Abstract
The paper presents a mathematical model describing kinetic behaviour of the injected fuel stream in a Gasoline Direct Injection Engine. Mathematical analysis of the stream aims at calculating the time length the stream requires to reach the piston, rebound from it, and reach the electrodes of the spark plug. Having given times of duration of particular phases of the stream movement as a function of crankshaft revolutions and injection pressure, the injection advance angle is calculated. Additionally the paper presents the results of computer simulation of the course of the injection process i.e. the shape of the stream at the very moment of injection, at the moment it reaches the piston, and at the moment of mixture ignition