This work aims at analyzing the fluid dynamic characteristics of a Ducati 4 valves SI engine, for racing motorcycle, during the intake and compression strokes, focusing on the correlation between steady state flow test data (experiments and simulations) and transient CFD simulation results, including the effect of variable valve actuation strategies with independent intake valve actuation.
Several steady state flow test data were available in terms of maps of the discharge, tumble and swirl coefficients, at any combination of asymmetric lifts of the two intake valves. From these steady state data it can be argued that asymmetric strategies could enhance engine full load and part load operation characteristics, by exploiting favourable trade off occurring between the opposing needs for high mass flow rate and high charge motion intensity. For a given mass flow rate, enhanced tumble or swirl intensities can be reached using asymmetrical lifts, compared to the standard symmetrical 2V lift.
Numerical simulations allowed a deeper understanding of the tumble/swirl motion characteristics at different lift combinations, especially for asymmetric low lift cases. Analyzing the transient CFD results the instantaneous values of discharge and tumble/swirl coefficients can be determined and compared to steady state data. The further aim of the present research line is to investigate the influence of the lift strategies on the evolution of the charge motion.