High power output, four stroke, motorcycle engines are characterised by specific power levels well beyond 150 HP/litre also in production engines. These power levels are obtained through extremely high values of volumetric efficiencies in the range of high engine speed, resulting from highly optimised gas exchange processes. In the present paper, a four cylinder, four valve per cylinder engine with a four-in-one exhaust is optimised for volumetric efficiencies by using state-of-the-art computational methods. These computational methods include static three dimensional computations as well as dynamic one and three dimensional computations. The engine geometric and operating parameters optimised by using these computations agree fairly well with those optimised by using experiments, thus demonstrating the effectiveness of the proposed computational practice.