An emissions-control system that reduces an engine's production of oxides of nitrogen by diluting the air/fuel mixture with exhaust gas so that peak combustion temperatures in the cylinders are lowered.

Exaust Gas Recirculation

Exhaust Gas Re-circulation. A mechanism for reducing engine emissions by re-circulating a percentage of exhaust gases back into the engine air intake system. A cooler is usually required to bring down the temperatures of the air re-entering the engine (referred to as Cooled EGR).

The EGR system collects one part of the exhaust gas and diverts them back to the engine via the intake manifold. It reduces the amount of oxygen used in the combustion process and thus also reduces temperature peak and nitrogen oxide emission.

Exhaust gas recirculation.