The functioning of the engine in a closed loop with lambda sensor and catalyzer makes the excess air factor to be maintained as close as possible to the value 1=1. Based on an own model, the authors realized an analytical calculation of the indicated diagram. The indicated diagram was also raised on an experimental stand in p-V coordinates, and the real indicated diagram in p-a coordinates. The equations for the thermal processes that take place in the engine have been determined and, after that, these were introduced in a computer. Using these equations, the state parameters in the characteristic points of the engine cycle were calculated.

the authors present the general aspects of theoretical modeling of gasoline injection, the principle modeling of some of the elements of gasoline injection, namely the gasoline pump model and the pressure regulator model. It is presented the general model of a spark engine with gasoline injection. The modeling of the motor cycles with spark engines and gasoline injection suggested by the authors is realized by executing a computer program for determining the variation of the three-dimensional and bi-dimensional parameters with the subprograms: program for calculating the SIE (dependence according to n and lambda at to=-35...+45ºC and po=1•102 kPa); program for calculating the SIE (dependence according to n and to at lambda=1 and po=1•102 kPa);program for calculating the SIE cycle with gasoline injection. It was realized a study for calculating the pressure from the admission gallery pga and the admission pressure pa.

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Abstract. The authors have proposed a model to simulate the processes that occur in a SI direct injection engine. The modelling of the engine's cycle consists of: the presentation of the initial data, the computer program, the calculus and the correlation between the expressions of the engine's parameters and the gasoline injection in order to realize the computational program. The proposed cycle is a helpful one for computer simulation of the gasoline direct injection. The computer simulation enables the determination of the proposed theoretical technical-economic parameters, the theoretical mechanical work, the coefficients corresponding to adjust the indicated diagram, the theoretical mean pressure, the theoretical efficiency and the theoretical specific fuel consumption. After calculating the mechanical losses, the effective theoretical technical-economic parameters are also determined.

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