Exhaust gas recirculation is a technique of using the exhaust gases again into the engine cylinder of an i.c. engine i.e. it recirculate the exhaust products to make it useful again in the process of power generation by i.c. engine.

EGR System

In the i.c. engine, the inter-coolers is installed. The exhaust gases will pass through the inter-coolers the gases will be absorbed here and then the useful gases will be extracted after passing through the inter-coolers and then the gases will be transferred to the inlet port of the engine to reuse it. In the engine the gases can be burn again to develop the power.

Recirculation increases the mileage and efficiency of the engine. It decreases the peak temperature in the engine cylinder. Exhaust gas recirculation makes the harmful exhaust gases not to enter into the environment so it makes the engine to affect lesser to the environment, rather it uses its temperature to increase the efficiency.

Exhaust gas recirculation mainly focuses on the oxides of nitrogen and carbon. Oxides of nitrogen is quit appropriate to use back in the inlet port from exhaust port.

The flow rate of the exhaust gas is controlled by a regulator or valve (EGR valve).

The EGR can be implemented by many methods e.g. By using camshaft, using VGT etc.


In the engine the EGR valve is installed in which all the necessary thing will be connected including inter-cooler and vacuum valves. The EGR is installed near to the engine cylinder. EGR valve is a medium of transferring exhaust gases to inlet port. That is why it is most important part in the whole system of EGR. If this valve do not work properly the whole system will be failed.

Advantages of EGR System

1.       It can decrease the emission of harmful gases even if the fuel has toxic substance.

2.       Overall emission in EGR engine is less and efficiency is high as compare to engines not using EGR.

3.       The concentration of oxygen in the combustion chamber can be controlled.

4.       Emission of oxides of nitrogen can be controlled.

5.       EGR system is more environment friendly then non-NGR engines.


EGR is an effective method to control the concentration of oxygen in the combustion chamber and to reduce the emission of nitrogen oxides. It makes the system sufficient thermally.

Different automobile companies using different methods for exhaust gas recirculation in their vehicle. There is always an effort by these companies to make this system better to increase the efficiency even more. 

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