The impact of turbocharging on Diesel exhaust emissions has been investigated by studying, on a 4-cyl IDI Fiat engine different configurations including fuel injection optimization, exhaust gas recirculation and oxidant catalysts. The experimental results obtained during bench and chassis dynamometer tests were compared with the same tests performed on the naturally aspirated 4-cyl engine. Mathematical models were used in order to identify the regions giving the maximum contribution to regulated emissions. Particulate and organic adsorbed compounds were also measured. It appears that turbocharging can represent a reasonably good approach in order to achieve low levels of regulated emissions and particulates associated with high fuel economy.