Many car enthusiasts have no idea how important a car's exhaust system is in trouble-free operation. power unit, and do not pay due attention to its maintenance, as a result of which, engine failure may occur. It is for this reason that you should carefully read the principle of the exhaust system, its design featuresand know what the exhaust system is made of.

Engine running internal combustion an important role is given to the timely removal of exhaust gases outside, which begin to accumulate in the combustion chamber of the cylinder head immediately after ignition fuel mixture... This task is designed to perform exhaust systems, or, as motorists say, mufflers, which are equipped with all modern cars... The proper operation of the exhaust system, aimed at removing the residues of the spent fuel mixture from the engine, entirely depends on the serviceability of all its constituent elements, which have some structural differences depending on the type of engine.

How the exhaust system works

The modern car exhaust system consists of several parts, in contrast to the first devices, which looked like a mechanical valve, which was forcibly opened by the driver of the car manually. All elements of the exhaust system, which are interconnected by means of fastening bolts through the flanges located at their ends, are intended for:

• exhaust from the combustion chamber of the engine exhaust gases and other unburned fuel mixture residues;
• reducing the noise emitted by the motor during operation;
• reducing the amount of toxic substances in the car exhaust;
• preventing entry into the salon vehicle toxic gases.

The device of the car's exhaust system has a rather simple principle of operation, which involves the removal of exhaust gases from the combustion chamber, passing them through pipes to the rear of the vehicle, while reducing the noise emitted by the engine due to the tightness of the entire structure and connections through flanges with heat-resistant seals.

Reducing the amount of toxic substances in the exhaust gases is achieved through the use of catalytic converters (catalysts) in the design of the exhaust system, the performance of which is monitored by a special sensor called a lambda probe. In modern diesel cars, to improve the environmental performance of the exhaust, manufacturers use particulate filter, which is also equipped with the diesel exhaust system.

In construction diesel engineas well as modern gasoline unitA turbocharger is often used, which uses an air mixture of oxygen and exhaust gases taken from the exhaust manifold to feed the combustion chamber. The amount of exhaust gases entering the turbine is regulated by a sensor located on the exhaust manifold housing.

The device of the structure and the purpose of its components

The parts that make up this structure have different functional loads and their own designations, reflecting the stages of their work. The very scheme of the exhaust system and the names of its parts are as follows:

1. exhaust pipe;
2. catalyst or otherwise catalytic converter;
3. resonator or flame arrester;

The exhaust manifold is a hinged type of equipment of the power unit, and is designed to receive exhaust particles and gases of the fuel mixture from the combustion chambers of each of the cylinders, and is made mainly of ceramics, cast iron alloys or stainless steel with increased thermal stability.

Downpipe, referred to by motorists as "pants", because of the similar appearance, is designed to combine several streams of exhaust gases into one, and for their further advance to the catalytic converter (catalyst). The pipe is often equipped with a so-called corrugation, with the help of which vibration is damped, transmitted to the entire structure of the exhaust system by a running engine.

The catalyst is a ceramic honeycomb, the surface of which is covered with a layer of an alloy of platinum and iridium, which allows exhaust gases to enter into a chemical reaction with them, resulting in their separation into oxygen and nitrogen oxide. The released oxygen in the catalyst helps to burn the remaining fuel mixture more efficiently, as a result of which exclusively nitrogen-deoxide-carbon mixture is supplied to the muffler. The operation of the catalytic converter is controlled by a special lambda probe, transmitting a signal to the control unit of the vehicle's power unit. A similar sensor is installed on the exhaust manifold to analyze the toxicity indicators of the exhaust gases entering the catalyst.

The resonator or flame arrester is designed to lower the high temperature of the exhaust exhaust gases, which is achieved through its cellular internal structure. The last detail in the design is the muffler, whose task is to reduce the noise of the running engine due to the perforated pipe inside its housing.

