In the case of turbocharged heavy duty diesel engines, the total efficiency of the turbocharger is higher than for smaller turbos for passenger cars. It is difficult to recirculate exhaust gas because of higher intake manifold pressure in comparison to exhaust gas pressure.
IHI has developed a new turbocharger for exhaust gas recirculation for heavy duty diesel engines. It has a recirculation port at compressor side. The port is connected with a narrow annular slit located at the diffuser inlet, where the static pressure is lower than intake manifold. The result of JIS diesel 13 mode test with this turbocharger showed 26 % lower NOx without significant penalty of fuel consumption.