Emission control systems (Opel Vectra C)

In order to reduce the level of emissions of toxic components into the atmosphere, which enter the composition of engine exhaust gases as a result of evaporation and incomplete combustion of fuel, and to comply with environmental standards, the models considered in this Manual are equipped with a number of special systems, which could be combined under the general name of engine management and exhaust toxicity reduction systems. The following systems should be included in the number of systems related to engine management and exhaust toxicity control:

• a) On-Board Diagnostics (OBD) system
• b) Electronic engine management system (ECM);
• c) Positive Crankcase Ventilation (PCV) system;
• d) Exhaust gas recirculation (EGR) system;
• e) Evaporative emission control system (EVAP);
• f) Catalytic converter and lambda probe (exhaust gas composition control).

The following Sections provide general descriptions of the operating principles of each system. Diagnostics of the elements of the toxicity reduction systems controlled by electronic devices requires the use of special, complex-to-use equipment and a certain qualification of the performer, and therefore, it would be reasonable to entrust its implementation to professional mechanics of a specialized service station.

The above does not mean that maintenance and repair of components of toxicity reduction systems in practice seem difficult to perform. Do not forget that one of the most common causes of failures is an elementary violation of the quality of vacuum or electrical connections, and therefore, first of all, you should always check the condition of the nipples and electrical connectors. The car owner can independently and quite easily perform a number of checks, as well as perform many routine maintenance procedures for most components of the systems at home using a standard set of adjustment and plumbing tools.

Crankcase ventilation system (PCV)

The PCV system is used to reduce emissions of hydrocarbon compounds into the atmosphere by removing crankcase gases from the engine. The block is purged by passing fresh air coming from the air cleaner through the crankcase, where it mixes with accumulated fumes and gases that have broken through the combustion chamber and is removed through the PCV valve into the intake manifold. The main components of the system include the PCV valve, the purge filter and a set of vacuum hoses connecting these devices to the engine. In order to maintain stable idle speed, the PCV valve closes the purge flow when there is a deep vacuum in the intake manifold. In the event of a malfunction of the engine (such as when piston rings wear out) the system removes excess crankcase gases through the ventilation tube back to the air cleaner.

Exhaust gas composition control

See also Chapter "Controls and operating techniques", Section 28. In order to minimize the emission of toxic components into the atmosphere: a catalytic converter is included in the exhaust system. Control is performed by a closed-type control system. Feedback with the engine management system is organized by means of a lambda probe mounted in the exhaust system inlet pipe. The catalytic converter is a component of the exhaust gas toxicity reduction systems, is included in the exhaust system and serves to reduce the emission of toxic components into the atmosphere. The vehicles considered in this Manual use two types of catalytic converters. A conventional oxidation converter reduces the content of hydrocarbons and carbon monoxide in the exhaust gases. A three-function catalytic converter additionally reduces the emission of nitrogen oxides NOx.



Lambda probe (oxygen sensor) monitors the oxygen content in the exhaust gas flow. When 02 molecules come into contact with the sensitive element of the probe, the sensor generates an amplitude signal depending on the oxygen concentration. The electronic module of the engine management system continuously monitors the signals coming from the lambda probe, if necessary issuing commands to adjust the composition of the air-fuel mixture by changing the duration of the opening of the injection injectors. Two lambda probes are used on the models of cars under consideration; the primary is located in the engine exhaust manifold, and the secondary is below the catalytic converter. By comparing the oxygen levels in the exhaust tract sections above and below the catalytic converter, the engine management system also determines the efficiency of the latter.

Evaporative Emissions (EVAP) System

The system accumulates fumes in the fuel tank and ensures their removal into the intake manifold for combustion during normal engine operation.

The general operating principle of the EVAP system is described below. The design described does not necessarily have to be exactly the same as the system installed on a specific vehicle, but the operating principle is common to all models.

Any EVAP system necessarily includes a special adsorber filled with activated carbon, which actually collects fuel vapors. The method of removing vapors from the adsorber may vary depending on the design of a specific system. The fuel filler cap is equipped with a two-way safety valve. In the event of a system failure, the valve ensures the removal of fuel vapors into the atmosphere.



Another shut-off valve (oRVR valve) is installed near the fuel tank and regulates the removal of fuel vapors into the carbon adsorber depending on the pressure/vacuum differences associated with temperature changes. On the way to the carbon adsorber, fuel vapors pass through a two-way valve and through ventilation hoses enter the carbon adsorber installed in the engine compartment, where they accumulate while the car engine is turned off. When the engine is started, the solenoid valve for purging the adsorber remains closed until it warms up to a certain temperature. When the engine temperature reaches a certain value, fuel vapors are released from the adsorber

through a diaphragm valve are blown into the intake manifold, from where they enter the combustion chambers, where they are burned out during normal engine operation. The fuel tank is also usually equipped with a sensor that monitors changes in pressure in the tank, both when the car is parked and when the car is moving.

Exhaust gas recirculation system

In order to reduce nitrogen oxide (NOx) emissions into the atmosphere, the engine design provides for the removal of part of the exhaust gases into the intake manifold through the EGR valve. Such mixing of exhaust gases with the air-fuel mixture leads to a decrease in its combustion temperature. The system consists of an EGR valve, an EGR valve opening degree sensor and a set of auxiliary information sensors. The system is controlled by an electronic module of the engine control system. The module monitors the optimal opening degree of the EGR valve for any engine operating conditions. A special information sensor constantly monitors the opening degree of the EGR valve, sending the corresponding signals to the control module. The electronic device compares the incoming information from the sensor with the optimal calculated value determined by the data received from other information sensors and, if necessary, makes the required adjustment of the volume of exhaust gases entering the engine.