Global Flow Characterization of a Four Cylinder Spark Ignition Engine during the Intake Phase

The paper aims to analyze the fluid dynamic behavior of a production internal combustion engine. A four-cylinder, spark-ignition engine was examined at the steady flow rig in order to have detailed information on the global volumetric efficiency. To this purpose the dimensionless discharge and the flow coefficients were used and the effect of the valve lift and throttle valve opening on the head permeability was investigated. The experimental analysis showed that the throttle angle significantly influences the fluid dynamic efficiency of the intake system. Specifically, the influence of the throttling process upsurges with the valve lift. Moreover, a comparison between the volumetric efficiency of the four cylinders was carried out and some differences in the permeability of the individual cylinder were found. Finally, the global analysis depicted that all experimental data can be correlated by a single curve if a new dimensionless plot is adopted and that it is possible to use the same plot to correlate data referred to different engines.