汽车专业英语翻译与课后答案--黄韶炯(全部单元都有)

Unit 1 Automotive Basics

Automobiles, trucks, and buses are essential forms of transportation. They are complex machines made up of many parts. These parts can be grouped into a number of systems. An understanding of how the system work will help you understand how the automobile works.

轿车、卡车和客车是交通运输的重要组成部分。它们都是由许多部件组成的复杂机器。这些部件可以归类为汽车的几个组成系统。了解这些各个小系统是如何工作的将有助于我们理解整个汽车系统是如何工作。

An automobile can be divided into two basic parts: a body and a chassis. The body is the enclosure that houses the engine, passengers, and cargo. It is the part of the automobile that you see. The chassis is that part of the automobile beneath the body.

汽车可以分为两个基本部分：车身和底盘。车身包围发动机、乘客和行李，它是汽车你所看到的部分。而车身以下的部分就是底盘。

1.1 THE BODY An automobile body is a sheet metal shell with windows, doors, a hood, and a trunk deck built into it. It provides a protective covering for the engine, passengers, and cargo. The body is designed to keep passengers safe and comfortable. For example, insulation in the body reduces noise and protects against heat and cold. The body styling provides an attractive, colorful, modern appearance for the vehicle. It is streamlined to lessen wind resistance and to keep the car from swaying at driving speeds.

轿车车身是一个钣金件壳体，它上面有车窗、车门、发送机罩和行李舱门等部件，它给发动机、乘客和行李提供防护。车身设计来确保乘客乘坐的安全和舒适。比如：车身绝热层可以减少噪音和抵御冷热。车身造型设计使得汽车有一个华美、现代、吸引人的外观。车身的流线型设计可以减少风阻，防止汽车行驰过程中发生摆动。

The automobile body has two basic parts-the upper body and the under body.

车身有两个基本部分-车身上部和车身下部。

1.2 The chassis The chassis is an assembly of those systems that are the major operating parts of a vehicle. The chassis includes everything except the body. The three important parts of the chassis are the frame, the engine, and the power train (also called the drive train). Each of these three parts is made up of a number of systems. A system is a mechanical or electrical unit that performs a specific function. Thus, each system (such as steering, brake, or fuel) has a certain job to do in running a vehicle. We shall look at each of these parts and systems to see how they fit together to form the automobile chassis.

底盘集中了汽车大部分的运动组件，它包括除了车身以外的所有部件。底盘有三个重要的系统：车架、发动机和传动系统。这三个系统又都有许多个完成某一个特定功能的机械或电气系统组成。为了保证汽车正常运转，每个系统（比如：转向、制动或燃油系统）都要实现一定的功能。下来我们看看这些系统和组件是如何相互连接从而组成汽车底盘的。

1.2.1 The frame The first major part of the chassis is the frame. It is made from tough steel sections welded, riveted, or bolted together. The frame looks like a steel ladder, though it sometime has an X shape for extra strength. It forms a foundation for the car body and the parts of the several systems. The body is joined to the frame with bolts. Rubber shock mounts or washers are used at each joint. These reduce vibration and road noise. In most modern cars the frame is built into the body. A car with the frame built into the body has a unitized body or unibody. The frame supports the suspension system, steering system, and the braking system.

底盘最重要的部分就是车架。车架由钢件通过焊接、铆接或螺栓联接而成，看上去就像一架钢梯。有时为了得到额外的强度，车架做成了X形状。车架为车身和很多系统部件提供了底座。车身和车架使用螺栓联接。每个联接使用橡胶防震支架或垫圈来减振降噪。现代轿车车架和车身做在了一起。采用这个形式的汽车车身叫做承载式车身。车架支撑悬架、转向和刹车系统。

The front and rear wheels are attached to the chassis by a suspension system. This system is made up of springs, shock absorbers, control arms, and stabilizers. These support the vehicle and cushion it from road bumps for better ride and handling.

前后轮通过悬架系统和底盘相连。悬架系统由弹簧、减振器、控制臂和横向稳定杆组成。它们支撑着车身，并减缓由于路面不平引起的颠簸，以获得更好的乘坐舒适性和操作稳定性。

The steering system controls the car’s direction of travel. It includes a wheel and column, steering gears, rods, and linkages. As the steering wheel is turned, its motion is transferred to the idler arm and tie rods. These cause the front wheels to turn to the right of left. On some cars, a power unit (called power steering) makes steering easier.

转向系统控制车辆行驰的方向。它包括方向盘、转向管柱、转向器、转向拉杆和转向传动装置。当转动方向盘，方向盘的运动被传递到随动臂和横拉杆，从而使得前轮向左或向右转动。有些车辆使用助力转向装置，从而使得转向更加轻便。

The brake system gives the automobile its stopping power. Hydraulic brakes are found on all modern cars. As the brake pedal is pushed with the foot, brake fluid is forced through brake lines into cylinders that press the brake shoes against a drum. This stops the motion of the car. Power units (power brakes) are used to make braking easier. Most modern cars have disc brakes on the front wheels. (Some have them on both the front and rear wheels.) Disc brakes work like a pair of pliers squeezing a rotating disc. Drum brakes are also used.

制动系统给车辆制动的动力。现代轿车都使用液压制动。当踩下制动踏板，制动液通过制动管路流入制动缸，强迫制动蹄接触制动鼓，从而阻止车辆运动。为了使刹车更加轻便，车辆也使用助力制动。现代轿车在前轮装备盘式制动器。（一些轿车在前后轮都使用盘式制动器。）盘式制动器工作原理类似一对钳子夹住旋转的盘

片。也有前后轮都使用鼓式制动器的汽车。

1.2.2 The engine The engine provides power to move the automobile. The most common type of automobile engine is the gasoline-burning piston engine. It is found in most automobiles. Diesel-fuel burning engines are also used in modern passenger cars, as well as in large trucks. All engines have fuel, exhaust, cooling, and lubrication systems. Gasoline engines also have an ignition system.

发动机给汽车提供动力。最常见的发动机是汽油机。大多数汽车都使用它。现代客车和大型卡车使用柴油机。所有的发动机都具有燃油、排放、冷却和润滑系统。汽油发动机还有一套点火系统。

The ignition system supplies the electric spark needed to ignite the air-fuel mixture in the cylinders. When the ignition switch is turned on, current flows from the 12-volt storage battery to the ignition coil. The coil boosts the voltage to produce the strong spark of 20,000V needed to ignite the engine fuel. The distributor directs the electrical current to the right spark plug at the right time. Diesel engines use the heat caused by engine compression to ignite the fuel charge. These engines are called compression ignition engines.

点火系统提供点燃气缸内油气混和物的电火花。当打开点火开关，电流从12V电池流向点火线圈。点火线圈升高电压，产生用于点火的20000V尖峰电压。分电器引导电流在正确的时刻流向正确的火花塞。柴油机使用压缩发动机产生的热量来点燃燃料，因此被称为压燃式发动机。

The automobile supplies all the electricity it needs through its electrical system. For example, the electrical system supplies electricity for the ignition, horn, lights, heater, and starter. The electricity level is maintained by a charging circuit. This circuit consists of the battery, alternator (or generator), and the regulator. The battery stores electricity. The alternator changes the engine’s mechanical energy into electrical ene rgy and recharge the battery. The regulator prevents damage to the system by regulating the maximum voltage in the circuit

汽车通过自身的电气系统给自身供电。比如：电气系统给点火系统、喇叭、灯光、供暖系统和起动器供电。系统电压通过充电系统保持稳定。充电系统由电池、发电机和调节器组成。电池储存电能。发电机将发动机的机械能转变为电能，并给电池充电。调节器调节电气系统的最大电压，提供过压保护。

The fuel system stores liquid fuel and delivers it to the engines. The fuel is stored in the tank, which is connected to a fuel pump by a fuel line. The fuel is pumped from the fuel tank through the fuel lines. It is forced through a filter (which removes moisture and dirt) into the carburetor, where it is mixed with air, or into the fuel injection system. The fuel is mixed with air to form a combustible mixture in the carburetor, the manifold, or the cylinders themselves.

燃油系统储存液态燃料，并且把燃料送至发动机。燃料储存在通过油管与油泵连接的油箱里。油泵通过油管将油箱内的油泵出，并通过滤清器（去除湿气和杂污）送达化油器与空气混合或者喷油系统。燃油在化油器、歧管或气缸自身内与空气混合，形成可燃混和物。

The exhaust system has four jobs:

1. To collect burned gases from the engines.

2. To remove dangerous emission that pollutes the air.

3. To reduce exhaust noises.

4. To get rid of the exhaust gases.

排放系统要实现四个功能：

1、收集发动机的废气。

2、去除污染空气的排放物。

3、减少排放噪音。

4、排出废气。

Exhaust gases contain carbon monoxide, unburned hydrocarbons, and oxides of nitrogen. Since all of these are harmful, the exhaust system is designed to reduce them as much as possible. In the United Stares all modern automobiles have emission control systems.

汽车废气包含一氧化碳，未燃烧的碳氢化合物和氮氧化合物。所有的这些都是有害的，排放系统设计要尽可能多减少这些有害物质。美国所有的现代车都配备了排放系统。

The cooling system removes excessive heat from the engine. The temperature in engine combustion chambers is about 1094°C. Since steel melts at around 1354°C, this heat must be carried away to prevent engine damage. Air and a coolant are used to carry away the heat. The radiator is filled with a coolant. The water pump circuits this coolant through the engine and the walls of the engine block and head. Heat also is removed by the radiator fan, which draws air through the narrow fins of the radiator. This system also supplies heat to the passenger compartment and the window defroster.

冷却系统去除发动机多余的热量。发动机燃烧室的温度可以达到1094摄氏度。钢的熔点大约是1354摄氏度，发动机多余的热量必须消除来防止发动机过热。空气和冷却剂用来带走这个热量。散热器内装满了冷却剂。水泵使冷却剂在发动机、发动机壳体和发动机盖循环流动。也可以使用冷却风扇来降温。冷却风扇将风从散热器狭窄的孔径吹出，从而带走热量。这个系统可以给乘客舱和车窗除霜器提供热量。

The lubrication system is important in keeping the engine running smoothly. Motor oil is the lubricant used in the system. The lubrication system has four functions:

1. It cuts down friction by coating moving parts with oil.

2. It produces a seal between the piton rings and the cylinder walls.

3. It carries away sludge, dirt, and acids.

4. It cools the engine by circulating the motor oil.

润滑系统非常重要，它使得发动机平滑工作。润滑系统使用机油作为润滑剂。润滑系统有四个功能：1、通过运动部件油膜，它可以减小摩擦。2、它在活塞环和气缸壁之间产生油封。

3、它可以带走金属碎屑、杂污和酸。

4、通过机油的循环，它可以冷却发动机。

To keep this system working effectively, oil filters and motor oil must be change regularly. All other moving parts in an automobile must also be lubricated. These include the transmission, differential, wheel bearings, and steering linkage.

为了使得润滑系统有效工作，机油滤清器和机油必须定期更换。汽车内所有的运动部件都必须要润滑，这包括变速器、差速器、轮轴轴承和转向传动机构。

1.2.3 The power train The power train, or drive system, delivers power from the engine to the wheels. The power from the engine moves through the transmission. Transmissions are either standard, with a manual shift lever and foot clutch, or automatic.

传动系统将发动机动力传给车轮。来自发动机的动力传递给变速器。变速器可以是一个带手动换档杆和离合器的手动变速器或者自动变速器。

The transmission has gears that control the amount of power delivered to the wheels. The transmission increases the power (torque) to start the car moving. This torque is reduced when the transmission changes gears at higher speeds. The transmission also contains a set of gears that can reverse the direction of the wheels. The transmission delivers the power to the differential. A drive (or propeller) shaft with universal joints at either end of the drive shaft allows axle movement of front-engine, rear-wheel drive cars. These flexible universal joint prevent the drive shaft from breaking. The differential delivers power to the wheels through axle. Certain gears allow one wheel to turn faster than the other wheel when the vehicle is turning a corner.

