The paper analyses the basic aspects of spark assisted direct injection (SADI) engines of the type with the start of combustion close to the beginning of fuel injection, and with no special arrangements for fuel vaporization on the combustion chamber walls. The analysis refers to the fuel sensitivity of the engine, the correlation between air motion and fuel injection, and the combustion development in this engine.
The analysis evidentiates the high sensitivity of this engine to certain characteristics of the fuel, and explains some particularities of the engine operation like the stabilized flame front, the necessity of spark assistance during the entire fuel injection, and the unstable operation in certain conditions. Also the influence of SADI engine characteristics on its performance is investigated.
Solutions for improving the operation of this engine, as well as the engine perspectives are discussed.