All components of the exhaust system are connected to each other through flanges using fastening bolts and heat-resistant seals, which are responsible for the tightness of this structure, without which full-fledged operation of the engine of a modern car is impossible.

Possible malfunctions, methods of their elimination and tuning options

The design of the exhaust system is ideal option for car tuning vehicle, thanks to the ease of installation component parts and the presence of a large assortment of various parts. The most common option for tuning a muffler is the installation of the so-called direct-flow exhaust, when the resonator is removed from the system.

The most frequent malfunctions of the exhaust system are associated with the loss of tightness of parts or their connections, the seals in which can be severely worn out. To replace sealing elements, it is necessary to purchase a repair kit for the exhaust system, and by unscrewing the mounting bolts, change them to new ones.

Parts of the exhaust system made of various metal alloys are exposed to significant heating, sudden temperature changes, and work under conditions of increased stress, as a result of which they are exposed to heavy wear and burnout of internal parts. Determining these breakdowns will allow the loud noise of a running engine and visual diagnostics of the exhaust system, after which, the damaged structural part must either be replaced with a new one, in case of internal malfunctions, or its body must be repaired using electric / gas welding.

IN modern cars the operation of the power unit is controlled by the control unit, which receives certain signals from numerous sensors located on all its structural units. In the design of the exhaust system, there is a sensor called a lambda probe that measures the amount of toxic substances in the exhaust gases. Its malfunction or incorrect operation can only be detected by the diagnostic stand, after which the sensor must be replaced.

03 Mar

What is a muffler in a car

In this article, we will consider the topic of a muffler in a car, the purpose and device, for sure all drivers understand that the recipe for quiet or quiet operation of the engine lies precisely in the quality and method of implementing the muffler in the car. And here's how it all works and what, more additional functions performs a car muffler and we will talk below.

Silencer in the car device and purpose

What is the main function of the muffler - it removes the exhaust gases from the car engine and at the same time reduces the sound of the engine and the sound of the exhaust gases by converting sound energy into thermal energy.

Car muffler device

The device of all mufflers is approximately similar and includes the required elements:

• Expansion and narrowing of the flow of exhaust gases, the so-called throttling, due to which the speed of the exhaust gases and the frequency of sound waves change
• The superposition of sound waves on top of each other due to which their amplitude changes - interference
• Absorption and dispersion of sound waves - there is a conversion of sound energy into heat, due to which there is a very significant reduction in the sound of the outgoing exhaust
• Reusable change in the flow of outgoing gases, the so-called labyrinth, also serves to reduce the rate of gas exit, its energy and conversion into thermal energy

Cutaway muffler

Let's see a sectional view of the car muffler device in this photo,

Here we see whether the muffler elements are required, or, so to speak, what the car muffler consists of:

1. Exhaust manifold (popularly called pants or spider for the similarity in design)
   
2. Flame arrester or resonator
   
3. Connecting pipes between silencer chambers
   
4. Silencer main frame
   
5. And the actual exhaust pipe itself
   

• Exhaust manifolds are pipes that are directly attached to the engine outlets to actively extract exhaust gases directly from the car's cylinders, so temperatures at the junction of the manifold and the engine can reach values \u200b\u200bof 1000 degrees Celsius
• Therefore, the requirement for the exhaust manifold is always high, this is the mandatory thermal stability of the material and strength in relation to mechanical stress, because of which the manifold is often made of cast iron or heat-resistant steel.
• The resonator of a muffler, as a rule, is a pipe with holes of different diameters drilled in it, which is located in a closed chamber due to the expansion and release of gases through the holes of this pipe and their resonance occurs, in fact, the damping of oscillations and changes in the oscillatory circuit of the sound wave
• The main muffler is essentially like a multi-room apartment, only the rooms are not connected there by doors and hollow pipes, and sometimes, in order to get into another room, the exhaust gases have to pass through pipes from other rooms back and forth several times - this is done to extinguish the energy of the gas and convert it into heat energy, because of this transformation of energy and there is a decrease in the sound wave

Well, I think that we answered the question of the muffler in the car, the purpose and the device, and now you have at least an idea of \u200b\u200bits structure.

