In-cylinder fuel behaviour and exhaust emissions during the cold operationof a spark ignition engine

A model has been developed from experimental results to describe the passag e and utilization of fuel after injection to its exhaust as fuel products o r loss to the crankcase during warm-up after a cold start. Engine-out emiss ions of unburned hydrocarbons (HCs) and carbon monoxide can be predicted fo r both quasi-steady and transient engine operating conditions during warm-u p. The model is phenomenological. Model coefficients, which are either cons tants or simple functions of engine coolant temperature, have been determin ed for best matching of predictions to experimental data covering a wide ra nge of conditions. The model has been used to investigate the variation in in-cylinder fuel film mass, fuel lost to the crankcase, exhaust air-fuel ra tio variations and engine-out emissions. The dependence of these on steady and transient engine operating conditions is described.