The principle strategy, the development emphasis, and the investigation parameters of a DI gasoline engine are discussed. Several different combustion systems are briefly described and one system where the spark plug is located near the fuel injector is investigated. In addition, the influence of different operating parameters are studied.
Some reasons for the improvement in the efficiency of a DI gasoline engine are shown with the help of thermodynamic analysis and simulation calculations. These show that at a constant operating point (engine speed = 2000 rpm, bmep = 2 bar) there is a reduction of the fuel consumption of 23% at unthrottled conditions in comparison to the homogeneous stoichiometric operation. In particular, the reduction of the pumping and heat losses and the reduction of the exhaust gas energy are responsible for this fuel consumption reduction. The engine design including the mixture formation and the ignition system, the in-cylinder charge motion, the fuel injection and ignition timing, and the exhaust aftertreatment system all effect the fuel consumption reduction.
It is however still necessary to develop for the DI - gasoline engine a special exhaust gas aftertreatment system to meet the future emission standards in the USA and in Europe.