signal that is received by the PCM.
Turbocharger Wastegate Control Solenoid Valve
This solenoid valve controls pressure to the turbocharger wastegate control actuator. The solenoid itself is controlled by the PCM. The following information describes the ports on the valve and where the pressure flows when the solenoid switches the valve on and off.
Turbocharger Bypass Control Solenoid Valve
This solenoid valve controls pressure to the turbocharger bypass control valve. The solenoid itself is controlled by the PCM. The following information describes the ports on the valve and where the pressure flows when the solenoid switches the valve on and off.
Turbocharger Boost Control Solenoid Valve
This solenoid valve controls pressure to the turbocharger boost control valve. The solenoid itself is controlled by the PCM. The following information describes the ports on the valve and where the pressure flows when the solenoid switches the valve on and off.
Turbocharger Control System Diagram
The turbocharger control system controls the boost pressure and the response of the turbocharger. The PCM controls the turbocharger wastegate control solenoid valve (duty controlled), the turbocharger bypass control solenoid valve (on/off controlled), and the turbocharger boost control valve (duty controlled). The boost pressure is monitored by the turbocharger boost sensor.
Turbocharger Wastegate Control System
This system controls the wastegate control solenoid to prevent the turbo from exceeding maximum boost pressure. This system is duty controlled by the PCM. The descriptions A and B are the two conditions of duty. Condition A (maximum duty) and condition B (minimum duty). At other times, the turbocharger wastegate control solenoid controls both the passages from the intake air duct (turbocharger inlet connecting tube), and the intake air duct (turbocharger outlet pipe) to the turbocharger wastegate control actuator.
Condition A (maximum duty):
When the turbocharger boost sensor signal is lower than the upper limit, the PCM turns on (maximum duty) the turbocharger wastegate control solenoid valve, and opens the passage between the intake air duct (turbocharger inlet connecting tube) and the turbocharger wastegate control actuator and closes the passage from the intake air duct (turbocharger outlet pipe) and the turbocharger wastegate control actuator. The pressure at the turbocharger wastegate control actuator is released to the intake air duct (turbocharger inlet connecting tube), and the spring in the turbocharger wastegate control actuator closes the turbocharger wastegate control valve. In this condition, all of the exhaust gas flows to the turbine. This increases the rpm of the turbine, increasing boost pressure.
Condition B (minimum duty):
When the turbocharger boost sensor signal reaches the upper limit, the PCM turns off (minimum duty) the turbocharger wastegate control solenoid valve, and opens the passage between the intake air duct (turbocharger outlet pipe) and the turbocharger wastegate control actuator and closes the passage from the intake air duct (turbocharger inlet connecting tube) and the turbocharger wastegate control actuator. The boost pressure from the intake air duct (turbocharger outlet pipe) pushes the turbocharger wastegate control actuator and opens the turbocharger wastegate control valve. In this condition, only a portion of the exhaust gas flows through the bypass passage bypassing the turbocharger wastegate control valve, and the amount of exhaust gas to the turbocharger decreases. This decreases the rpm of the turbine decreasing boost pressure.
Turbocharger Bypass Control System
This system improves the boost response of acceleration immediately after deceleration. This system also protects the turbocharger from the negative effects of compressor surge during high boost. The descriptions A and B are the two conditions of the turbocharger bypass control solenoid valve on and off. Condition A (on) and condition B (off).
Condition A (Solenoid Valve ON):
When the vehicle is in cruise or accelerating, the PCM turns on the turbocharger bypass control solenoid valve, and opens the passage between the charge air cooler and the turbocharger bypass control valve and closes the passage between the intake manifold and the turbocharger bypass control valve. The boost pressure from the charge air cooler pushes the turbocharger bypass control valve, and closes the passage between the charge air cooler and the intake air duct (turbocharger inlet pipe). By doing this, all compressed air is routed to the intake manifold.
Condition B (Solenoid Valve OFF):
During the deceleration with the throttle valve closed, the PCM turns off the turbocharger bypass control solenoid valve and opens the passage between the intake manifold and the turbocharger bypass control valve and closes the passage between the charge air cooler and the turbocharger bypass control valve. The vacuum pressure from the intake manifold pulls the turbocharger bypass control valve and opens the passage between the charge air cooler and the intake air duct (turbocharger inlet pipe). By doing this, the compressed air flows from the charge air cooler to the intake air duct (turbocharger inlet pipe) to keep the turbine spinning. This improves the acceleration response of the turbocharger after deceleration.
Turbocharger Boost Control System
This system controls the exhaust gas passage to the turbine by changing the variable flap angle. The variable flap is moved by the turbocharger boost control actuator, and it is duty controlled by the PCM depending on the driving condition.
When the variable flap is fully closed, all exhaust gas flows to the inner scroll of the turbocharger. Under this condition, the exhaust gas speed is accelerated, and the turbocharger response is improved. When the variable flap is fully opened, the exhaust gas flows through both the outer and the inner scroll of the turbocharger. Under this condition, the exhaust gas is efficiently used to improve the maximum boost. Because of this system, the turbocharger functions both as a quick responding small size turbocharger, and high capacity turbocharger.
The description A and B are the two conditions of duty. Condition A (maximum duty) and condition B (minimum duty). At other times, the turbocharger boost controls both the passages from the intake air duct (turbocharger inlet connecting tube), and the intake air duct (turbocharger outlet pipe) to the turbocharger boost control actuator.
Condition A (maximum duty):
Under a low engine speed/low load condition (with only a small amount of exhaust gas), the PCM turns on (maximum duty) the turbocharger boost control solenoid valve and opens the passage between the intake air duct (turbocharger inlet connecting tube) and the turbocharger boost control actuator and closes the passage between the intake air duct (turbocharger outlet pipe) and the turbocharger boost control actuator. The pressure at the turbocharger boost control actuator is released to the intake air duct (turbocharger inlet connecting tube), and the spring inside the turbocharger boost control actuator closes the variable flap. With the variable flap closed, the exhaust gas flows at high speed through the inner scroll of the turbocharger improving the turbo response.
Condition B (minimum duty):
Under a medium or high load conditions (with large amount of exhaust gas), the PCM turns off (minimum duty) the turbocharger boost control solenoid valve and opens the passage between the intake air duct (turbocharger outlet pipe) and the turbocharger boost control actuator and closes the passage between the intake air duct (turbocharger inlet connecting tube) and the turbocharger boost control actuator. The boost pressure from intake air duct (turbocharger outlet pipe) pushes the turbocharger boost control actuator which opens the variable flap. With the variable flap opened, the exhaust gas flows through both the inner and the outer scroll for efficient turbo operation at medium and high engine speed.