Car muffler repair

As a rule, Hyundai Santa Fe or any other car comes down to welding rotten holes in the main muffler, as a rule, only fierce enthusiasts are taken to digest the internal parts. Yes, and there is no point in digesting the insides on the old muffler as such. Because the metal is already tired from the sound and temperatures and has become, so to speak, loose and rotten, therefore it is easier to buy a new muffler. But, and there everyone looks, of course, according to their financial capabilities and mood of the soul.

Here is another photo of a car muffler diagram, so to speak, for completeness of understanding, here two types of muffler are clearly visible, an ordinary muffler and a straight-through muffler, as you understand in a straight-through, because of its device, the sound will be much louder, since there are no extinguishing chambers for sound

Do-it-yourself soundproofing of a car muffler

There is no consensus among the drivers in the sound insulation of the muffler, and this is understandable, here, as they say, a stick of two ends, on the one hand, the noise insulation of the muffler will reduce the level of noise vibrations, but on the other hand it will create overheating of all parts of the muffler.

Basically, materials such as asbestos fabric or more modern heat-resistant and vibration-resistant materials are used for noise insulation of the muffler.

The sound insulation itself is usually reduced to wrapping all parts of the muffler with this heat-resistant and sound-absorbing material.

Some craftsmen even wrap the exhaust manifold of the car's muffler, which also raises a lot of questions, both for overheating of the manifold itself and the difficulty in cooling part of the engine at the junction of the exhaust manifold with the engine. Here it is worth weighing the pros and cons of such a procedure. But the fact that there will be a large overheating of the entire muffler due to its winding noise with insulating materials is one hundred percent.

How to paint a car muffler

Sometimes some car owners wonder how to paint a car muffler, this is usually due to two reasons

1. The desire to hide the rust on the muffler
2. Give beautiful stylish look car

In any case, paint for this type of work will be very expensive, since the main requirement for such a paint will be enormous heat resistance and the ability to withstand large temperature drops,
and even when buying such a paint, if it is used in the collector area where the temperature is 1000 degrees Celsius, it is unlikely that if it resists, it will not change its color from such high temperatures. Therefore, the very idea of \u200b\u200bpainting the muffler has a place to be, but as they say, at your discretion.

In order to fight the sound of a shot, it would be logical to understand what is the source of the sound when firing. And there are several such sources:

1) The sound of the weapon mechanism triggering, the striker hitting the capsule, the clang of the shutter, etc. On a quiet night in an open area, the sound of the impact of metal parts of the AK mechanism is clearly audible at a distance of up to 50m. That is why, when one absolutely silent shot is required, they use a single-shot weapon.

2) The sound created by the air in the barrel before firing, and displaced by the bullet and powder gases; sound created by expanding (from a pressure of about 200 kg / cm 2 to the usual atmospheric pressure of 1.9 kg / cm 2) and cooling (from hundreds of degrees to air temperature) powder gases at the moment of exiting the barrel, and these gases for the most part follow the bullet , but some of them still break through into the gap between the barrel and the bullet, and, therefore, outrun the bullet. It is with this cause of the sound that the muffler allows you to fight.

3) An acoustic shock wave that forms behind the bullet if it exceeds the speed of sound (~ 330 m / s). It occurs due to the fact that a bullet, passing through the air, creates waves in it, similar to those that arise on the water when a boat sails; the volume of these waves is not great if they move faster than a bullet; however, if the bullet moves faster, it seems to accumulate the energy of the wave following it, and therefore, to human hearing, it is perceived as a blow, something like thunder in a thunderstorm. The only way to get rid of this cause of the sound is to reduce the speed of the bullet, which can be achieved by using special cartridges with a smaller charge of powder or by shortening the barrel of the weapon.

