Do-it-yourself direct-flow muffler, is it worth installing it on your car?

What is a direct-flow exhaust system

To understand why to install a direct-flow muffler, it is important to know how the car’s exhaust system works.

Main goals:

1. Filling the cylinders with a prepared fuel-air mixture, and in diesel cars - forming the fuel mixture in the combustion chamber;
2. Ensuring the removal of spent fuel gases from the engine and passenger compartment outside the vehicle;
3. Reducing the emission of toxic gases and harmful substances into the atmosphere thanks to the built-in catalytic converter;
4. Reducing noise levels in the cabin and surrounding area.

The operating principle of the exhaust system is partly based on the law of inertia.

Thanks to the action of this law, a vacuum zone is formed behind the exhaust valve into which gases rush, and their place is immediately taken by a fresh portion of the fuel mixture.

This happens due to the fact that the phases of fuel intake and exhaust gases overlap each other, as is provided for in the design of modern engines.

After the exhaust valves are closed, next to the high-pressure zone formed as a result of exhaust gases escaping under pressure, another low-pressure zone is formed in the manifold, which moves along the exhaust pipe at the speed of sound.

Entering the muffler, the vacuum zone encounters resistance in the form of partitions, is reflected and goes in the opposite direction to the valves.

The ideal case is when this zone approaches the motor at the moment the valves open, but this depends on the frequency of the engine and the distance to the obstacle.

And since in modern cars such a distance is large, the vacuum zone from one cylinder, as a result, at the moment the valve opens, ends up in another, and not in the one from which it left.

Thanks to the design of the “spider” (exhaust manifold), where pipes of the same length are provided, the effect of vibration damping occurs, since the vacuum zones go from 4 pipes into one, where resistance is created at the junction of the latter, and they also partially dampen each other.

But the muffler plays a leading role in noise reduction, because the exhaust manifold and other elements are unable to greatly reduce noise.

But on many sports cars such a device may not be found; the role of a muffler there is played by a special turbine, which smoothes out vibrations and reduces the force of the exhaust by grinding the outgoing gas flow.

About direct flow or PG

A direct-flow muffler (PG) is an improved alternative to a stock exhaust, which is not capable of ensuring a quick and timely release of gases from the engine system (ICE). The standard exhaust system especially suffers (chokes) after installing a sports camshaft or after boring the cylinder head cylinders (in other words, on a forced engine).

A straight-through muffler is designed to improve the exhaust system

The GHG is designed to modernize the exhaust system, which increases gas emissions. In addition, a correctly installed PG will provide an increase in internal combustion engine power by 10–15 hp. However, you need to be prepared for drastic changes: everything will need to be replaced, from the catalyst to the tip.

Increasing the power of a power unit using a PG, unfortunately, also has a “other side of the coin”, associated primarily with a loud sound attack of about 120 dB. This is the norm for sports cars, but hardly for civilian ones. And this explains the mass of cases of fines issued by law enforcement inspectors to the owners of such cars.

To minimize this modernization flaw, craftsmen use various methods to reduce sound. Installing a flute muffler, oval or round resonator are all types of methods to improve the performance of a forward flow muffler. “Form and content” can make it quiet.

For example, craftsmen say that a square resonator installed in the middle of the path (the path for gases to escape into the aircraft) reduces noise much better than an oval or round one. And in general, it’s better not to use a round one, but to use an oval one as a last resort, since it has a larger volume of cans and, accordingly, a quieter sound.

Oval resonators from Volvo S60R and Saab have proven themselves to be quite good.

Before thoroughly understanding what GHG is, you should remember the functioning of the vehicle exhaust system. Many motorists do not even suspect how many tasks it performs, although it does not seem so at first glance.

The forward flow kit is a ready-made option for tuning

Of course, the main task of the exhaust is to remove gases. But an equally important function is to ensure timely and high-quality ventilation of the internal combustion engine cylinders.

Ventilation of the cylinders is carried out as follows. When the valves of one cylinder of the internal combustion engine are closed, a vacuum is created in the exhaust manifold. It moves through the system at high speed, and, having been reflected from obstacles, returns to the collector. At the moment the gases leave the cylinder, a reduced pressure is created here, which promotes better ventilation and purge.

Among other things, the exhaust system (ES) is designed to combat noise. This is what the muffler is designed for.

Compared to a conventional standard muffler, the PG does not have many separate sections inside. Accordingly, it has a more simplified design. It is this fact that allows craftsmen to make it at home or in the garage.

