SYSTEM / ECM System EGR (EXHAUST GAS RECIRCULATION) CONTROL Purpose: Re-circulates a part of exhaust gas in the intake manifold and combines it with in- take-air. Therefore, combustion temperature is lowered and generation of oxide of nitro- gen (NOx) is controlled. Operation: EGR Gas Amount Control 1. ECM decides EGR gas amount according to en- gine speed, fuel flow rate, coolant temperature, atmospheric pressure and intake-air temperature. 2. ECM drives EGR motor, opens EGR valve and exhausts EGR gas in response to engine condi- tion so that EGR gas is combined with intake-air. 3. At the same time, ECM detects the opening amount of EGR valve by using EGR motor posi- tion sensor.
EGR Gas Cooling 1. EGR gas is cooled by the cooling system in EGR gas passage. 2. Cooled EGR gas is combined with intake-air so that combustion temperature is lowered and NOx is generated lower. Lead Valve 1. The lead valve prevents fresh air from entering into the EGR gas passage and EGR gas from flowing in reverse direction. 2. Therefore, EGR gas flows to one direction and EGR gas amount increases. T2-3-12