Citroen Xantia

since 1993 of release

Repair and car operation

Systems of decrease in toxicity and production of the fulfilled gases

All petrol models are adapted for filling by unleaded fuel. In addition, systems of their food are developed taking into account the last rigid requirements to environmental protection and allow to lower rather effectively toxicity of the fulfilled gases let out in the atmosphere. The standard complete set of all models includes system of ventilation of a case. The majority of petrol models are equipped with the catalytic converter and system of catching of fuel evaporations (EVAP) (see above in the present Chapter).

On all diesel models strict control of composition of the fulfilled gases is also provided and the system of ventilation of a case is provided. On some models the catalytic converter is established. Even more elimination of toxic components is promoted by introduction on separate models of system of a retsirkulyatsiya of the fulfilled gases (EGR). On equipped with turbo-supercharging system EGR cars it can be used in pair by system of compensation of changes of atmospheric pressure.

Below principles of functioning of separate systems and the devices which use promotes decrease in toxicity of the fulfilled gases are in more detail described.

Petrol models

System of ventilation of a case

The system allows to lower issue level in the atmosphere of hydrocarbons containing in karterny gases. The block of the engine is executed tightly, breaking in it bypassing piston rings from combustion chambers gases together with oil evaporations compulsorily are removed from a case in the inlet pipeline, and destroyed in the course of normal functioning of the engine. Before getting to the inlet pipeline karterny gases are banished through a mesh oil separator.

At increase of depth of depression in the inlet pipeline (single turns, braking by the engine) karterny gases are exhausted from the engine. If depth of depression is low (acceleration, movement with completely open butterfly valve), gases are pushed out at the expense of relative increase of pressure in a case. If the engine is strongly worn-out, pressure in its case will be constantly raised (at the expense of more intensive blowing off of gases from combustion chambers bypassing piston rings) that provides continuous return of a part of a gas stream at any pressure in the inlet pipeline.

Catalytic converter and l-probe

For the purpose of decrease in level of issue in the atmosphere of toxic products of combustion in system of release of some models the catalytic converter is established. Thus included in release system the oxygen sensor (l-probe) provides feedback with ECU of a control system of the engine. On the basis of the analysis of information received from the sensor about level of the content in the fulfilled gases of ECU oxygen carries out instant correction of structure of an air and fuel mix, constantly supporting optimum conditions for functioning of the catalytic converter.
the l-probe is equipped with the built-in electric heating element which functioning via the relay of the oxygen sensor carries out ECU of a control system of the engine. The working tip of the sensor registers level of the content in the fulfilled O2 gases and functions effectively only at rather high working temperatures which maintenance provides a heating element. The sensor develops the tension which amplitude is directly proportional to level of the content of oxygen in the fulfilled gases. At injection in the engine of the reenriched air and fuel mix the content of oxygen in products of combustion is rather insignificant, and the sensor develops a low-voltage signal. In process of mix pauperization the amplitude of a signal developed by the sensor raises. To the most complete combustion of a mix with the minimum maintenance of toxic components in products of combustion there corresponds a ratio of the content of gasoline to air 1 : 14.7, i.e. one weight part of fuel should fall on one weight part of air. This ratio is called as stekhiometrichesky number. Near this point change of amplitude of a signal developed by the sensor occurs wide jumps, ECU thus immediately develops command for the corresponding correction of structure of an air and fuel mix at the expense of change of time of opening of injectors/nozzles.

System of catching of fuel evaporations (EVAP)

This system allows to lower essentially issue level in the atmosphere of not burned down hydrocarbonic connections. The system is established on the models equipped with the catalytic converter. The cover of a jellied mouth of a fuel tank is closed tightly. Behind a radiator, on the left wall of an impellent compartment the coal adsorber accumulating in fuel evaporations, being allocated in a tank is established during car parking. The adsorber purge after start of the engine is carried out at the command of control system ECU. The special valve, opening, provides a conclusion of the fuel which has accumulated in an adsorber to the inlet highway, from where it arrives in chambers of combustion and is burned out in the course of normal functioning of the engine.

In order to avoid violation of stabilization of turns of idling and for protection of the catalytic converter against effect of influence of the reenriched mix the valve of a purge of a coal adsorber opens only after the engine will not get warm to normal working temperature and it will not appear under loading. Further ECU develops commands for periodic turning on switching off of the electromagnetic valve. In the course of such modulations also there is a conclusion of the fuel which has accumulated in an adsorber to the inlet highway of the engine.

Release system

Information on functioning of system of release is presented in the section System of production of the fulfilled gases - the general information, removal and installation.

Diesel models

System of ventilation of a case

See above subsection "Petrol models - systems of ventilation of a case".

Catalytic converter

The catalytic converter enters into a complete set of separate models and represents the close-meshed grid placed in the metal container with inclusions of catalytic metals. Through a grid the fulfilled gases of the engine warmed up to high temperature are banished. The catalyst promotes the accelerated oxidation of such connections as carbon monooxide (WITH), not up to the end burned down hydrocarbonic connections, soot, etc., allowing it is essential to reduce toxicity of an exhaust.

System of a retsirkulyatsiya of the fulfilled gases (EGR)

The system provides a retsirkulyatsiya of a part of the fulfilled gases to the inlet highway of the engine and their inclusion in process of burning of an air and fuel mix. Level of the contents in products of combustion of toxic oxides of nitrogen (NOx) thus decreases.

The volume of a retsirkulyatsiya is supervised by the electronic control unit of system.

Function chart of system of a retsirkulyatsiya of the fulfilled gases (EGR)

The system functions at temperature of cooling liquid 60°С and loading not above adjusting value of the switch (2) on TNVD. The control unit opens the electromagnetic valve (7) supervising functioning of all system. Created located on the camshaft end the vacuum pump depression forces to work the EGR (5) valve established in a final collector, and this operation occurs only at the open valve of management (7).

In addition, the inlet pipeline is equipped with the lamellar zaslonka, allowing to correct a ratio of structure of a mix of the fulfilled gases submitted to an inlet path with air soaked up in the engine. Besides, the zaslonka prevents giving in the pipeline of the fulfilled gases at working at single turns or under low loading the engine when the valve in a final collector is completely open.
The control unit of system develops teams on the basis of the analysis of information arriving on it about temperature of cooling liquid and frequency of rotation of the engine (VMT sensor).

System of compensation of changes of atmospheric pressure

The system allows to suspend correction of an advancing of the moment of injection for the purpose of decrease in level of smoke at certain ratios of temperature of the engine and atmospheric pressure. The system functions together with preheat system (see. Preheat system - diesel models), using information arriving from the sensor of temperature of cooling liquid and the sensor switch of atmospheric pressure.

Release system

Information on functioning of system of release is presented in the section System of production of the fulfilled gases - the general information, removal and installation.