S-class W202 Mercedes
1993-2000 of release
Repair and car operation
+ 1.2. General information
+ 2. Maintenance
+ 3. Engines
+ 4. Greasing system
+ 5. Cooling system
+ 6. Heating, ventilation
+ 7. Ignition system
- 8. Fuel system
+ 8.1.1. Introduction
+ 8.2. System of injection of petrol engines
+ 8.3. System of injection and food of diesel engines
- 8.4. System of production of exhaust gases
8.4.2. Main and average exhaust silencers
8.4.3. Cars with the catalyst
8.4.4. Device of neutralization of exhaust gases of the diesel car
8.4.5. Rub in one – or how to save the catalyst
+ 9. Transmission
+ 10. Running gear
+ 11. Steering
+ 12. Brake system
+ 13. Body
+ 14. Electric equipment
+ 14.2. Electroschemes
Replacement of the refused catalyst will run into money, therefore it is good know in advance, what problems happen to it, as business with them in the market of spare parts is.
Until recently we knew about the catalyst only the following: it is such piece which unclear why is necessary, it is unclear as works that our gasoline "kills" her, generally – one troubles. To cut out – and any problems! But gradually we started to get used to that that the catalyst – a thing after all reasonably useful, at least thoughts on "surgical intervention" in an exhaust system visit everything more rare and the lesser quantity of the heads.
In the spring when the staff of GAI begins "fight for purity of air", one more problem falls down us – it is necessary to adjust WITH. Owners of the cars equipped with catalysts, do not reflect on it at all, and check posts WITH pass without a shiver in knees and fear for the purse. However, the same purse can decently "grow thin" for other reason. Penalties for level excess WITH will seem cheap in comparison with expenses on purchase and catalyst replacement if it fails. Therefore not so harmfully to the nobility as with it to address, and for this purpose it is necessary to understand at first, as it устрон and as works.
How they work?
At combustion of a working mix a row unhealthy the person of products of combustion, in particular, a carbon oxide (WITH), various hydrocarbons (SN) and nitrogen (NO) oxides is formed. Though these substances also make only 1 % from the general exhaust (the rest is a nitrogen, dioxide of carbon and water vapor), they are very harmful and neutralization demand. There are some ways of fight against harmful exhausts – for example, mix pauperization at which the engine or an exhaust retsirkulyatsiya works – but any of them will not be compared by efficiency to catalytic converter.
As experts speak, catalytic converter is a simple device in which there is a difficult chemical process. "In the case from stainless steel there is the ceramic or metal "brick" having cellular structure. At this monolith the huge area of a surface, and all it is covered with the thinnest layer of a special alloy – actually the catalyst containing platinum, rhodium and a palladium. These precious metals are responsible for wonderful properties of the catalyst, they define its high cost".
Exhaust gases "wash" a monolith surface, and when the temperature reaches "critical" value 270 ° With, catalytic reaction begins. The oxide of carbon turns into dioxide (carbon dioxide), hydrocarbons turn into water and besides carbon dioxide, and oxides of nitrogen turn into water and nitrogen. All this for environment less harmfully.
Catalytic converters are capable to reduce quite effectively toxicity of an exhaust, thus they do not influence consumption of fuel and engine capacity. In the presence of the catalyst return pressure of an exhaust from what the engine loses 2–3 h.p., but it, practically, all "payment" for exhaust cleaning slightly increases. However, installation of catalytic converter – not the ideal decision. Theoretically, it should serve infinitely as aforementioned precious metals serve only as the catalyst which at chemical reaction, as we know, is not spent. In practice life of the catalyst has the limit...
What them ruins?
Refusal of catalytic converter can occur for several reasons though, usually, it is process gradual, to catch which without the special equipment it is impossible.
"Core" of the majority of catalysts is made of ceramics - a material known for the fragility. The car can get for the speed to a hollow, hit about something or even it is simple to "strike" the catalyst case on a stone, and from it catalytic "brick" can burst. After that loss by "core" of the working qualities – time business.
The converters of new generation containing a metal monolith, are not so vulnerable in this respect. To break them, of course, it is possible, but, in any case, not so simply.
Enemies of the catalyst
Except physical destruction there is one more frequent reason of failure of the catalyst. Fuel. It is extremely sensitive to composition of fuel. If gasoline etilirovanny, тетраэтил the lead, containing in it, is postponed on an active surface of catalytic "brick" and quickly "salts" it from what any reactions stop., Apparently, on fillings and tips of hoses began to put the different size, and distributing columns paint in different colors, and write about it at every turn, and all the same consumers sometimes confuse and fill in not that gasoline. And after all it is enough to "burn" half-tank of such gasoline, and the catalyst will be lost irrevocably.
But not only etilirovanny gasoline – the enemy of the catalyst. The catalyst can be ruined and unleaded if the control system of the engine is faulty, short burns down a mix or the engine it is strongly worn-out.
Threefold catalytic converters ("threefold" because as the catalyst set of three precious metals serves) establish only on those cars which engines are equipped with the closed monitoring system of an exhaust. In front of the catalyst the oxygen sensor which traces structure of an exhaust is established and transfers these data in the central processor. Depending on the content of oxygen in an exhaust, BEU regulates composition of gas mixture and ignition so that their optimum values were supported. It serves as the main protection for the catalyst, and also provides economy of fuel and overall performance of the engine. The catalyst does not transfer big deviations as a part of a working mix. Badly adjusted engine with the raised content of hydrocarbons in an exhaust simply ruin the catalyst. If the mix too poor, it can cause a sharp overheat of the catalyst from what the monolith, only already "physically" again will suffer. Thus, "life" of the catalyst depends on serviceability of a control system of the engine.
A lot of things depends and on serviceability of the most oxygen sensor. With "age" it becomes "lazy" or absolutely fails that affects structure of a mix and, respectively, on serviceability of the catalyst.
Spoil the catalyst the exhaust of strongly worn-out engine burning oil can also. It, getting together with an exhaust to the catalyst, "is baked" on a monolith surface, like a varnish, and let's to the catalyst work.
There are also other harmful factors. For example – candles. Improper candles will not give complete combustion that can cause in the catalyst pernicious reaction of fusion".
Be very careful in application of additives to gasoline or oil. The majority does not reflect on it, and after all additives too can harmfully influence the catalyst. If on a product it is not written: "it is compatible to the catalyst", do not risk better.
One more dangerous case – engine start by towage. Thus there can be a hit in the catalyst of simply pure gasoline. It, first, poisons the catalyst, but also can cause instant reaction and even explosion. Look also where go – try not to get to deep pools. The working temperature of the catalyst makes about 900 ° Page. Its sudden hit in water can be fatal.
As a whole, it is noticed that service life of the catalyst is influenced by service conditions. Catalysts by the cars maintained in city conditions when the engine often get more suffer. On the other hand, at long high-speed driving on highways the catalyst also spoils from that overheats.
At last, you arrive reasonably if will begin to examine all system of an exhaust regularly. If arms are broken or rubber suspension brackets fell off, the exhaust pipe will vibrate, transferring to the catalyst unnecessary loadings.