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The device and principle of operation of the catalytic converter. What is a catalyst and why is it needed? Catalyst life

From this article you will learn what a catalytic converter is in a modern car, and the design of the exhaust tract of an internal combustion engine will also be considered. Catalysts have been used in the design of machines relatively recently. You will not find them on carburetor engines, since these devices operate under the control of a microprocessor unit. It should also be noted that catalysts are successfully used not only on gasoline engines, but also on diesel ones. Installation is made either immediately behind the exhaust manifold, or before the muffler.

General design

This device consists of a carrier unit enclosed in a heat-insulating layer and a housing. It is necessary to consider in more detail the block carrier itself, since it is the most important element of the entire structure. This is the basis of the entire catalyst. It is made of ceramics, and having a special composition. The main property is fire resistance. And if suddenly the device is out of order, then a replacement of the catalytic converter will be required. Nobody is going to fix it.

Inside the carrier unit there are many cells and cells arranged longitudinally. They allow many times to increase the usable area of ​​contact with exhaust gases. In these honeycombs, there is a very thin layer of substance on the surface. The cost of the neutralizer is very high, since the active substances in it are precious metals. This is platinum, as well as rhodium and palladium.

Processes in the catalyst

With the help of catalysts, all reactions in the device are accelerated. For example, palladium and platinum are oxidation catalysts. With their help, all hydrocarbons are oxidized, which did not have time to burn out in the engine cylinders. The hydrocarbon is converted into pure water vapor. It also converts carbon monoxide into carbon dioxide.

But rhodium is a reducing catalyst. Nitric oxide NO 2 is dangerous for the environment. With the help of rhodium, it is converted into nitrogen that is safer for people and nature. From this we can conclude that when installing three catalysts, the content of several very dangerous substances in the exhaust gases decreases at once. Such neutralizers are usually called three-way. About what kind of catalytic converter malfunction you can expect will be discussed below.

Mounting

The block carrier is located in an iron case. There is a heat-insulating layer between the carrier unit and the housing. The lambda probe (oxygen sensor) is mounted directly into the catalytic converter housing. For the device to work as efficiently as possible, it must be at a temperature of at least 300 degrees. The reason is that it is at this temperature that more than 90 percent of all harmful compounds that are present in exhaust gases are retained. Of course, you should not allow overheating of the catalytic converter to develop, because this can easily cause the body to melt.

In order for the catalyst to warm up faster, it is necessary to take into account some properties so that when the engine starts, the maximum heating of the exhaust system occurs.

  • First, you need to mount the catalytic converter immediately behind the exhaust manifold.
  • Secondly, the first time after starting, you should make the exhaust gas temperature as high as possible. This is achieved by enriching the air-fuel mixture.
  • Thirdly, additional elements are used to warm up the exhaust gas catalytic converter. These are electronic filaments that increase the temperature to the required value and allow the device to start working faster in normal mode.

Causes of breakdowns in the exhaust system

The operation of the exhaust system of any modern car takes place in very harsh conditions. To a greater extent, the extremely high temperature that exhaust gases have has an effect on the life of the catalytic converter. In addition, the impact of the environment is great. All components of the structure are very vulnerable.

They are not protected by any elements, so if you drive carelessly, you can easily damage them. Unfortunately, certain malfunctions in the exhaust system can sometimes appear. The muffler itself may become unusable. Often the catalytic converter breaks down. The most common failure is in two lambda probes located before and after the converter.

Catalyst failure

In any modern car there is a self-diagnosis. With its help, total control of all elements of the engine and exhaust system is carried out. In particular, the catalytic converter is diagnosed. To determine how well this device works, there are two lambda probes. One is mounted before the converter, the second - after. In the event that there is any deviation from normal functioning, the driver will see the Check Engine warning light on the dashboard.

In this case, a code is written in the central control unit that corresponds to this breakdown. If the GAS catalytic converter has become unusable, then there will be obstacles for the exhaust gas. An immediate change in engine performance will be noticeable. Power will be lost, the speed will become unstable, the dynamics seem useless, and the consumption of gasoline or diesel will increase several times. If suddenly you smell a rotten egg in the cabin, then this directly indicates that the catalytic converter has become unusable. It only needs to be changed, repaired or restored to no avail.

