During the intake stroke, air is sucked into the cylinder along with some exhaust gas, supplied by the exhaust gas recirculation system (EGR). The purpose of exhaust gas re-suction is to improve the oxidation of hydrocarbons and carbon monoxide from previous engine operation cycles. The presence of exhaust gases during the combustion of the mixture in the cylinder significantly reduces the amount of nitrogen oxides formed during the oxidation of the fuel.
Working with a layered mixture is divided into two stages, which occur during the compression stroke. Just before the end of the stroke (ok. 15 degrees before ZZ) a dose of fuel is injected into the cylinder. Its atomized stream hits the "fin" shaped piston bottom and is reflected from it and directed directly at the spark plug electrodes. Before the fuel reaches the candle, mixes with air, in its immediate vicinity and in the recess of the piston crown. When the first fuel particles reach the spark plug, a spark on the electrodes ignites the mixture. The flame covers the entire cloud at the top of the cylinder and does not spread any further. The fuel supplied to the cylinder burns up completely, because there is still an excess of oxygen during combustion – its "reserve" is stored in the air layer in the cylinder area, where the gasoline stream from the injector reflected from the piston did not reach. The mixture stratification in the cylinder allows the engine to run with a lambda value of 1,5-5-3. By reflecting the fuel stream off the piston and directing it to the spark plug, it is possible to obtain a thin layer of the mixture around its electrodes with a lambda coefficient of approx.. 0,8. This layer is capable of being ignited by the spark on the spark plug and it ignites the rest of the fuel supplied to the cylinder.
As the engine load increases, the control computer switches the supply system to work with a homogeneous mixture. Petrol injection begins on the second part of the intake stroke before the piston is internally turned, and its stream hits the swirling stream of air sucked into the cylinder. Because at the time of injection, the piston is far from the injector, the fuel does not bounce off its specifically shaped bottom and mixes with all the air sucked into the cylinder. Ignition occurs at the end of the compression stroke, and the flame covers the entire volume of the cylinder. In this mode of operation, the fuel dose is adjusted like this, so that the lambda coefficient becomes 0.8-M. The control system also reduces the amount of exhaust gases, which is directed back to the cylinders. In this mode of operation of the supply system, the engine can reach its maximum torque values. Changing the operating mode from economy (lean lean mixture combustion) to dynamic (combustion of a homogeneous mixture with a stoichiometric composition) takes place with the participation of an electronic control system. Its operation takes into account such quantities as the amount of air drawn in, injected fuel dose and ignition timing, matching them to the required torque value at a given moment. The latter is defined, among others, by. based on information about the position of the accelerator pedal and the gear engaged. The injection system includes a pressure accumulator (listwa common rail) powered by a high pressure pump (pressure in the rail approx. 100 bars). The injectors are electromagnetically controlled, which enables precise selection of the beginning and duration of injection and precise determination of the fuel dose volume.