Nissan Air Injection Valve (A.I.V.) System Description - EF & EC-22 Manual Page

This is a scanned page from a factory service manual, section 'EF & EC' (Engine Fuel & Emission Control), page EF & EC-22, describing the Exhaust Emission Control System — specifically the Air Injection Valve (A.I.V.) System. The description explains that the A.I.V. system sends secondary air to the exhaust manifold by using the vacuum created by exhaust pulsation: exhaust pressure pulsates with the opening and closing of the exhaust valve and periodically drops below atmospheric pressure, allowing secondary air to be drawn in proportionally to the vacuum. The system's purpose is to reduce CO and HC emissions in exhaust gases. A large schematic diagram shows the secondary air flow path from the air cleaner, past the air injection valve, through the air injection pipe, past the carburetor and A.B. valve, into the exhaust manifold, with arrows marking secondary air flow. A second section, 'AIR INJECTION VALVE,' explains that when exhaust pressure is below atmospheric pressure, secondary air is sent to the exhaust manifold, and when it is above atmospheric, a reed valve prevents air from flowing back to the air cleaner. A small illustration labels the reed valve and stopper. The right margin text is slightly cut off, and the page carries no explicit year, make, or model.