4) The sound of a bullet hitting a target.

Now that we know the reasons for the sound of the shot, we can consider the principle of the silencer. The main task of the muffler is to reduce the pressure and temperature of the powder gases. In order to reduce the pressure, it is necessary that the gases have the opportunity to expand before contact with atmospheric air. It is for this purpose that the muffler chambers serve. Powder gases escaping from the barrel after it consistently lose energy in each such expansion-cooling chamber. It is clear that with an increase in the number of chambers, the pressure difference between the outlet gas and the outside air becomes smaller and, accordingly, the sound decreases. However, this reasoning is true only for the gases following the bullet. And as it was said, some of the gases are ahead of it. Since the diameter of the bullet holes in the baffles is larger than its own diameter, this part still flows out of the muffler at supersonic speed, creating a ballistic shock wave. To cut off and slow down supersonic gases, instead of diaphragms with holes, for example, membranes of elastic material with slots that let the bullet pass and close again are used, or blind gaskets are installed - shutters.

The simplest homemade muffler - usual plastic bottletaped to the trunk with duct tape. At the moment of the shot, all the powder gases will be in the bottle, and the bullet, breaking through the bottom, will fly out. Despite the bulkiness and reduced firing accuracy, such a silencer makes the sound of a shot from a small-caliber cartridge no louder than the crackle from a broken plastic ruler.

There are many different designs of mufflers that use various tricks to reduce the temperature and pressure of the propellant gases. For example, the legendary "Bramit" in the version for the "three-line" was a cylinder with a diameter of 32 mm and a length of 140 mm, internally divided into two chambers, each of which ends with an obturator - a cylindrical gasket made of soft rubber 15 mm thick. The first chamber contains a cut-off device. Two holes with a diameter of about 1 mm each are drilled in the walls of the chambers for bleeding the powder gases. When fired, the bullet pierces alternately both obturators and leaves the device. The propellant gases, expanding in the first chamber, lose pressure and are slowly vented out through the side holes. Part of the propellant gases, which escaped with the bullet through the first obturator, expands in the same way in the second chamber. As a result, the sound of the shot is extinguished. A similar muffler with a large number of chambers was also developed for the Nagant revolver of the 1895 model.

A fairly typical example of a modern silencer is the domestic PBS, that is, the "Silent Shooting Device", which is screwed onto the muzzle of the barrel of AKM or AK-47 assault rifles. At some distance in front of the muzzle is a thick rubber washer. The leading gases are retained by it and through special channels are directed into the expansion chamber, from where they flow smoothly into the air. When the bullet pierces the washer, most of the gases follow; but, successively passing through several expansion chambers, these gases escape into the atmosphere, losing a significant part of the energy. PBS reduces the volume by 20 times. Therefore, a shot from an AKM is practically inaudible already at a distance of 200 m. The survivability of the PBS without replacing the washer is up to 200 shots, which is quite acceptable for special weapons. The disadvantage of this design is the aging of the rubber, and the spare plugs also age - even without being used in the muffler. Nowadays, there are literally innumerable options for multi-camera devices. Here is the device of one of the foreign silencers for a Kalashnikov assault rifle -

But along with the increase in the number of chambers and the complication of their configuration, the improvement of designs goes in a variety of ways. A bulky muffler body often covers conventional sights, so it is positioned eccentrically - the axis of the device is much lower than the axis of the barrel. But, of course, the channel for the passage of the bullet must be strictly aligned with the barrel, because even with a light touch of it against the internal partitions, the accuracy of the fire is sharply reduced. And the weakening of the attachment point of the device body on the weapon can generally lead to shooting through its front wall ...

The flat partitions of the expansion chambers are often replaced by convex ones - conical or of some other shape, which deflect the flow of powder gases to the peripheral part of the muffler, which prevents it from overtaking the bullet. The same effect is produced by a helical baffle that runs along the entire length of the device.

