Table of contents: Exhaust gas control systems ↓ Crankcase ventilation system ↓ Emission Control - Petrol Models ↓ Exhaust gas control - diesel models ↓ Fuel Evaporative Recovery System -… ↓ Exhaust systems ↓
Exhaust gas control systems
All petrol engines are designed to run on unleaded petrol to meet stringent emission requirements. All models are fitted with a crankcase gas management system and a catalytic converter to minimise emissions. All models are also fitted with an exhaust gas recirculation (EGR) system and a fuel vapor recovery system to further reduce engine emissions.
All diesel engines are designed to meet stringent exhaust emission requirements. All diesel models also feature a crankcase gas management system and a catalytic converter to reduce emissions to a minimum. All models are also equipped with an exhaust gas recirculation (EGR) system to further reduce exhaust gas toxicity.
Crankcase ventilation system
To reduce the release of unburned hydrocarbons from the crankcase into the atmosphere, the crankcase gas management system is closed, crankcase gases and oil vapors are extracted from the crankcase and fed to the intake manifold through an oil separator with a wire mesh, for afterburning during the normal combustion process in the cylinders.
The gases are sucked out of the crankcase by the vacuum in the intake manifold. If the vacuum in the intake manifold is small, the gases are removed from the crankcase by the vacuum in the intake manifold (respectively) increased crankcase pressure. When the engine is worn out, increased crankcase pressure forces gases to return to the intake manifold at all vacuums in it. To regulate the flow of crankcase gases, all diesel engines are equipped with a pressure regulating valve installed in the valve cover.
Emission Control - Petrol Models
To minimize the level of harmful emissions into the atmosphere, a catalytic converter is installed in the exhaust system. The system is a closed type with an oxygen sensor (lambda probe), which provides feedback through the engine control unit. The control unit regulates the mixture composition, creating optimal operating conditions for the catalytic converter.
The oxygen sensor has a built-in electric heating element, controlled by a command from the ECU via a relay for accelerated drive of the sensor tip to the optimum operating temperature. The oxygen sensor sends a voltage signal to the ECU, changing depending on the oxygen content in the exhaust gases: low voltage corresponds to a low oxygen level, with a leaner mixture and an increase in the oxygen content in the exhaust gases, the voltage increases. The peak voltage value is obtained at a stoichiometric mixture ratio of 14.7 parts (by weight) of air and 1 part of fuel. Around this value, the voltage from the sensor varies within wide limits, changing the width of the injector opening pulse. Removal and installation of the sensor are described in detail in chapter 4A.
Exhaust gas control - diesel models
To minimize the level of harmful emissions into the atmosphere, a catalytic converter is installed in the exhaust system. In the converter, gaseous hydrocarbons and carbon monoxide are burned to the state of water and carbon dioxide.
All diesel engines are also equipped with an exhaust gas recirculation (EGR) system. This system reduces the level of nitrous oxides in the exhaust gases by returning a portion of the exhaust gases back to the intake manifold through a plunger valve under certain operating conditions. The system is controlled by commands from the ECU.
Fuel Evaporative Recovery System - Gasoline Models
To minimize the evaporation of unburned hydrocarbons into the atmosphere, a fuel vapor recovery system is installed on all gasoline models. The fuel tank is vented into the atmosphere through a carbon adsorber installed in the front right part of the engine compartment behind the bumper support. The adsorber captures fuel vapors from the tank when the car is parked and stores them until the engine is started and warmed up, the purge valve (on command from the BEU) will open and the vapors will enter the cylinders through the intake manifold, where they will burn in the normal combustion mode.
In order not to over-enrich the mixture during warm-up and under load and not to cause premature failure of the catalytic converter, the system purge valve opens and closes on command from the ECU.
Exhaust systems
On petrol models with ADP, ADR and AFY engines, the exhaust system consists of an exhaust manifold (with oxygen sensor), downpipe, catalytic converter, intermediate pipe with muffler and exhaust pipe with muffler. On AHL petrol models the exhaust system consists of an exhaust manifold (with oxygen sensor), an inlet pipe with a built-in catalytic converter, an intermediate pipe with a muffler and an exhaust pipe with a muffler. On petrol models AEB and AJL, the exhaust system consists of an outlet manifold, a turbocharger, a catalytic converter with an oxygen sensor, an inlet pipe, an intermediate pipe with a muffler and an exhaust pipe with a muffler.
On all diesel models, the exhaust system consists of an exhaust manifold, turbocharger, downpipe with integrated catalytic converter, short connecting pipe, intermediate pipe with muffler and exhaust pipe with muffler. The system is suspended on rubber bushings and/or rubber rings. The intermediate and rear parts of the muffler are manufactured as a single unit, but they are also supplied separately as spare parts.
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