But is it even worth it for an ordinary motorist to change the standard muffler to a PG one? Certainly not. If he does not prefer active driving, does not intend to use the car for sporting purposes, does not have complexes about a “gray” car that does not stand out from the general traffic flow, then he should not carry out modernization.

On the contrary, if the bassy and thoroughbred roar of the engine resonates in the soul of the car enthusiast, then the installation of direct flow must be carried out. Moreover, this gives many advantages of the following nature:

• the power of the internal combustion engine increases due to increased throughput;
• The service life of the entire aircraft is extended due to the use of high-quality materials.

As for the disadvantages of modernization, these are:

• problems with the law due to loud noise (can be excluded if the installation of GHGs is carried out using a new system);
• possible difficulties with service maintenance;
• greater sensitivity of the power unit to low temperatures;
• decreased clearance.

Do not confuse forward flow with a muffler. The fact is that the entire exhaust system is called direct flow, and in most cases only part of it is subject to modernization - the muffler.

Types of devices

The standard exhaust system of a modern car includes a resonator (the first one comes from the engine) and the muffler itself.

The resonator cuts off low-frequency vibrations, and the muffler cuts both low-frequency and high-frequency vibrations, which together leads to a good result.

But the above scheme, both jointly and separately, may include the following types of mufflers:

1. Made of aluminized steel;
2. Stainless steel;
3. Silencers, limiters, absorbers and reflectors;
4. Resonator type;
5. Direct-flow (sports) analogues.

Aluminized steel

Devices made of aluminized steel are characterized not only by a long service life, from 5 to 10 years, but also by a high price.

It will be difficult to choose such a muffler for your car, since only a few companies produce such devices, and making it yourself will be problematic.

Stainless steel

The devices are in the inexpensive segment, but their service life is only from 2 to 5 years. A big plus is that you can match the element to almost any car.

Limiters

They are usually used as an additional device installed in front of the main one.

The operating principle is based on creating low acoustic resistance.

Structurally, this is done like this: in the pipe, a large diameter turns into a small one, then there is a sharp increase in volume according to the principle of a large bottle with a narrow neck. The sound, entering a large space, decreases.

Reflectors

Used as a secondary muffler installed after the main one.

Exhaust gases entering the device encounter a group of acoustic mirrors on their way. Reflecting from them, the gases dissipate their energy one by one, and the output is a weak sound.

Absorbers

Can be used as a main muffler. The principle of operation is based on the absorption of vibrations by a porous material, usually glass wool, the fibers of which are heated by oscillating, thereby converting sound into thermal energy. Structurally close to direct-flow analogues.

They are considered ineffective because they absorb only high-frequency vibrations and transmit low-frequency ones.

Resonator type

As a rule, they are used first in exhaust systems as additional ones.

The principle of noise absorption is based on the presence of chambers of different sizes, through which the sound is effectively muffled.

Everything is arranged like this: a pipe with slots runs through the center of the resonator, which is surrounded by chambers of different volumes. Through the slots, exhaust gases penetrate into the chambers, where their energy is lost.

After this, the sounds enter the main device, where they are further reduced.

Direct flow

They are also called sports mufflers. As a rule, they are made of stainless steel. Installed on sports and tuned cars.

After installing a direct-flow muffler, the suction of the air-fuel mixture into the cylinders is improved, and the resistance in the exhaust system created by conventional analogues is reduced.

A direct-flow muffler is structurally somewhat similar to a resonator; there is the same pipe with holes and empty cavities separated by partitions. Only the cavities themselves are filled with basalt wool (or other material), which can withstand high temperatures.

Consisting of long mineral fibers, basalt wool absorbs sounds well, but only until it is blown out of the direct flow and even special protective metal mesh does not save the situation.

If the direct-flow muffler, when you tap on it, begins to sound like an empty metal container, then it needs to be filled again with cotton wool or replaced. And the sound produced by the exhaust system will be different.

Why does the muffler deteriorate over time?

The metal of the exhaust system works in difficult conditions. Car exhaust contains water vapor heated to a very high temperature and a number of more aggressive chemicals.

These are ideal conditions for corrosion to occur, especially under conditions of large temperature differences between engine operation under load and long periods of stoppage. The situation is aggravated by external corrosion, since the mufflers are located under the bottom of the car and are subject to attack by all the chemicals that are picked up by the wheels from the road.

Manufacturers of exhaust systems try to protect their products with all kinds of coatings, from aluminum powders to galvanizing, and also make mufflers from different types of heat-resistant and stainless steel.

