EXHAUST EMISSION CONTROL SYSTEM Air Injection Valve (A.l.V.) System The air injection valve system (A.l.Vt) is designed to send secondary air to the exhaust manifold, utilizing a vacuum caused by exhaust pulsation in the exhaust manifold. The exhaust pressure in the exhaust manifold usually pulsates in response to the opening and closing of the exhaust valve and it decreases below Air injection valve Description atmospheric pressure periodically. If a secondary air intake is opened to the atmc phere under vacuum conditions, secondary a can be drawn into the exhaust manifold in propc tion to the vacuum Therefore, the air injection valve system (A.lt. reduces C0 and HC emissions in exhaust gases. /Air cleaner Carburetor Air inimiun pipe C: : Secondnrv air AIR INJECTION VALVE When the exhaust pressure is below atmospheric pressure (negative pressure), secondary air is sent to the exhaust manifold. When the exhaust pressure is above atmospheric pressure, the reed valve prevents secondary air from being sent back to the air cleaner. sEc: