The exhaust system carries exhaust gases from the engine’s combustion chamber to the atmosphere and reduces, or muffles, engine noise. Exhaust gases leave the engine in a pipe, traveling through a catalytic converter and a muffler before exiting through the tailpipe.

排气系统将来自发动机燃烧室的废气排放到空气中去，并减小或消除发动机噪音。废气从发动机排出，经过排气管道通过催化转换器和消声器，最后通过尾管排到大气中去。

6.1 

The tailpipe is a long metal tube attached to the muffler. It sticks out from under the body of a car, at the rear, in order to discharge the exhaust gases from the muffler of the engine into the air outside the car.

尾管是与消声器相连的长长的金属管，它从汽车车身后部伸出，将来自发动机消声器的废气排到汽车以外的大气中去。

6.2 

Exhaust gases leave the engine under extremely high pressure. If these gases escaped directly from the engine, the noise would be tremendous. For this reason, the exhaust manifold sends the gases to a muffler where they go through metal plates, or tubes, with a series of holes. The pressure of the gases is reduced when they pass through the muffler, so they go out of the tailpipe quietly,

废气在高压下离开发动机。如果这些废气直接从发动机排出，将会产生巨大的噪音。因此，排气歧管将废气送到消声器，废气通过有着许多孔洞的金属盘或管道。当废气通过消声器，压力被减小，这样废气就可以安静地排出尾管。

The muffler is made of metal and is located underneath the body of a car. It’s connected between the tailpipe and the catalytic converter.

消声器由金属做成，位于汽车车身下面。它与尾管和催化转换器相连。

There are two types of muffler design. One type uses several baffled chambers to reduce noise. The other type sends the gases straight through perforated pipe wrapped in metal or fiberglass. This type of muffler is designed for the purpose of reducing backpressure and, consequently, makes slightly more noise.

有两种形式的消音器设计。一种是采用一些挡板隔腔来减小噪音，另一种是将噪音直接送到由金属或玻璃纤维包裹的多孔管道中。这种消音器的设计是用来减小背压，从而减小噪音。

The muffler quiets the noise of the exhaust by muffling the sound waves created by the opening and closing of the exhaust valve. When an exhaust valve opens, it discharges the burned gases at high pressures into the exhaust pipe, which is at low pressure. This type of action creates sound waves that travel through the flowing gas, moving much faster than the gas itself (up to 1400 mph) that the muffler must silence. It generally does this by converting the sound wave energy into heat by passing the exhaust gas and through perforated chambers of varied size. Passing into the perforations and reflectors within the chamber forces the sound waves to dissipate their energy.

消声器通过消除打开和关闭排气门产生的噪音来减小排气噪音。当排气门打开，它排出高压的燃烧气体至低压的排气管。这个动作产生声波，在废气中传播，并且速度要比废气本身速度更快（达到1400英里每小时）。这个噪音是消音器必须要消除的。消音器一般将废气通过不同尺寸的多孔腔室，从而将声波能转换为热能。废气通过腔室的孔洞及其在腔室内的反射可以消耗声波的能量。

Car manufacturers are experimenting with an electronic muffler, which uses sensors to monitor the sound waves of the exhaust noise. The sound wave data are sent to a computer that controls speaker near the tailpipe. The system generates sound wave 180 degrees out of phase with the engine noise. The sound waves from the electronic muffler collide with the exhaust sound waves and they cancel each other out, leaving only low-level heat to emerge form the tailpipe.

汽车生产商正在实验一种电子消声器，它使用传感器来检测排气噪音声波。声波信号被送到计算机，控制尾管附近的扬声器来产生一个与发动机噪音180度反相的声音。来自电子消声器的声波与排气噪音声波相撞，互相抵消，只将较少的能量由尾管排出。

6.3  

The exhaust manifold, usually constructed of cast iron, is a pipe that conducts the exhaust gases from the combustion chambers to the exhaust pipe. It has smooth curves in it for improving the flow of exhaust.

排气歧管一般由铸铁做成，将废气由燃烧室送到排气管。排气歧管内有着光滑的表面，这是为了提高废气的流动。

The exhaust manifold is bolted to the cylinder head, and has entrances for the air that is injected into it. It is usually located under the intake manifold.

