BMW 3 series E30

Since 1983-1994 of release

Repair and car operation

14.34. Three in one – or how to save the catalyst

THE GENERAL DATA

Replacement of the refused catalyst will manage недешево, therefore it is good to 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 not clearly what for is necessary, it is not clear as works that our gasoline "kills" her, in general – one troubles. To cut out – and any problems! But gradually we have started to get used to that that the catalyst – a thing all the same reasonably useful, at least thoughts on "surgical intervention" in an exhaust system visit all less often and the lesser quantity of goals.

In the spring when employees of GAI begin "struggle for cleanliness 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 posts of check 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 excess of level WITH will seem cheap in comparison with expenses on purchase and catalyst replacement if it fails. Therefore completely not harmfully 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 number of the unhealthy person of products of combustion, in particular, окись carbon (WITH), various hydrocarbons (СН) and nitrogen oxides (NO) is formed. Though these substances also make only 1 % from the general exhaust (the rest is a nitrogen, dioxide of carbon and water steam), they are very harmful and neutralisation demand. There are some ways of struggle against harmful exhausts – for example, mix pauperisation on which the engine or рециркуляция an exhaust works – but any of them will not be compared by efficiency with catalytic neutralizer.

As experts speak, каталитический neutralizer is a simple device in which there is a difficult chemical process. "In the case from stainless steel there is ceramic or metal" a brick ", having cellular structure. At this monolith the huge area of a surface, and all it is covered by the most thin 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, reaction begins каталитическая. Окись carbon turns to dioxide (carbonic gas), hydrocarbons turn to water and besides carbon dioxide, and nitrogen oxides turn to water and nitrogen. All it for environment less harmfully.

Katalitichesky neutralizers are capable to reduce effectively enough toxicity of an exhaust, thus they do not influence consumption of fuel and capacity of the engine. 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 clearing slightly increases. However, installation каталитического neutralizer – not the ideal decision. Theoretically, it should serve infinitely as aforementioned precious metals serve only as the catalyst which at chemical reaction, as it is known, is not spent. In practice the catalyst life has the limit...

What them ruins?

Refusal каталитического neutralizer can occur for the 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 is simple to "strike" the catalyst case on a stone, and from it каталитический "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, anyway, not so it is simple.

Enemies of the catalyst

Except physical destruction there is one more frequent reason of failure of the catalyst. Fuel. It is extremely sensitive to fuel structure. If gasoline этилированный тетраэтил the lead, containing in it, it is postponed on an active surface каталитического "brick" and quickly "salts" it from what any reactions stop., Apparently, on refuellings and tips of hoses began to put the different size, and distributing columns paint in different colours, 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 этилированный gasoline – the enemy of the catalyst. The catalyst can be ruined and неэтилированным if the control system of the engine is faulty, short burns down a mix or the engine it is worn strongly out.

Threefold каталитические neutralizers ("threefold" because as the catalyst set of three precious metals serves) establish only on those cars which engines are equipped by the closed monitoring system of an exhaust. In front of the catalyst the oxygen gauge which traces structure of an exhaust is established and transfers this data in the central processor. Depending on the oxygen maintenance in an exhaust, БЭУ regulates structure of a 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 an engine overall performance. The catalyst does not transfer the big deviations as a part of a working mix. Badly adjusted engine with the raised maintenance 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, catalyst "life" depends on serviceability of a control system of the engine.

Much depends and on serviceability of the most oxygen gauge. With "age" it becomes "lazy" or absolutely fails that affects structure of a mix and, accordingly, on serviceability of the catalyst.

Spoil the catalyst the exhaust of strongly worn out engine churning butter can also. It, getting together with an exhaust to the catalyst, "is baked" on a monolith surface, like a varnish, and does not allow to the catalyst to work.

There are also other harmful factors. For example – candles. Improper candles will not give full combustion that can cause in the catalyst pernicious reaction of fusion ".

Be very cautious in application of additives to gasoline or oil. The majority does not reflect on it, and after all additives too can influence the catalyst harmfully. If on a product it is not written: "it is compatible to the catalyst", do not risk better.

One more dangerous case – start of the engine 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 an order 900 ° S.Vnezapnoe its hit in water can be fatal.

As a whole, it is noticed that catalyst service life 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 that overheats ".

At last, you arrive reasonably if begin to examine regularly all system of an exhaust. If arms are broken or rubber suspension brackets have fallen off, the exhaust pipe will vibrate, transferring to the catalyst unnecessary loadings.