Exhaust Gas Recirculation: Description and Operation

Fig. 5 Gasoline engine exhaust gas recirculation system (typical):

GASOLINE ENGINES
In the exhaust gas recirculation system, Fig. 5, (complete system schematics are located in ``Vacuum Hose Routings'') a part of the exhaust gas is returned to the combustion chamber to lower spark flame temperature during combustion. This results in a reduction of the nitrogen oxide content in the exhaust gas.
Components used in this system vary according to year and model. The main component is the EGR control valve which controls the quantity of exhaust gas allowed to enter the combustion chamber.