排气歧管使用螺栓连接在气缸盖上，有着供空气喷入的通道。它同样位于进气歧管的下面。

A header is a different type of manifold, it is made of separate equal-length tubes.

集气管是另一种形式的歧管，它由许多独立等长的管道组成。

6.4  

There are several types of gaskets that connects the exhaust pipe to the manifold.

有几种类型连接排气管和歧管的垫圈。

One is a flat surface gasket. Another type uses a ball and socket with springs to maintain pressure. This type allows some flexibility without breakage of the seal or the manifold. A third type is the full ball connector type, which also allows a little flexibility.

一种是平面垫圈。另一种使用球铰式垫圈，使用弹簧来保持压力，它可以在不破坏密封和歧管的条件下允许产生一定的变形。第三种是全球式接头垫圈，它也允许产生少量的变形。

6.5  

Hangers hold the exhaust system in place. They give the system flexibility and reduce the noise level. The hanger system consists of rubber rings, tubes and clamps.

排气管吊耳将排气系统固定住，并且使得排气系统有一定的灵活性和减小噪音级别。吊耳系统由橡胶圈，管子和夹具组成。

6.6  

The exhaust pipe is the bent-up or convoluted pipes underneath a car. Some are shaped to go over the rear axle, allowing the rear axle to move up and down without bumping into the exhaust pipe, some are shaped to bend around under the floor of the car, connecting the catalytic converter with the muffler. Exhaust pipes are usually made out of stainless steel, since the high heat conditions involved with the muffler system will cause rust.

排气管弯曲盘旋于汽车底部。一些排气管布置在后轴上，这样后轴上下跳动就不会撞击到排气管，一些盘旋弯曲于汽车底盘上，连接催化转换器和消声器。由于消声器的高温环境容易产生锈，所以排气管一般采用不锈钢做成。

6.7    

The advantage of a dual exhaust system is that the engine exhausts more freely, thereby lowering the backpressure, which is inherent in an exhaust system. With a dual system, a sizable increase in engine horsepower can be obtained because the breathing capacity of the engine is improved, leaving less exhaust gases in the engines at the end of each exhaust stroke. This, in turn, leaves more room for an extra intake of the air-fuel mixture.

双排气系统的优势就是发动机能够更自由地排气，因此可以降低排气系统固有的背压。装有双排气系统的发动机可以获得相当大的功率提升，这是因为发动机进气的能力得到了改善。每次排气冲程末端，更少的废气被留在发动机内，从而给发动机吸入可燃混和气留下更多的空间。

5  exercise

1  Carbon monoxide (CO) also increases the rate at which the photochemical smog is formed by speeding up the conversion of nitric oxide (NO) to nitrogen dioxide.

一氧化碳也增加了光化学烟雾形成的几率。因为一氧化碳促进了一氧化氮向二氧化氮的转变。

2 Oxide of sulfur were initially ignored in the exhaust system, since the sulfur content of gasoline as a fuel is less than 1/10 of 1 percent. Because of this small amount, it was felt that it contributed very little to the overall pollution problem. However, the automobile exhaust system, when equipped with a catalytic converter, changes the sulfur dioxide into sulfur trioxide. When this combines with water vapors, a sulfuric acid mist is formed and is a very difficult pollutant to handle since it is extremely corrosive.

排气系统中的硫氧化合物之前是被忽视的，因为汽油作为燃料，硫的比例小于千分之一。由于这么低的含量，它曾经被认为总污染造成不了多大的影响。但是，装有转换器的排放系统将二氧化硫转换为三氧化硫。当它与水蒸汽混合，就形成了硫酸酸雾。这是非常难于解决的污染物，因为它有强烈的腐蚀性。

3  By visually inspecting the tailpipe emission, a determination can be make as to where an engine to defect may exist. An engine with light gray or blue smoke emitting from the tailpipe normally indicates an increase in the oil consumption through burning due to internal engine wear. Black smoke would indicate a defective fuel delivery system, causing the engine to operate in a rich mode.

通过肉眼观察排气管的排放，可以判断发动机哪里存在问题。发动机排气管排出白色或蓝色烟雾通常表示由于发动机损耗使得耗油量增加。黑色烟雾意味着燃油喷射系统可能存在问题，从而使得发动机运行在浓的工况下。