变速器使用齿轮来控制传递到车轮力矩的大小。当车辆起步时，变速器增大扭矩。当车速增大，变速器改变齿轮来减小扭矩。变速器还有一套使得车轮反向运动的齿轮。变速器将扭矩传递给差速器。发动机前置后轮驱动轿车的驱动轴两侧装有万向节，可允许产生轴向运动。万向节防止驱动轴断裂。差速器通过半轴将扭矩传递给车轮。当车辆转弯时，齿轮使得一侧车轮比另一侧车轮旋转得更快。

These are the basic systems of the automobile. Each of the systems is designed for a specific job.

以上就是汽车的基本系统。每个系统都为了一个专门的功能而设计。

1 Exercises

The automobile’s further development will be determined by already existing and steadily increasing requirements, by additional further requirements and by the technical possibilities for meeting these requirements. The following focal points for development and research efforts can be discerned:

汽车的进一步发展取决于已经存在的、目前稳定增长和未来的需求以及为了满足这些需求的技术。下来给出发展研究的几个要点：

Further improvements of the automobile through products innovation in all classis functions, i. e. performance, fuel economy, environmental impact, safety, comfort and reliability.

Further development of new technologies such as electrics, alternative materials, new test and production methods.

Long-range solutions for traffic problems such as highway congestion, smog in cities and carbon dioxide enrichment of our atmosphere.

传统功能的产品革新，比如：性能、燃油经济性、环境友好、安全、舒适性和可靠性。

新技术的发展，比如：电气、替代材料、新型测试和生产技术。

解决交通问题的技术，比如：交通拥堵，城市烟雾和温室效应。

Unit2 Automotive engine

2.1 Purpose and locations of engines The purpose of an automobile engine is to supply the power needed to move the vehicle. The engine produces this power by burning fuel inside it. Because the engine burns fuel inside, or internally, the engine is known as an internal combustion engine (ICE).

汽车发动机的功用是提供汽车行驰所需的动力。发动机通过发动机内部燃烧燃料来产生这个动力。由于燃料燃烧在发动机内部进行，这种发动机被称作内燃机。

Most automobile engines are located at the front of the vehicle. Many engines drive the rear wheels. This requires a long drive shaft extending from the front wheels to the rear wheels. Other engines drive the front wheels. In the rear-wheel-drive arrangement, the engine sits longitudinally. Its long dimension is from front to back.

对于大多数汽车，发动机布置在汽车前部。许多发动机驱动后轮，这就要求从前轮到后轮的长驱动轴。其余发动机驱动前轮。对于后轮驱动的汽车而言，发动机由前到后纵向布置。

In the front-wheel-drive arrangement, the engine sits crosswise, transversely. With either arrangement, the power is carried to the drive wheels (rear or front) by gears and shafts.

对于前轮驱动的布置，发动机横置。无论哪种布置方式，能量都是通过齿轮和传动轴传到驱动轮（前轮或后轮）。

Some cars have the engine mounted in back of the front seat. This is called a mid-engine arrangement. Other cars have been built with the engine mounted at the rear, in back of rear seat. The Volkswagen “beettle” is an example of rear.

有些汽车的发动机位于前排座椅的后面。这种布置被称为发动机中置。还有些汽车的发动机位于后部，安置在后排座椅后面。大众汽车的甲壳虫就是发动机后置的一个例子。

2.2 Engine types Various kinds of engine are used in automotive vehicles. The two major types are:The piston engine inwhich pistons move up and down, or reciprocate, in the engine cylinder. This is the engine used in all cares

today, except for some models of Mazda.

2. The Wankel rotary engine in which rotate, or spin. The Mazda Motor Corporation of Japan is the major manufacturer of this engine.

汽车上使用着不同种类的发动机。它们可以分成两大类：

1、往复活塞式发动机：发动机在气缸内作上下往复运动。除了马自达公司的几款以外，现今几乎全部轿车都采用这种发动机。

2、转子发动机：活塞在气缸内作旋转运动。日本的马自达公司是这类发动机的主要生产商。

There are two types of piston engines-spark ignition (SI) and compression ignition (CI). Spark-ignition engines use an electric system with spark plugs. Electric sparks at the spark plugs ignite, or set fire, the fuel in the engine cylinders. The combustion of the fuel makes the engine run and produce power. This is the engine used in most produce power. This is the type of engine used in most automotive vehicles.

活塞式发动机可以分为两类：点燃式和压燃式。点燃式发动机使用带火花塞的点火系统。火花塞的电火花点燃发动机气缸内的燃料。燃料燃烧驱动发动机，并做功。这是大多数动力源采用的发动机，也是大多数汽车采用的发动机形式。

The compression-ignition engine uses the heat of compression to ignite the fuel.When air is compressed, it gets very hot. In the diesel engine, the air is compressed so much that its temperature goes up to 538 degrees Celsius or higher. The diesel fuel is sprayed into this very hot air and is ignited by the heat. Some automobiles have diesel engines. Many heavy-duty trucks and buses are powered by diesel engines.

压燃式发动机使用压缩产生的热量来点燃燃料。当空气被压缩，它可以达到非常高的温度。对于柴油式发动机，压缩空气可以使得空气温度达到538度或者更高。此时，柴油被喷射到这炽热的空气中，被空气的热量点燃。一些轿车使用柴油发动机。重型卡车和客车普遍使用柴油发动机。

There are other engines still in the experimental stage that might someday become important. These include gas-turbine engines, steam engines, Stirling engines, and electric motors.

还有一些目前尚且处于试验阶段，但未来可能会非常重要的发动机，比如：燃气涡轮机、蒸汽机、斯特灵发动机和电动机。

2.3 Basic engine systems A spark-ignition engine requires four basic systems to run. Diesel engines requires three of these systems. They are fuel system, ignition system (expect diesel), lubricating system and cooling system. Each performs a basic job in making the engine run. These are described briefly below.

点燃式发动机运转需要4个基本系统，而柴油发动机需要3个基本系统。它们是燃油系统、点火系统（柴油发动机不需要），润滑系统和冷却系统。每个系统实现一个基本功能来使得发动机运转。下文将简短介绍这些系统。

2.3.1 fuel system The fuel system supplies gasoline or diesel fuel to the engine. This fuel is mixed with air to make a combustible mixture (a mixture that will run). Each cylinder is repeatedly filled with the mixture. Then, the mixture is ignited or burned, producing high pressure. The high pressure makes the piston move (or rotors spin). This turns shafts that rotate the wheels, causing the vehicle to move.

燃油系统给发动机提供汽油或柴油燃料。燃油与空气混合形成可燃混合气。发动机的每个气缸重复充满这种可燃混合气，然后它们被点燃或压燃，产生高压。这个高压使得发动机活塞运动（或者转子旋转），驱动轴来旋转车轮，从而使得汽车行驶。

2.3.2 ignition system Every time the fuel system delivers air/fuel mixture to a cylinder, the ignition system follows up by a delivering an electric spark. This ignite the mixture which creates the high pressure that moves the pistons and turns the car wheels. The action is repeated many times each second while the engine is running.

每当燃油系统将可燃混合气送至气缸，点火系统接着就发出电火花来点燃缸内的可燃混合气，从而产生高压，使得活塞运动和汽车行驶。当发动机运转时，每秒钟要点火多次。

The ignite system takes the low voltage of the battery and builds it up to a very high voltage: as high as 47,000 volts in some systems. This high voltage jumps the gaps in the spark plugs, producing the sparks that ignite the air/fuel mixture in the engine cylinders.

点火系统将电池的低电压升压到高压。对于某些系统，可以达到47000伏。这个高压击穿火花塞间隙，产生电火花，点燃发动机气缸内的可燃混合气。

2.3.3 The lubricating system The engine has many moving metal parts. If metal parts rub against each other, they will wear rapidly.To prevent this, engines have lubricating oil. The oil gets between the metal parts so they slide on the oil, and not on each other.

发动机有许多运动金属部件。如果这些金属部件相互摩擦，那它们磨损就会很快。为了防止这种情况，发动机使用润滑油。润滑油在金属部件之间，使得金属部件在油膜上滑动，而不是彼此之间的摩擦。

The lubricating system has an oil pan at the bottom of the engine which holds several quarts (liters) of oil. An oil pump, driven by the engine, sends oil from this reservoir through the engine. After circulating through the engine, the oil drops back to the oil pan. The oil pump continues to circulate the oil as long as the engine is running.

发动机润滑系统在发动机底部有一个储存几升汽油的油底壳。由发动机驱动的油泵将油从油底壳泵到发动机循环流动。在发动机循环后，润滑油流回到油底壳。只要发动机在运转，油泵就始终使润滑油循环流动。2.3.4 Cooling system Where there is fire (combustion), there is heat. Burning of the air/fuel mixture raises the

temperature inside the engine cylinders several thousand degrees. Some of this heat produces the high pressure that moves the pistons to produce power. Some of the heat leaves the cylinders with the exhaust gas. The exhaust gas is what is left after the air/fuel mixture burns. It is cleared out of the cylinders after the combustion is complete.

哪里有燃烧，哪里就有热量。可燃混合气的燃烧使得发动机气缸内温度上升数千度。部分热量产生高压来驱动活塞产生动力。部分热量伴随排放气体被带出气缸。排放气体指的是可燃混合气燃烧后剩余物。当燃烧结束，排放气体被排出气缸。

Some of the heat is removed by the circulating oil. After the hot oil drops down into the oil pan, the oil gives up some of this heat to the air passing under the oil pan. The rest of the heat is removed by the cooling system.

部分热量被循环油带走。当温度较高的油流回到油底壳，热量通过油底壳下流动的空气带走。剩余的热量就要使用冷却系统来带走。

2.3.5 Other engine system An engine will run with the four basic systems described above-fuel, ignition, lubricating and cooling. However, three other related systems are also necessary. These are the exhaust system, the emission-control system, and the starting system.

具备上述的燃油、点火、润滑和冷却系统，发动机就可以运转。但是，其余相关的3个系统也是非常必需的。它们是排放系统、排放控制系统和启动系统。

The exhaust system reduces the noise of the burned gases leaving the engine cylinders and carries these exhaust gases safely away from the people in the car. The emission-control system is required by law to reduce the air pollution the engine could produce. The starting system is needed to crank the engine. A battery provides the electric power to operate the starting motor and the ignition system during cranking.

排放系统减少发动机气缸可燃混合气燃烧时的噪音，并且将废气安全带走，使其远离车厢内的人。排放控制系统是法律强制要求的，用来减少发动机产生的空气污染。启动系统是用来启动发动机。启动过程中，由电池给启动电机和点火系统提供能量。

2.4 Energy conversion The internal combustion engine is a device used to convert the chemical energy to the fuel (gasoline or diesel fuel) into heat energy, and then to convert this heat energy into usable mechanical energy. This is achieved by combining the appropriate amounts of air and fuel, and burning the mixture in an enclosed cylinder at a controlled rate. A movable piston in the cylinder is forced down by the expanding gases of combustion.

发动机是一个将燃料（汽油或柴油）的化学能转化成热能，再将热能转化成可利用的机械能的装置。实现这个能量的转化是通过混合适当的空气和燃油，并在密封的气缸内以一个可控的速率燃烧这个可燃混合气来实现的。燃烧产生的膨胀气体强迫气缸内的活塞运动。

An average air/fuel ratio for good combustion is about 15 parts of air to 1 part of fuel by weight. This means that for every gallon of gasoline burned, the oxygen is about 9,000 to 10,000 gallons of air is required. Air is about 21% oxygen and 78% nitrogen.

可燃烧良好的空燃比，按质量大约是15：1。这就意味着燃烧1加仑汽油需要的9000到10000加仑的空气里的氧气。空气大约有21%的氧气和78%的氮气。

Diesel engine operate on a much wider air/fuel ratio, since air intake is not regulated on most diesels. Ratios may range from about 20:1 to 100:1. The fact, plus the high compression of the diesel, makes it a very fuel efficient engine.

