Only in 16V engines
The purpose of secondary air injection is to cause additional oxidation of exhaust gases during the engine warm-up phase and reduce the start-up time of the catalytic converter.
The blown-in air serves to burn off the unburned components still contained in the exhaust gases. For this purpose, the secondary air pump with an electric drive (installed in front on the left next to the battery) squeezes out — depending on the engine operating mode — cleaned air into its exhaust ducts. The air filter is located behind the radiator grille. There is no specified filter replacement period.
Due to this, additional oxidation of exhaust gases occurs on the way to the catalytic converter, resulting in a reduction in hydrocarbon and carbon monoxide emissions; the exhaust gas temperature increases. Due to this, the catalytic converter and lambda probe reach operating temperature faster; lambda control kicks in earlier.
The secondary air boost is activated after the engine has started. It does not have a separate control unit, it is activated by the ignition/injection control unit. The secondary air boost is switched off with the activation of the lambda control. The air flow is controlled by a shut-off valve, which is opened and closed by a changeover valve due to the reduced pressure of the intake manifold. A check valve near the engine prevents pressure surges in the pipeline system from reaching the secondary air pump. The function of switching the secondary air pump on and off is performed by the ignition/injection control unit. Due to the current consumption of the pump, an intermediate relay is installed, which is located in the relay box (in the engine compartment next to the battery).
Visitor comments