Related article: Why water drips from a car muffler

Naturally, this approach is very limited both because of the high cost of the material and because of the technological difficulties of welding work on stainless steel. Therefore, not all exhaust pipes, resonators, catalyst housings and mufflers of production cars are made this way.

Sounds made and their features

After installing a direct-flow exhaust system, the sound emanating from the car immediately changes; as a rule, it is low-frequency “growling”, “bass” and “mumbling”.

This happens because mineral wool placed in the co-current cavities removes only the high frequencies, while leaving the low bass unchanged.

The resistance to exhaust gases is also greatly reduced, and this affects the increase in engine power (but only in combination with other measures).

But the nature of the sounds largely depends on the number of holes and their diameter in the central pipe, as well as the characteristics of the material embedded in the cavity.

As was noted, mineral wool does not support low frequencies, and in most cases the engine produces sounds in the low range.

Therefore, it is not surprising when a car with direct flow makes sounds of engine operation through the muffler, and the higher the frequency the latter operates, the more it clogs the ears.

This is felt especially well inside the car, when such sounds, coinciding in frequency with body vibrations (and they are close to the frequency of the engine), lead to resonant vibrations inside the car and the strength of the sound increases significantly.

Therefore, it is almost impossible to make a quiet direct-flow muffler.

Noise standards and liability for exceeding them

Responsibility for loud exhaust from a muffler is provided for under Article 8.23 ​​of the Code of Administrative Offenses. The driver is charged for operating a vehicle with excess noise levels in accordance with the Technical Regulations of the Customs Union 018/2011 “On the safety of wheeled vehicles”, paragraph 9.9.

Table: dependence of the maximum permissible sound level on the vehicle category

Category M1, N1 and L are passenger cars with no more than 8 seats, trucks with a permissible maximum weight of no more than 3.5 tons, motorcycles/mopeds/ATVs. Category M2 and N2 are cars with more than 8 seats (except for the driver), but whose maximum weight does not exceed 5 tons, and trucks with a permissible maximum weight from 3.5 to 12 tons, respectively. Category M3 and N3 are full-fledged buses and trucks with a permissible maximum weight of more than 12 tons (trucks, most dump trucks).

According to 12.5.1 of the Code of Administrative Offenses, the driver (or owner) is charged for making changes to the design of the car without the permission of the supervisory authority - the traffic police.

So, the fine for a straight-through muffler can be either a warning plus a fine of 500 rubles, or two fines of 500 rubles each (in practice, two warnings cannot be issued).

The manufacture of a direct-flow muffler and its further improvement is within the power of most car enthusiasts. Despite the restrictions on the operation of such devices in our society, there are more and more people who want to make their own and install a direct-flow muffler on a car. Thanks to detailed instructions with photographs and videos, it will be much easier to make a forward flow.

Power and forward flow, three different opinions

Many owners of VAZ cars or, for example, Mitsubishi Lancer 10, Mazda 3, installing direct-flow exhaust systems on their vehicles pursue several goals, as a rule, there are two of them:

1. Tuning your car;
2. Increase the engine power, they say installing a sports analogue will leave many behind when starting at a traffic light.

The first opinion is that this is true. There is no debate about tuning; we are missing this point. But there is another opinion about increasing power, and it is the opposite.

The second opinion is that a sports muffler without deep tuning of the engine will not give an increase in power and partly it coincides with the opinion of experts.

The third opinion from professionals is that a noticeable increase in engine power is possible only after significant processing, and a direct-flow muffler is a secondary part of the issue.

The tuned power unit produces more exhaust gases, and, therefore, the standard exhaust system will not cope with its tasks, especially at high speeds.

Therefore, it will be necessary to increase the diameter of all pipes, install a tuned manifold, and only then a direct-flow muffler.

It is on sports cars that they install not simple engines, but ones that require special attention. And the direct-flow exhaust system fits into the overall picture of the tuning engine.

Muffler replacement

The noise reduction device must be changed from time to time. In most cases, after a certain period of use, it begins to make loud and unpleasant sounds during operation. This is facilitated by the development of corrosion, burnout of perforated areas of pipes, and breakdown of sound reflectors.

First of all, you need to park the car on a flat, hard surface, make sure that the car does not roll anywhere, and jack it up. It is better to install it on trestles after lifting the car, but you can also use an inspection hole.

