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2018-02-04 15:25

Don't just listen to the sound

Writer:     Views: 427

        In the modification of the power part, the refitted intake and exhaust is usually referred to as the specified action. By changing the high performance intake and exhaust system to the vehicle, the engine can absorb more rows and improve the power performance, which is also the simplest and effective modification method. Relatively speaking, modification of the exhaust is more common in the country, I think the most important reason is not only to improve the performance, the exhaust pipe and the exhaust noise sounds pretty more can attract the attention of passers-by, many owners of the main purpose is to refit exhaust.
        Hear the blood boiling the exhaust noise is reminiscent of car modification, or that many people know of the vehicles is to have exaggerated noise (of course, this understanding is one-sided). We can see the universality of the modified exhaust system in the car modification, and this time we talk about the widespread misunderstandings on the modified exhaust system.


■ Common mistakes - modification of the exhaust system:
        The original exhaust system is used by manufacturers for repeated testing, vehicle dynamic performance, environmental performance and fuel economy and production costs and other aspects of product design is considered, and the vehicle powertrain collocation is more reasonable, especially for the weak power of small cars, the original factory exhaust usually not too smooth, but this kind of design instead of optimizing the characteristics of small displacement engine itself low torque is insufficient, the appropriate exhaust back pressure will produce resonance effect (details of the), can improve the efficiency of exhaust rate under low speed, more suitable for city road use.
        Some high performance models, the exhaust system in the original design will be used to improve the low back pressure of the maximum power output of the engine, the exhaust manifold optimization design, usually linear type large diameter pipe, a tail throat and loud exhaust noise is their common characteristics.
        "For some performance models, the design of the original factory exhaust exhaust system will use the back pressure low, even more will be used as the exhaust manifold (the exhaust manifold of Lexus IS250).
 
☆ Misunderstandings 2: the greater the sound, the greater the horsepower, and the tail section can improve the power output.
        The bigger the voice is, the bigger the horsepower is. It's wrong for the exhaust system. For the exhaust system, the main role of exhaust is the exhaust tail and the middle part, especially the tail muffler. In fact, only modified straight tail section, you can get the exhaust noise is not small, but the engine power output is almost never been much change. The reason is very simple, engine emissions need to go through the exhaust manifold (closest to the engine part is connected with the exhaust hole of each cylinder), three yuan (responsible for the catalytic converter in the exhaust manifold, the harmful gas, then exhaust conversion) (middle reducing resonance and noise reduction), and finally we you can see at the rear of the tail section (for silencing before), the tail section, each of the parts formed on the exhaust resistance, so the sound is not equal to horsepower.
        Just refitting the exhaust section will not increase the horsepower of the vehicle (even if it is small enough to be ignored), and if the whole exhaust pipe is replaced by a high-performance model, it will help a lot in improving the horse power (especially after the intake system is modified). High performance exhaust pipe than the original thick, the lining is smooth, less curved, the design of the engine produces a lot of gas at high RPM can smoothly through high speed, can significantly improve the efficiency of the exhaust.
        Don't believe the claim that the S drums produced by the unknown small workshops have claimed both power and low twisting. In the domestic popularization of the horse power machine, the deceptive modification product has been confirmed for a long time. A 1.8 liter family car has replaced the S drum produced by a domestic brand, and the highest power result measured on the horsepower machine is worse than that of the original plant.

☆ Misunderstanding 3: the more rough the exhaust pipe is, the better the exhaust backpressure is, the better the better
        A friend who knows something about the exhaust system will know that the most important factor affecting exhaust performance is back pressure, which can directly change the power output characteristic and maximum power of the engine. But if the back pressure is lower, the better the power performance is.
         Of course not, first of all we have to figure out the indicators to measure the performance of power. For example, good performance of high output models such as Honda S2000, understand the car power output characteristics of driver can open it quickly very smoothly, but for ordinary people, the output characteristics of low twist deficient to very good open feeling (but not suitable for city road congestion), at the same time don't feel the power performance of this car how much good. This principle is also applicable to the modification of exhaust system. Too low back pressure will make the exhaust too smooth and slow down the airflow speed at low turning state, which will affect the exhaust efficiency at low speed and decrease the torque output in low speed region. Refit the exhaust system must be modified according to your driving habits and needs.
      When we retrofit the exhaust system, we need to take into account the power output characteristics of the vehicle itself and our driving habits. For those owners who feel low speed and torque output is not ideal, retrofitting exhaust is not a good choice. Because the modified exhaust is basically the performance optimization for the medium high speed area, the modification is usually at the cost of the loss part of the low twist. Of course, some professional modification plants have already introduced variable valve exhaust, which takes account of the requirement of back pressure when low speed. At high speed, the exhaust valve can be smoother by controlling valves. But expensive prices (usually at thousands of dollars to tens of thousands of dollars) are not acceptable to all car owners.