Oxygen sensor failure

The lambda probe breaks down much more often than the entire catalytic converter (its resource is 2-2.5 times less). During operation, either one or two sensors may fail. There may be several reasons for this. For example, there is a breakdown of the heater. Perhaps the ceramic tip burned out or became covered with dirt, or destruction, oxidation of the connecting contacts occurred. The service life of the lambda probe depends on the quality of gasoline or diesel, on the presence of oil in the exhaust gas, on the adjustment of the ignition timing.

Its resource is no more than 80 thousand kilometers. Car self-diagnosis allows you to detect a malfunction of the lambda probe. The Check Engine warning lamp comes on when the oxygen sensor fails. You may also notice that the engine is unstable at low speeds, the dynamics are reduced, fuel consumption increases. But you should not immediately sin on the lambda probe, since breakdowns in the injection and ignition systems are accompanied by similar signs. It is better to contact a diagnostician, since it is expensive to replace a catalytic converter, the price, together with work, will be 8-12 thousand rubles.

Many people ask what a catalyst is and what it serves for only after they are informed in the service about the malfunction of such a part. So in this article, in simple terms, we will try to talk about what a catalyst is, why it is so expensive and what can be done if the catalyst is out of order.

What is a catalyst and how does it work.

A catalyst (or catalytic converter) is a part of the exhaust system that reduces the content of harmful substances in exhaust gases. Such as, CO (carbon monoxide), CH (hydrocarbons) and NO, NO2 (nitrogen oxides). All of these are poisonous and are one of the components of smog. So, a catalyst is an element containing noble metals, which, reacting with harmful substances, “burn out” them to environmentally friendly standards.
Inside the catalyst housing is either a ceramic or metal honeycomb structure on which a thin layer of a platinum-iridium alloy is deposited. The honeycomb structure in the catalyst is necessary to increase the contact area of ​​the exhaust gases with the surface on which the catalytic layer is deposited. As a result, a chemical reaction of oxidation of CO and CH occurs, and at the output we get completely harmless CO2 and N2.

Why and how the catalyst fails.

Under normal conditions, the catalyst fails after the catalytic layer burns out. And then to say that he was out of order is not entirely correct. More correctly, due to a decrease in the area of ​​the catalytic layer, the catalyst cannot burn out all the exhaust gases, and therefore the level of harmful gases at the outlet gradually begins to increase. When the value passes the threshold value that is set in the vehicle control unit, the “CHECK” error will light up on the instrument panel, and when decrypted, it will give the error “Inefficient operation of the catalyst”. Typically, the catalyst resource is designed for 100 t.km.
Information about the state of the exhaust mixture after the catalyst is provided by the lambda probe located behind the catalyst.
In addition, the catalyst can fail much earlier if the ignition system or the mixture formation system malfunctions. Then the honeycombs are simply clogged, not allowing the catalyst to oxidize the mixture. Also, premature failure of the catalyst can occur due to the poor quality of gasoline, which contains a lot of tetraethyl lead (to artificially increase the octane number). In this case, part of the catalytic layer is simply covered with a layer of tetraethyl lead, which prevents the catalytic layer from working properly.

What to do if the catalytic converter fails.

It needs to be changed. Most often, dealers refuse to change this under warranty, citing that it is because of the poor quality of gasoline that you refueled. And they offer to change this part. This is where the fun begins. The cost of the original catalyst ranges from 35 to 150 thousand rubles. However, there is no full warranty for this item. Why is the catalyst so expensive? Here you need to understand that on modern cars, the entire exhaust pipe is called a catalyst - a rather complicated part, including the exhaust manifold, complex flange connections, most often the corrugation and the catalyst barrel itself. It is clear that such a detail is very complex and expensive to manufacture. In addition, the catalysts contain precious metals that are expensive in themselves. Add more special conditions for customs clearance of parts with precious metals and such a “cosmic” price will come out. And at the same time, it doesn’t matter to the dealer that of all these elements, only the catalyst has failed. Therefore, specialized services offer alternative catalytic converter solutions.
- Universal Catalyst Installation. The universal catalyst is directly the catalyst barrel itself. It is welded into a regular part, instead of a failed catalyst. Those. it is precisely that part of the exhaust system that has failed that is replaced, and not the entire exhaust pipe. This option is more correct and much more budgetary 10-16 tr. depending on the dimensions and requirements for the catalyst block.
- Replacing the catalyst with a flame arrester. This work generally removes the catalyst from the system. Instead of a catalyst, a flame arrester (pre-resonator) is installed, which does not clean the exhaust gases, but only “levels” the exhaust flow, removing extraneous sounds that will occur if you simply remove the catalyst.