Before removing the muffler, it is recommended that you lubricate all bolts and clamps that will need to be removed with a penetrating lubricant such as WD-40. You can try removing the rust with a stiff steel brush. In the worst case, you will have to cut the bolts, as the flanges often become sour.

Next you need to remove the muffler itself. First, you need to unscrew the bolts on the flanges, after which you separate the muffler from the exhaust pipe, which is then recommended to be secured with a rope or some kind of wire to the steering rack so that it does not dangle.

The muffler is then removed from the rubber pads that cushion it.

After unscrewing all the bolts and removing all the cushions, the muffler should simply be pulled out.

The new muffler must match your car model and make. It is recommended to buy it from trusted auto stores and trusted brands.

It is worth paying attention to the quality and thickness of the steel on the tank. On average it varies from 1.2 to 1.5 mm

Installing a new muffler is carried out in the reverse order described above. In general, there is nothing complicated.

You can watch the video for more information about replacing the muffler:

Making a direct-flow muffler with your own hands

If you want to manufacture and install direct flow on your car, then it is better to conduct such experiments with domestic cars, for example, VAZ.

It is better to tune the exhaust system of Mitsubishi Lancer 10, Mazda 3 and other foreign cars by contacting special companies that do this professionally.

We discussed the design of the direct flow above. The difference between a sports muffler and a regular muffler is shown below.

We will be tuning the exhaust system of a VAZ-2110 (8 valve 1.6 liter volume).

To do this you will need the following materials and tools:

1. Metal pipe with a diameter of 52 millimeters (a little more than 2 inches);
2. Grinder with a disc for cutting metal 1 (1.6) mm;
3. Welding machine, preferably inverter;
4. Metal sponges (brushes) for cleaning dishes - at least 50 pcs.

Work progress

Dismantle the old device or prepare a similar one taken, for example, from disassembly.

Cut out the gutter and all the insides as shown below.

Leave a 4 cm protrusion on both sides so that a new pipe can be welded into this area.

Prepare a new pipe by cutting it to size and drilling holes with a diameter of 6-8 mm in it at a distance of 1-2 cm from each other.

This is labor-intensive work, so you can use an alternative method - using a grinder with a 1.6 - 3.2 mm disc, cut holes in the pipe in the shape of a herringbone at a distance of 1-2 cm from each other.

Weld a pipe with holes to the sections in the muffler and fill the entire space with metal pipe cleaners.

On the reverse side, the electrode may be missing, no problem, the hole left will be additional to the rest drilled or sawn. But if you go by principle, you will have to cut out the other side of the muffler.

Weld the outer part back and, if necessary, update the pipe running from the forward flow towards the exhaust.

Completely clean the device, prime it with primer and paint, this will extend its service life.

It’s worth taking a closer look at the filler. In the example described above, a metal mesh was used, but still the best option would be expanded clay (in the middle), and put fire-resistant mineral wool on top.

Install forward flow - change the image of your car

The forward flow will change not only the sound of the car, but also its appearance. In this case, you can install not one, but two nozzles. Place them in different corners or bring them out on one side in paired form.

A straight-through or straight-through muffler can be painted in different colors, but the most common are silver and metallic. You can, of course, pick up an exhaust pipe in a store, find a universal product, but it will cost a decent amount of money. If you don’t have them or want to save money, then it’s better to use the information above and create a homemade one. But at the same time, you must have the skills to work with an angle grinder and a welding machine. Be able to do the work accurately and have enough time to complete it.

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

We make direct flow from scratch

To do this you will need to use the services of a turner. We order two pipes:

1. One made of steel 2 mm thick with a diameter of 130 mm and a length of 42 mm.
2. The second is made of steel with a thickness of 2.5 mm, a diameter of 52 mm and a length of 42 mm with holes with a diameter of 8-10 mm, every 2 cm;

Two flanges with a diameter of 130 mm with an internal hole of 52 mm, metal thickness 2-2.5 mm can be ordered separately.

Prepared:

1. Asbestos rope;
2. Glass wool or mineral wool.

Asbestos rope is wrapped around the inner pipe. This is done in order to protect the mineral wool, which will be the top layer, from overheating.

We fill the top layer, assemble and scald the structure. We weld the fasteners and attach the forward flow to its regular place. For beauty, you can put a muffler attachment on it.

Another design of the device is shown below.

Blueprints

There are a lot of ways to make a direct-flow muffler; the main thing here is to understand the principle of operation of the device and use your imagination. And for car owners who find it difficult to do this, use the methods and drawings described above, they are simple and accessible to many.

