Exhaust emission control systems
All gasoline models must be fueled with unleaded fuel only. The engine management system performs general control over the functioning of the power unit, ensuring the optimal ratio between the power developed by the engine, vehicle controllability and the composition of exhaust gases. Additionally, the car is equipped with a number of systems that reduce the toxicity of exhaust gases. All petrol engines are equipped as standard with a crankcase ventilation system and a catalytic converter. Due to the functioning of these systems, the overall level of emission of toxic products of combustion of fuel and crankcase gases into the atmosphere is reduced. In addition to the systems mentioned, petrol models are also equipped with a fuel vapor recovery system.
The crankcase ventilation system is also standard on all diesel-equipped models. In addition, diesel models are equipped with a dual-function catalytic converter and an exhaust gas recirculation system (EGR), allowing to reduce the overall level of emission toxicity.
Crankcase ventilation system
In order to reduce the emission of crankcase gases into the atmosphere containing unburned hydrocarbon compounds, the engine block is sealed, and the gases that escape from the combustion chambers and oil vapors accumulating inside it are removed from the crankcase and through the air cleaner enter the combustion chambers, where they are burned out during the normal operation of the engine.
Under the influence of deep vacuum in the intake manifold (idling or engine braking) crankcase gases are pulled out of the engine by gravity. With a decrease in the depth of rarefaction (acceleration, full throttle driving) the removal of gases and vapors occurs due to a relative increase in crankcase pressure. As a result of the wear of the components of the piston groups and engine cylinders, the intra-crankcase pressure increases due to a more intensive breakthrough of gases from the combustion chambers, which leads to a forced return of a part of the output flow at any vacuum in the intake pipeline.
Exhaust Gas Composition Management System (petrol models)
In order to minimize the level of toxicity of exhaust gases emitted into the atmosphere, a catalytic converter is included in the exhaust system of all gasoline models. Oxygen sensor installed in the exhaust system (λ probe) closes the feedback loop of the power supply system, informing the ECU of the engine management system about the level of O2 content in the exhaust gases. Based on the analysis of the incoming data, the ECU makes an appropriate adjustment to the composition of the air-fuel mixture, thereby optimizing the process of its combustion.
A heating element is mounted in the oxygen sensor, the operation of which is controlled by the ECU through a special relay. The task of the element is to accelerate the heating of the λ-probe to the optimum operating temperature. The working tip of the sensor is sensitive to the content of oxygen in the surrounding space. As a result, depending on the level of oxidation of the exhaust gases, the sensor outputs a signal of the appropriate amplitude to the ECU. The minimum toxicity of the combustion products of the air-fuel mixture is achieved at a completely certain weight ratio of its components, namely: 14.7 parts of air should fall on 1 weight part of the fuel. This ratio is called the stoichiometric number. The change in the amplitude of the sensor output signal near this point occurs in large steps, which allows the ECU to use the incoming signals as a reference when calculating the required air mixture. The composition of the mixture is adjusted by changing the duration of opening of the fuel injection injectors. A description of the procedures for removing and installing the λ-probe is given in Section Removal and installation of λ-probe.
Exhaust Gas Composition Management System (diesel models)
A dual function catalytic converter is installed in the exhaust system of all diesel models. The converter helps to prevent the emission of most of the gaseous hydrocarbon compounds, carbon monoxide into the atmosphere (SO) and solid microparticles.
Additionally, diesel models are equipped with an exhaust gas recirculation system (EGR). The system allows to reduce the level of emission of toxic nitrogen oxides formed during the combustion of the air-fuel mixture by periodically returning part of the exhaust gases to the intake pipeline. Exhaust gases are returned through the EGR plunger valve under certain engine operating conditions. Control over the functioning of the EGR system is provided by an electronic diesel control unit.
Evaporative Emission System (petrol models)
In order to minimize the emission of unburned hydrocarbon compounds into the atmosphere, all gasoline models are equipped with a fuel vapor recovery system. The filler neck of the fuel tank is closed with a sealed cap. A carbon adsorber is installed on the mudguard of the left wheel arch, into which all fuel vapors accumulated during the parking of the car in the tank are discharged. The evaporating fuel accumulates in the canister and, after starting the engine, is removed from it through the purge plunger valve into the intake tract, where it is burned during the normal operation of the vehicle. In order to protect the catalytic converter from the effects of over-enriching the mixture during the engine warm-up process or while it is idling, the ECU does not allow the canister purge control valve to open until the unit is finally warmed up. With an increase in the load on the engine, the solenoid valve begins to function in a pulsed mode, sequentially outputting the contents of the adsorber to the engine intake tract.
Exhaust system
The exhaust system consists of an exhaust manifold, a downpipe, a catalytic converter, two box mufflers, a set of support brackets and tubular connecting sections. On 1.6L diesel and petrol models, the catalytic converter is included in the downpipe section of the exhaust system, while on 1.3L models, the downpipe and converter are installed separately from each other.