■ The basic principle of refitting exhaust gas:
        It is not said that the cost of manufacturing, usually in the design of the original model, will take into account whether the engine output characteristics are suitable for daily use. Especially in the city road, the filling of low speed torque output can give consideration to the advantages of saving oil. The appropriate high exhaust back pressure design ensures the low speed and high torque output characteristics of the engine, but the designed exhaust system will form resistance at high speed, which will cause maximum power to be blocked. The modified exhaust can reduce the exhaust pressure by design and material, and improve the intake efficiency of the engine at the same time, so as to achieve maximum power output and change the output characteristics of the torque.

■ In the modification of the exhaust system is easy to overlook the problem:
☆The importance of 1. exhaust backpressure
        Since the basic principle of refitting the exhaust is more smooth, the exhaust resistance is smaller. But in fact, the better the exhaust system is, the better it is. The working principle of the engine is in each cylinder work combustion, exhaust and exhaust, so the process is not continuous to the car to blow out the exhaust gases from the engine is the wave (when idling, the speed is very low, we put our hands in the exhaust pipe after it can feel exhausted from the exhaust) system.
Take the general household car, the engine in the low speed region, every time the exhaust process will form a greater pressure in the exhaust pipe, exhaust gas is discharged when the wave, in the exhaust gas behind will produce negative pressure, the negative pressure wave to exhaust the equivalent of sucking force, can help the next wave of waste gas from faster out of the vehicle, so the cycle can improve the efficiency of the exhaust. This is the resonance effect that we call the exhaust backpressure (also called back pressure).


        When the engine is at high speed, if the exhaust system does not change, the excessive back pressure will cause excessive resistance in the exhaust pipe. When the engine is at high speed, the working gap of each cylinder becomes smaller, so that the effect of the resonance is not as significant as that of low speed. At the same time, the high speed in unit time when the intake and exhaust quantity are greatly improved, the original exhaust structure can not cope with the exhaust volume per unit time increased, resulting in high speed exhaust efficiency and reduce the exhaust efficiency and poor exhaust is not smooth, again the intake must also be affected, so it can reduce the exhaust back pressure effectively improve the dynamic performance of high speed.
        But if the exhaust is too smooth and free of resistance, it will weaken the sipping effect produced by the exhaust backpressure, making the exhaust pressure small and inefficient. This can explain why the refitted vehicles often output less torque than the original type at low speed. The back pressure level set depends on the dynamic characteristics of the demand, the owner must not emphasize low torque can use the exhaust system is too smooth, and pay attention to the high dynamic performance it is suitable for low pressure conversion products

        In addition, for the modification of the exhaust system, it is also necessary to select the specific vehicle. Naturally aspirated engine, small displacement or displacement is not high and small horsepower automatic car, itself the power output is characteristic of low torque weak, with low pressure exhaust system will deteriorate low twist deficient phenomenon, The loss outweighs the gain. Therefore, the modified exhaust system should be selected to be targeted to get the ideal effect.
☆ 2. most critical exhaust manifold modification and exhaust resonance effect
        We mentioned modified exhaust, the first thought is double, four or large diameter exhaust and exhaust middle conversion, also innumerable different brands for a vehicle products on the market, in fact, in addition to the exhaust end of conversion, on the performance of the engine has the most direct impact is the exhaust manifold. We all know that after the engine work links will need to exhaust from the combustion chamber of each cylinder according to a fixed order of suction pressure discharged (four stroke) cycle for the entire exhaust system, the most directly affect the exhaust efficiency is part of the exhaust manifold (Guangdong called banana).
        The exhaust manifold is directly connected with the engine exhaust channel, and is the first channel after the exhaust is discharged from the combustion chamber. The exhaust manifold is usually the original cast iron products, a large number of mold wall roughness, will form a certain resistance to airflow, and because to take into account the engine room arrangement, so the original exhaust manifold will not consider the length of the cylinder exhaust pipe (except for some high performance models), different length lead to different exhaust manifold the running distance of each cylinder, so in together will be blocked together, conflict with each other, forming block, this phenomenon is more in high speed is more serious.


