You have to change this place first so that the whole community can know you.

At 8: 40: 30 in the morning, I got up and looked out of the window. The weather is very good today. By the way, I had breakfast. The 30th spoon just finished this oatmeal breakfast. After seeing the empty bowl, I thought about it. After 32 seconds, I decided to drive out for a walk.

Unlock, open the door and get on the bus. At the moment I lit the fire, the whole community knew that I was out, especially the neighbor opposite my house. Fortunately, his surname is not Wang.

With the gradual deepening of the throttle, the sound of the engine gradually became violent. I was looking forward to it, blushing, and finally found a remote place, and suddenly the floor was oiled. The roaring sound was accompanied by the downshift in my heart. Generation, like an electric current, passes through the whole body, and the corners of the mouth are slightly tilted unconsciously. He glanced at the dashboard, and the hateful pointer just pointed to 80 km/h, hehe, this is the experience of the person who changed the exhaust.

Collect oil, turn around and go home. Without the trace of that land, I won't remember my arrival, only slowly dissipate the tail gas in the air.

If you change the exhaust, I think you will have the same experience as me. Exhaust is the first step for me to modify the small 4. There are thousands of reasons for modification. The reason why I changed the exhaust first is very simple, that is, it sounds good!

Modification is generally divided into two factions, racing faction and potted faction. Of course, there are many sub-groups, so I won't elaborate here. As the name implies, racing teams are fast, fast and fast, and tend to be modified in terms of power. The potted group is more interesting, that is, it pursues beauty, individuality and posture instead of speed. No matter how many seconds you spend, I will be more handsome than you.

I only changed the exhaust, which group does not have it at present, and which group also has it. Because changing the power to change the exhaust, the posture should also change the exhaust, which is the most basic entry.

It is said that the modification is as deep as the sea. Where is it? Because of various brands of modified parts, various software programs, various technologies and various modification schemes, it is difficult not to go the wrong way. Every modified boss is also tried out step by step. I also did a lot of research before the reform, hoping to take as few detours as possible.

For exhaust, we should understand it first and then modify it. First, what does it do?

The engine needs air when it works, and the generated exhaust gas will be discharged from the exhaust pipe. At the same time, it also has the functions of purification, noise reduction, shock absorption and power interval control. ?

Simply put, the exhaust pipe can usually be divided into head section, middle section and tail section. The pipe we usually see behind the car is the tail throat of the exhaust pipe, which belongs to the tail section, and there are silencers in the middle and tail sections.

Exhaust modification, to put it bluntly, is to make the original exhaust smoother and sound better. There are several modification methods: 1. Replace muffler or remove it. 2. Structural changes of silencer. 3. Change the pipe diameter. 4. Remove the three-way catalytic converter (that is, what we call the straight-through type).

In order to sound good, I only changed the middle and tail parts. Personally, I don't like straight row. Although the removal of the three-way catalytic lamp in the original factory is loud, it is too polluting to the environment.

Some friends may want to ask, if you plan to change the exhaust, how should you choose?

This problem is simple and simple, complicated and complicated. The simple thing is that the exhaust technology in the whole vehicle is relatively low, so you can weld one with stainless steel pipe yourself. The complexity lies in the fact that factors such as material, welding process, noise elimination process and modeling will all cause differences in exhaust gas. Even if it is a single brand, there will be choices such as import, domestic production, joint venture and domestic OEM. And the price ranges from thousands to hundreds of thousands, so we have to price first and then choose. In fact, just like choosing a car, we choose our favorite exhaust gas from our own budget.

I chose domestic exhaust? HSR (commonly known as braised pork), 70 diameter double-sided single outlet, with electronic valve. This is a domestic exhaust manufacturer specializing in BMW. The advantage is good sound (personal preference), and the key is cheap! Find a familiar refit shop after selecting the exhaust ~

(unpacking)

(smells good)

(The tail is as big as a sandbag)

(Start shelving)

(original factory exhaust)

(Installation of Electronic Valve Air Pump)

The advantage of having a valve is that it can be controlled. I usually turn off the valve when I drive out, trying not to disturb the people.

Let's talk about the advantages and disadvantages of modified exhaust. The advantage is that the sound is loud enough and exciting enough, and it can also improve the power for cars with large cylinders and large displacement. Car white knows that the smoother the intake and exhaust, the greater the power. Actually, it's because of back pressure. The word back pressure will be explained in detail later.

The disadvantages of modified exhaust are also obvious, especially for cars with small displacement. Everyone has heard a word called low twist. Why is the exhaust smooth but the low twist becomes lower? This is what we want to talk about back pressure, because the knowledge points involved are long and complicated, so let's stop here.

The general engine workflow is divided into intake, compression, ignition and exhaust. Driven by the camshaft, the intake valve opens first, and as the cylinder descends, fresh gas is sucked into the cylinder from the intake valve. Then close the intake valve, start compression and ignition, and finally open the exhaust valve, the cylinder goes up, and the exhaust gas is discharged from the exhaust valve to complete a working cycle.

In the operation of the engine, there is also the process of valve overlap. When the exhaust gas is not discharged, the intake valve opens. At this time, both the intake valve and the exhaust valve are open, which is called valve overlap. During this trip, some fresh air will be mixed with the incompletely burned exhaust gas, because the incompletely burned exhaust gas is easier to ignite. (This is also the reason why many small-displacement Japanese cars usually have high back pressure. However, after changing the exhaust gas, the exhaust gas is smoother, the back pressure is reduced, and there is no chance of mixed combustion of exhaust gas. Generally, the combustion is not sufficient below 3000 rpm, so the low torque is reduced.

However, at high speed, the combustion is basically sufficient, and the exhaust gas has no combustion value but will affect the combustion, so it is necessary to discharge the exhaust gas faster, which is also one of the advantages of the improved exhaust gas mentioned above.

For a car owner with a small displacement like me, if he wants to have a good voice, his power will not be greatly improved.

Another puzzling shortcoming of the exhaust system is the vibration. I have to drain the system, especially at 1500-2000 rpm. I will get used to it.

As we all know, sound is a sound wave generated by the vibration of an object. There are several factors that affect exhaust vibration: matching degree of exhaust mold opening, material, muffler and installation technology.

Here, we choose a slightly higher technical content to talk about knowledge points. Mufflers are divided into resistance type, resistance type and compound type according to their working principles.

The working principle of resistance muffler is: using sound-absorbing cotton to absorb sound. This kind of muffler is usually used in the middle muffler and the tail muffler, mainly for the treatment of medium and high frequencies.

The working principle of reactive muffler: the structure is discontinuous by means of pipe punching and pipe disconnection, and the sound is reflected back at these discontinuous structures, thus achieving the purpose of reducing the sound. This muffler is mainly used for the treatment of medium and low frequencies.

Working principle of compound muffler: In fact, it is a combination of resistive muffler and reactive muffler to reduce noise in all frequency bands. Exhaust includes muffler, which is linked to the price. Besides, the only thing we can do is to find a reliable shop and a reliable master to install it.

When we understand and study the modification, we can know what kind of modification we need. Finally, I appeal to everyone to make reasonable modifications, play with cars in a civilized way and cherish the hard-won environment for playing with cars. I haven't decided where to change trains next until I have saved enough money.

Some pictures come from the internet.

This article comes from car home, the author of the car manufacturer, and does not represent car home's position.