Influence of Intake Port Design on Permeability and Rate of Combustion in a Four Valve High Performance Engine

The paper presents improvements of intake port and valve assembly, for better permeability and rate of combustion, in a new Ferrari engine. The engine has 5.5 liters displacement, twelve cylinders, four valves per cylinder, a pentroof combustion chamber, and is naturally aspirated. A slight increase of effective areas has been verified during steady test rig experiments. Full engine experiments have finally shown smaller values of turbulent combustion durations (10-90% fuel burnt), and therefore reduced spark advances for maximum brake torque. A computational analysis has been carried out by using the STAR-CD code, in order to improve the understanding of this experimental behavior. A first numerical simulation of steady test rig experiments has been performed. A pseudo intake stroke simulation, where the piston moves from a near top dead center position up to bottom dead center has also been realized. Steady results show changes in the relative magnitude of intake fluxes towards the exhaust and the cylinder bore. Unsteady results show changes in the tumble strength. As expected, the engine configuration with faster combustion has an increased steady flow towards the exhaust and an increased unsteady tumble vortex strength.