The idea of a piston I.C. engine with a disintegrated process is represented and evaluated. A detailed analysis is made of the S.I. version particulary from the point of view of engine performance parameters, fuel tolerance and emission, as the most important criteria for engines for vehicle application. The estimations regarding performances are based on model computations of the thermodynamic cycle, applying the analytical models of combustion, mass and heat flows within the simplifications common in similar preliminary computations of processes in today engines. Regarding the above mentioned last two criteria, the results of computations can not be significant in the phase of idea: taking into acconnt the experiences with conventional engines, analysing the similarities and differences, it is the only acceptable way.