Intake Port Shutoff Function
Shown on engine 647
In the charge air distribution pipe, there is one swirl intake port and one filling intake port per cylinder. The filling intake ports can be closed by flaps. The flaps are connected together via a linkage which is operated by the intake port shutoff motor. In a de-energized condition the flaps are held by the integrated spring and the integral spring in the intake port shutoff motor in an open condition.
The position of the flaps at the filling intake ports is determined by a performance map stored in the CDI control unit (N3/9). The intake port shutoff motor is actuated by means of a PWM signal (pulse width modulated signal) for this purpose.
In the lower rotational speed and load range all the filling inlet ports are closed by valves. The complete air mass flows in solely via the swirl inlet ports. The resultant high eddy causes a more effective mixing of the fuel with air. This improves combustion whereby a high engine torque and reduction of the soot particles in the exhaust is achieved.
As the rotational speed and loads increases the filling intake ports are continuously opened so that the best possible eddy and required air mass is available for each engine operating point. This improves the exhaust characteristics and engine torque.