Air Management: Notes
Auxiliary Air Flaps: Each air cleaner housing incorporates an auxiliary air flap in its side wall. The auxiliary air flaps supply the engine with enough air volume to attain the maximum performance. The auxiliary air flaps are closed in the lower RPM ranges so that only cooler ambient air is drawn in for hot idling and stop and go driving.
The auxiliary air flaps are actuated by vacuum diaphragms which are located inside the air cleaner housings. Both diaphragms are supplied with vacuum from a common solenoid valve.
The auxiliary air flaps are fully opened by the ECM:
- In driving position "D" with kickdown operation from 3500 RPM
- In driving position "S" from 3000 RPM and simultaneous full load recognition.
10-15% additional air is drawn in from the engine compartment when the auxiliary air flaps are open. It is not necessary to draw in additional cold air from outside the engine compartment since the engine compartment is adequately ventilated at full load.
Intake Manifold Pressure Sensors: The pressure sensors (one per bank) are located in the back of intake manifold (1 peizo-electric). The voltage supply from the ECMs is 5 V. The varying resistance of the sensors is dependent on manifold pressure. The output voltage signal is processed by the ECMs. The intake manifold pressure is calculated by the ECMs and is compared with the ambient pressure (internally measured in ECM 1).
A minimum intake manifold vacuum of 50 mbar is required for the fuel tank evaporative purge function.
This vacuum is set by the electronic throttle valves (4) and monitoring with the intake manifold pressure sensors.
Shown to the right is the intake manifold (upside down) with both sensors (1).