Fuel carbon pathway in the first cranking cycle of a gasoline direct injection engine

Abstract

The fuel carbon pathway for the cold-start first cranking cycle in a gasoline direct injection engine is characterized quantitatively. The engine is fired for a single cycle in one cylinder at a specified cranking speed and at a coolant temperature of 20 °C. The fuel carbon is accounted for from measurements of the exhaust carbon (CO[subscript 2], CO, and hydrocarbon). The remaining carbon is assumed to go into the oil and crankcase. The parameters studied are the amount of injected fuel, the injection timing, the intake pressure, the injection pressure, and the cranking speed. Substantial fuel enrichment is needed to produce stable combustion in the first cycle, with significant residual fuel that goes into preparing the mixture of the second cycle and into the oil and crankcase. The first cycle hydrocarbon emissions as a fraction of the fuel are not sensitive to the fuel enrichment, the manifold absolute pressure, and the injection pressure.