Exhaust system: the device, the principle of operation, repair

The design of the car uses a lot of systems - cooling, oil, injection system and so on. But very few people pay attention to the exhaust. But this is no less important component of any car. Over the years, the design of this system is being improved. About what the car's exhaust system consists of and how it works, we'll talk in our today's article.

Appointment

As is known, the ignition of the mixture occurs in the engine during operation. This ignition is accompanied by a characteristic sound. In the explosion, a colossal pusher energy is formed. It is so great that it can lift the piston to the top dead center. The last step of the work is the release of gases. They pressurize the atmosphere under pressure. But why do we need an exhaust system? It serves to extinguish sound vibrations. After all, without it, the work of even the most technological engine would be loud and unbearable.

Thus, the exhaust system performs the following functions:

• Output of combustion products from the cylinders of the engine.
• Reduction of the level of toxicity of gases.
• Excluding the ingress of combustion products into the interior of the car.

Device

This system combines several components. In addition, it is directly related to the operation of the timing. So, the classic exhaust system of VAZ consists of:

• The intake pipe.
• Catalyst.
• Resonator.
• The muffler.
• Various fastening and sealing elements.
• Oxygen sensor.

If we consider diesel cars, then the design will also have a particulate filter. What are all these elements? The device of each of them will be considered below.

Receiving tube

This element is the first in the list and goes right after the exhaust manifold. In the intake pipe are still not cooled gases. Therefore, the temperature can reach 600 or more degrees Celsius. In the common people, the intake pipe is called "pants" for its characteristic shape. This element is made of especially durable and fire-resistant metal. Usually it is rough (rusting over the years), but on more expensive cars it is made of stainless steel. If it is an engine with a large volume of the combustion chamber, several such pipes can be used in the system design. This is done to reduce the resistance of gases. Otherwise, the engine will "choke" its own gases.

Resonator

It is made in the form of a cylindrical can. It is in the resonator that the first separation of the exhaust gas flows. Also, by increasing the diameter, the speed of the exhaust is reduced. Gases are gradually dissipated in this chamber. Due to this, vibration and partially sound are extinguished. As well as "trousers", the resonator is made of fire-resistant metal.

Catalyst

This, perhaps, is the most complex and expensive component in any exhaust system. The body of this element is also made of fire-resistant metal. However, unlike the resonator and the receiving tube, it is multilayer. Inside this "jar" there is a ceramic rod. In addition, the catalyst is equipped with a wire mesh. It covers the second element of the ceramic material. In addition, the device has a layer of thermal insulation with double walls. Why is the catalyst so expensive? In addition to ceramics, expensive materials such as palladium or platinum are used here. It is these components that convert harmful gases into hydrogen and safe vapors. In view of this, the minimum cost of the new neutralizer is 40 thousand rubles.

Diesel particulate filter

If we consider the device of the exhaust system of a diesel engine, it is worth noting this element. It is in addition to the catalytic converter. At the heart of the filter is a matrix made of silicon carbide. It has a cellular structure and has channels of small cross section. The latter are alternately closed from one side and the other. The lateral part of the element plays the role of a filter and has a porous structure.

Until recently, the matrix cells had a square shape. Now manufacturers use 8-coal cells. So the best capture of soot and settling it on the filter walls is made. How does this element work? The particulate filter operates in several stages. At the first, soot filtration takes place. Gases fall into the element, and harmful substances settle on the walls. The second stage is regeneration. She may be:

• Passive.
• Active.

In the first case, harmful gases are purified by passing through the ceramic element. In the second, a special liquid is added - AdBlue. Usually such a system is used on trucks. It allows you to reduce the toxicity of emissions by 90 percent. In the machine there is a separate tank for this liquid, and the system after injecting the corresponding signal injects part of AdBlue into the catalyst. So, from the tube comes a practically clean exhaust, containing an atmosphere that is harmless to the atmosphere hydrogen.

