Turbocharger Boost Control System

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 mid 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 mid and high engine speed.