Recent four valve HSDI Diesel engines are able to controlthe swirl intensity, in order to enhance the in-cylinder flowfield at partial load without decreasing breathing capabilities atfull load.Making reference to a current production engine, thepurpose of this paper is to investigate the influence of portdesign and flow-control strategies on both engine permeabilityand in-cylinder flow field.Using previously validated models, 3-D CFD simulationsof the intake and compression strokes are performed in orderto predict the in-cylinder flow patterns originated by thedifferent configurations.The comparison between the two configurations in termsof airflow at full load indicates that Geometry 2 can trap3.03% more air than Geometry 1, while the swirl intensity atIVC is reduced (-30%).The closure of one intake valve (the left one) is veryeffective to enhance the swirl intensity at partial load: theSwirl Ratio at IVC passes from 0.7 to 2.6 for Geometry 1,while for Geometry 2 it varies from 0.4 to 2.9.