Variable Air Duct System (MAZDA6)
WARNING: This page does not describe the selected car, but rather 9 other vehicles, including the 2003 Mazda Tribute, 2003 Mazda Protege5, 2003 Mazda Protege, 2003 Mazda MX-5 Miata, and 2003 Mazda MPV. However, it is still accessible from the selected car via links, so may be relevant.
The Variable Air Duct (VAD) control system opens the VAD shutter valve in the air cleaner only at high engine speeds, so engine performance does not decrease at high engine speeds, due to insufficient mass airflow amount.