Sometimes the expansion chambers are partially filled with heat-absorbing material - fine aluminum mesh or simply shavings, copper wire. By heating them, the gases are cooled more actively. But these fillers are difficult to clean from powder carbon deposits, and they have to be changed periodically. The damping efficiency is also influenced by the material of the partitions themselves: for example, replacing steel with aluminum, more heat-conducting ones, gives a noticeable decrease in volume. However, with frequent shooting with such a silencer, as the pressure in the chambers increases and the heat sink heats up, the device's performance decreases sharply; if a dozen or two shots are fired from it in a row, the "silent" weapon turns into the most common one. Therefore, it is recommended to fire with single shots and with long pauses to allow the entire structure to cool.

Sometimes, to improve the operation of the muffler, it is pre-moistened with water. Literally a tablespoon is enough. In this case, the muffler is cooled due to the evaporation of water (the principle of operation of a frion in a refrigerator). Also, adding water to the muffler slightly changes the sound of the shot, from a metal "melon" to a more dull "tan". There is usually enough water for 10-20 shots.

The efficiency of the muffler is also increased by complex and meticulous calculations of the internal gas dynamics. For example, due to the use of curly partitions of a certain profile, countercurrents and turbulent eddies of gas are created in the chambers. As a result, its molecules, repeatedly colliding in different directions, extinguish each other's energy.

Original designs have been developed providing for the reflection of the gas flow from the inner surface of the front wall of the muffler. After that, the energy of the gases decreases due to multiple reflection and counter-damping of shock waves inside the housing. Such devices can also be multi-chamber.

A completely exotic device has also been invented, which looks ridiculously primitive outwardly: just a muzzle cone-diffuser enclosed in a tube with open ends. But a very significant reduction in sound is provided here by a virtuoso calculation of the interference of shock waves inside the cone, and most importantly - by a surprisingly ingenious way of cooling the powder gases. Breaking out of the cone, they intensively eject the external air, as if instantly sucking it out of the inner volume of the tube, which causes a sharp drop in its pressure and temperature. And gases, mixing with this rarefied cold air, immediately lose energy. So, probably, a shot would have sounded somewhere at a twenty-kilometer height ...

The simplest muffler 1 - rubber membrane with a gap 2 - expansion chamber 3 - connecting nut	Silencer with reflector reflector 1 - parabolic reflector 2 - case 3 - nut 4 - trunk
Multi-chamber muffler 1 - camera 2 - partition	Double chamber eccentric muffler 1 - camera 2 - partition
Silencer with preliminary removal of powder gases from the bore 1 - hole in the barrel with a return channel 2 - front multi-chamber part of the muffler 3 - expansion rear chamber	Silencer with obturation 1 - spacer sleeve 2 - rubber (ebonite) obturator 3 - expansion chamber
Multi-chamber muffler with heat-absorbing filler 1 - nut 2 - wire mesh

The design of the muffler, despite the seemingly great work it does in suppressing such a powerful sound from the engine, is actually quite simple: inside the muffler you will find a deceptively simple set of pipes with holes made in them. These tubes, along with special chambers, are actually arranged as a finely tuned musical instrument, which today not only muffles the engine, but also creates a special sound that is pleasing to the hearing of many motorists, especially when used on sports cars.

Cutaway muffler

Thus, mufflers are designed to reflect the sound waves produced by the engine in such a way that they (the waves) partially suppress themselves. Silencers use technology that is subtle enough to suppress this noise. So how does a muffler work? Let's figure it out! But first, we need to learn a little more about the physics of sound.

The location of the muffler in the car relative to the entire exhaust system

About sound

Sound waves are formed from pulses of alternating high and low air pressure in the engine cylinders. These pulses make their way through the air at the speed of sound. These impulses are generated in the engine at the time when the exhaust valve, and the exploded mixture of fuel and air under high is suddenly released into the exhaust system. Molecules in this gas collide with molecules in the pipe under lower pressure. They, in turn, collide with molecules further down the pipe, resulting in this sound. Thus, the sound wave travels down the exhaust system (more precisely, from front to back) much faster than the exhaust gases come out of it.