Lambda probe

It is also called an oxygen sensor. Installed near the catalyst in a threaded connection. It is a sensitive element that comes in contact with exhaust gases. The task of the sensor is to determine the temperature of the gases and the presence of oxygen in them. Based on the read data, the ECU sends a signal to the intake manifold. If necessary, additional fuel is injected into the cylinders. What is it for? The fact that the catalyst is fully functional only at elevated temperatures (not less than 600 degrees). If the gases are colder, no filtration and conversion will occur. Therefore, the system adds more fuel so that the temperature of the catalytic rod is within the operating range. On the fuel consumption, this system has practically no effect (provided it is in good order).

Muffler

This is the most recent element in the system. Silencers are of two types:

• Standard.
• Sports.

The first are installed on all civilian vehicles. The design of such a silencer implies the presence of several metal partitions. Also in the body there is a perforated pipe, through which gases are sent from one partition to another. This scheme produces the greatest reduction in noise and vibration. The factory silencer is made of refractory metal. However, practice shows that its lifespan is an order of magnitude lower than that of sports. The reason for this is the absence of a nickel-plated surface and a too thin metal of entrails.

As for sport silencers, they have a simpler design. This is a straight pipe with a perforation, having an expansion in the middle and filled with glass wool. The exhaust pipes of this type of silencer are very large. As a rule, the straight-through diameter of the exhaust port is 1.5-2 times higher than that of the standard one. Thanks to this, a quick gas outlet and a good "exhaust" are produced. But why such mufflers are not installed on cars from the factory (with the exception of sports versions)? It's all about the level of their noisiness. As practice shows, such mufflers practically do not fight with damping of sound vibrations. Their task is to divert as much gas flow as possible in the shortest possible time. On the run, these mufflers emit a buzz, and when they dial, they start to "yell" even louder. Therefore, straight-through is not suitable for everyday comfortable driving. Although their design is more reliable and practical than that of "civilian" brethren.

Sealing elements

So, we have listed the main components of the exhaust system and their design. However, we did not talk about how they connect with each other. Fastening is made on bolts and collars. The receiver tube is connected to the exhaust manifold and resonator on two gaskets. Depending on the type of vehicle, the gasket can be manufactured from pressed corrugated foil or solid metal. Additionally, a washer can be used. As for the muffler itself, it connects to the resonator thanks to the clamp, overlapping. On some machines, a ring can be used (for example, at the domestic "eight"). For better compaction, experts recommend using a heat-resistant sealant (up to 1100 degrees). It perfectly compacts all the gaps and does not allow the gases under pressure to break out ahead of time.

Malfunctions of system of an exhaust

The main symptom is the characteristic sound of gas removal. The car starts to "yell", an unpleasant smell of petrol or diesel appears in the cabin. Also, the car stops driving normally. And if the exhaust gasket is worn out, the "Check" on the instrument panel will light up. It signals the malfunction of the oxygen sensor. Along with this, fuel consumption also increases (because the system can not accurately dose the fuel, as before). The way out is to replace the exhaust manifold gasket. Also inspect the condition of the pipes themselves. If they start to rot or there are cracks in the joints, an exhaust system repair is required. Rot is carved by a Bulgarian and a new sheet of metal is welded. But as practice shows, a more practical and quick way is to replace the obsolete element with a new one. Remember that the silencer is consumable. In 2-3 years it is subject to replacement. The same goes for the other elements, but their resource is slightly larger. For example, "trousers" burn after five years of operation.

About corrugation

The exhaust system (straight-through including, among others) can have a corrugation in its composition. It is an additional damping element. Thanks to it, the load on the remaining parts of the exhaust system is reduced. The sound of the gas outlet becomes quieter. But it is worth noting that the corrugation in the exhaust system is the lowest-lying element. In view of this, the owners often damage it. Repair is not subject to corrugation. They change it or weld a piece of a new pipe into its place. As practice shows, the noise level practically does not increase after such repair. The main thing is to achieve maximum tightness in the sealing elements. After a burnt gasket can become a serious cause of deterioration in the performance of the car.

Conclusion

So, we have considered the installation of the exhaust system and its main malfunctions. Finally give a little advice. When removing the particulate filter or catalytic converter, it is worthwhile to worry about removing the oxygen sensor. If this is not done, the engine will "overfill" - the fuel consumption will increase and the error on the instrument panel will light up. After removing the catalyst (it is changed to a flame arrester), a new firmware is injected into the ECU. And replace the sensor with a plug.