Modeling of individual cylinder air-fuel ratio for IC engines with multi-cylinders

In internal-combustion engines with multi cylinders, fuel is injected into cylinders and exhaust gas is discharged from cylinders serially and cyclically. After going through runners, exhaust gas flows into the confluence region of exhaust manifold where oxygen sensor is equipped for the air-fuel ratio measurement of the mixed gas. This paper aims to present a modeling approach from individual cylinder fuel injection to the output of the sensor. With consideration of above features of the exhaust system, a BDC-scaled periodic model is proposed. For further illustration, some previous models are compared with new model. Simulation shows that the new model describes appropriately the relation between individual fuel injection and mixed air-fuel ratio.