When these pressure pulses reach your ear, they act on the eardrum, causing it to vibrate. And your brain interprets this movement of the membrane as sound. Two main characteristics of a wave determine how we perceive such sound:

1. Sound wave frequency - more high frequency waves simply means that the air pressure fluctuates faster. The faster the engine runs, the higher the tone we hear (let's remember the humming of Formula 1 cars or high speed sport motorcycles). Slower vibrations sound a lower pitch (the most characteristic sound is made by engines, Harley Davidson motorcycle engines at idle or low rpm).
2. Air pressure level - The amplitude of the wave determines how loud the sound will be. Sound waves with large amplitudes of movement of our eardrums have more pressure, and we register this sensation as a larger volume of noise.

But it turns out that you can combine two or more sound waves together and get (!) A smaller sound. Let's take a look at how it works with a muffler device as an example!

The main feature of our perception of sound waves is that the resulting noise in our ear is actually the sum of all sound waves that reach the eardrum in one unit of time. If you, for example, are listening to any of Metallica's songs, then you can hear simultaneously playing on a drum kit and on three guitars in the form of a single combined music, but if you listen to any such song, you can hear several different sound sources (except except to distinguish between playing drums and bass guitar) - sound pressure waves, reaching the eardrum, are added together, so that your eardrum only feels one pressure at any given time.

And now the practical part of the muffler device in terms of sound suppression: the fact is that you can produce a sound wave that is directly opposite to another wave that is identical to it, and this is the basis for noise suppression - two identical waves simply either muffle each other, or form a wave with twice the amplitude. Take a look at the animation below. The wave coming from above and the wave in the middle are pure identical tones. If these two waves are in unison - that is, if they are superimposed on each other at the same frequency, then they form one wave, but with twice the amplitude. In science, this is called constructive interference. But, if they are superimposed on each other in opposite phases, when the lowest point of the amplitude of the first wave at one moment of time coincides with the highest point of the amplitude of the second wave, then they simply suppress each other down to zero sound. And this is already called destructive interference. While the first wave reaches its maximum pressure, the second wave reaches its minimum. If both of these waves hit the eardrum at the same time, then you would not hear anything, because these two waves always cancel each other out.

How does a muffler work from the inside?

A muffler is essentially a set of pipes. These tubes are designed to create a reflection of sound waves that interfere with each other and eventually counterbalance each other.

Exhaust gases and sound waves along with them (although, as we already know, much earlier) enter the muffler through the central exhaust pipe. They bounce into the rear wall of the muffler and are reflected through the hole in the main muffler. They then pass through a series of holes to another chamber where they are quenched again and exit through the last tube, leaving the muffler.

The second chamber is called resonator, which is connected to the first chamber through a hole. A resonator contains a certain volume of air and has a certain length, which is calculated with pedantic precision to obtain a wavelength that can compensate for a certain frequency of sound. How does this happen? Let's take a closer look at the muffler ...

Resonator

When the wave hits the muffler, part of it continues to go into the second chamber through the hole, while the other part is reflected. The wave propagates in the second chamber, enters the rear wall of the muffler, bounces off it and exits through the same hole again. The length of this second chamber is calculated so that this wave leaves the resonator only after the next wave is reflected from outside second chamber ( inside first camera). Ideally, part of the sound wave high pressure, which left the second chamber, will be damped by a part of the low pressure wave, which is reflected from the outer side of the wall of the second chamber, and it is these two waves that will balance each other.

The animation below shows how the resonator works in a simplified muffler:

In fact, the sound emanating from the engine is a mixture of different frequencies of sound, and since many of these frequencies are dependent on engine speed, the sound is almost never included in the correct frequency ranges to damp it perfectly. The resonator is designed to operate in the best frequency range, where the motor makes the most noise, but even if the frequency is different, it will still produce a significant amount of destructive interference.