由于大多数的柴油机并不控制进气，柴油机的空燃比范围很宽，从20：1到100：1。再加上柴油混合气具有很高的压缩比，这使得柴油机的效率很高。

The movable piston in the cylinder is connected to the top of a connecting rod. The bottom of the connecting rod is attached to the offset portion of a crankshaft. As the piston is forced down, this force is transferred to the crankshaft, causing the crankshaft to rotate. The reciprocating (back and forth or up and down) movement of the piston is converted to rotary (turning) motion of the crankshaft, which supplies the power to drive the vehicle.

气缸内的活塞与连杆的上部相连，而连杆的下部与曲轴的偏移部连接。因此，当活塞向下运动时，这个运动传递到曲轴，使得曲轴旋转。活塞的往复运动（前后或者上下）就转化为曲轴的旋转运动，从而给汽车行驶提供动力。

The efficiency of the internal combustion, reciprocating piston engine in converting the potential energy in fuel into mechanical energy is only about 33%. Of the available heat energy in the fuel, about one-third is lost through through the exhaust system and one-third is absorbed and dissipated by the cooling system. Of the remaining one-third, about one-half is lost through available at the vehicle’s drive wheels.

往复活塞式内燃机将燃料的能量转化为机械能的效率大约是33%。燃料中可利用的热量有三分之一通过排气系统丢失掉，另有三分之一被冷却系统吸收和带走，剩下的三分之一大约有一半的能量在汽车的驱动轮消耗掉。

The overall efficiency of the diesel engine is considerably higher than that of the gasoline engine. The reason for this are: the higher compression ratio, the higher air/fuel ratio, and the higher heat value of the fuel. The useful power developed at the drive wheels by a diesel engine is about 25% compared to 15% by a gasoline.

与汽油机相比，柴油机的总体效率要高很多。这是因为柴油机具有更高的压缩比，更高的空燃比，柴油的热量也要更高。对于柴油机，驱动轮得到的能量大约可以达到总能量的25%，而汽油机只有15%。

2.5 four stroke-cycle gasoline engine operation The movement of the piston from its uppermost position (TDC, top dead center) to its lowest position (BDC, bottom dead center) is called a stroke. Most automobile engines operate on the four stroke-cycle principle. A series of events involving four strokes of the piston completes one cycle.

These events are: (1) the intake stroke, (2) the compression stroke, (3) the power stroke, and (4) the exhaust stroke. Two revolutions of the crankshaft and one revolution of the camshaft are required to complete one cycle.

活塞从它在气缸内的最高位置(上止点)运动到最低位置(下止点)称为一个冲程。大多数汽车发动机采用四冲程工作循环，由活塞的四个冲程组成一个工作循环，分别是：进气冲程、压缩冲程、作功冲程和排气冲程。发动机的一个工作循环需要曲轴旋转两次，凸轮轴旋转一次。

On the intake stroke the piston is pulled down in the cylinder by the crankshaft and connecting rod. During this time the intake valve is held open by the camshaft. Since the piston has moved down in the cylinder, creating a low-pressure area (vacuum), atmospheric pressure forces a mixture of air and fuel past the intake valve into the cylinder. Atmospheric pressure is approximately 14.7 pounds per square inch (about 101.35 kilopascals) at sea level. Pressure in the cylinder during the intake stroke is considerably less than this. The pressure difference is the force that causes the air/fuel mixture to flow into the cylinder, since the liquid or a gas (vapor) will always flow from a high-pressure to a low-pressure area.

吸气冲程过程中，气缸内的活塞被曲轴和连杆向下拉动。此时，凸轮轴使得进气门打开。由于活塞在气缸壁向下运动，产生了一个低压区（真空区），大气压力使得可燃混和气从进气门进入气缸。海平面的大气压大约是每平方英寸14.7磅（大约101.35千帕）。吸气冲程时，气缸内的压力要远远小于大气压。由于液体和气体总是从高压区流向低压区，因此，气缸内外的压力差就使得可燃混和气流入气缸。

As the piston is moved up by the crankshaft from BDC, the intake valve closes. The air/fuel mixture is trapped in the cylinder above the piston. Further piston travel compresses the air/fuel mixture to approximately one-eighth of its original volume (approximately 8:1 compression ratio) when the piston has reached TDC. This completes the compression stroke.

当曲轴推动活塞从下止点起向上运动，进气门关闭。可燃混和气被限制在活塞以上的气缸区域内。当活塞达到上止点时，活塞压缩可燃混合气至其原有容积的1/8（大约8:1的压缩比）。此时，压缩冲程结束。

When the piston is at or near TDC, the air/ fuel mixture is ignited. The burning of the air/fuel mixture (combustion) takes place at a controlled rate. Expansion of the burning mixture causes a rapid rise in pressure. The increased pressure forces the piston down on the power stroke, causing the crankshaft to rotate.

当活塞达到或接近上止点时，可燃混和气被点燃，并且在一个可控的节奏下进行。可燃混和气的膨胀使得压力急剧上升，并推动活塞向下运动作功，使得曲轴旋转。

当活塞达到或接近上止点时，可燃混和气被点燃，并且在一个可控的节奏下进行。可燃混和气的膨胀使得压力急剧上升，并推动活塞向下运动作功，使得曲轴旋转。

At the end of the power stroke, the camshaft opens the exhaust valve, and the exhaust stroke begins. Remaining pressure in the cylinder, and upward movement of piston, force the exhaust gases out of the cylinder. At the end of the exhaust stroke, the exhaust valve closes and the intake valve opens, repeating the entire cycle of events over and over again.

作功冲程结束时，凸轮轴打开排气门，排气冲程开始。气缸内剩余的压力和活塞向上的运动把废气排出气缸。排气冲程结束时，排气门关闭，进气门开启，从而再次重复整个循环。

To start the engine, some method of cranking the engine is required to turn the crankshaft and cause piston movement. This is done by the starter motor when the ignition key is in the start position. When sufficient air/fuel mixture has entered the cylinders and is ignited, the power strokes create enough energy to continue crankshaft rotation. At the point, the ignition key is released to the run position and starter is disengaged.

为了起动发动机，需要转动曲柄来使得活塞运动。当点火开关置于起动位置时，起动电机转动曲柄，起动发动机。当足量的可燃混和气进入气缸并被点燃，作功冲程产生的能量足以使得曲轴连续转动。此时，点火开关释放到正常位置，起动机推出啮合。

Sufficient energy is stored in the flywheel and other rotating parts on the power stroke to move the piston and related parts through the other three strokes (exhaust, intake, and compression). The amount of air/fuel mixture allowed to enter the cylinder determines the power and speed developed by the engine.

在作功冲程中，大量的能量被储存在飞轮和其他旋转部件上，从而在其余三个冲程中可以使得活塞和相连部件运动。进入气缸的可燃混合气的数量决定了该发动机的功率和转速。

2 Exercises

ⅠWhat is the purpose of an automotive engine?Ⅰ

To supply the power needed to move the vehicle.

What is the difference between a gasoline engine and a diesel engine?

A gasoline engine uses an electric ignition system with spark plugs to ignite the fuel. And a diesel engine uses the heat of compression to ignite the fuel.

What are the basic systems to run a spark-ignition engine required?

Fuel system, ignition system, lubricating system and cooling system.

List the strokes of a four-stroke-cycle gasoline engine operation.

The intake stroke, the compression stroke, the power stroke and the exhaust stroke.

What is the function of the flywheel?

It is used to store sufficient energy to move the piston and related parts through the other strokes (exhaust, intake and compression).

Ⅱ 1 A car usually has a piston engine. It consists of several moving part: pistons, connecting rods, crankshaft,

camshaft, valve lifters, intake valves and exhaust valves. The cast iron or aluminum engine block holds the moving parts. The engine block has a series of holes which are called cylinders. The cylinders can be arranged in line or in a V-shape and in the upper part of the block. Each cylinder holds a piston and the connecting rod. A circular ring is used to seal the small gap between the piston and the cylinder wall. The lower part of the block is called crankcase which holds the crankshaft with bearing mounts. Pistons are connected to the crankshaft by connecting rods.

汽车一般使用活塞式发动机。活塞式发动机由活塞、连杆、曲轴、凸轮轴、气门挺杆、进气门和排气门等运动部件组成。这些运动部件安置在铸铁或铝合金机体内。发动机体上有些凹洞，这些凹洞被称作气缸。气缸在机体上部呈直列式或V型排列。每个气缸都有活塞和连杆。活塞和气缸壁之间的微小缝隙通过一个圆环密封。机体的下部是曲轴箱，里面是带有轴承的曲轴。活塞和曲轴之间通过连杆连接。

2 The cylinder heads are the top covers of the cylinders which are tightly bolted to the top of the block. The cylinder heads contain combustion chambers. Each combustion chamber contains at least one intake and exhaust valve and one spark plug per cylinder. The valves are opened and closed in a specific sequence with valve lifters controlled by the camshaft. The camshaft is connected to the crankshaft through a time belt.

气缸盖是气缸的上盖，其通过螺栓与上机体连接。气缸盖下是燃烧腔。每个气缸的每个燃烧腔都至少要有一个进气门，一个排气门和一个火花塞。气门被由凸轮轴控制的气门挺杆按一定的顺序打开和关闭。凸轮轴和曲轴之间通过正时带连接。

Unit 3 Automotive Lubrication System

3.1 Lubrication principles Reducing friction to minimize wear and loss of power is the primary job of a lubrication system must perform. Residual oil on engine parts also provides lubrication for engine start-up.

减少摩擦，降低磨损和动力损失是润滑系统必须完成的主要工作。发动机部件上残余的油也可以为起动发动机提供润滑。

The engine oil forms a seal between the pistons, rings, and cylinders. It also helps to cool engine parts. Without the cleaning action of the lubrication system, carbon and varnish buildup would be excessive. The engine oil also absorbs the shock and dampens the noise of moving parts.

发动机油在活塞、活塞环和气缸之间形成了密封。它也有助于冷却发动机。如果没有润滑系统的清洁作用，气缸内就会累积过量的积炭。发动机油也有助于吸收振动和减少运动部件产生的噪音。

3.2 Parts of the pressure-lubrication system

3.2.1 oil pan How successful the lubrication system is in performing all these functions depends on a number of factors and conditions. There must be an adequate supply of good-quality lubricant delivered to all moving engine parts under sufficient pressure to provide hydrodynamic lubrication for rotating parts and oil adhesion to surface subject to sliding friction.

一个润滑系统成功实现以上功能取决于许多条件和状态。润滑系统必须要有足够量的高品质润滑油，并在充足的压力下将润滑油提供给发动机所有运动的部件，从而给旋转部件提供液力润滑，并给滑动的表面提供油膜。

The oil pan bolts under the engine block, where it seals off the bottom of engine. Shaped like a trough, this sheet-metal pan serves as the reservoir for about 5 quarts of oil. As oil flows from the engine, it drains downward into the oil pan. The oil pump sucks oil from the top of the oil pan, the oil sump. Many oil pans have baffles, which are thin metal partitions. These keep the oil in the sump when the car corners hard or brakes suddenly. A drain plug at the bottom of the sump allows oil to be drained from the engine. The oil-pan gasket fits between the oil pan and the bottom of the engine block.

油底壳使用螺栓与发动机气缸体连接，并对发动机底部形成密封。油底壳是一个钣金件槽形体，可以储存5夸脱的润滑油。油从发动机流出，并流回到油底壳。机油泵从油底壳上层吸油。许多油底壳有薄金属的挡油板。当车辆急拐弯或者急刹车时，挡油板可以把油保持在油底壳内。油底壳下部有一个放油螺栓，可以把发动机的油排干。油底壳和气缸体之间有油底壳垫圈。

In most engines, the oil circulates in the engine, and then returns to the pan. It stays in the pan until drawn back into the engine by the oil pump. During operation, the sump usually holds 2 to 3 quarts oil. The rest of the oil moves through the passageways of the lubrication system. With the engine off, the pan holds about four quarts of oil. The fifth quart is in the oil filter. Because a pool of oil always rests in the sump, the type of lubrication system is called a wet-sump oiling system.