Also tell us in the comments what type of forward flow is installed on your car and how you can do it yourself, this will help many people understand this topic.

Work execution algorithm

It is not difficult to guess that the forward flow is made with your own hands from an old conventional muffler. The order of the operation is as follows:

1. Remove the part from the car and disassemble it using an angle grinder. In this case, you need to leave the inlet pipe and the housing. If the partitions remain, holes must be drilled in them. They will allow exhaust gases to escape.
2. Make a lot of small holes on the inner pipe, that is, perforate it. This can be done by any possible method. The diameter of such a pipe should correspond to the dimensions of the inlet pipe or be approximately 30% larger. It is better to let the initially obtained pipe have a slightly larger diameter than needed.
3. Place metal kitchen nets over the perforated area.
4. Wrap the resulting structure tightly with metal mesh. It is advisable to wind it in 2-3 layers, since one may not be enough. Secure the mesh with clamps or steel wire.
5. Prepare the product for welding by first cleaning it. Weld it to the standard place.
6. Fill the internal space of the element with the material selected for this purpose.
7. Weld the body, making several clamps at the end so that nothing moves.
8. Make one or a couple of small holes in the housing so that the condensate comes out better and faster, and the product lasts longer.
9. Paint the created direct flow with paint to protect against corrosion.
10. After drying, install it on the car.

How to make mufflers quieter?

There are several simple ways to make your muffler quieter.

To do this, you will need to do one of the following actions, namely:

• install an additional resonator;
• replace the resonator with a new one that has a sound-absorbing filler;
• replace the muffler with a new and high-quality one.

Any of the above options can make the sound of the muffler quieter. It remains to comment on the points, and let's start with the last one.

Muffler replacement

If you haven’t changed the standard muffler in your car for a long time, then it itself can operate in high noise mode.
Why is this happening? Due to corrosion processes and elevated temperatures, over time, perforated sections of pipes and parts of partitions inside the muffler can begin to burn out, and sound reflectors become unusable. All this changes the picture of sound absorption not for the better. And often problems with excessive noise from car operation lie in the loss of its properties by the muffler. If you are changing a muffler, then buy a product from trusted brands, with the proper thickness of steel on the can. The muffler must exactly match your make and model of car, taking into account the technical parameters of the engine and overall dimensions.

Installing an additional resonator

An additional resonator is installed between the main resonator and the muffler. For this:

• cut out a part of the pipe between the main resonator and the muffler;
• weld (mount) an additional resonator in this place;
• adjust the ignition system and fuel supply due to changes in the exhaust system.

The latter is worth checking, as any modifications to the exhaust system will affect the engine. It is unpleasant to receive a decrease in power or an increase in fuel consumption as a result of the pursuit of silence.

Installation of a resonator with an absorbing filler

The only drawback of such a resonator is its price in comparison with the standard model, however, it copes with its task perfectly.

Advantages

A car enthusiast is thinking about replacing a conventional muffler with a homemade direct-flow version due to the following reasons:

1. Replacing the muffler with a supply version will help increase the car's power by several horsepower. Of course, this improvement can only be felt, as they say, by seeing the data after measurement on paper. After all, it’s almost impossible to really feel the difference of a couple of horsepower. But the feeling that the car has become a little more powerful is pushing car enthusiasts all over the world to replace the conventional factory muffler with a direct-flow muffler.
2. Giving the engine a noble sound, which is characteristic of powerful versions of machine power units. It is also worth noting that using various design options you can choose the appropriate sound timbre. However, whatever one may say, if you put next to a car with a powerful engine and a simple, direct-flow muffler, the sound from it will be better, mesmerizing and penetrating deep into the body, than from a conventional installed engine. But the opportunity to do something like this pleases many car enthusiasts.
3. The desire to remake the car for yourself. This desire is not caused by the desire to achieve any result, but is perceived as a system for improving the car.

A straight-through muffler will help increase the car's power.

Why is this necessary?

It goes without saying that the modified exhaust system will give the car super-power, but the level of roar created by the engine can scare neighbors and passers-by who inadvertently find themselves next to the “swallow”. But on the highway, your car will be passed ahead and looked at with surprised glances by drivers of “cool” foreign cars, the engines of which have even more power than yours. But a conventional exhaust system that has not undergone modernization or so-called tuning does not allow the engine to operate at full power.

This is what a straight-through muffler looks like:

Direct flow muffler

Just two pipes of different diameters, placed one inside the other. But what an effect!