The principle of operation of the engine management system is designed in such a way as to get the most out of the engine with minimal fuel consumption and the content of toxic components in the exhaust gas. The following systems for reducing the toxicity of exhaust gases are installed: crankcase ventilation system (PCV), exhaust gas circulation system (EGR, diesel models only) and a catalytic converter with lambda probes. On petrol models, an additional fuel vapor recovery system is installed (EVAP). Some diesel engines are fitted with a diesel particulate filter (DPF), as evidenced by the PR number "7MG" on the vehicle data sticker (see Introduction). The presence of a particulate filter can also be indicated by a PR number "7GG", "WW7" or "7MG".
Controlled crankcase ventilation system (PCV)
In internal combustion engines, due to the difference in pressure between the combustion chamber and the crankcase, air flows between the piston rings and the working surface of the cylinder, the so-called crankcase gases, occur. To eliminate leakage of unburned hydrocarbons into the atmosphere, the engine is completely sealed. Gases and oil vapors formed in the crankcase are fed into the intake manifold and burn in the cylinders along with the fuel (except for oil vapors lingering in the oil separator).
Gases are removed from the crankcase due to the pressure difference in the crankcase and inlet pipeline (pressure in the crankcase is higher).
The pressure control valve is used to regulate the pressure in the PCV system. It consists of a membrane and a spring. The valve limits the vacuum in the crankcase when crankcase gases are pumped out of it. Too much vacuum can damage the engine seals. With a slight vacuum in the intake manifold, the valve opens under the action of a spring. With a strong vacuum in the intake manifold, the valve closes. In order to reduce the harmful effect of turbulence in gas flows, an outlet calming chamber is installed at the inlet of the inlet pipeline after the centrifugal oil separator. In this chamber, the movement of gases leaving the centrifugal oil separators is slowed down and calmed down. In addition, a certain amount of oil, which remains in the gas stream, also settles on the walls of this chamber.
Exhaust gas recirculation system (EGR)
The EGR system reduces the amount of nitrogen oxides (NO) in exhaust gases. To do this, a small part of the exhaust gases is diverted back into the combustion zone of the fuel-air mixture. This reduces the proportion of oxygen in the fuel-air mixture, which leads to a slowdown in the combustion process. The peak combustion temperature of the mixture is reduced, and the level of emission of nitrogen oxides is reduced.
The amount of exhaust gas returned is controlled by the EGR valve in response to signals from the ECM, and depends mainly on the engine speed, the amount of fuel injected, as well as the volume, temperature and pressure of the intake air.
On models with diesel engines complying with the Euro 5 standard, a wide-band lambda probe is located in the exhaust line before the particulate filter, with which the oxygen content in the exhaust gas is monitored over a wide range. The signal from the lambda probe in the EGR system is used as a correction value for adjusting the amount of exhaust gases returned. If the oxygen content in the exhaust gas differs from the set EGR characteristic parameter, the ECM sends a control signal to the EGR valve and accordingly changes the amount of exhaust gas returned.
The EGR liquid cooler makes it possible to further reduce the combustion temperature by cooling the returned exhaust gases and allows more exhaust gases to be recirculated. With a switchable EGR cooler, the engine and diesel particulate filter reach the required operating temperature faster (Exhaust gas is cooled only after the operating temperature has been reached). The uncooled exhaust gas supply ensures that the engine and the diesel particulate filter reach the operating temperature in a shorter period of time when the engine is started cold. The supply of cooled exhaust gases, especially at high combustion temperatures, helps to reduce the level of nitrogen oxides in the combustion chamber. The EGR radiator changeover valve is an electro-pneumatic valve and is responsible for supplying the vacuum to the air actuator of the EGR radiator, which is necessary to turn on the cooling. The EGR radiator is connected when the coolant temperature is above 37°C. The EGR radiator is a compact module that includes a heat exchanger, control flap, EGR valve, and flap position sensor.
