Pulsed Secondary Air Injection: Description and Operation
Pulsed Secondary Air InjectionThe pulsed secondary air injection advances the activation of the catalytic converter and reduces the hydrocarbons (HC), carbon monoxide (CO), and oxides of nitrogen (NOx) in the exhaust gas.
The system operates after the engine starts under these conditions:
- The engine coolant temperature is between 32 degree F and 158 degree F (0 degree C and 70 degree C).
- The difference is more than 36 degree F (20 degree C) between the engine coolant temperature when the engine is started and when the engine was stopped in the previous driving cycle.
When the engine is cold and first started, the air pump pumps fresh air into the exhaust ports. The amount of air entering the exhaust is regulated by an air control valve which is controlled by the ECM. The system does not work for more than 60 seconds at a time. Actual operating time will very depending on the difference Between engine coolant temperature and intake air temperature.
When fresh air reacts with any unburned exhaust gases, the exhaust gas temperatures rise. This rise in temperature promotes faster warm-up of the catalytic converter, resulting in cleaner emissions during cold start-up.
When the air induction system is not operating, the air control solenoid closes the air control valve to prevent any exhaust gases from flowing back into the system.