Pros and cons of catalytic converter replacement options.

When installing universal catalyst there is only one drawback. The universal catalyst, like the original one, is very dependent on external factors. Therefore, it is impossible to give a full guarantee on it. Usually they serve 60-80 t.km, but they can fail even earlier if a failure occurs in the ignition system or in the engine operation system.
The flame arrester does not depend on the operation of the engine, but the exhaust gases will not be environmentally friendly. Which will lead to air pollution. In addition, there will be difficulties during the inspection.

CONCLUSION:
It is preferable to install a universal catalyst:

  • If the car is under 5 years old
  • If you pass inspection yourself
  • If you don't want to pollute the atmosphere
  • If you are planning to travel abroad

In other cases, a more preferred option with a flame arrester.

Most car owners are interested in the question of what a car catalyst is and what function it performs only after a malfunction of this part is detected. In the proposed article, we will try to explain in an accessible language why a catalyst is needed in a car, why it has a high cost and what to do if the mechanism fails.

Approximate location of the catalyst in the car

The catalytic converter (catalyst) is an integral part of the exhaust system, which is responsible for reducing the concentration of harmful substances in the exhaust gases. These are CH (hydrocarbons), NO2 and NO (nitrogen oxides), CO (carbon monoxide). They are poisonous and are part of the smog. The task of the catalyst is to first heat up from the exhaust gases, and then burn the harmful substances and bring the exhaust up to the established environmental standards. Inside the device is a metal or ceramic structure in the form of honeycombs. A layer of a special platinum-iridium alloy is applied on top of it. The honeycomb structure is necessary to increase the contact area of ​​the exhaust gases with the plane that has the catalytic layer. An oxidation reaction of CH and CO occurs, and as a result, harmless N2 and CO2 are obtained.

Causes of catalyst failure

During normal operation, the device most often begins to malfunction as a result of the combustion of the catalytic layer. A decrease in the area of ​​this layer contributes to the fact that the catalyst ceases to burn the exhaust efficiently and the level of emissions of harmful substances begins to increase. When the value becomes greater than the value set in the control unit, the CHECK ENGINE light on the instrument panel will light up. When diagnosing, it will be possible to see that the error stored in the ECU means "inefficient operation of the catalyst." The resource of the device is approximately designed for 100,000 km. Data on the state of exhaust gases is issued by a special lambda probe sensor, which is located behind the catalyst.

Often a flame arrester is installed in place of a faulty catalyst.

Malfunctions in the mixture formation and ignition systems can also affect the premature failure of the catalyst. In this case, the cells become clogged, which does not allow the device to fully oxidize the mixture. Also, poor quality gasoline can be the cause of a malfunction. Such fuel contains a large amount of tetraethyl lead, which is added to artificially increase the octane number. It turns out that part of the catalytic layer is covered with tetraethyl lead, which disrupts the correct operation of the device.

How to deal with a faulty catalytic converter

The catalytic converter cannot be repaired and must be replaced. Dealers often refuse to replace under warranty. They justify this by saying that the device failed due to the use of low-quality gasoline, and they offer to install a new part. The cost of the original catalyst is 35-150 thousand rubles. Also, no one provides a full warranty for the device. Why is a catalyst so expensive? It should be understood that this device on modern cars is a complex part, which consists of flange connections, an exhaust manifold and a tank. Of course, such a mechanism is expensive and rather complicated to manufacture. Precious metals are also present in the catalysts, and they themselves are very expensive. Taking into account the special conditions of customs clearance, and as a result, an exorbitant price is obtained. Specialized car workshops offer several alternatives in case of a catalytic converter failure:

