Air Induction System: Operation: Notes

The Air Induction System is designed to send secondary air to the exhaust manifold, utilizing a vacuum created by exhaust pulsations in the exhaust manifold.

Exhaust pressure in the exhaust manifold usually pulsates in response to opening and closing of exhaust valves, and periodically it decreases below atmospheric pressure. When this happens, a vacuum is created and a secondary air intake is opened and secondary air is drawn into the exhaust manifold in proportion to the vacuum.

Fig 1: Datsun Sentra M.P.G. Air Induction System

Courtesy of NISSAN NORTH AMERICA, INC.

Note direction of flow. 

Fig 2: Datsun Sentra Non-M.P.G. & 310 Air Induction System

Courtesy of NISSAN NORTH AMERICA, INC.

Note direction of flow. 

Fig 3: Datsun 210 Air Induction System

Courtesy of NISSAN NORTH AMERICA, INC.

Note direction of air flow.