对于大多数发动机，机油在发动机循环，然后流回到油底壳，并储存在油底壳内，直至被机油泵再次吸回到发动机。在这个循环过程中，油底壳通常储存2-3夸脱油，剩余的油在润滑系统的油管内流动。当发动机停止时，油底壳储存大约4夸脱油，剩余的一夸脱油在机油滤清器内。因为油底壳内总是有机油，这种润滑系统被称作湿式油底壳润滑系统。

A dry-sump oil system is used in many racing engines. This system has a separate storage tank for the oil. A second oil pump draws oil from the oil pan as soon as the oil drains from the engine. As a result, a dry-sump system can circulate more oil through the engine than a wet-sump system.

干式油底壳润滑系统在许多赛车中得到应用。这种系统有一个单独的机油箱。一旦发动机的机油开始循环，一个单独的油泵从油底壳吸油。因此，这个系统能够比湿式油底壳循环更多的油。

3.2.2 oil pump In most cars, the oil pump is in the crankcase above the sump. It draws oil through a tube that extends downward into the sump. This tube, called the oil-pump pickup tube, has a filter screen over its bottom end. The screen keeps large pieces of sludge and dirt from being drawn into the pump. The tube may be hinged on the

pump end so that it can move up and down as the oil level changes in the sump. Thus, the pump always draws oil from the top of the sump, not from the bottom where the dirt and sludge tend to settle. Modern cars use one of two common types of oil pump-the gear-type and rotor-type.

对于大多数汽车，机油泵位于油底壳上部的曲轴箱内。机油泵通过延伸到油底壳的油管吸油。这个油管被称作机油吸油管，在它的末端有一个滤网，可以阻止大块的油泥和污垢吸入到油泵内。油管可以绞接在机油泵底部，这样它就可以随着油底壳内油面的变化上下漂动，从而保证油泵总是从油底壳上部吸油，而不是从油泥和污垢易于沉淀的下部。现代汽车一般使用齿轮式油泵或者转子式油泵。

3.2.3 oil filters A modern engine uses a full-flow filtering system. In this system, the output of the oil pump flows through the oil filter before moving through engine. In other words, the oil is filtered and cleaned before each trip through the engine. When an engine runs at 3,000 rpm, its entire five quarts of oil pass through the filter at least once every minute. Thus the oil filter ensures that only clean oil enters the engine.

现代发动机使用全流式滤清器系统。在这个系统，机油泵输出的机油在流入发动机之前先通过机油滤清器。也就是说，在发动机的每次循环之前机油都进行了滤清。当发动机转速为3000转/分时，油底壳内的全部5夸脱油每分钟都得到一次滤清。这样，机油滤清器就确保进入发动机的机油是干净的。

Modern engines use replaceable oil filters. When dirty, such a screw-on filter is replaced with a new one. Inside the steel outer casing of the unit, a special paper acts as a filter. Folded and tightly packed, this paper has just the right porosity. These tiny holes in the paper allow oil to pass through, but filter out dirt and sludge. The paper is treated to protect it from acid or water in the oil.

现代发动机采用可替换型机油滤清器，滤清器和机体采用螺纹固定。这样，可以拆下脏的滤清器，换上新的滤清器。在滤清器钢外壳的内部是特殊的纸滤芯。纸滤芯具有适当的微孔，被折叠并压紧在滤清器里。这些微孔可以让机油通过，但把油泥和杂质截流在滤芯上。滤纸经过特殊的处理，可以抵御机油里的酸和水（抗腐蚀性和抗湿性）。

Normally, oil enters the oil filter from the outside. Oil enters the filter around the outer edge of the base. The oil flows through the paper to the center of the container. It then flows out to the engine. Most filters also have a pressure-relief valve, or bypass valve. Such a valve allows oil to flow to the engine without going through the filter. This is necessary when the filter becomes too clogged for oil to pass through it. Thus, a plugged filter allows dirty oil to circulate through the engine. To prevent this, the oil and oil filter should be changed regularity.

一般而言，机油从滤清器底部的外边缘流入滤清器，并通过滤纸流入滤清器的中心，然后流进发动机。多数滤清器设置了卸压阀或者旁通阀。这个阀可以使机油不通过滤清器直接流入发动机。当滤清器被严重堵塞以至机油无法通过滤芯时，卸压阀就非常必要。被堵塞的滤清器使得没有滤清的机油在发动机内循环。因此，需要定期更换机油和机油滤清器。

3.3 Engine lubrication An internal combustion engine would not run for even a few minutes if the moving parts were allowed to make metal-to-metal contact. The heat generated due to the tremendous amounts of friction would melt the metals, leading to the destruction of the engine. To prevent this, all moving parts ride on a thin film of oil that is pumped between all the moving parts of the engine. Once between the moving parts ,the oil serves two purposes. One purpose is to lubricate the bearing surfaces. The other purpose is to cool the bearing by absorbing the friction-generated heat. The flow of oil t o the moving parts is accomplished by the engine’s internal lubricating system.

如果发动机的运动部件是金属与金属的直接接触，内燃机运行无法超过几分钟。摩擦产生的巨大热量可以熔化金属，从而损坏发动机。因此，发动机所有的运动部件之间都要有一层薄油膜。作用在运动部件之间的机油有两个功用。一个作用是润滑轴承面，另一个作用是吸收摩擦产生的热量，冷却轴承。发动机的内润滑系统使得机油流到各个运动部件。

The oil pump is of the gear type, consisting essentially of two gears in mesh and requires no attention or adjustment. It is housed in the sump, being driven by a shaft and skew gearing from the camshaft.

齿轮泵式燃油泵实际上由两个相互啮合的齿轮组成，无需调整。它位于油底壳底部，由来自凸轮轴的一根轴和斜齿轮驱动。

3.4 Lubrication oils Motor oils for automobile engines fall into two basic categories: petroleum-based oils and synthetic oils. Petroleum-based oils, however, contain a variety of additives, so in fact they, too, are partly synthetic. Some of the major additives include those described here.

发动机机油可以分为两类：石油基润滑油和合成润滑油。实际上，石油基润滑油也包含大量的添加剂，因此，部分上它也是合成润滑油。主要使用的添加剂如下所述。

Antiscuff additives help to polish moving parts, including cams, pistons, and cylinder walls. This is particularly important during new engine break-in and after an engine overhaul. Since heat is the prime enemy of antiscuff additives, operating conditions that produce excessively high engine temperatures reduce the life expectancy of these additives. This type of the operation requires more frequent oil changes than does normal operation.

抗磨损添加剂可以抛光运动部件，比如：凸轮、活塞和气缸壁。这对于新发动机磨合和大修后的发动机尤其重要。热量是这种添加剂最大的敌人，使得发动机过热的运行工况就会减小抗磨损添加剂的使用寿命。因此，这种运行工况下要比正常使用要求更加频换的更换机油。

Corrosion inhibitors reduces the formation of harmful acids by attacking the acid-forming ingredients. Combustion produces a number of by-products, including acid and water. Corrosion inhibitors neutralize these combustion

by-products before they can do any harm to the engine. A cold engine, rich fuel mixture, a poorly turned engine and much short trip, cold-weather driving increases the amount of acid produced

腐蚀抑制剂可以通过攻击酸形成的成分从而减小有害酸的形成。燃烧会生成大量的副产品，比如：酸和水。腐蚀抑制剂中和这些燃烧副产品，避免其对发动机腐蚀。冷机、成分丰富的可燃混合气、工况较差的发动机以及短途和寒冷天气下的行驰会加剧这些酸的产生。

Detergent-dispersants clean engine parts during operation and keep these contaminants in suspension in the oil. As the oil is forced through the filter, the majority of these contaminants are trapped by the filter.

当发动机运行时，清洁分散剂可以清洁发动机部件，并使得污垢悬浮在油中。当机油通过滤清器，大部分污垢被滤清器过滤掉。

Viscosity index improvers tend to stabilize or improve the viscosity of engine oils at various temperatures. They tend to give the oil more body when the oil is cold. In other words, they improve the body and fluidity of the oil. The ability of the oil to carry a load at high temperature is improved by this additive, and the ability of the oil to flow when cold is also improved

黏度改善剂可以稳定或改善机油在不同温度下的黏度。当机油过冷时，它可以提高机油的流度。也就是它可以改善机油的黏度和流度。高温时，黏度改善剂提高了机油承载的能力，低温时，黏度改善剂提高了机油的流度。

Foam inhibitors reduce the tendency of oil to foam. Heat and agitation mix the the oil with air to create foam. Oil foam reduces the lubrication ability of the oil and causes oil starvation and failure of engine parts. Loss of oil pressure due to foaming increases this problem.

泡沫抑制剂可以阻止机油形成泡沫。热量和搅动使得机油和空气混合形成泡沫。泡沫减少了机油的润滑能力，造成了发动机部件表面的供油不足。泡沫形成降低了油压，这也加剧了这个问题。

3 Exercises

1 What is the purpose of automobile lubrication system?

Reducing friction to minimize wear and loss of power

3 Explain what the function of oil is.

Form a seal between the pistons, rings, and cylinders.

Cool engine parts.

Clean carbon and varnish.

Absorb the shock and dampen the noise.

4 Name at least three common additives used in compounding oils.

Antiscuff additives.

Corrosion inhibitor.

Detergent-dispersant.

Foam inhibitor.

Viscosity index improver.

6 Explain how oil reduces friction.

All moving parts ride on a thin film of oil instead of metal-to-metal contact.

7 Define the word viscosity.

The body and fluidity of the oil.

8 What is detergent oil?

Clean engine parts during operation and keep contaminants in suspension in the oil.

What is the difference between the full flow filter system and the bypass filter system?

1 The bypass filter system allow oil to circulate through the engine when the filter becomes too clogged for oil to pass through it.

The purpose of the lubrication system is to circulate oil through the engine. Many parts inside the engine, such as the camshaft, crankshaft, connecting rods, and pistons are connected to other metal parts. When parts rub together, friction is created. Friction produce heat. Although two metal surfaces may appear smooth to the naked eye, they may look rough when seen through a microscope.

润滑系统的作用是让润滑油在发动机循环。发动机内部许多部件，如：凸轮轴，曲轴，挺杆和活塞都与其他金属部件相连。当这些部件相互接触，就产生了摩擦。摩擦就会产生热量。肉眼看上去，两个金属的表面非常光滑，但通过显微镜观察，它们实际上非常粗糙。

2 An engine must have a good lubrication system. Without it, the friction heat from the contact of the moving parts would wear the parts and causes loss. Oil, when placed between two moving parts, separates them with a film. This oil film prevents the parts from rubbing against each other. This oil film also cushions the parts, giving quieter and smoother engine operation.

发动机必须要有好的润滑系统。没有润滑系统，运动部件之间摩擦产生的热量会磨损部件和耗费功率。当润滑油位于两个运动部件之间时，就会产生一层油膜来分离这两个部件。油膜可以防止两个部件相互摩擦，还起到类似缓冲垫的作用，可以让发动机安静平稳的工作。

Unit 4 The Cooling System

The purpose of the engine’s cooling system is to remove excess heat from the engine, to keep the engine operating at its most efficient temperature, and to get the engine up to the correct temperature as soon as possible after

starting. Ideally, the cooling system keeps the engine running at its most efficient temperature no matter what the operating conditions are.

发动机冷却系统的作用就是取出发动机多余的热量，保持发动机在最佳效率温度点运行，并在启动发动机后尽可能快使得发动机达到适合的温度。理想状态下，无论什么样的运行状态，冷却系统都可以使得发动机运行在最佳效率温度点。

Fuel burning engines produces enormous amounts of heat, tem perature can reach up to 4000 F when the air-fuel mixture burns. However, normal operating temperature is about 2000F.

发动机要产生大量的热量。当可燃混和气燃烧时，温度可以达到4000F，而发动机的运行温度大约是2000F。The exhaust system takes away much of the heat, but parts of the engine, such as the cylinder walls, pistons, and cylinder head, absorb large amounts of the heat. If a part of the engine gets too hot, the oil film fails to protect it. This lack of lubrication can ruin the engine

排放系统可以带走大量的热量，但是发动机的一些部件，如：气缸壁，活塞和气缸盖会吸收许多热量。如果发动机的部件过热，油膜就会失去保护作用。而缺乏油膜的润滑就会损坏发动机。

On the other hand, if an engine runs at too low a temperature, it is inefficient, the oil gets dirty (adding wear and subtracting horsepower), deposits form, and fuel mileage is poor- not to mention exhaust emissions! For these reasons, the cooling system is designed to stay out of the action until the engine is warmed up.

