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In the present investigation, a parametric study of the geometric characteristics of a two-cylinder four-stroke gasoline engine was carried out. Engine power, torque, specific consumption, engine efficiency, in-cylinder pressure for both the cylinders and pressure along the intake and exhaust manifolds at different positions were experimentally measured for engine speeds ranging from 5000 to 9500 rpm. All measurements were made under steady state conditions and full load. Engine characteristics were calculated by means of a 1-D model, which was used to calculate wave propagation in the intake and exhaust manifolds. A zero dimensional model was used to account for the in-cylinder phenomena. In the 1-D model the effects of pipe curvature, restriction geometry, gas friction, and heat transfer to the manifolds walls were considered. Numerical results showed good agreement with the measurements over the investigated range of operating conditions.

A mono-cylinder engine was built, because of its costs and the semplicity of designing, as flexible prototype. A scavenging system with four ports, two by two simmetrical, was chosen to respect the modern theory of scavenging optimization. The scavenging flow was supplied by a carter-pump; it has been used as first experimental solution. The prototype has been entirely realised and the following experimental measurements have been carried out: the pressure in combustion chamber, in carter pump, in pipes and injection system, as well as the fundamental parameters of engine functioning.