Abstract: The paper compares the basic parameters of the process of combustion in the Fiat MultUet 1.3 SDE 90 KM with and without an exhaust gas recirculation system, running according to load characteristics with the following engine crankshaft rotational speeds: n=l200 ipm, 1750 rpm and 3000 rpm. During testing, the engine was supplied with commercial diesel oil. The tested engine was provided with external exhaust gas recirculation consisting in supplying a specific amount of exhaust gas back to the cylinder via an EGR electric solenoid valve. The exhaust gas delivered to the cylinder was cooled. Exhaust gas is composed of inert gases that do not take part in the combustion process. This causes, above all, a lower rate of pressure increase in the cylinder and a lower heat release rate. Thanks to exhaust gas recirculation, lower maximal temperatures prevail in the cylinder, and the engine's operation is "softer." During experimental testing, the variation of cylinder pressure and chamber pressure, the injector operation control current magnitude, effective power, torque and the hourly fuel consumption, as well as the exhaust gas recirculation rate. Actual indicator diagrams plotted were used for determining the heat release characteristics, based on which the percentage fractions of the burned out fuel charge injected during one engine running cycle namely 5, 10, 50 and 90% fractions were determined. In addition, the indicator indices were determined. The paper has demonstrated the effect of exhaust gas recirculation on the processes occurring inside the cylinder in the self ignition internal combustion engine.
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