另一方面，如果发动机运行在过低的温度下，发动机的效率就会低下，燃油变脏（增加损耗，减少马力），积炭形成，燃油里程数变差，更不要说排放了。正是因为这些原因，冷却系统被设计为并不工作直到发动机变热。

There are two types of cooling systems, liquid cooling and air cooling. Most auto engines are cooled by the liquid type, air cooling is used more frequently for airplanes, motorcycles and lawnmowers.

目前有两种冷却系统：液体冷却系统和空气冷却系统。大多数汽车发动机使用液体冷却系统，空气冷却系统经常在飞机、摩托车和除草机上得到应用。

The cooling system of a water-cooled engine consists of the engine’s water jacket, a thermostat, a water pump, a radiator and radiator cap, a cooling fan (electric or belt-driven), hoses, and usually an expansion (overflow) tank.

水冷式发动机冷却系统由发动机水套、节温器、水泵、散热器、散热器盖、冷却风扇（电或皮带驱动）、水管和溢流槽。

The pump sends the fluid into the engine block, where it makes its way through passages in the engine around the cylinders. Then it returns through the cylinder head of the engine. The thermostat is located where the fluid leaves the engine. The plumbing aro und the thermostat send the fluid back to the pump directly if the thermostat is closed. If it is open, the fluid goes through the radiator first and then back to the pump.

水泵将冷却液泵入发动机壳，然后冷却液沿着发动机内的通道在气缸周围流动，接着通过发动机气缸盖流回到水泵。节温器位于冷却液离开发动机的位置。如果节温器关闭，节温器周围的水管将冷却液直接送回到水泵。如果节温器打开，冷却液先流经散热器，之后再流回到水泵。The water pump is a simple centrifugal pump driven by a belt connected to the crankshaft of the engine. The pump circulates fluid whenever the engine is running. 冷却系统的水泵是简单的离心式水泵，由与发动机曲轴相连的皮带驱动。只要发动机在运转，水泵就要循环冷却液。

4.1 The water pump The water pump uses centrifugal force to send fluid to the outside while it spins, causing fluid to be drawn from the center continuously. The inlet to the pump is located near the center so that fluid returning from the radiator hits the pump vanes. The pump vanes fling the fluid to the outside of the pump, where it can enter the engine.

水泵一旦旋转，水泵产生的离心力将冷却液甩向外侧，源不断从中心吸取冷却液。水泵的入水口位于中心周围，这样当冷却液从散热器流回。冷却液冲击水泵叶片。水泵叶片将冷却液甩向水泵外侧，并进入到发动机。

4.4 The water jacket The water jacket is a collection of passages within the block and head. There passages let the coolant circulate around the hot spots (valve seats and guides, cylinder walls, combustion chamber, etc.) in order to cool them off.

水套是发动机壳体和发动机盖内部冷却液通道的集合。这些通道使得冷却液在热点（气门座和导管，气缸壁，燃烧室等）周围流动，从而冷却它们。

Temperature in the combustion chamber of the engine can reach 4500F, so cooling the area around the cylinder is critical. Areas around the exhaust valves are especially crucial, and the almost all of the space inside the cylinder head around the valves that is not needed for structure is filled with coolant. If the engine goes without cooling for very long, it can seize. When this happens, the metal has actually gotten hot enough for the piston to weld itself to the cylinder. This usually means the complete destruction of the engine.

燃烧室的温度可以达到4500F ，气缸周围区域的冷却非常重要，尤其排气门周围的区域是至关重要的。因此，在满足结构强度的要求下，缸盖内排气门周围几乎所有的空间都充满了冷却液。如果发动机没有长时间冷却，发动机就会损坏，此时，金属的温度已经可以使得活塞与气缸焊接在一起。这通常意味着发动机彻底的损坏。One interesting way to reduce the demands on the cooling system is to reduce the amount of heat that is transferred from the combustion chamber to the metal parts of the engine. Some engines do this by coating the inside of the top of the cylinder head with a thin layer of ceramic. Ceramic is a poor conductor of heat, so less heat is conduced through to the metal and more passes out of the exhaust.

一个有趣的减少冷却系统需求的方法是减少燃烧室到发动机金属部件热量的传递。一些发动机通过在发动机盖顶端内侧覆盖上一层薄陶瓷层来实现减少热量的传递。陶瓷导热性很差，这样较少的热量传递到金属，而较多的热量由排放系统带出。

4.3 radiator A radiator is a type of heat exchanger. It is designed to transfer heat from the hot coolant that flows through it to the air blown through it by the fan.

散热器是一种热交换器。它的设计是将流经散热器较热的冷却液的热量传递至由风扇吹过的空气。

Most modern cars use aluminum radiators. These radiators are made by brazing thin aluminum fins to flattened aluminum tubes. The coolant flows from the inlet to the outlet through many tubes mounted in a parallel arrangement. The fins conduct the heat from the tubes and transfer it to the air flowing through the radiator.

大多数现代轿车使用铝散热器。这些散热器由将薄的铝叶片焊接到扁平的铝管上制成。冷却液通过并联布置的铝管从入口流向出口。叶片将热量从铝管导出，并传给流过散热器的空气。

The tubes sometimes have a type of fin inserted into them called turbulator, which increases the turbulence of the fluid flowing through the tubes. If the fluid flowed very smoothly through the tubes, only the fluid actually the tubes would be cooled directly. The amount of heat transferred to the tubes from the fluid running through them depends on the difference in temperature between the tube and the fluid touching it. So if the fluid that is in contact with the tube cools down quickly, less heat will be transferred. By creating turbulence inside the tube, all of the fluid mixes together, keeping the temperature of the fluid touching the tubes up so that more heat can be extracted, and all of the fluid inside the tube is used effectively.

有时候铝管插有叫做湍流管的叶片，用来增加管道中冷却液的湍流现象。如果冷却液平滑从管道中流过，实际上只有与管道接触的冷却液能够直接冷却。从管道内流过的冷却液交换到管道的热量取决于管道和与管道接触的冷却液的温度差。因此，如果与管道接触的冷却液迅速冷却，较少的热量被传递。通过制造管道内的湍流，所有的冷却液混合在一起，保持与管道接触的冷却液温度较高，从而更多的热量被传递，有效地利用管道内的所有冷却液。

4.4 pressure cap The radiator cap actually increases the boiling point of your coolant by about 45F. How does this simple cap do this? The same way a pressure cooker increases the boiling temperature of water. The cap is actually a pressure release valve, and on cars it is usually set to 15 psi. The boiling point of water increases when the water is placed under pressure.

散热器盖实际上将冷却液的沸点提高了大约45F。它是如何做到的呢？高压锅使用同样的方法增加水的沸点。压力盖实际上是个压力释放阀。轿车上，它一般被设定为15psi。当水在压力下，水的沸点会提高。

When the fluid in the cooling system heats up, it expands, causing the pressure to build up. The cap is the only place where this pressure can escape, so the setting of the spring on the cap determines the maximum pressure in the cooling system. When the pressure reaches 15 psi, the pressure pushes the valve open, allowing coolant to escape from the cooling system. This coolant flows through the overflow tube into the bottom of the overflow tank. This arrangement keeps air out of the system. When the radiator cools back down, a vacuum is created in the cooling system that pulls open another spring loaded valve, sucking water back in from the bottom of the overflow tank to replace the water that was expelled.

当冷却系统的冷却液被加热，冷却液体膨胀，引起压力上升。散热器盖是压力唯一可以逃离的地方，因此散热器盖的弹簧设置决定了冷却系统的最大压力。当压力达到15psi，压力推开阀门，使得冷却液流出冷却系统。冷却液从溢流管流向溢流箱底部。这个设置使得空气排出冷却系统。当散热器冷却下来，冷却系统内形成一个真空，从而将另一个弹簧阀拉开，将之前排到溢流箱底部的冷却液再次吸回到散热器。

4.5 Thermostat Any liquid-cooled car engine has a small device called the thermostat that sits between the engine and the radiator. The thermostat’s main job is to allow the engine to heat up q uickly, and then to keep the engine at a constant temperature. It does this by regulating the amount of water that goes through the radiator. At low temperature, the outlet to the radiator is completely blocked – all of the coolant is re-circulated back through the engine.

任何一个液体冷却的轿车发动机都有一个叫做节温器的装置，位于散热器和发动机之间。节温器使得发动机快速升温，然后保持发动机在一个恒定的温度。节温器通过调节流过散热器冷却液的流量实现以上目的。低温下，节温器的出口完全堵塞，所有的冷却液在发动机内部循环。

Once the temperature of the coolant rises to between 180F to 195F, the thermostat starts to open, allowing fluid to flow through the radiator. By the time the coolant reaches 200F to 218F, the thermostat is open all the way.

一旦冷却液温度升到180F与195F之间，节温器开始工作，使得冷却液流向散热器。当冷却液温度位于200F 与218F之间，节温器处于全开状态。

The secret of the thermostat lies in the small cylinder located on the engine-side of the device. This cylinder is filled with a wax that begins to melt at around 180F (different thermostats open at different temperatures, but 180F is a common one). A rod connected to the valve presses into this wax. When the wax melts, it expands significantly, pushing the rod out of the cylinder and opening the valve. By letting the engine warm up as quickly as possible, the thermostat reduces engine wear, deposits and emissions.

节温器工作的秘密就在节温器发动机侧的一个小圆缸内。这个圆缸充满了蜡，蜡的熔点大约在180F（不同的节温器在不同的温度下开启，但180F是常用值）。一个与阀门联接的连杆推入到蜡里。当蜡开始溶化，蜡会显著膨胀，从而将连杆推出圆缸，并打开阀门。通过让发动机尽可能快升温，节温器减小了发动机损耗，积

炭和排放。

4.6 Fan Like the thermostat, the cooling fan has to be controlled so that it allows the engine to maintain a constant temperature.

和节温器一样，冷却风扇也需要进行控制来使得发动机在恒定的温度下运行。

Front-wheel drive cars have electric fans because the engine is usually mounted transversely, meaning the output of the engine points toward the side of the car. The fans are controller either with a thermostatic switch or by the engine computer, and they turn on when the temperature of the coolant goes above a set point. They turn back off when the temperature drops below that point.

前轮驱动式轿车使用电风扇冷却，这是因为前轮驱动式轿车的发动机通常是横向安置。这就意味着发动机的输出正对着轿车的侧面。冷却系统使用温控开关或者发动机计算机来控制风扇。当冷却液温度高于设定点时，打开风扇。一旦温度低于设定点，风扇关闭。

Rear-wheel drive cars with longitudinal engines usually have engine-driven cooling fans. These fans have a thermostatically controlled viscous clutch. This clutch is positioned at the hub of the fan, in the airflow coming through the radiator.

采用发动机纵置的后轮驱动轿车通常采用发动机驱动冷却风扇。这种风扇使用一种温控液体粘性离合器进行控制。这个离合器位于风扇的中心，面向来自散热器的气流。

4 Exercises

1 What is the function of the cooling system?

To remove excess heat from the engine, to keep the engine operating at its most efficient temperature, and to get the engine up to the correct temperature as soon as possible after starting.

2 What are the most common causes of engine overheating?

Fuel burning engines produce enormous amounts of heat. The exhaust system takes away much of the heat, but parts of the engines, such as the cylinder walls, pistons, and cylinder head, absorb large amounts of the heat.

3 Will installing a lower temperature thermostat help the engine run cooler and prevent it from overheating? No. The thermostat’s main job is to allow the engine to heat up quickly, and then to keep the engine at a constant temperature.

4 Why are liquid-cooling system pressurized?

It can increase the boiling point of the coolant.

1The fan’s activity is not always necessary, and it take power from the engine to spin. For this reas on a thermostatic control, or fan clutch, is often used to reduce drive torque when it isn’t needed (variable-speed fan).

