Abstract
A model for the determination of dynamical behaviour and the friction losses in an automotive internal combustion engine sparked ignited is presented. A theoretical analysis is carried out to analyse the analytical approximate description of hydrodynamic lubrication regime about the piston skirt and the crankshaft journal bearings. The analytical approach to the behaviour of a system is more effective than a numerical investigation and makes it possible to study not only the individual case but also the whole class to which the system in question belongs. Besides, this paper shows the mathematical models realized to investigate about the friction forces of piston assembly-cylinder liner contact and crankshaft journal bearings. An estimation of mechanical friction is required whenever changing component geometry/configurations of existing engines such as bore, piston stroke, piston skirt length, etc. The geometry of engine components (piston assembly, valve train, crankshaft) needs to be optimised to minimize mechanical friction and component weight. The mathematical models involved in this research activity allow to investigate about other important engine dynamic behaviour as piston secondary motions, piston noise and crankshaft journal bearings orbits.