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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.

This paper deals with a passenger-car direct-injection-diesel-engine with electronically controlled unit-injector. It is being investigated how far emissions and fuel-consumption can be influenced by exhaust-gas-recirculation (EGR) and pilot-injection especially when they are in combination with each other. The results reveal that the NOx-emission can be decreased much more by EGR than by pilot-injection. The lowest NOx-emissions however can only be reached by combination of EGR and pilot injection.. In the investigated area of the engine map a decrease in soot-emission can be obtained with rising EGR-rates by pilot-injection. On the other hand pilot-injection results in an increase of soot emission at high EGR-rates at the engine operating point N=2000 rpm, bmep=2 bar. Pilot-injection in combination with EGR effects no deterioration of fuel-consumption and HC-emission.

Modern commercial vehicle engines are equipped with turbocharging and intercooling. This results in low emissions and fuel consumption. In the lower speed and load range and under transient conditions, these engines have disadvantages, as the fuel injection rate has to be limited to avoid excessive smoke emission. Also, the engine braking performance of highly charged, small displacement engines is also lower than that of large displacement engines. Mercedes-Benz decided to develop a combination of turbocharger and mechanical supercharger. In the lower speed range higher torque levels are possible and maximum torque is available without any lag especially in the transient mode with low smoke emission and fuel consumption. Vehicle performance during acceleration can be improved by up to 30%. During engine braking operation, the mechanical supercharger is activated throughout the whole engine speed range which results in a distinctive increase in braking power.