因为风扇需要从发动机吸取能量来旋转叶片，风扇并不需要持续运转。因此，当不需要风扇运转时，温度控制器或者风扇离合器经常被用来减小转矩（变速风扇）

2A different type of fan uses centrifugal force to move its flexible plastic blades, by flattening them when the engine rpm is high (flexible-blade fan). The less angle the blade have, the less power they use. The idea of these units is to save horsepower and to reduce the noise the fan makes.

当发动机转速较高时，有一种风扇使用离心力来移动可动的塑料叶片（变叶片风扇）。叶片的迎风角越小，风扇所消耗的功率越小。这些部件的设计是用来减小功率和风扇产生的噪音。

3A fan can have from four to six blades to suck the air through the radiator. Often the radiator has a shroud for the fan to keep it from re-circulating the same hot air that has collected behind the radiator. Many fans have irregularly spaced blades to reduce resonant noise.

风扇拥有4到6个叶片来吸取来自散热器的空气。通常散热器被裹盖，防止风扇将散热器后部聚集的热空气重复循环。许多风扇有着不规则的叶片来减小共振噪音。

4Another function of the expansion tank is to remove air bubbles from the cooling system. Coolant without air-bubbles is much more efficient than coolant with air bubbles, because it absorbs heat much faster. The advantage of the expansion tank is that while the level of coolant contained in it rises and falls, the radiator is always full.

溢流箱的另一个作用是去除来自冷却系统的气泡。没有气泡的冷却液要比含有气泡的冷却液更有效，因为它可以更快地吸收热量。无论溢流箱内的液位上升或下降，散热器总是满的。

Unit 5 Fuel Injection System

Fuel injection systems have been used on vehicles for many years. The earliest ones were purely mechanical. As technology advanced, electronic fuel injection systems became more popular. Early mechanical and electronic fuel injection systems did not use feedback controls. As emissions became more of a concern, feedback controls were adapted to both types of fuel injection systems.

燃油喷射系统已经在汽车上运用了许多年。最早期的喷射系统都是机械式的。随着技术的进步，电子燃油喷射系统逐渐得到普及。早期机械式和电子式燃油喷射系统都没有采用反馈控制。由于排放问题越来越得到重视，反馈控制在这两种系统中都得到了应用。

Both mechanical and electronic fuel injection system can be found on gasoline engines. Diesel engines are most commonly found with mechanical type systems, although the newest generation of these engines have been using electronic fuel injection (EFI)

汽油发动机使用机械式或电子式燃油喷射系统。柴油机通常使用机械式燃油喷射系统，但是最新一代的柴油发动机也已经在使用电子式燃油喷射系统了。

5.1 Basic theory EFI uses solenoid valves called injectors to meter fuel delivery. Most vehicles today use 1 injector per cylinder. When the solenoid is energized, fuel sprays out into the valve port. Fuel is delivered to the injector by a high-pressure electric pump at around 40 psi. Fuel delivery is controlled by the injectors which are cycled by the computer. The computer produces a signal to open the injectors for a certain length of time depending on engine conditions relayed by sensors. The longer that the injector is open, the more fuel is injected. As engine load and rpm are increased, the injector open times are increased to match increasing airflow. This computer output signal is called the injector pulse width. The longer the pulse width, the more fuel is injected.

电子式燃油喷射系统使用被称作喷油器的电磁阀来控制喷油量。今天大多数汽车1个气缸使用1个喷油器。电磁阀一上电，燃油就被喷射至电磁阀口。高压电动燃油泵以大约40psi的压力将燃油送到喷油器。喷油量是由喷油器控制的，而喷油器的开启和关闭又是被计算机控制的。计算机根据传感器送来的工况信号，向喷油器发送开启以及开启持续时间的信号。喷油器打开时间越长，喷出的燃油越多。随着发动机负载和转速的增加，喷油器打开的时间也

要增加来匹配进气量的增加。计算机输出信号被称作喷油器脉冲宽度。脉冲宽度越大，喷出的燃油越多。5.2 Engine Requirements Stand spark ignited, 4 stroke engines require that the correct proportion of fuel be mixed with the incoming air for efficient operation. This proportion is in the range of 13 parts air to 1 part fuel for best power, 15 to 1 for best emission and 17 to 1 for best economy. Most modern engines aim for a ratio of around 14.7 to 1 for the majority of cruising and medium power conditions. This is the chemically correct ratio which results in the lowest average emissions and reasonable power. A rich condition is characterized by an excess of fuel, and a lean condition is characterized by an excess of air or lack of fuel.

标准四冲程点火式发动机为了获得高的效率，要求合适的空燃比。为了获得最佳动力性，空燃比是13比1，为了获得最佳排放，空燃比是15比1，为了获得最佳经济性，空燃比是17比1。大多数现代发动机在大多数巡航工况和适中的动力性条件下，空燃比控制目标为14.7比1。这是化学分析上适当的空燃比，可以获得最低的平均排放和适当的动力性。燃烧浓工况意味着燃料过多，稀工况意味着空气过量或燃料不足。

As rpm is increased, up to a point, airflow also increases and fuel flow must increase to match it. As the throttle is opened at a given rpm, airflow increases to a certain point and again, fuel flow must follow airflow.

当发动机转速上升到某一点，空气进气量也随之上升，此时进油量也必须对应随之上升。在某一发动机转速下，当节气门打开，空气进气量上升到某一数值下，同样进油量必须跟随空气进气量。

5.3 fuel system EFI fuel system consists of a tank, pump, fuel rail,, regulator, out an excess of fuel injectors and return line. Fuel is drawn from the tank by the pump which steps up pressure to around to 40 psi. Fuel pressure is controlled by the fuel pressure regulator located on one end of the fuel rail by bleeding fuel back to the tank through the return line. The pump always puts out an excess of fuel so large quantities are returned back to the tank during idle and low speed conditions and less as engine demand increases. The fuel rail is essentially a tubular fuel manifold designed to carry fuel to the injectors as well as hold them in place on the intake manifold. The injectors are usually sealed with O-rings on each end. One end has the fuel entering from the rail and the other end spigots into the manifold. The injector has a 2 pin electrical plug to carry switching current to the solenoid winding. When energized, the solenoid core is pulled back which pulls back a sealing pintle, disc or ball, allowing fuel to spray out in a fine, conical pattern,

电子喷油系统由油箱、油泵、油轨、调节器、喷油嘴和回油管路组成。燃油由油泵从油箱吸出，并被加压到大约40psi。油压通过位于油轨一端的燃油调节器控制。燃油调节器将燃油通过回油管路放回到油箱实现对油压的控制。油泵总是泵出过多的燃油。因此，空转或低速工况下，多余的燃油就返回到邮箱。随着发动机负载的增加，返回邮箱的燃油减小。油轨实际上就是油路歧管，用来将燃油送到喷油嘴，同时把燃油存在进油歧管内。通常使用O型环把喷油嘴的两端密封。喷油嘴一端与油轨相连，另一端与歧管采用连接管接合。喷油嘴有一个两脚电子开关来承载电磁线圈的开关电流。当电磁线圈上电，衔铁吸回，带动密封轴、密封盘或密封球，从而使得燃油细密呈圆锥形喷出。

5.4 Air metering and measurement The amount of air entering the engine is controlled by a conventional butterfly valve on most engines located in a throttle body assembly.

一般大多数发动机使用一个蝶形阀来控制进入到发动机的空气。这个阀位于节气门体总成上。

Airflow measurement is by one of two basic methods: Mass Airflow and speed Density. The mass airflow method uses either a spring loaded flap attached to a potentiometer or a heated mire mounted in front of the throttle body to sense actual airflow. The position of the flap or amount of current required to keep the wire heated to a certain temperature is relayed to the computer as a voltage signal. A certain voltage equals a certain airflow rate.

发动机进气量的测量有两种基本方法：空气流量计和速度密度法。空气流量计法使用与电位计相连的弹簧接片或位于节气门体总成前端的热线来测量实际空气流量。弹簧接片的位置或保持热线在一定温度下所需的电流被转换为电压信号传给计算机。一定的电压信号对应着一定的空气进气速率。

The speed density system uses a solid state pressure transducer to measure the pressure in the intake manifold with rpm and air temperature to indirectly determine airflow. Again, a certain pressure relates to a certain voltage which is relayed to the computer.

速度密度系统使用晶体管压力传感器测量进气歧管的压力，并联合发动机转速和空气温度来间接确定进气量。同样，一定的压力对应着一定的电压信号，然后被传给电脑。

5.5.1RPM Most systems measure rpm off of the ignition coil tachometer pulse or crank triggered magnetic/Hall effect sensors. Rpm is considered a primary input signal on all EFI systems. Most systems generate an injection pulse

for every tach pulse so as rpm is increased, the frequency of injection pulses is also increased.

发动机转速大多数燃油喷射系统实用点火线圈转速计脉冲或曲轴触发磁场/霍尔效应传感器来测量发动机转速。发动机转速是所有燃油喷射系统最重要的一个输入信号。大多数系统对每一个测速脉冲信号产生一个喷射脉冲信号。因此，随着发动机转速的增长，喷射脉冲信号频率也随着增长。

5.5.2 airflow On mass airflow type system, this input is also considered a primary input signal. X amount of air requires Y amount of fuel. As rpm and throttle opening is increased, airflow increases to a point

空气进气量对于空气流量计系统，空气进气量也是一个非常重要的输入信号。X份的空气要求Y份的燃油。随着发动机转速和节气门开度的增加，空气进气量也随之增加到一个数值点上。

5.5.3Manifold Pressure On speed density type systems, this input is essential when combined with the rpm signal to calculate airflow. As the throttle is opened, the manifold pressure increases which will require more fuel.

歧管压力对于速度密度式系统，歧管压力非常重要，它需要和联合发动机转速信号来计算空气进气量。当节气门打开，歧管压力增加，这就需要更多燃油。

5.5.4 Throttle Position This input is a secondary input on most systems. It is required mainly for acceleration enrichment when the throttle is rapidly opened. By looking at the rate of change of throttle blade angle, the computer can determine how quickly the throttle is being opened and can supply the extra fuel required momentarily to alleviate the lean condition. Throttle position is measured by a potentiometer attached to the throttle shaft.

节气门位置节气门位置信号对于大多数系统是个较为次要的信号。它主要是用于当节气门被快速打开时，加快燃油浓工况的过程。通过观测节气门叶片角度的变化率，计算机可以判断节气门以多快的速度打开，从而瞬时间提供过量的燃油来减轻较稀的工况。节气门位置是用于节气门轴相连的一个电位计来测量。

5.5.5Water Temperature Water temperature is a secondary input required mainly to ensure proper starting and warm-up of the engine. When the engine is cold, the air to fuel ratio must be very rich to enable enough fuel to vaporize for proper starting. The computer increases the injector pulse width to supply extra fuel when cold and tapers this fuel off as the water temperature increases. Once the water warms past 120 degrees or so, the computer does not need to add any extra fuel.

水温水温信号也是一个次要输入信号，主要用来保证发动机适当启动和热机。当发动机处于冷态，为了保证发动机较好的启动，空燃比必须变得很浓，来确保足量的燃油被蒸发。冷态时，计算机增加喷油嘴脉冲宽度来提供额外的燃油，并随着水温的升高逐步减少额外的燃油喷射。当水温超过大约120度，计算机不再提供额外的燃油喷射信号。

5.5.6 Air Temperature T his is a secondary input required especially on speed density systems. The sensor is usually mounted in the intake manifold or air filter area. As the air temperature drops, its density increases. Dense air requires more fuel. As the temperature of the inducted air increases, the computer reduces the pulse width to compensate for lower density. Mass airflow systems are not critically affected by operation without air temperature sensor because the airflow meter is already measuring the air mass entering the engine.