A faulty catalytic converter cannot be repaired, it is simply thrown away

  1. Installation of a universal catalyst. Such a device is the catalyst barrel itself. It is welded into the exhaust system instead of a faulty catalyst. It is the failed part that is replaced, and not the entire tube. This is a more correct and profitable option, which will cost from 10 to 16 thousand rubles, depending on the required dimensions and characteristics.
  2. Installation of a flame arrester. In this case, the catalyst is completely dismantled from the system. Instead, a preliminary resonator (flame arrester) is installed. However, it does not clean the exhaust gases. The device stabilizes the exhaust flow and removes unwanted extraneous sounds.
  3. There is another extremely cheap, but not environmentally friendly option - to put a snag of a lambda probe. It can be either a spacer that moves the sensor away from the exhaust gases, or a small circuit of a capacitor and a resistor. This circuit distorts the readings from the oxygen sensor in such a way that the control unit sees a perfectly clean exhaust, while anything can be done with the catalyst itself, it may even not exist at all.

How does an engine work without a catalyst?

A lambda probe (oxygen sensor) is required to determine the oxygen concentration in the exhaust gases. Efficient operation of the internal combustion engine is ensured by maintaining a stable ratio of fuel and air in the system. This is possible through the use of an oxygen sensor, which is located in the outlet. The process of controlling the oxygen content in the exhaust is called lambda regulation. Often two sensors are installed: in front of the converter and behind it. The sensor installed in front of the catalyst sets the optimal ratio of fuel and air for efficient engine operation.

Catalyst system with two lambda sensors

Among motorists there is an opinion that the sensor installed after the catalyst is only needed to determine the malfunction of the catalyst. This is true, but what will happen if the catalyst is removed, and how will the control unit react to this? Imagine the situation that the catalyst had to be dismantled. In this case, the second sensor will detect a malfunction and automatically begin to reduce the temperature in the combustion chamber. The system can perform such an operation only by adding fuel. As a result, the mixture is enriched, engine power is reduced, and fuel consumption increases. In other words, the control unit starts to work in some emergency mode and prepare the appropriate average mixture, so long as the engine runs without trying to set the optimal fuel supply mode.

It is possible to prevent excessive fuel consumption by returning engine operation from emergency mode to normal. The defective catalytic converter should be replaced and the electronic control unit reprogrammed to EURO2 mode. Well, or as already mentioned, you can put a special snag on the second oxygen sensor.

The work of the exhaust system of the car is provided not by one device, but by several. One of them is the catalytic converter. In this article we will talk about what is a converter and what is its role in the exhaust system of a car?

Purpose and device of the catalytic converter

The catalytic converter is installed in the exhaust system of the car and is used to reduce the toxicity of the exhaust gas as much as possible. The use of this device is carried out on both diesel and gasoline engines and is mandatory for all vehicles equipped with an internal combustion engine.

The modern design of the neutralizer is a special carrier unit, a device housing and thermal insulation. The main element is the carrier block, which is made of special refractory ceramics. Inside the block is a large number of cells (or, in other words, cells). This design allows you to significantly increase the contact area of ​​the working parts of the converter with exhaust gases. The surface of the cells is covered with a special layer of catalytic substance. Rhodium, platinum or palladium can be used as a neutralizer.

The essence of the catalyst is as follows. The car engine cannot ensure complete combustion of fuel and sends a large amount of harmful gases to the car exhaust system. Once in the catalytic converter, harmful gases come into contact with the catalytic layer and are oxidized. In the process of passing the exhaust gas throughout the carrier unit, harmful substances are oxidized to the end, and the output is the most common carbon dioxide.

The use of three metals ensures the complete oxidation of three different substances. In addition to carbohydrate and carbon monoxide, the exhaust gases may contain nitric oxide, which also undergoes complete oxidation and turns into ordinary harmless nitrogen. Thus, the exhaust gas becomes less harmful and has less negative impact on the environment.

