Effects of cooled and super-cooled low pressure EGR systems on the LD Diesel engine performances

The present paper details the results of an experimental study on the effect of the use of a Low Pressure EGR system on the performance of a LD diesel engine at the state of the art of the current engine technology. The study was performed within a collaborative project between Istituto Motori and Centra Ricerche Fiat aimed to carry out an exhaustive analysis of the potentiality of the cooling (with engine water at 90°C) and super-cooling (with external water at 20°C) of the low pressure EGR flow gas on the simultaneous reduction of fuel consumption and pollutant emissions. The effects were evaluated running the engine in several engine operating points critical for the pollutant emissions performance on the NEDC test procedure. The overall results identified benefits on both the fuel consumption and emissions with the use of a low pressure EGR system with respect to the conventional high pressure EGR one. The cooled EGR system showed a further advantage at medium and high speed/load operating points, while the super-cooled system didn't add significant benefits.