What About The Refitting Of The Exhaust System?

- May 29, 2018 -

We often hear that modified exhaust cars have different voices. The exhaust noise of racing cars on the track is very high and sharp, and the sound of modified cars in everyday life is quite thick and deep.

What is the reason for this? What effect will this modification result on the car? Now let's talk about the modification of exhaust.

Bilateral double outlet exhaust pipe

At present, the purpose of refitting car friends to reload and exhaust can be divided into two categories. One is to make the engine's intake and exhaust more smooth by refitting it into the exhaust system, and the other is to get a kind of sound that you want by refitting.

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Let's first talk about the principle of retrofitting exhaust. The most notable thing is the concept of exhaust pressure. Because the exhaust gas from the engine is discontinuous, but one strand, each of the exhaust gas will have a lot of pressure in the tube, the exhaust gas will become a high pressure area at the outlet of the exhaust pipe, and the area near the engine will form a low pressure area, and then the next exhaust gas will form a suction force, making the next stock. The exhaust gas can be discharged more smoothly. This is the function of the exhaust backpressure.

Universal Exhaust System

Some people say that if the exhaust system is not installed, directly exhaust the engine exhaust, no exhaust resistance will not be more conducive to the performance of the engine? This statement is unworkable. First, the exhaust noise from the engine is very large (usually more than 150 decibels). Without a silencer, we can't stand it at all. Drivers also need to wear earplugs; secondly, the exhaust contains a lot of CH, CO, N, and other harmful gases, if not. The filtering effect of the three element catalyst in the exhaust system will not only make the emissions exceed the standard, but also make the ECU with the self diagnosed car alarm and affect the safety of normal driving.

Universal Exhaust System

S drum exhaust pipe

When the engine is at low speed, the flow rate of exhaust gas in the slender tube is faster and the discharge time is longer. The exhaust back pressure can guarantee the absorption of one strand of one strand of exhaust gas and the working state of the engine will be more stable. When the engine is working at a high speed, when the engine is working at a high speed, the exhaust back pressure will hinder the discharge of the exhaust gas. After the exhaust efficiency is reduced, the intake of the engine will be affected, the engine is bound to be affected, the engine will be affected by the engine. The performance will not be able to play out. The performance of daily life is that when we step on the accelerator, the engine's speed rises, it feels weak, the performance of the car can't be played, and sometimes it will fall.


Understand the principle of exhaust, and what should I pay attention to when I start to refit?

1, some owners believe that the original exhaust system is not good, that the replacement of large diameter exhaust pipe can enhance the performance of their cars. In fact, this idea is inaccurate. The original exhaust system is designed according to the performance, economic type and most of the driving environment. It is reasonable to match the whole vehicle. Enough exhaust back pressure can not only guarantee the performance of the car at low torsion, but also meet its occasional "Satan". However, if a large caliber exhaust pipe is replaced, the exhaust gas cooling will speed up, the flow rate will be reduced, the engine's intake and exhaust will be greatly affected and the engine efficiency will be reduced, especially for the engine with small displacement naturally aspirated. In some high-performance cars, designers usually use a lower back pressure exhaust system, although it will sacrifice some low twist performance, but it can make the car maximize the performance of the vehicle at a high speed, and the sound of the exhaust will be more loud and thick. So before changing, you must know your car and choose the right way to adapt to different needs and driving modes.

Universal Exhaust System

2, the sound of the exhaust does not represent Ma Liqiang. We often hear sharp, loud exhaust sounds in the rally arena. In fact, the practice of these cars is to change the exhaust system into a straight line or dismantle the muffler in the middle and tail section of the exhaust system to reduce the weight of the car, so as to ensure that the car engine has a better dynamic performance at high speed. If the exhaust system is changed into a straight line in daily life, it can not only solve the problem that the back pressure affects the smooth exhaust, but also makes the noise too much to affect the normal life of the people.

Universal Exhaust System

Replacement of a large bore tailpipe

3, many retrofitted vehicle owners focused on the modification of the mid tail section, ignoring the influence of exhaust manifold (exhaust section) on engine performance. We all know that the working process of the four stroke engine is "suction pressure burst", and the exhaust gas of the combustion chamber will be discharged into the exhaust manifold after the end of the working cycle. The order of the exhaust manifold will be different because of the different working order of each cylinder. The original vehicle takes into account the space and cost of the engine compartment. The inner wall of the manifold will be rough and the length of the pipeline will be different. The problem is that the exhaust gases from each cylinder will eventually converge to the middle section of the exhaust pipe through different distances. In this process, there is a great possibility of gas conflict, blocking, and increased gas resonance, and the higher the engine speed, the more obvious.

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The solution to this problem is to replace the equal length of the exhaust manifold, allowing the exhaust gas from the cylinder to maintain a certain sequence and uniform pressure in the tube, thereby reducing the gas blockage and performing the engine performance. Replacing the isometric exhaust manifold to improve engine power is sometimes more effective than the tailrace exhaust.


Taking the four cylinder engine as an example, the most used is the four out and two out of one (two exhaust manifold converges first, four out to two, the two pipes converge into a total exhaust pipe and two out into one out) exhaust system, which can effectively improve the performance of the engine and the high speed in the engine. The smoothness of the air flow is greatly increased.

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Equal length exhaust manifold

The material of the exhaust system affects the dynamic performance and exhaust noise. Usually, the exhaust system is made of stainless steel. The smooth inner wall can reduce the resistance of the exhaust gas flow. The weight will be 1/3 lighter than that of the original factory. The higher grade exhaust system will use titanium alloy material, which has high strength and heat resistance, and the weight is about half lighter than the original factory. Because the exhaust pipe wall of titanium alloy is thin, the exhaust will pass through a more sharp and split sound, and the sound of stainless steel will be more thick.

Now there is also an exhaust system that changes the sound of the exhaust through the electronic system, which does not affect the power performance and simply changes the sound to satisfy the fan's preference for the exhaust sound. As for the sound of the exhaust, everyone will love it.

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Stainless steel exhaust pipe

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Exhaust tailpipe made of titanium alloy

With the development of science and technology and the need of modification, a variable valve exhaust system has been developed. The principle is to close a set of exhaust pipes to meet low torsion performance when the engine runs at low speed. When the engine runs at high speed, the valve is opened and the performance of the engine at high speed is brought into play, thus the dynamic performance of the high and low speed engine is taken into account.

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Variable valve exhaust

A sophisticated exhaust system can improve the performance of a vehicle, but it is necessary to find a suitable method of modification.


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