BMW 3 series E30

Since 1983-1994 of release

Repair and car operation

14.33. The catalyst

THE GENERAL DATA

The device

Katalitichesky neutralizer of the fulfilled gases has the case from stainless steel to which welding attaches inlet and final cones with branch pipes and fixing flanges, and also теплоотражатели, keeping a ceramic covering. All internal volume of the case is occupied by the ceramic porous monolith fixed by rings or a grid from stainless steel. The monolith structure is similar to the usual filter, but all internal and external surface of the time contacting to gases, is covered by very thin molecular layer of an alloy which contains platinum, rhodium and a palladium. Porosity of a monolith has the big area of the surface covered with this alloy from very expensive metals that basically and defines the high price of neutralizers.

Work principle

The engine throws out in atmosphere together with the fulfilled gases products full (water steam Н₂О, nitrogen N₂, etc.) and incomplete (оксид carbon WITH, and also CnHm, оксиды nitrogen NO_x) fuel combustion. Total number of components which contain in these gases, exceeds some hundreds, and the majority of them are unhealthy the person.

The fulfilled gases, getting through a porous surface of a monolith, first, heat up it, and secondly, доокисляются. From WITH it turns out СО₂ that is nontoxical carbonic gas, CnHm in some stages passes in СО₂ and Н₂О, NO_x turns in molecular N₂ which contains in usual air, and in water. In a word, in neutralizer there are difficult enough chemical reactions thanks to a heat and presence of a special covering from expensive metals serving by catalysts.

So, the main positive effect of this adaptation – full neutralisation of three components – WITH, CnHm, NO_x, – which in the fulfilled gases more than other harmful substances. Also it is reached not only thanks to presence of platinum, rhodium and a palladium. The important role plays, as I have already told, the temperature maintained in borders 300–800 ° by S.Esli it decreases to 250 ° With, chemical reactions of neutralisation WITH, CnHm, NO_x, despite presence of metals-catalysts, will not occur. And at temperature nearby 900 ° With begins плавиться and to collapse каталитическая a film.

Operation

Not to put out of action serviceable neutralizer, it is necessary to adhere to rules of its operation strictly. First of all, it is impossible to use этилированный gasoline. It is enough to spend 20–30 l of this gasoline, – and the active surface of the catalyst will become covered by lead that will lead to breakage.

It is necessary constantly and to watch closely for technical an engine condition. Neutralizer does not maintain considerable deviations as a part of a fuel mix. At engine work on rich and very rich mixes it is quickly hammered by a soot and other adjournment, and on poor and very poor – overheats before fusion of an active layer. For maintenance of structure of a mix in necessary borders on cars with neutralizers the oxygen gauge – a ljambda-probe is necessarily established, – on which signal the electronic block of management measures structure of a fuel mix. Serviceability and correct work of system of regulation in many respects define durability of neutralizer. Therefore at any failures in work of the engine because of system of ignition or the complicated start-up – it is necessary to find and eliminate malfunction.

It is forbidden to start the engine from a tow, long to twist its starter or it is frequent with short intervals to try to start not heated-up. Besides, not to admit occurrence of cracks, it is necessary to avoid blows about road barriers. The reason of mechanical damage owing to sharp temperature difference can become car hit in a deep hollow with water and sharp cooling нагретого to 800–900 ° From neutralizer.

It is necessary to notice that recently have started to let out каталитические neutralizers with a metal monolith that raises their durability. They thanking большей stability to different mechanical and temperature influences but therefore they and are more expensive than ceramic analogues much more reliably.

As already marked, neutralizer with a ceramic monolith is very sensitive to blows, therefore it it is impossible to drop or use a percussion instrument at work with system. And to avoid adjournment of fats, it is forbidden to concern with hands of a working surface of the gauge of oxygen. It is impossible to check presence of a spark by removal of a tip from any spark plug or to use supernumerary candles, and also to check an overall performance of cylinders a method of switching-off of a spark мотортестером. These actions can cause hit of not burnt down fuel in the catalyst, about consequences of that is told above.

Pluses and minuses

The first and basic plus of this adaptation – almost full neutralisation наивреднейших (considering their total concentration and toxicity) components of the fulfilled gases. The second plus consists that motor-car manufacturers without additional expenses for improvement of serial engines, having established neutralizer and control systems топливоподачей with a ljambda-probe, can continue release of cars which, for example, the Euro-2 and even Euro-3 completely answer rigid norms of toxicity of the fulfilled gases.

But is at neutralizer and minuses. One of its essential lacks – low reliability, and not only because of fragility of a ceramic monolith, but also because of refusal owing to infringement of rules экплуатации, and even when these rules are not broken. According to inspections, faster catalysts break in the conditions of city driving with frequent starts of the engine and short run. And also – at steady high-speed movement on highways. In the first case neutralizer is simply hammered by fuel and a soot, after all at each start it should get warm to working temperature, and on it time is necessary. In the second – from overheating.

The rare car will long work for us with neutralisation system, considering a road condition, security неэтилированным gasoline and quality of this gasoline, no less than professional and ecological consciousness of drivers and repairmen. This expensive, but not "long-playing" system operates in the car before occurrence of the first problems. And then, as a rule, the monolith is beaten out from the case and it simply throw out.

The logic of similar "measures" is clear: first, it is much cheaper, faster and is easier, than to search, agree and wait, while will bring new neutralizer; secondly, these actions will not entail any negative consequences because almost all foreign cars with serviceable system of injection of gasoline keep within GOST operating nowadays (that for the automobile owner, unfortunately, will not tell about many SNGOVSKY cars).

So arrive at us and how at "them" where also norms on toxicity more rigid, and газоаналитический the control is adjusted, and money at the people is found, and are expensive as it should be, and service at height? There, if neutralizer has failed, it simply replace to avoid too high penalties for the raised toxicity. By the way, replace too not always обоснованно because and at them not everyone HUNDRED has the complete set of the necessary equipment and corresponding details. The discontent of consumers arising in this connection, raises demand for cars without neutralizers. These are cars with gas, diesel and gazo-diesel engines, and also with direct injection of gasoline, and others, keeping within norms of Euro-3 without neutralizers.