OUTLINE
The TWCs (Three-Way Catalytic Converters) reduce emissions by the oxidation of CO and HC in exhaust gas and reduction of NOx.
The ECM performs the air-fuel ratio feedback control based on signals from the air-fuel ratio sensor and the heated oxygen sensor, and controls the fuel injection amount so that the air-fuel ratio comes close to the stoichiometric air-fuel ratio at which the highest purifying efficiency of CO, HC and NOx is obtained.
An EGR control, which reduces the combustion temperature by recirculation of exhaust gas and also reduces NOx emissions, is used.
Integrating the exhaust gas passage into the cylinder head sub-assembly cools the exhaust gas effectively, and also contributes to make the engine compact.
A blowby gas ventilation system that reduces emissions by forcibly drawing blowby gas which includes a large amount of HC into the air intake side and combusting it again is used.
An evaporative emission control, which regulates the purge flow of evaporative emission (HC) into the canister in accordance with the engine conditions, is used.
An air fuel ratio sensor and an oxygen sensor heater control, which maintain the temperature of the respective sensors at an appropriate level, are used, to improve the detection accuracy of oxygen concentration in exhaust gas.