Idling effect of injection pressure and timing and their effects on performance and emissions of a compression ignition engine fuelled with biodiesel

Injection parameters are known to impact most on diesel engine emissions and performance but there is little work in literature regarding the effect of injection parameters on biodiesel engine performance. Studies of the effect of injection timing and pressure on emissions and brake specific consumption has been carried out on a 48 kW, VW Polo, MK3, four-cylinder, four-stroke, indirect injection engine which is naturally aspirated and air cooled. Engine modifications were carried out for each fuel used except petroleum diesel. The input factors for the modification include injection timing only, injection pressure only and their effects on brake specific energy consumption and exhaust emissions particularly carbon monoxide, hydrocarbons and oxides of nitrogen. Injection timing was varied at six levels including advance of 7 degrees, 5 degrees, 3 degrees, 0 degrees settings and retardation settings of 3 degrees and 5 degrees. Nozzle injection pressures were varied at 150, 175, 200, 225 and 250 bars. Generally, injection advance led to significantly lower hydrocarbon and carbon monoxide emissions because there was ample time for combustion to reach completion. Though not significant, higher nozzle pressures accounted for lower emissions except NOx. Injection timing was found to have the most profound effect on engine emissions and brake specific energy consumption.