The permanent aim of the automotive industry is the further improvement of the engine efficiency and the simultaneous pollutant emissions reduction.
The aim of the study was the optimization of the gasoline combustion by means of a passive prechamber. This analysis allowed the improvement of the engine efficiency in lean-burn operation condition too. The investigation was carried out in a commercial small Spark Ignition (SI) engine fueled with gasoline and equipped with a proper designed passive prechamber.
It was analyzed the effects of the prechamber on engine performance, Indicated Mean Effective Pressure, Heat Release Rate and Fuel Consumption were used. Gaseous emissions were measured as well. Particulate Mass, Number and Size Distributions were analyzed. Emissions samples were taken from the exhaust flow, just downstream of the valves. Four different engine speeds were investigated, namely 2000, 3000, 4000 and 5000 rpm. Stoichiometric and lean conditions at full load were considered in all tests. The results were compared with those obtained with the engine equipped with the standard spark plug. The results indicated that both performance and emissions were strongly influenced by the prechamber.