Exhaust gas recirculation technology is recycling of small amount of the exhaust gas to reduce oxides of nitrogen (Nox) that is one of the air polluting gas, by lowering the temperatures of engine interiors and absorption of vibration and heat expansion from engine.
EGR tube assembly carries unburnt gas vapours from the exhaust manifold chambers to the intake manifold and is reintroduced into the engine firing sequence. It is used in conjuction with catalytic converter for better performance. It also enhances the life of critical engine moving parts. The gases are cooled before they are fed back.
The typical external EGR tube is mounted between the exhaust manifold or crossover pipe and the EGR control valve. Because the gas temperatures can exceed 650ºC. (1200ºF), the resulting thermal expansion loads on the tube can cause early valve, tube, or manifold failure.
Without using a very efficient EGR, the emission regulation of 2005 for Japan and Euro-4 regulation for Europe will be very hard to pass.