The flow and combustion processes of a three-valve, stratified charge engine with small prechamber are examined for exhaust emissions. The exhaust emissions from a single-cylinder version of this engine are shown to depend on the internal flow processes as well as mixture supply stoichiometry.A theoretically-based simulation model of the engine flow and combustion processes is described. Model predictions are compared with time-resolved prechamber air-fuel ratio measurements made during intake and compression strokes. These comparisons are used to illustrate and describe the complex flow phenomena which take place in this engine.The combustion process is then examined with the aid of calculations using the simulation model. The complexity of the combustion process is illustrated by showing that, in addition to burned gas temperatures, the cylinder and prechamber burned gas air-fuel ratios change with time. NO kinetic calculations are compared with exhaust measurements as prechamber flow and stoichiometry are changed.