Variability of the resistance to motion at engine crank-piston set

The resistance to motion that accompany the combustion engine run affects its technical and economical indices. Appropriate modifications in design of constitutive parts as well as proper selection of kinematic pairs' collaboration data might lead to the minimization of resistance, above all the frictional one. In order to estimate precisely this resistance as well as the area and reasons of their generation certain measurement methods are implemented that facilitate size of resistance and changes occurring within a single cycle. Beside methods requiring interference into engine's construction other methods are used, among other the motoring method. Despite the advantages like simplicity, there are also problems with the use of this method. The most important are: different measuring conditions (no fires) and measurement of the resistance average value. In a course of described simulations evaluation of mutual relations between friction forces and torques relative to different sources have been carried out, in particular those relating to the crank - piston assembly. A trial to give the answer if it is possible to distinguish the effect of individual resistances at certain engine subassemblies in the total resistance torque was the main effect of presented analysis. Exemplary calculations have been carried out for the 170A.000 type engine.