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

A model has been developed from experimental results to describe the passage and utilization of fuel after injection to its exhaust as fuel products or loss to the crankcase during warm-up after a cold start. Engine-out emissions of unburned hydrocarbons (HCs) and carbon monoxide can be predicted for both quasi-steady and transient engine operating conditions during warm-up. The model is phenomenological. Model coefficients, which are either constants or simple functions of engine coolant temperature, have been determined for best matching of predictions to experimental data covering a wide range 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 ratio variations and engine-out emissions. The dependence of these on steady and transient engine operating conditions is described.