VOLKSWAGEN GOLF IV

since 1997 of release

Repair and car operation



Foltsvagen Golf 4
+ 1. Maintenance instruction
+ 2. Engine
+ 3. Cooling system
+ 4. Fuel system
- 5. Exhaust system
   5.1. Catalyst
   5.2. Removal and installation of an exhaust system
   5.3. Alignment of an exhaust system
   5.4. Replacement of the average / back exhaust silencer
   5.5. Removal and installation of one exhaust silencer
   5.6. Removal and installation lambda sensor
+ 6. Ventilation and heating system
+ 7. Coupling
+ 8. Transmission
+ 9. Suspension brackets and power shafts
+ 10. Steering
+ 11. Wheels and tires
+ 12. Brake system
+ 13. Body
+ 14. Electric equipment and electroschemes






5.1. Catalyst

GENERAL INFORMATION

Catalyst

1–case;

2–consolidation;

3–honeycombs of catalyst

The elements entering into the catalyst and products, leaving the catalyst


On all cars catalysts for reduction of quantity of the harmful substances released into the atmosphere with exhaust gases are established.

The catalyst of exhaust gases has the case from stainless steel to which welding attached inlet and final cones with branch pipes and fixing flanges, and also the heatreflectors holding a ceramic covering. All internal volume of the case is occupied with the ceramic porous monolith fixed by rings or a grid from stainless steel. The structure of a monolith represents the ordinary filter, but all internal and external surface of the time contacting to gases, is covered with very thin molecular layer of an alloy which contains platinum, rhodium and a palladium. The porous monolith has the big area of the surface covered with this alloy from very expensive metals that in the basic and defines the high price of catalysts.

In the catalyst there is a reaction as a result of which potentially dangerous hydrocarbon and a carbon oxide in exhaust gases turn into safe gases and water vapor.

The engine releases into the atmosphere together with exhaust gases products full (H2O water vapor, N2 nitrogen, etc.) and incomplete (WITH carbon oxide, and also CnHm, NOX nitrogen oxides) fuel combustion. Total number of components which contain in these gases, exceeds some hundreds, and the majority of them are unhealthy the person.

Exhaust gases, getting through a porous surface of a monolith, first, heat up it, and secondly, доокисляются. From WITH CO2 turns out, that is nontoxical carbon dioxide, in some stages passes CnHm to CO2 and H2O, NOH turns into molecular N2 which contains in usual air, and in water. In a word, in the catalyst there are quite difficult chemical reactions, thanks to high temperature and existence of a special covering from expensive metals.

The main positive effect of the catalyst – complete neutralization of three components – WITH, CnHm, NOH, – which in exhaust gases more than other harmful substances. Also it is reached not only thanks to availability of platinum, rhodium and a palladium. The important role is played by the temperature which is maintaining in borders of 300-800 ° by S.Esli it decreases to 250 ° With, chemical reactions of neutralization WITH, CnHm, NOH, despite availability of metals catalysts, will not occur. And at temperature about 900 ° With the catalytic film starts to melt and collapse.

Petrol engines


On all models with the catalyst a power supply system fuel of the closed type, that is on the basis of a signal from the sensor of the oxygen established in an exhaust system, the control unit constantly optimizes structure fuel - an air mix. Depending on the content of oxygen in exhaust gases the sensor of oxygen induces tension from 0,1 In (the high content of oxygen, a poor mix) to 0,9 In (the low content of the oxygen, a rich mix). On the basis of these data the control unit the engine changes time of opening of fuel nozzles and changes a fuel ratio in fuel - an air mix. A metric ratio of a fuel mix at which there is its complete combustion and in exhaust gases there are no harmful substances are 14,7 weight parts of air on 1 part of fuel.

The catalyst works effectively at temperatures +300 ° With to +800 ° Page.

Diesel engines

On cars with diesel engines purification of exhaust gases is made by the noncontrollable oxidizing catalyst.

Reduction of percentage of oxides of nitrogen in exhaust gases of the diesel engine is reached at the expense of installation on the car of system of repeated burning of a part of exhaust gases (EGR). The EGR valve of system of repeated burning of exhaust gases is established in a knee of an exhaust system and copes a vacuum regulator. The EGR valve on the heated-up engine sends a part of exhaust gases to chambers of combustion of the engine therefore the temperature decreases and thus the percent of oxides of nitrogen in exhaust gases decreases.

Operation of cars with the catalyst


The catalyst is a reliable and simple device which does not need any service, but there are some facts which the owner should know for the maximum service life of the catalyst.

Do not use etilirovanny gasoline in the car equipped with the catalyst as lead will cover precious metals in a catalyst lattice, reducing efficiency of their transformation and finally will put out of action the catalyst.

Always contain ignition and fuel system in a full order.

If at operation of the engine ignition admissions are observed, do not maintain the car before malfunction elimination.

If at operation of the engine the control lamp of engine management lights up, it is necessary to address as soon as possible on service station. If there is an engine management damage, except increase in fuel consumption and reduction of dynamic characteristics of the engine, the catalyst can fail.

Do not start the engine a towage method.

Do not switch off ignition on high turns of the engine.

Do not use an additive to fuel and engine oil as additives can contain the substances, capable to injure the catalyst.

Do not use the car if from an exhaust pipe the trace of a dark blue smoke is visible.

After an engine stop an exhaust system the long time continues to radiate a significant amount of heat therefore it is necessary to avoid a car parking on a grass and dry leaves. Remember that the catalyst is fragile, therefore avoid blows at removal of the catalyst or an exhaust system.

The catalyst used on well adjusted car, should serve from 100 to 160 thousand km of run of the car.