An Analytic Model for Cylinder Pressure in a Four Stroke SI Engine

An analytic model for cylinder pressures in spark ignited engines is developed and validated. The main result is a model expressed in closed form that describe the in-cylinder pressure development of an SI engine. The method is based on a parameterization of the ideal Otto cycle and takes variations in spark advance and air-to-fuel ratio into account. The model consists of a set of tuning parameters that all have a physical meaning. Experimental validation on two engines show that it is possible to describe the in-cylinder pressure of a spark ignited combustion engine operating close to stoichiometric conditions, as a function of crank angle, manifold pressure, manifold temperature and spark timing.