The controllable swirl flaps are located in the intake pipe and are closed or opened depending on the operating status. The flaps are closed at engine speeds below approx. 2000 rpm and injection volume below 30 mm^3.
The pressure converter connects the vacuum unit with the vacuum supply by means of hoses. When activated by the DDE control unit, the changeover valve switches vacuum to the vacuum unit thus operating the control rod and closing the swirl flaps. The control rod is up against the rear stop when the swirl flaps are open.
Fault code 1A22 "Swirl flaps" is stored if a defect occurs in the activation of the pressure converter.
Swirl flaps stick in open position: Deterioration in exhaust gas characteristics in lower speed ranges otherwise no effect.
Swirl flaps stick in closed position: Power loss of approx. 10 % at higher engine speeds.