        The modification of the isometric manifold, most will use a smooth inner wall of stainless steel material, exquisite manufacturers are still manifold even the base and contact angle of the welding parts, the use of special processing and try to defuse the corner, to reduce the resistance and accelerate the airflow effect, as long as the design is in order to solve the interference problem. The exhaust pressure each manifold within the same value, so that the exhaust pulse consistency (contributes to the resonance effect of exhaust). In the structure of some of the exhaust manifold will be in the exhaust gas of each cylinder together before adding a group of lines, such as four cylinder car frequently used 4 out of 2 out of 1 exhaust manifold (each cylinder of an air outlet pipe, and then the 22 one and two, the last two pipes are combined into a). This kind of practice is to appropriately increase the exhaust back pressure to keep the low speed torque of the play. The carefully designed isometric exhaust manifold can improve the dynamic performance more effectively than the tail section of the exhaust.
☆ 3: changing the position of the exhaust pipe will reduce the passing capacity of the vehicle
        Some of the pursuit of large horsepower output system will be designed to exhaust pipe layout line, no longer use the chassis of the original exhaust reserve position, this modification usually makes the exhaust pipe to the ground (increase the caliber of the tail section will also affect the performance of the vehicles, through) through the performance variation, increase the probability of underpinning. In the modification, it is necessary to take into account whether the vehicle environment is allowed to reduce the height of the exhaust pipe.

■ Recommended exhaust type: street type original exhaust system
        Compared with some competitive exhaust systems, the original location street type refit exhaust system can optimize the whole exhaust system without changing the line of the chassis pipeline, improving the power output while making the installation more convenient. And the street oriented design will not make the exhaust back pressure too low and extreme. At the same time, the exhaust system produced by experienced exhaust modification plant can improve the performance and control the noise in a more reasonable range. In the selection of the original installation, the choice of the exhaust can be chosen as the first choice, or as far as possible to choose a number of large factory products with years of repackaging experience.

 
■ The difference between the material of the exhaust system:
        The material of exhaust system is also one of the key factors that we must not neglect in refitting. The exhaust pipes of different materials affect not only the power performance but also the weight and sound. Usually modified exhaust is made of stainless steel, smooth inner wall can improve the speed of exhaust air flow, and generally modified stainless steel exhaust pipe will be lighter than original product 1/3. The higher level of the exhaust will use titanium alloy products (of course more expensive).


        The titanium alloy, known as "space metal", has the characteristics of high strength, corrosion resistance and excellent heat resistance, which was originally used in the aviation field. Because the titanium alloy density is only 60% of steel, but the strength is more outstanding, so the titanium alloy material with the same strength than the exhaust pipe of stainless steel lighter (equivalent to half the weight of the original product), which made a great contribution to reduce vehicle weight, suitable for the pursuit of the ultimate owner of the modified lightweight. Only titanium alloy has higher requirements for welding, which is more difficult than ordinary steel materials. This is another reason for the higher price of titanium alloy exhaust pipe besides the cost of material itself.

        Two kinds of exhaust pipe in sound quality is not the same, the wall titanium exhaust is very thin, so when high speed exhaust gas wave through, there is more hair splitting sound, more shrill but slightly loose. The stainless steel exhaust voices relatively low-key and thick, unlike the titanium exhaust style, heavy and low quality. As for the tone, I think the turnip cabbage love it, feeling completely on their own. In addition to the visual titanium exhaust is unique, the exhaust pipe of ultra-thin design after high temperature baking after showing a unique blue appearance (for beauty, now some stainless steel exhaust start imitation titanium alloy products, deliberately made blue).


■ Rational refitting, civilized driving:
        I think this is needless to say, despite the appearance of performance factors such as street car, we choose the modified exhaust system must pay attention to the modification of the exhaust noise, the noisy exhaust must not choose, one is a long time I can't stand (many cars of the Lord, and on the other hand the wise remark of an experienced person) is a nuisance. As I have said before, exhaust system is not necessarily loud enough to be an excellent product. Otherwise, it doesn't mean that it must be noisy. Many excellent performance retrofitted exhaust valves are very noisy at idle speed and gentle driving.
Summary: in fact, for the refitting of the exhaust system, many people are not strange. However, compared with the exhaust section of the middle and the tail section that we all know, many owners of the modified exhaust system have ignored the influence of exhaust manifold on exhaust performance and the understanding of exhaust back pressure. Although only pay attention to the auditory effect is not wrong, but by understanding the principle and structure of the exhaust system, we can according to the deficiency of the original car was optimized, Why not? To achieve visual and auditory performance, to enhance the synchronization effect? Of course, if we want to achieve a better performance improvement, we need to match the modification of the intake system. Please continue to focus on the car home modification channel, in the next stage of the modification error series, we will analyze the intake system modification for you.


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