空气温度对于速度密度式系统，空气温度信号是一个次要的输入信号。这个传感器一般位于进气歧管或者空气滤清器区域。当空气温度下降，空气密度上升。空气密度越大，所要求的燃油越多。随着进气温度的上升，计算机减小喷油嘴的脉冲宽度来补偿密度的降低。由于空气流量计已经测量了进入发动机的进气量，空气流量计系统严格意义上无需温度传感器。

5.6 oxygen sensor This sensor is employed in closed loop systems to modify the basic pulse width after the fact. It is mounted into the exhaust manifold area. By looking at the oxygen content of the exhaust gases after combustion, the computer can determine if the air/fuel ratio is too rich or too lean for optimum combustion and adjust the next few injections accordingly. This sensor is primarily employed for emission control and to a lesser degree, fuel economy. For the lowest average emission, the air/fuel ratio must be kept around 14.7 to 1.

氧气传感器被用在闭环系统来根据实际情况调整基本脉冲宽度。它位于排气歧管区域。通过检测燃烧后排放的废气中氧气的含量，计算机能判断出对于最佳燃烧而言，空燃比是否过浓或过稀，从而调整接下来喷油量。氧气传感器首先被用来排放控制，其次用于燃油经济性控制。对于最低的平均排放，空燃比必须要控制在14.7：1左右。

Under full throttle conditions, this sensor is ignored by the computer so that the engine can produce more power. This is called open loop mode and the computer is supplying the injector pulse width from tables based on all of the other sensors inputs.Once throttle opening and rpm are reduced to cruising conditions, most systems will jump back into the closed loop mode where they will stay for a large portion of the time on most street driven applications.

当节气门全开状态下，氧气传感器的输入被计算机忽略，从而使得发动机产生更大的功率。这被称作开环模式。此时，计算机根据其他传感器的输入信号基于数据表提供喷油嘴脉冲宽度。一旦节气门开度和发动机转速减小到巡航状态，大多数系统会再回到闭环控制模式。对于大多数街道驾驶的情况，系统主要采用闭环控制模式。

5.7 basic operation As explained in the Basic Theory section, the computer processes all of the voltage signals from the various sensors to determine the engine operation conditions at the moment and delivers the appropriate pulse width to the injectors. If engine airflow increases by 10%, the pulse width is also increased by about 10% to keep the air/fuel ratio constant. If the rpm is doubles from 2000 to 4000 rpm, the number of injections are also doubled to double the fuel flow.

正如基本理论一节中所介绍的，计算机处理来自不同传感器的所有电压信号来判断发动机所处的实时工况，并向喷油嘴发送适当的脉冲宽度。如果发动机进气量增加了10%，脉冲宽度也要相应的增加大约10%来保证空燃比恒定。如果发动机转速从2000转/分变为4000转/分，喷油脉冲个数也要翻倍来匹配翻倍的空气进气量。

The computer looks at the changes in sensor inputs every few milliseconds in order to be ready to modify the pulse width if any parameter changes.

每隔几微秒，计算机就要观察传感器输入的变化，从而调整脉冲宽度，以适应参数的变化。

5 exercise

1 The injection pump in the jerk pump system is used to time, meter and pressurize the fuel. This is the most common and utilized system. The plungers are driven by a camshaft that is designed to control the injection characteristics of the engine.

高压燃油喷射泵系统中的喷油泵用来给燃油分配，测量和施加压力。它是最普遍使用的系统。活塞由凸轮轴驱动，设计用来控制发动机的喷油特性。

2Compared to gasoline engines, diesel have a number of important advantages. One is fuel economy. Diesel engines are unthrottled, so pumping losses are reduced. This improves breathing efficiency for more fuel-efficient operation. Diesel engines also run much leaner air/fuel ratio than their gasoline counterparts, and have much higher compression ratios which improves thermal efficiency and helps squeeze even more power out of every drop of fuel.

与汽油机相比，柴油机具有许多重要的优势，其中之一就是燃油经济性。柴油机没有节气门，从而减小了泵的能量损失。这为更有效的运行改善了发动机呼吸效率。柴油机与汽油机相比，可以运行在更稀的空燃比下，有更高的压缩比，从而提高了热效率，有助于从燃油上更多地获取能量。

3The injection systems that delivers fuel to a diesel engine operates at much higher pressure than a gasoline: as much as 17400 psi for traditional pump, line and injector systems up to 23500 psi for common rail system, compared to 35 to 90 psi for most gasoline EFI system. The fuel is also sprayed directly into the combustion chamber rather than into the intake port.

给柴油机送燃油的喷射系统工作油压要比汽油机高出许多。传统柴油机泵的优雅达到17400 psi，一般的喷油泵-高压油管-喷油器系统可以高达23500psi，而大多数汽油电子喷射系统只有35到90psi。对于柴油机，燃油并不是喷射到进油口，而是直接喷射到燃烧室内部。

4 Diesel engines have no ignition system, so there are no spark plug, plug wire or distributor to cause problems. The fuel is ignited by the heat of compression and controlled by injection timing. For cold starting, diesels use a glow plug system as an additional heat source to aid in the combustion process until the engine is running and generating its own heat.

柴油机没有点火系统，因此也就没有可能引发问题的火花塞、火花塞线圈或分电器。柴油被压缩产生的热量点燃，并由喷射时间加以控制。对于冷机启动，柴油机使用电热塞来作为额外的热源，从而给燃烧提供帮助，直至发动机运转，可以产生自己的热量。

5 The HEUI System develops injection pressures as high as 18000-24000 psi, by applying high-pressure oil to the top of an intensifier piston. By varying the oil pressure, injection rate can be controlled independently of the crank or cam. Thus injection timing, rates, and pressures are no longer dependent on camshaft position, speed or cam ramp velocity. This is all controlled by a solenoid-actuated valve that determines when high-pressure oil is applied to the piston.

HEUI系统（美国卡特匹勒公司的电控中压共轨式喷油系统）通过将高压油施加在强化过的活塞上部，可以产生高达18000至24000psi的喷射油压。通过改变油压，可以独立于曲柄或凸轮来控制喷射频率。因此，喷射的时间，频率和压力都不再依赖于凸轮轴位置，车速或凸轮斜面速率。这些都可以通过一个电磁作动阀进行能够控制，这个阀决定了向活塞施加高压油的时间。

Unit 6 Exhaust System

The exha ust 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。

6.3The 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。

6.5Hangers 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。

UNIT 7 THE IGNITION SYSTEM

背景知识：点火系统的基本功用是在发动机各种工况和使用条件下，在气缸内适时、准确、可靠地产生电火花，以点燃可燃混合气，使发动机作功。按其组成和产生高压电方式的不同可分为传统蓄电池点火系统、电子点火系统、微机控制点火系统。传统点火系统主要由电源(蓄电池和发电机)、点火开关、点火线圈、电容器、断电器、配电器、火花塞、阻尼电阻和高压导线等组成。

分电器由断电器、配电器、电容器和点火提前调节装置等组成。它用来在发动机工作时接通与切断点火系统的初级电路，使点火线圈的次级绕组中产生高压电，并按发动机要求的点火时刻与点火顺序，将点火线圈产生的高压电分配到相应气缸的火花塞。

配电器由分电器盖和分火头组成。用来将点火线圈产生的高压电分配到各缸的火花塞。分电器盖上有一个中心电极和若干个旁电极，旁电极的数目与发动机的气缸数相等。分火头安装在分电器的凸轮轴上，与分电器轴一起旋转。发动机工作时，点火线圈次级绕组中产生的高压电，经分电器盖上的中心电极、分火头、旁电极、高压导线分送到各缸火花塞。电容器安装在分电器壳上，与断电器触点并联，用来减小断电器触点断开瞬间，在触点处所产生的电火花，以免触点烧蚀，可延长触点的使用寿命。

There are many different types of ignition systems. Most of these systems can be placed into one of three distinct groups: the conventional breaker point type ignition systems (in use since the early 1,900s); the electronic ignition systems (popular since the mid 70s); and the distributorless ignition system (introduced in the mid 80s).

点火系统有多种不同类型的。其中大部分系统属于（可划分为）以下三种：传统触点型点火系统（19世纪早期使用），电子点火系统（从70年代中期开始流行），无分电器点火系统（80年代中期引入）。

The automotive ignition system has two basic functions: it must control the spark and timing of the spark plug firing to match varying engine requirements, and it must increase battery voltage to a point where it will overcome the resistance offered by the spark plug gap and fire the plug.

汽车点火系统有两个基本功能：一是控制火花塞的电点火（能量）以及点火时刻，使其与发动机工作需求相匹配。二是将蓄电池电压升至能够击穿火花塞间隙并产生电火花（点火）的高压。

7.1 Point-Type Ignition System

An automotive ignition system is divided into two electrical circuits - the primary and secondary circuits (Figure 7-1). The primary circuit carries low voltage. This circuit operates only on battery current and is controlled by the breaker points and the ignition switch. The secondary circuit consists of the secondary windings in the coil, the high-tension lead between the distributor and the coil (commonly called the coil wire), the distributor cap, the distributor rotor, the spark plug leads and the spark plugs.

汽车点火系统可分成两个电路，初级电路和次级电路。初级电路提供低压，它只在蓄电池电流下起作用，由断电器和点火开关控制。次级电路包括点火线圈的次级绕组，分电器和点火线圈之间的高压导线，分电器盖，分电器转子（分火头），火花塞引线和火花塞。

distributor rotor分火头lead 引线，导线

The distributor is the controlling element of the system. It switches the primary current on and off and distributes the current to the proper spark plug each time a spark is needed. The distributor is a stationary housing surrounding a rotating shaft. The shaft is driven at one-half engine speed by the engine’s cams haft through the distributor drive gears. A cam near the top of the distributor shaft has one lobe for each cylinder of the engine. The cam operates the contact points, which are mounted on a plate within the distributor housing.

分电器是系统的控制元件。它控制着初级电流的通断，并把每次点火后所产生的（高压）电流分配至合适的

火花塞。配电器是围绕（分电器）转轴的固定壳体。分电器轴由发动机凸轮轴通过分电器传动齿轮驱动，其转速是发动机转速的一半。分电器轴顶端的凸轮凸角数与发动机气缸数相对应。凸轮控制着断电器触点的打开和闭合，断电器触点安装在分电器壳体内的一个金属板上。

Stationary静止的，固定的

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A rotor is attached to the top of the distributor shaft. When the distributor cap is in place, a spring-loaded piece of metal in the center of the cap makes contact with a metal strip on top of the rotor. The outer end of the rotor passes very close to the contacts connected to the spark plug leads around the outside of the distributor cap.

分火头连接在分电器轴的顶端。当分电器盖在原位不动时，分电器盖中心的弹簧金属片与分电器轴顶端的金属条相接触。分火头外端与分布在分电器盖外围的触点非常接近，触点与火花塞引线相连。

The coil (Figure 7-2) is the heart of the ignition system. Essentially, it is nothing more than a transformer which takes the relatively low voltage (12 volts) available from the battery and increases it to a point where it will fire the spark plug as much as 40,000 volts. The term "coil" is perhaps a misnomer since there are actually two coils of wire wound about an iron core. These coils are insulated from each other and the whole assembly is enclosed in an oil-filled case. The primary coil, which consists of relatively few turns of heavy wire, is connected to the two primary terminals located on top of the coil. The secondary coil consists of many turns of fine wire. It is connected to the high-tension connection on top of the coil (the tower into which the coil wire from the distributor is plugged).

点火线圈是点火系统的核心（关键）。实质上，它只是一个变压器，将从蓄电池得到的低压升至40000伏的火花塞点火电压。术语线圈可能是误称，因为实际上是两个线圈缠绕着一个铁芯。这些线圈之间彼此绝缘，整个装配浸在油箱中。相对而言，初级绕组匝数很少，导线粗，该绕组两端分别连接到点火线圈上部的两个初级绕组接线柱上。次级绕组匝数较多，它连接在点火线圈上部的高压接头上。

coils of wire线圈，线匝

Under normal operating conditions, power from the battery is fed through a resistor or resistance wire to the primary circuit of the coil and is then grounded through the ignition points in the distributor (the points are closed) . Energizing the coil primary circuit with battery voltage produces current flow through the primary windings, which induces a very large, intense magnetic field. This magnetic field remains as long as current flows and the points remain closed.

