Contents: Preventing Crankcase Emissions ↡ Reducing toxicity of exhaust gases ↡ Emission Control System - Diesel…↡ Fuel Evaporative Recovery System -…↡ Exhaust systems ↡
All petrol models can run on unleaded petrol and are controlled by engine management systems that are configured to provide the best compromise between vehicle performance, fuel consumption and emissions. Additionally, several systems are installed that help minimise harmful emissions into the atmosphere - all models are equipped with a crankcase ventilation system that reduces the emission of contaminants from the engine lubrication system; most models are equipped with a catalytic converter to reduce exhaust pollution, and all models are equipped with a gasoline vapor recovery system that reduces the emission of hydrocarbons from the gas tank. Additionally, many models are equipped with an exhaust gas recirculation (EGR) system and / or an additional air injection system that reduces emissions of partially unburned fuel.
All diesel models are equipped with a quarry ventilation system. Additionally, to reduce harmful emissions, some models are equipped with a catalytic converter and an EGR system.
Preventing Crankcase Emissions
To reduce the emission of unburned hydrocarbons from the crankcase into the atmosphere, a forced crankcase ventilation system is used. In this case, the engine is sealed, and the gases that have broken through into the crankcase, as well as oil vapors, are removed from the crankcase through the oil separator into the intake tract to be burned in the engine combustion chamber.
At high vacuum in the manifold (idling, slowing down) gases will be forcibly sucked from the crankcase. At low vacuum in the manifold (acceleration. full throttle) gases are expelled from the crankcase (relatively) higher crankcase pressure; if the engine is worn out, increased pressure in the crankcase (due to increased gas breakthrough) will force gases to return to the intake manifold under any of its conditions.
Reducing toxicity of exhaust gases
To minimize the amount of pollutants released into the atmosphere, all models are equipped with a catalytic converter in the exhaust system. The control system is built on a closed type, in which the oxygen sensor in the exhaust system provides the fuel injection system electronic control unit with constant feedback on the oxygen content in the exhaust gases. This allows the electronic control unit to adjust the mixture by changing the injection duration, thus providing the best conditions for the converter to operate.
Oxygen sensor (Lambda probe) has a built-in heating element, switched on by the electronic control unit, allowing the sensor's sensitive element to reach its effective operating temperature more quickly. The sensor is sensitive to oxygen and supplies the control module with a changing voltage depending on the amount of oxygen in the exhaust gases; if the mixture at the engine inlet is too rich, the exhaust gases contain little oxygen, so the sensor sends a voltage proportional to the amount of oxygen detected, when the mixture is lean, the voltage changes because the amount of oxygen in the exhaust gases increases. The greatest efficiency in converting all major pollutants occurs when the composition of the working mixture is maintained in the chemically correct ratio for complete combustion of gasoline - 14.7 parts by weight of air to one part of fuel (the "stochometric" ratio). The voltage at the sensor output near this point changes in large increments, the electronic control unit uses the signal change to adjust the working mixture by changing the opening time of the injectors. Details of removing and installing the Lambda probe are described in Chapter 4B.
Some models use an additional air intake system, which is designed to reduce the emission of gaseous hydrocarbons and carbon monoxide. A mechanical air pump, driven by the accessory drive belt, forces air into the exhaust manifold where it mixes with particles of partially burned fuel. The oxygen-rich air mixes with the contaminants and allows oxidation, converting some of the hydrocarbons and carbon monoxide into harmless carbon dioxide and water vapor.
The exhaust gas recirculation system is installed on models for certain markets. It reduces the level of nitrogen oxides, which are formed during fuel combustion, by returning a portion of the exhaust gases back to the intake manifold through a valve under certain engine operating conditions. The system has an electro-pneumatic drive and is controlled by an electronic control unit (ECU).
Emission Control System - Diesel Models
For some markets, diesel models are equipped with an oxidation catalyst in the exhaust system. This eliminates a large proportion of gaseous hydrocarbons and carbon monoxide present in the exhaust gases. For certain markets, a trap is built into the muffler to capture solid hydrocarbon particles suspended in the exhaust gases. Certain diesel models are equipped with an EGR system.
The exhaust gas recirculation system reduces the level of nitrogen oxides formed during fuel combustion by returning a portion of the exhaust gases back to the intake manifold through a valve under certain engine operating conditions. The system has an electro-pneumatic drive and is controlled by an electronic control unit (ECU).
Fuel Evaporative Recovery System - Gasoline Models
To reduce the release of hydrocarbons from the fuel system into the atmosphere, all gasoline models are equipped with a gasoline vapor recovery system. The gas tank filler cap is sealed and an absorber filled with activated carbon is installed under the left wing, which captures gasoline vapors from the gas tank (and on carburetor models from the float chamber).
The absorber holds the vapors until an electric purge valve, controlled by the fuel injection/ignition control system controlled by the electronic control unit, opens. When the valve opens, the vapors are sucked into the intake tract and then burned in the engine.
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The flow of gasoline vapor from the absorber through the valve to the throttle chamber is controlled by a thermal valve, which does not allow the purge valve to open until the coolant temperature reaches a certain value. This is necessary to ensure normal operation of the engine when it is not yet warmed up and to protect the catalytic converter from an enriched mixture. In addition, since the purge valve is controlled by the vacuum in the intake manifold, the absorber opens only when the engine is under load. This prevents over-enrichment of the mixture when idling and driving at low speeds.
Exhaust systems
The exhaust system consists of an exhaust manifold, a set of mufflers and intermediate pipes (depends on model and specification), catalytic converter (where it is installed) and a set of support brackets and rubber supports.
The turbocharger, which is installed on turbocharged models, is oil-cooled and has a built-in pressure limiting valve. In the event of failure of the compressor pressure control valve, the overload protection valve (controlled by a switch mounted on the intake manifold) opens and limits the amount of fuel supplied to the engine through an actuator mounted on the high-pressure fuel pump.