Experimental investigation on high quality Diesel Fuels effects in ligth duty CR Diesel

In this paper some preliminary results on the emission performance of a modern CR DI diesel engine running on reformulated diesel fuels are discussed. The engine employed in the tests was a Fiat M724 1910cc, installed on Alfa Romeo 156 1.9 JTD. Modern injection systems can modify the spray structure with respect to a spray of a classical rotary injection pump so the well-consolidated knowledge on the correlation between fuel parameters and pollutant emissions may not be valid for the new generation of DI diesel engines. Two high quality fossil fuels and a synthetic fuel were selected for the tests. Tests were directed to analyze the relative influence on exhaust emissions between injection parameters and fuel quality. One engine test point (2000 rpm x 2 bar of b.m.e.p.) was chosen, with different setting of injection pressure, EGR ratio and pilot injection activation. Moreover a comparison between the performance of the CR engine and a light duty DI engine equipped with a classical distributor pump (Bosch VE pump) is also presented. With common rail systems, the soot increase, due to the EGR, is evident only at relatively low rail pressure while at high injection pressure the soot emissions are not influenced by the EGR rate. Contrary to the engine with the distributor pump injection system, the main characteristic of CR engine appears a moderate sensibility of NOx emissions and a poor particulate dependence from fuel quality.