在正常工作条件下，蓄电池通过一个电阻器向点火线圈的初级绕组供电，然后，从初级绕组流出的电流又通过断电器触点（位于分电器内部）搭铁（触点闭合时）。接有蓄电池电压的线圈初级电路通电，电流通过初级绕组，会产生一个强磁场。只要有电流且触点闭合，磁场就不会消失（会一直保持）。

As the distributor cam rotates, the points are pushed apart, breaking the primary circuit and stopping the flow of current. Interrupting the flow of primary current causes the magnetic field to collapse. Just as current flowing through a wire produces a magnetic field, moving a magnetic field across a wire will produce a current. As the magnetic field collapses, its lines of force cross the secondary windings, inducing a current in them. Since there are many more turns of wire in the secondary windings, the voltage from the primary windings is magnified considerably up to 40,000 volts.

当（断电器）触点被旋转的分电器凸轮顶开时，初级电路被切断，电流流动停止（消失）。初级电流中断会使（感应）磁场消失。正如电流流过线圈时会产生磁场，磁场穿过线圈也会产生电流。当磁场消失时，磁力线穿过次级绕组，会在次级绕组中产生感应电流。因为次级绕组中有多匝线圈，初级绕组电压会被放大至40000伏。Just as正如

The voltage from the coil secondary windings flows through the coil high-tension lead to the center of the distributor cap, where it is distributed by the rotor to one of the outer terminals in the cap. From there, it flows through the spark plug lead to the spark plug. This process occurs in a split second and is repeated every time the points open and close, which is up to 1,500 times a minute in a 4-cylinder engine at idle.

线圈次级绕组电压通过线圈高压导线引至分电器盖中心（电极），然后由分火头分配至分电器盖内的旁电极，最后通过火花塞线流到火花塞。这个过程是瞬间发生的，在每次断电器触点打开和闭合时重复，对于4缸发动机怠速（运行），每分钟可达到1500次。

split second 瞬间，极短的时间

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7.2 Electronic Ignition Systems

The need for higher mileage, reduced emissions and greater reliability has led to the development of the electronic ignition systems. These systems generate a much stronger spark, which is needed to ignite leaner fuel mixtures. Breaker point systems needed a resistor to reduce the operating voltage of the primary circuit in order to prolong the life of the points. The primary circuit of the electronic ignition systems operates on full battery voltage, which helps to develop a stronger spark. Spark plug gaps have widened due to the ability of the increased voltage to jump the larger gap. Cleaner combustion and less deposit have led to longer spark plug life.

高行驶里程要求，低排放和高可靠性导致电子点火系统的发展。这些系统产生非常强的电火花，用来点燃稀混合气。为了延长触点的使用寿命，触点系统需要一个电阻器来降低初级电路的工作电压。电子点火系统初级电路的工作电压为蓄电池的满电压，它有助于产生强火花。火花塞间隙被加大，因为电压增加，能够击穿更大的间隙。清洁燃烧和低沉淀也会延长火花塞寿命。

On some systems, the ignition coil has been moved inside the distributor cap. This system is said to have an internal coil as opposed to the conventional external one.

在一些系统中，点火线圈被移到分电器盖内。这种系统与传统外部线圈相反，它有一个内部线圈。as opposed to 与…相反，与…相对比

电子点火系统并不像它们初次出现时那样复杂。事实上，它们只与传统触点式点火系统有稍许不同。与传统点火系统相似，电子系统有两个电路：初级电路和次级电路。整个次级电路与传统点火系统相同。此外，蓄电池和线圈接线柱之间的初级电路也与传统点火系统相同。

Electronic ignition systems differ from conventional ignition systems in the distributor component area. Instead of a distributor cam, breaker plate, points, and condenser, an electronic ignition system has an armature (called by various names such as a trigger wheel, reluctor, etc.), a pickup coil (stator, sensor, etc.), and an electronic control module.

电子点火系统与传统点火系统不同的地方在于分电器区域。电子点火系统使用电枢，传感线圈（定子，传感器等）以及电子控制模块来代替分电器凸轮，断电器金属板，断电器触点和电容器。电枢有各种各样的名字，比如触发轮，磁组分配头等等。

Armature电枢reluctor磁组分配头pickup coil传感线圈，拾波线圈，感应线圈

7.3 Distributorless Ignition Systems (DIS)

The third type of ignition system is the distributorless ignition. The spark plugs are fired directly from the coils. The spark timing is controlled by an Ignition Control Unit (ICU) and the Engine Control Unit (ECU). The distributorless ignition system may have one coil per cylinder, or one coil for each pair of cylinders.

第三种点火系统是无分电器点火系统。火花塞由点火线圈直接点燃。点火正时由点火控制单元和发动机控制单元控制。无分电器点火系统每气缸或每对气缸有一个点火线圈。

Some popular systems use one ignition coil per two cylinders. This type of system is often known as the waste spark distribution method. In this system, each cylinder is paired with the cylinder opposite it in the firing order (usually 1-4, 2-3 on 4-cylinder engines or 1-4, 2-5, 3-6 on V6 engines, Figure 7-4). The ends of each coil secondary leads are attached to spark plugs for the paired opposites. These two plugs are on companion cylinders, cylinders that are at Top Dead Center (TDC) at the same time. But, they are paired opposites, because they are always at opposing ends of the 4-stroke engine cycle. When one is at TDC of the compression stroke, the other is at TDC of the exhaust stroke. The one that is on compression is said to be the event cylinder and one on the

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exhaust stroke, the waste cylinder. When the coil discharges, both plugs fire at the same time to complete the series circuit.

一些通用系统每两个气缸有一个点火线圈。这种系统常被称为废火（同时点火）分配方式。这个系统中，点火时序相反的两个气缸配成一对（分为一组），对于4气缸发动机，通常为1-4, 2-3，或6气缸发动机的1-4, 2-5, 3-6。每个线圈次级（绕组）导线一端（同时）连接到这对气缸的火花塞上，一对气缸上有两个火花塞，两个气缸同时达到上止点。但是其配对相反，因为它们总是位于4冲程发动机循环周期相反的一端。当其中一个处于压缩冲程的上止点，另一个则处于排气冲程的上止点。处于压缩冲程的气缸据说是做功（有效）气缸，而位于排气冲程的气缸是废缸。当点火线圈放电时，串联在一起的两个火花塞在同一时间完成点火。

Be known as 被称为event事件，过程，冲程

Since the polarity of the primary and the secondary windings are fixed, one plug always fires in a forward direction and the other in reverse. This is different than a conventional system firing all plugs the same direction each time. Because of the demand for additional energy; the coil design, saturation time and primary current flow are also different. This redesign of the system allows higher energy to be available from the distributorless coils, greater than 40 kilovolts at all rpm ranges.

因为初级绕组和次级绕组的极性是固定的，所以一个火花塞总是正向发火，而另一个总是反向发火。（指电流流动方向）这与传统系统每次对所有火花塞按同一方向点火不同。因为它需要附加（点火）能量，所以线圈设计，磁饱和时间和初级电流流动也不同。系统重新设计可从无分电器点火线圈获得更高的点火能量，在全部转速范围内，可超过40千伏。

Be different than 不同于

The distributorless ignition system uses either a magnetic crankshaft sensor, camshaft position sensor, or both, to determine crankshaft position and engine speed. This signal is sent to the ignition control module or engine control module, which then energizes the appropriate coil.

无分电器点火系统可采用磁性曲轴传感器，凸轮轴位置传感器，或两者相结合来测定曲轴位置和发动机转速。（测量）信号被发送至点火控制模块或发动机控制模块，然后由它对相应点火线圈通电。

The advantages of no distributor, in theory, are:

1. No timing adjustments.

2. No distributor cap and rotor.

3. No moving parts to wear out.

4. No distributor to accumulate moisture and cause starting problems.

5. No distributor to drive thus providing less engine drag.

无分电器（点火系统），理论上的优点在于：不需要调整点火时间，没有分电器盖和分火头，没有运动部件磨

损，不会发生分电器受潮所引起的起动问题，不需要驱动分电器，因此可减小发动机（转动）阻力。

The major components of a distributorless ignition are:

1. ECU or Engine Control Unit.

2. ICU or Ignition Control Unit.

3. Magnetic Triggering Device such as the Crankshaft Position Sensor and the Camshaft Position Sensor.

4. Coil Pack.

无分电器点火系统的主要组成有：ECU（即发动机控制单元），ICU（即点火控制单元），磁性触发器设备，比如曲轴位置传感器和凸轮轴位置传感器，线圈组件（Coil Pack）。

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EXERCISES

I ．Answer the following questions：

1 ．Describe the functions of an automobile ignition system．

2 ．Explain the operation of point-type ignition system.

3 ．What does the term“waste spark" mean?

4 ．Explain why a distributorless ignition system has more than one ignition coil.

5 ．Describe the purpose of the ignition coil．

II ．Translate the following passage into Chinese：

1．The ignition system provides for the timely burning of the fuel mixture within the engine. Not all engine types need an ignition system-for example，a diesel engine relies on compression ignition，that is，the rise in temperature that accompanies the rise in pressure within the cylinder is sufficient to ignite the fuel spontaneously ．All conventional petrol engines，by contrast，require an ignition system．

点火系统为可燃混合气在发动机内的定时燃烧做准备。并非所有的发动机都需要点火系统，柴油机是通过压缩点火。伴随气缸内压力升高所产生的温度上升足以使燃料自燃。相反，所有传统汽油机都需要点火系统。provides for做准备

2．The time that the fuel takes to burn is roughly constant．But the speed of the pistons increases as the engine speed increases．This means that the faster the engine goes，the earlier the spark has to occur ．This is called spark advance：The faster the engine speed，the more advance required．

燃料开始燃烧的时间一般说来是不变的。但是活塞的速度是随着发动机速度的增加而增加。这说明发动机运转越快，火花产生的时间越早。这叫做点火提前：发动机速度越快，提前的越多。

3．Ignition timing is the measurement，in degrees of crankshaft rotation，of the point at which the spark plugs fire in each of the cylinders．It is measured in degrees before or after Top Dead Center（TDC）of the compression stroke．点火时刻是指火花塞在每个气缸中的点火时，曲轴的旋转角度。它按照压缩冲程上止点之前或滞后的度数来测量。

4．Ignition timing on many of today’s vehicles is controlled by the engine control computer and is not adjustable．However the timing can be read using a scan tool connected to the data link connector．

在现在的车辆上，点火时刻由发动机控制计算机来控制，而且是不能调整的。但是点火时刻可以采用与数据传送连接器相连的扫描工具来读取。

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Reading material：Basics of Engine Management

背景知识：

在以汽油机为动力的现代汽车上，发动机管理系统（Engine Management System，简称EMS）以其低排放、低油耗、高功率等优点而获得迅速发展，且日益普及。

EMS采用各种传感器，把发动机吸入空气量、冷却水温度、发动机转速与加减速等状况转换成电信号，送入控制器。控制器将这些信息与储存信息比较，精确计算后输出控制信号。EMS不仅可以精确控制燃油供给量，以取代传统的化油器，而且可以控制点火提前角和怠速空气流量等，极大地提高了发动机性能。

Modern engine management systems（EMS）do a fine job of ensuring that engines run cleanly and efficiently in a wide variety of conditions，they are for the most part reliable and require little or no maintenance．The two basic functions performed by an EMS are as follows：

1．To meter fuel to the engine in the right quantity．

2．To provide a spark at the right time．

现代发动机管理系统可以保证发动机在各种条件下清洁有效运行。它们在很大程度上是可靠的，几乎不需要维护。EMS的两个基本功能如下：计量发动机供油量和在适当时刻提供火花。

for the most part 在极大程度上，对大部分little or no 几乎没有

What is an engine management system？

An EMS is a self contained custom built computer which controls the running of an engine by monitoring the engine speed，load and temperature and providing the ignition spark at the right time for the prevailing conditions and metering the fuel to the engine in the exact quantity required．

发动机电子管理系统是一个单独定制的嵌入式计算机系统，通过监测发动机的转速、负荷以及温度情况来控制发动机的运行，并根据发动机工况来提供合适的点火时刻，（它能够使运行在各种工况下的发动机都能够在