Nowadays, the modified parts of the *** are not exhaustive. It seems that after installing a large-caliber and surprisingly sound exhaust pipe, the vehicle will run faster. In fact, this is a misunderstanding. The replacement of the exhaust pipe is negligible for the improvement of horsepower. Especially for some small-displacement natural intake vehicles, it is quite difficult to obviously feel the improvement of horsepower. Conversely, a large-caliber exhaust tail drum has a considerable impact on low-speed torque loss, but a smoother exhaust at high speed is understandable for power improvement.
The key to exhaust performance is speed back pressure
Although the four-stroke engine was originally designed to be completely combustible, the exhaust pipe is pure because of the large number of cylinders in the car, the lack of a separate exhaust pipe for each cylinder, and the consideration of noise, space, overall configuration, and mass production cost. Silencing and cooling the exhaust gas, so there will be problems that are not smooth enough to reduce the engine's performance. Therefore, it is better to describe the modification of the exhaust pipe to increase horsepower. It is better to find the horsepower and play the original output.
The patency of the exhaust pipe is also known as the "back pressure", or it can be called back pressure, back pressure, in short, it is the resistance inside the exhaust pipe, and the design of the banana head, the middle diameter The thickness, the total length of the catalyst, the angle of the beam, and the size of the muffler are all related, and are directly reflected in the exhaust efficiency. The main purpose of the modified exhaust pipe is to reduce the back pressure to make the intake and exhaust flow more smooth, and this is also a disguised extension of the valve overlap time to enhance the vital capacity, thus changing the engine characteristics, thereby improving the response and power of the high speed range. . However, the back pressure is not to say that the lower the better, because if the exhaust is excessively unobstructed, the mixed gas will not be completely burned at the middle and low turn, and the torque will be sacrificed, even when the oil is changed. Low, there is also the possibility that the exhaust gas will flow back to the combustion chamber, so a certain back pressure is needed.
The diameter of the pipe diameter is 10-15%
In general, most of the modification of the exhaust pipe starts from the middle and the tail. The common method is to increase the diameter of the pipe, reduce the silencer, etc., and emphasize that the competition will be more linear. Improve the characteristics of the linear exhaust pipe (due to the chassis interference, it is difficult to achieve true straightness), the path is shortened and the angle is smooth and the obstacle is reduced, but everyone should know that the shorter exhaust pipe is the pursuit of high turnover. Horsepower (low back pressure), slender type is good at low turning torque (high back pressure), the reason is that the pressure in the latter tube is high, the low and medium speed exhaust gas will be discharged very quickly, but the high speed will face the weakness of the blockage. However, the former has a problem of slow flow in the middle and low turn, but it can be smooth when it is turned to high exhaust.
Exhaust pipes based on the use of roads should actually choose a longer-length style as a condition for accumulating gas, and then the change in pipe diameter can take into account the performance of the full-speed domain, according to most people. According to the experience, the increase of the pipe diameter in the middle section is almost 10-15% better than the original factory (the engine is not modified), that is, the naturally aspirated engine is around 55-60, and the turbine engine is about 65-70. Of course, if your car's exhaust capacity is large enough, and after a heavy upgrade with the strength of 400hpover, then it is necessary to use more than 80 pipe diameter.
Regarding the arrangement of the pipe diameter, it is more suitable for those who value the torque, but it is suitable for people who value the torque. However, if you are the pursuer of the horsepower, it is suitable for the form of progressive enlargement. The design is to gradually expand the diameter of the pipe, so that the more rapid expansion to the rear, constitutes the exhaust gas speed increase, especially in the case of continuous high speed, which is also a trend of the current modified exhaust pipe .
Please note the resonance phenomenon in the catalyst/intermediate part
In the modification of the middle section exhaust pipe, there is also an important component that is the catalyst and the medium elimination. Although the basic function of the catalyst is to purify the exhaust gas, it has the same effect as eliminating the resonance sound, and is densely packed with many kinds of metals. The composition of the catalyst, according to the modification of the eyes, is indeed a major culprit hindering the smooth exhaust, but also a nasty hot spot, so many people will replace the shell type instead of the tube (straight tube is easy to cause resonance), often just this A small amount of straight through, you can feel the exhaust is much smoother, the sound will not be stuffy inside.
Modification of the exhaust pipe, the medium elimination, the catalyst charge, will be done shorter and smaller, to improve the smoothness of the exhaust, but if some of the pipe diameter is too thick, this part will not shrink too much to ensure The power of low to medium. In addition, when you feel that the exhaust is too much and the torque is too much, you may be able to improve a lot of this phenomenon by knowing a so-called "cannonball".
Tail elimination internal structure partition plate and linear type
The tailpipe exhaust pipe, which is mainly used for muffling, is naturally a place where resistance is generated, which involves the design of the inside of the muffler. The structure of the tail elimination can be roughly divided into two categories. The first one is to reduce the low volume by means of a staggered partition to cause reflected waves. The original products are almost all secondary forms, and the second type is a linear type of sound absorbing cotton commonly used in the modification. From the standpoint of fluid mechanics, the baffle-type exhaust resistance must be large, and the horsepower boost is not as dominant as the linear one.
In order to reduce the exhaust obstruction of the tail elimination, it is not only necessary to straighten the passage and enlarge the diameter of the inner tube. It is necessary to miniaturize the entire silencer, and it is also possible to add some ingenuity, such as installing one before entering the tail elimination. The movable valve; or the infinitely designed double-loop accelerating airflow, so that the back pressure is reduced in view of the increase in the rotational speed. The purpose is a good workaround.
The straight line of the modified exhaust pipe tail, the noise absorption needs to be achieved by the muffler surface. In this case, most manufacturers use glass wool, but after a long time, the glass wool which is in a high heat environment for a long time will definitely be deteriorated. There are problems with resonance and loudening. Therefore, some products will now be marked with durable stainless steel wire. This is a perforated outer casing that is covered with stainless steel wire and then filled with glass wool. The stainless steel wire prevents heat from being transmitted to the glass wool, thereby extending the overall life.
Confirm preferences before modification
After reading the above instructions, you must confirm the characteristics you want before modifying the exhaust pipe. It is like replacing the exhaust pipe of Taitong with the self-discharge car. Otherwise, you will lose the low-turn torque. Even high-speed horsepower can't accumulate. In addition, judging whether the performance of an exhaust pipe is excellent or not, in fact, it is a good way to start from the sound. The condition that the exhaust gas is not smooth, the first thing is that the sound cannot be stuffed inside, but this does not mean that loud sound is a good phenomenon. If the sound is large but empty, it is not solid, it must be that its back pressure is too small, and the sound is full and thick exhaust pipe, which indirectly indicates that it can quickly discharge the exhaust gas, so the back pressure should be appropriate and correct.
** It is worth noting that when you change, the resonance may be too large, and the exhaust pipe may be shaken left and right. At this time, ** replace the hardened lifting lug rubber (overweight) It is also necessary to crack the joint, and a well-designed exhaust pipe can be completed at a considerable cost. Under the premise that the engine has not been greatly modified, the effect of replacing only the exhaust pipe is unobtrusive. Nowadays, many people also replace the tail section of the exhaust gas and remove the three-way catalytic converter. This will definitely increase the emission of exhaust gas. We stand against the practice in the environmental protection position. Being able to grasp these principles, you will certainly enjoy the fun of modifying the exhaust.