Comparative analysis of the fluid dynamic efficiency of standard and alternative intake strategies for multivalve spark-ignition engines

The work aims at investigating the fluid dynamic performances of a multivalve spark-ignition engine and at evaluating the influence of the throttling process on the engine permeability. To this purpose, a production four-stroke internal combustion engine is analysed during the intake phase. The experimental characterisation is carried out at the steady flow rig in terms of dimensionless discharge and flow coefficients.

The global investigation illustrates the noticeable effect of the valve lift on the engine head breathability. Furthermore, the experimental analysis demonstrates that the throttling process has a significant influence on the volumetric efficiency of the intake system and this effect increases with the valve lift. Finally, alternative strategies are studied in order to improve the engine fluid dynamic efficiency at partial loads. Specifically, the research shows that inlet valve deactivation and the adoption of asymmetric intake valve lifts assure an increase in head permeability.