Geometric Parameters of Four-Valve Cylinder Heads and Their Relationship to Combustion and Engine Full Load Performance

Mathematical relationships are established between valve sizes, valve included angle (VIA) and bore diameter for four-valve pentroof chambers. Graphical results show the effects of these relationships on geometric breathing capacity and links them to cylinder displacement, rated speed, bore/stroke ratio, intake valve lift, and intake/exhaust valve diameter ratio. A “geometric engine” mathematical model relates these parameters to combustion chamber surface to volume ratio and easily determines the piston top configuration. Current production engines are analyzed to produce relationships between these geometric parameters and full load performance.