BMW 3 Series E30

since 1983-1994 release

Repair and operation of the car

Device

Catalytic converter 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 busy with the ceramic porous monolith recorded by rings or a grid from stainless steel. The structure of a monolith is similar to the ordinary filter, but all internal and external surface of the time contacting to gases is covered with very thin molecular layer of alloy which contains platinum, rhodium and palladium. Porosity of a monolith has big surface area, covered with this alloy from very expensive metals that generally and determines the high price of converters.

Principle of work

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

Exhaust gases, getting through a porous surface of a monolith, first, heat it, and secondly, dookislyatsya. From WITH _CO2 that is nontoxical carbon dioxide turns out, CnHm in several stages passes into _{CO2 and H2O}, _NOx turns into molecular _N2 which contains in usual air, and in water. In a word, in converter there are quite difficult chemical reactions thanks to high temperature and existence of a special covering from expensive metals serving as catalysts.

So, the main positive effect of this adaptation – full neutralization of three components – WITH, CnHm, _NOx, – which in exhaust gases is more, than other harmful substances. Also it is reached not only thanks to availability of platinum, rhodium and palladium. Plays an important role as I already told, temperature which is maintained in borders of 300-800 °C. If it decreases to 250 °C, chemical reactions of neutralization WITH, CnHm, _NOx, despite availability of metals catalysts, will not occur. And at a temperature about 900 °C the catalytic film begins to melt and collapse.

Operation

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

It is necessary constantly and to watch closely for technical a condition of the engine. Converter does not maintain considerable deviations as a part of fuel mix. During the operation of the engine on rich and very rich mixes it is quickly hammered with a soot and other deposits, and on poor and very poor – overheats before fusion of an active layer. For maintenance of composition of mix in necessary borders on cars with converters the oxygen sensor – a lambda probe surely is installed, – on a signal of which the electronic control unit measures composition of fuel mix. Serviceability and the correct work of system of regulation in many respects define durability of converter. Therefore at any failures in operation 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 the tow, to long twist it a starter or it is frequent with short intervals to try to start not heated-up. Besides, not to allow emergence of cracks, it is necessary to avoid blows about road barriers. The reason of mechanical damage owing to sharp temperature difference can become hit of the car in a deep hollow with water and sharp cooling of the converter heated to 800–900 °C.

It should be noted that recently catalytic converters with a metal monolith began to release that increases their durability. They it is much more reliable thanks to bigger resistance to different mechanical and temperature influences, but therefore they more expensively than ceramic analogs.

As already noted, converter with a ceramic monolith is very sensitive to blows therefore it it is impossible to drop or use a percussion instrument during the work with system. And to avoid adjournment of fats, it is forbidden to touch by hands of a working surface of the sensor of oxygen. It is impossible to check existence of a spark removal of a tip from some spark plug or to use emergency candles, and also to check overall performance of cylinders by method of shutdown of a spark a motortester. These actions can cause hit of not burned down fuel in the catalyst, is told about consequences of what above.

Pluses and minuses

The first and main plus of this adaptation – almost full neutralization of the most harmful (considering their total concentration and toxicity) components of exhaust gases. The second plus consists that car makers without additional costs of improvement of serial engines, having established converter and control systems of fuel feeding with a lambda probe, can continue release of cars which completely answer rigid standards of toxicity of exhaust gases, for example, with Euro-2 and even Euro-3.

But converter has also minuses. One of its essential shortcomings – low reliability, and not only because of fragility of a ceramic monolith, but also because of refusal owing to violation of the rules of an ekpluatation, and even when these rules are not violated. According to inspections, quicker catalysts break in the conditions of city driving with frequent starts of the engine and short run. And also – at the steady high-speed movement on highways. In the first case converter is simply hammered with fuel and a soot, at each start it has to get warm up to the working temperature, and on it time is necessary. In the second – from overheating.

The rare car will long work for us with system of neutralization, considering road condition, security with unleaded gasoline and quality of this gasoline, as well as professional and ecological consciousness of drivers and repairmen. This expensive, but not "long-playing" system works in the car before emergence of the first problems. And then, as a rule, the monolith is beaten out from the case and it is just thrown out.

The logic of similar "measures" is clear: first, it is much cheaper, quicker and more simply, than to look for, agree and wait until bring new converter; secondly, these actions will not entail for the car owner any negative consequences because practically all foreign cars with serviceable system of injection of gasoline keep within GOST operating nowadays (what, unfortunately, you will not tell about many Sngovsky cars).

Act at us this way and how at "them" where also norms on toxicity more rigid, and gas-analytical control is adjusted, and money at the people is found, and are expensive as it should be, and service at height? There, if converter failed, it is just replaced to avoid too high penalties for the increased toxicity. By the way, replace too not always reasonably because and at them not everyone HUNDRED has a complete set of the necessary equipment and the corresponding details. The discontent of consumers arising in this regard increases demand for cars without converters. These are cars with gas, diesel and gas-diesel engines, and also with direct injection of gasoline, and another, keeping within norms Euros-3 without converters.