Exhaust gas recirculation (EGR) system:

The exhaust gas recirculation (EGR) is a system which is designed to reduce the amount of oxides of nitrogen created by the engine during operating conditions.

The EGR system reduces NOx generation by recirculation small amount of exhaust gases into the intake manifold where it mixes with the incoming fresh charge. This portion of exhaust inert gases does not take participation in the combustion process and absorbs some heat of combustion of the combustible products. As a result the park combustion temperature and pressure is reduced and therefore an overall reduction of NOx Output.

The theoretical volume of recirculated exhaust gas known, EGR ratio should be regulated precisely under different operating conditions. If too much gas is recirculated, the engine performance suffer. If too EGR flows, the engine may knock and will not meet strict emission standard. EGR flow should flow the following operating conditions:

1. High EGR flow is necessary during cruising and mid-range acceleration.

2. Low EGR flow is needed during low speed and light load calculation.

3. No EGR flow should occur during engine warm up and idle conditions, in this situation the EGR flow could adversely affect engine operating efficiency.