Some cars, especially luxury ones, where quiet operation is a key feature, there is another component in the exhaust that looks like a muffler but is called resonator... This device works like a chamber resonator in a muffler - the dimensions are calculated so that the muffled waves then produce a certain "beautiful" sound at the output in order to surprise and delight those around them and, in fact, people in the cabin of such cars.

There are other features inside the muffler that help it reduce sound levels in different ways. The muffler body is usually made in three layers: two thin layers of metal and one thicker, slightly insulated layer in between. This allows the muffler to absorb some of the pressure impulses. In addition, the inlet and outlet pipes leading to the main chamber are perforated with holes. This allows thousands of tiny pressure pulses to be damped in the main chamber, "eating" each other to some extent in addition to being absorbed in the muffler.

Muffler Disadvantages and Other Muffler Types

One of the important disadvantages of a muffler is its resistance to the pressure that the engine exerts on it - this characteristic is called back pressure... Because of all the convolutions and holes in the muffler, the exhaust has to go a long way in order to eventually escape into the surrounding atmosphere. The mufflers described above produce a sufficiently high back pressure, which takes away a little engine power, because an open cylinder valve allows the burned out to escape, and this fuel comes out due to an explosion in adjacent cylinders, as we remember from the article on engine operation.

There are other types of mufflers that can reduce back pressure. One such type, sometimes called " glass unit", uses only absorption, not reflection, to reduce sound. In such a muffler, the exhaust pipe is directly connected to the intake pipe, which is perforated with holes. A layer of glass insulation is applied around this pipe, which absorbs some of the pressure impulses. The insulation is surrounded by a steel layer.

Muffler device - "glass unit"

Such mufflers also have a significant drawback: they produce much less back pressure, thereby only slightly "eating" the power of the car, but they do not reduce the sound level as well as conventional mufflers.

30 august 2017

During the ride crankshaft the car engine makes from 1.5 to 5-7 thousand revolutions per minute. Accordingly, 25–120 fuel flashes and micro-explosions occur in the cylinders every second. The result is energy that pushes the pistons, exhaust gases and powerful sound waves. To remove the loud rumble and noise from exhaust pipe, causing inconvenience to the driver and others, a sound-absorbing device was invented - a silencer. Since it does not last forever, it will be useful for motorists to know how the element is arranged and whether it can be repaired in the event of a malfunction.

Where is the item and what does it look like?

The main source of noise is the combustion chambers of a running engine. The sound waves generated there cannot penetrate through solid metal walls and tend to go out along the path of least resistance - through the exhaust pipe along with the exhaust gases. There a muffler is installed in the form of a round or oval metal barrel.

The scheme of the car's exhaust system looks like this:

1. A vibration-isolating corrugation is installed first behind the exhaust manifold. Its task is to smooth out the vibrations transmitted to the pipe from the motor.
2. After passing the corrugation, smoke and sound waves enter the catalytic converter... Its task is to burn off the remnants of combustible gases so as not to be thrown into the atmosphere. Inside the part there are small ceramic honeycombs that partially absorb and scatter sound.
3. After the neutralizer, the exhaust passes into the resonator reservoir. This is the first stage of noise suppression.
4. The last in the chain is a muffler, which finally dampens sound vibrations.

In fact, a resonator is also a muffler, you will learn its structure and principle of operation from the next section.

The resonator tank always stands along the axis of the car, and the muffler can be installed across (in the rear of the car). There are options when both elements are combined in a single body in order to save space. On cars with V-shaped engines high power, a distributed exhaust system for 2 pipes is installed. Accordingly, the number of all parts is doubled.

Design and principle of operation

There are 4 ways to suppress powerful sound impulses in different vehicles:

• limiting noise;
• reflection;
• resonant noise suppression;
• absorption.