The EGR valve is an electrically actuated poppet valve assembly with a position sensor. The electric drive provides precise stepless adjustment. The rotational movement of the e / motor is converted by an eccentric and a backstage into a reciprocating movement. The stroke of the valve disc controls the amount of exhaust gas returned.
Catalytic converter and lambda probes
To reduce the amount of harmful emissions into the atmosphere, a catalytic converter is integrated into the exhaust system. On diesel models, an oxidation catalytic converter is used, which serves to carry out the following chemical reactions: 2CO + O2 -> 2SO2 and 2C2H6+7O2 -> 4CO2 + 6H2A. Gasoline models use a three-function catalytic converter in which the following chemical reactions take place: 2CO + O2 -> 2SO2; 2C2H6+7O2 -> 4CO2 + 6H2ABOUT; 2NO + 2CO -> N2 + 2CO2.
The broadband lambda probe on diesel models constantly informs the engine control unit about the composition of the exhaust gases. On diesel engine 1.9 l "WHE" lambda probe is not used. Depending on the received data, the control unit corrects the quality of the mixture supplied to the combustion chambers and, thus, optimizes the conditions for fuel combustion. The working surface of the lambda probe is sensitive to changes in the oxygen content in the exhaust gas. The lambda probe is used to correct the amount of injected fuel and optimize the operation of the EGR system.
On petrol models, the fuel injection control system has feedback, which includes two lambda probes that constantly inform the control unit about the composition of the exhaust gas. Depending on the received data, the control unit corrects the quality of the mixture supplied to the combustion chambers and, thus, optimizes the conditions for fuel combustion. The working surface of lambda probes is sensitive to changes in the oxygen content in the exhaust gas. Depending on its concentration, the output voltage of the sensor changes. If the mixture is too rich (the oxygen content in the exhaust gas is very low), the lambda probe sends low voltage signals. The voltage increases as the mixture becomes leaner and the oxygen content of the gases increases. The converter works most efficiently with the optimal composition of the combustible mixture (14.7 parts air to 1 part gasoline).
Particulate filter (DPF)
Note: Soot particles may accumulate in the exhaust pipe after the DPF. The accumulation of soot particles should not be considered a problem since the DPF is not 100% effective at filtering soot. During the DPF regeneration process, white smoke may come out of the exhaust pipe, this is a side effect of the regeneration process, which is also not considered a sign of any malfunction.
To comply with Euro5 emission standards, a particulate filter is fitted as standard close to the engine ("DPF"). The DPF reduces the level of pollution created by diesel vehicles by filtering out soot particles from the exhaust gases. The DPF filter system additionally includes a lambda probe, as well as exhaust gas pressure and temperature sensors. The signals from these sensors are used by the engine control unit to control the regeneration of the particulate filter (the need for regeneration and the optimal time for its implementation). Under normal operating conditions, the regeneration process occurs when the ECM calculates that the particulate filter needs to be regenerated and a number of pre-set conditions are met (e.g. coolant temperature, vehicle speed and engine load).
Due to the fact that the operating temperature of the diesel particulate filter is reached quickly, continuous passive regeneration is possible. Active regeneration via the engine control unit takes place if the particulate filter is filled with soot particles (e.g. after short trips with part load). In this case, the soot particles are burned off by means of a special exhaust gas temperature increase.
Evaporative Emission System (EVAP)
The EVAP system is designed to reduce the emission of unburned hydrocarbons from gasoline engines into the atmosphere. The main element of the EVAP system is an adsorber with activated carbon granules that adsorb fuel vapors formed in the tank while the car is parked. The filler neck of the fuel tank is hermetically closed by a spring-loaded flap. Fuel vapors are retained in the charcoal canister until the canister purge is signaled by the ECM. During purge, fuel vapors are fed through the purge valve into the intake manifold, where they are combined with the working mixture and then burned in the usual way in the combustion chambers.
To ensure normal engine operation at idle and during warm-up, the engine control unit keeps the EVAP solenoid valve closed. This prevents unburned fuel from entering the catalytic converter (mixture is too rich at high idle). After the engine warms up, the valve begins to open and close, regulating the supply of fuel vapor to the intake tract.