Secondary Air Injection

GENERAL
Before the oxygen sensor and the three-way catalytic converter reach working temperature, air is blown into the exhaust manifold to assist the combustion of hydrocarbons and carbon monoxide. This means that the three-way catalytic converter reaches temperature more quickly.

This function is activated by the engine control system when starting, and running time depends on the engine temperature and the time the oxygen sensor starts to work.





FUNCTION
Secondary air injection pump (A), located in front of the left-hand wheel housing, sucks in air from the hose after the engine air filter (B) and blows the air through a charge air bypass control valve (C) and one or two check valves (D) to the exhaust manifold.

The charge air bypass control valve is actuated by the engine vacuum through the engine control system opening the secondary air injection system control valve (E). The check valve is intended to make sure that the exhaust gasses do not flow back and damage the control valve or the injection pump.





SECONDARY AIR INJECTION
The secondary air injection system consists of an air pump which blows air into the two exhaust manifolds via a vacuum-controlled valve.

To get the catalytic converter working as soon as possible after a cold start, ambient air is pumped into the two exhaust manifolds where the oxygen in the air starts a chemical reaction together with CO and HC pollutants, thus generating heat.

This process is activated when the engine has been started if the following conditions are fulfilled:
^ coolant temperature________ 1-35°C (34-95°F)
^ intake air temperature ____ 1-5O°C (34-122°F)
^ engine speed _________________ <4000 rpm

The process is activated for 70 seconds or until the temperature of the coolant reaches 65°C (149°F).





The pump relay receives its power supply from the main relay and is grounded from pin 26 of the control module.

To compensate for the increased alternator power requirement, the control module increases the flow of air through the idle air control valve just before the process is activated.