17.7.
Exhaust Emission Control
In the year 1966, first time the controls for exhaust gases were introduced. Today, exhaust emission control devices can be placed under five categories as follows :
(i) Air injection system or pulse air system.
(ii) Engine design modification, also called clean air system.
(Hi) Spark timing.
(iv) Exhaust gas recirculation (EGR) system.
(v) Catalytic converter system.