The carrier block itself is usually placed in a metal case, which protects the converter from mechanical influences, for example, bumps on the unevenness of the road surface. A layer of thermal insulation is laid between the block and the body to prevent heat transfer to the body. The use of thermal insulation is associated with the features of the converter. The fact is that a high temperature is necessary for the successful oxidation of harmful substances. The lowest temperature for successful afterburning of exhaust gases should be within 300 degrees Celsius. For sports cars, this parameter can reach 1500-3000 degrees Celsius. Thermal insulation allows you to maintain the temperature within the specified limits and ensures the normal operation of the catalytic converter.

An oxygen sensor is installed inside the block. This electrical device tells the driver when the catalyst needs to be replaced. If the cells become clogged or the ceramic layer becomes smaller, the sensor is triggered and sends a signal to the electronic engine control unit, which puts the engine into emergency mode and signals with a lamp on the instrument panel that it is necessary to check the health of the systems. Often, in order to get rid of premature and accidental activation of the sensor, a special converter trick is created, which tells the sensor that the catalyst is still normal. This is due to the fact that the replacement of the catalytic converter is very expensive, and not every driver can afford such a repair. So, most drivers just roll the old part to exhaustion and change the converter later.

In addition to thermal insulation, it is possible to regulate the operating temperature of the neutralizer not only with the help of thermal insulation. The installation location can also affect the temperature of the converter. So, for example, to increase the temperature of the catalyst, it is placed directly behind the exhaust manifold, since the latter has a high heating rate and temperature.

Another condition for the successful operation of the converter is an increased enrichment of the air-fuel mixture.

Video - What kills the gas neutralizer?

Diesel engine converter

The use of converters in diesel engines has become inappropriate. The fact is that the operating temperature of a diesel engine is lower than that of a gasoline internal combustion engine, which means that the catalyst will not be able to cope with the task. Automotive experts have developed a device that injects urea into the exhaust system before the exhaust gases reach the catalyst. This approach allows you to speed up the oxidation process and clean the exhaust of the car as much as possible. Ultimately, more water vapor comes out of the pipe than combustion products.

Let's summarize. The catalytic converter is the main part of the exhaust system and is designed to clean harmful exhaust gases. Operation of the vehicle without this device is prohibited and contrary to environmental laws.

How many cars are there in the world today? Experts say that the number of passenger vehicles is more than 1 billion units, and every year the indicators of harmful substances emitted into the atmosphere are growing. In order to protect themselves from toxic emissions, all cars since the middle of the twentieth century have been equipped with catalytic converters.

Automotive exhaust catalysts have been installed in exhaust systems since the early 1970s. Around the same time, the first standards for the content and chemical composition of harmful substances in engine exhaust gases were developed.

Catalysts are installed on all exhaust systems of modern cars with an internal combustion engine and serve to reduce emissions of harmful substances into the atmosphere.

Since high temperatures are required for its operation, such elements are always installed immediately after the exhaust manifold or are built into the vehicle manifold itself.

The flame arrester is a steel corrugated pipe, insulated with a special non-combustible material (mineral wool or metal shavings), the whole structure is enclosed in a casing. As the flame arrester passes, the exhaust gases expand and fill the space between the casing and the pipe. Colliding with non-combustible materials, they lose some of their energy.

Replacing the catalyst with a flame arrester: the pros and cons

Obviously, by installing a flame arrester instead of a catalyst, one cannot talk about the full replacement of one node with another. First of all, the installation of flame suppression equipment instead of catalysts will affect the amount of emissions.

It is not recommended to install a flame arrester instead of a catalyst if the car moves within the European Union. In Europe, catalysts are subject to mandatory replacement after 100 thousand kilometers, regardless of their condition.

Installing a flame arrester will help stabilize the exhaust system, lower the temperature of the exhaust gases, but will not solve the problem. On the other hand, flame arresters are cheaper than new catalysts, and in terms of budget savings, this is an almost ideal way to debug an exhaust system.

One of the compromise solutions will be to find and install a universal catalyst. The cost of such elements is several times cheaper than the original ones, but it will also ensure the regular operation of the engine, in compliance with environmental standards. You will probably still have to adapt the firmware for the new exhaust and test the operation of the entire exhaust.

Car owners who have installed such a device on their motor can safely pass inspection and be confident in the environmental friendliness of their vehicle.

If you have any questions - leave them in the comments below the article. We or our visitors will be happy to answer them.