The limiting device is the simplest version of the muffler used on some tractor models. The element is a tapered pipe placed inside a metal tank. The disadvantages of the product are obvious - the noise is partially suppressed, and the engine power is noticeably reduced.

Mirror elements are used on motorcycles and scooters. The principle of operation of the muffler is as follows: gases from the exhaust elbow enter the reflective can, change the direction of movement and are thrown out. The reflection dampens sound vibrations and reduces the noise level. The part functions successfully with two-stroke motorsbut its efficiency is not enough for a car.

The third method is implemented in automotive resonators. There are several partitions inside the steel tank, and resonance chambers connected by steel tubes are arranged between them. Smoothing noise pulses is achieved through two factors:

1. Gases and sound waves change direction of movement several times, reflecting from partitions.
2. The dimensions of the chambers and nozzles are designed in such a way that the frequency of sound vibrations coincides. Then the waves are damped due to the resulting resonance.

It should be understood that the design of the resonator is not universal for all machines. Cars are equipped with engines different poweremitting noises of different amplitudes and frequencies. The sound absorber is developed separately for each car make and model.

The device of a car muffler in section, acting on the principle of noise absorption, is shown in the diagram.

As in the resonator, baffles and bridges in the form of tubes are installed here. Only in the latter are many holes of various diameters (perforation) made, and non-combustible absorbent material is laid on the sides. As a rule, for these purposes, basalt or kaolin wool is used, which calmly withstands gas temperatures of 600-700 ° C.

Sound waves passing through adjacent nozzles with holes are partially scattered and damped by superimposing one another. The second part of the vibrations is absorbed by the filler, and the third is smoothed out by the baffles and the change in flow direction.

About the direct flow system

Any car muffler reduces engine power, creating significant resistance in the path of the flue gas flow. This is the price to pay for comfort and virtually silent exhaust. But for motorists who are tuning their " iron horses», There is an alternative option - a sound absorber of the direct-flow type.

The purpose of this element is to reduce power losses while continuing to absorb sound vibrations from engine operation. Co-current is a compromise solution, because for the sake of power, it dampens noise not as efficiently as standard auto elements. What such a muffler consists of:

• metal case equipped with two nozzles;
• inside there is a perforated straight pipe connecting the inlet and outlet;
• sound-absorbing material - kaolin or basalt wool - is laid between the body and the pipe.

Sounds traveling along a straight pipe with holes are partially absorbed by the fiber, but the other part passes out unhindered, because there are no partitions and resonance chambers. Therefore, cars equipped with forward flow make a rumbling sound, especially when you press the accelerator pedal.

The highest level of tuning - combined system exhaust with a damper controlled from the passenger compartment. With its help, the flow of gases can be switched between two branches: the first has a conventional effective silencer, and the second has a forward flow. This allows you to use the power of the engine only when necessary, and under normal conditions to drive around the city without unnecessary "roar" from the exhaust pipe.

Typical faults

There is one reason why a car muffler fails - prolonged exposure to high-temperature exhaust gases. Sooner or later, the metal body of the element burns out, which is accompanied by a rumble under the bottom of the car (from where the faulty part is located).

The service life of a muffler is highly dependent on the material from which it is made:

• ordinary "black" metal with a special coating;
• stainless steel.

The cheaper version, made of "black" rolled metal, is capable of burning out after 20-30 thousand kilometers, while the stainless steel body will work 100 thousand kilometers or more. Another thing is that during long term the insides of the muffler may burn out and the noise level will increase markedly.

Malfunctions are eliminated in two ways: replacing the muffler and repairing by welding. In any case, you will have to visit a car service, where, after diagnostics, the wizards will help you make the right decision. If the fistula opening is small, then an experienced specialist will weld it right on the machine. The second option is to apply a metal patch, for which the muffler will need to be removed. An element with burnt-out insides cannot be repaired, only replaced.