专业英语教学7

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 camshaft 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
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
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
Electronic Ignition systems are not as complicated as they may first appear. In fact, they differ only slightly from conventional point ignition systems. Like conventional ignition systems, electronic systems have two circuits: a primary circuit and a secondary circuit(Figure 7-3) . The entire secondary circuit is the same as in a conventional ignition system. In addition, the section of the primary circuit from the battery to the battery terminal at the coil is the same as in a conventional ignition system.（此段较简单，找学生翻译）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
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）。

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。

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精确的时刻获得火花）并且能够精确地计量发动机所需的燃油量。

self contained独立的，自持的custom built定制的prevailing condition当时情况
There are two discrete subsystems in operation within the EMS，the fuel injection system and the ignition system ．It is possible to run an engine management system which just provides one of these subsystems，for example just the ignition system ．It is much more common to use the mapped ignition within an EMS in isolation than it is to use just the injection．
EMS有两个离散子系统在运行，燃油喷射系统和点火系统。

可以单独让EMS的一个子系统运行，比如点火系统。

在发动机电子管理系统中，单独使用映射式（电子）点火系统的情况比单独使用（电控）喷射系统的情况更多一些。

句中it is to use just the injection为省略句，应该为it is common to use just the injection within an EMS。

in isolation分离，隔离
What is a‘map’？
Most of us have heard the term‘Mapped ignition’and programmed or mapped injection but may not understand what this actually is．Whilst the engine is running its requirements for fuel and ignition timing will vary according to certain engine conditions，the main two being engine speed and engine load ．A‘map’is no more than a lookup table by engine speed and load，which gives the appropriate fuel or timing setting for each possible speed and load condition．There will normally be a map for the injector timings（fuel map）and a separate map for the ignition timing settings（ignition map）within the EMS．
我们大多数人曾经听说过“映射式点火”和按程序工作的或映射式喷射，但可能不明白实际是什么。

当发动机运转时，它的燃油需求量和点火时刻会随发动机的工作条件而改变，主要是发动机转速和负载。

映射只是一个根据发动机速度和负载进行查找的表。

它为每一个可能的发动机转速和负荷条件给出合适的供油以及点火时刻设置。

正常情况下，发动机管理系统会有一个喷油器正时映射（燃油映射）和一个独立的点火时刻设置(点火映射)。

Each map has entries for a pre-determined range of engine speeds（called speed sites）and a predetermined
range of engine load conditions（called load sites），which generally indicate how far open the throttle is．The EMS knows the engine speed（derived from the crank sensor or distributor pickup）and the engine load（from the Throttle Position Sensor or airflow meter) and will use these two values to‘look-up’the appropriate fuel and timing settings in each map．
每个映射分别为预定的发动机转速和负荷范围设置一个入口，这通常表示节气门打开的大小。

发动机管理系统知道发动机的转速（从曲轴传感器和分电器传感线圈获得）和负载（从节气门位置传感器或空气流量计获得），并根据这两个值在每个映射中查找合适的供油和点火设置。

If the current engine telemetry falls between the sites in the map then the value is interpolated between the nearest two sites．Normally there will be speed sites every 500 or so RPM and 8 to 16 load sites between closed and open throttle．In the example below（Table 7-1）speed sites are spaced every 1，000 RPM and the 8 load sites are numbered 0 to 7．
如果当前发动机遥测数据落入到映射表中的两个映射地址之间，则这个值是离它最近的两个地址之间的内插值。

通常情况下，大约每隔500转/分会有一个转速地址，而在节气门的开闭之间有8-16个负荷地址。

在下表的例子中，转速地址之间相隔是1000转/分，8个负荷地址是按0-7编号。

In this example the engine load increases as the load site numbers in the left column increase．If the engine were running at 3,000RPM，load site 3，then the value looked up would be 26，i.e. 26 degrees of advance ．If the engine were running at 3,500RPM，load site 3 then the EMS would interpolate between the value for 3,000RPM （26）and the value for 4,000RPM（30）and calculate a value of 28 degrees．
在这个例子中，发动机负荷按照左栏的负荷地址编号依次增加。

如果发动机转速为3000转/分，负载地址为3，那时查出的映射值是26，也就是提前26度。

如果发动机转速为3500转/分，负载地址为3，那么发动机管理系统会计算3,000RPM（26）和4,000RPM（30）的内插值为28度。

Timing adjustments
In the normal course of events with the engine operating at the correct temperature in defined conditions，the EMS will use load and engine speed to derive the correct ignition timing from the map，however there are circumstances under which the EMS may need to vary the ignition timing．These normally boil down to four circumstances，engine/coolant temperature，air temperature，knocking and start-up．
按照事件的正常程序，发动机在规定的合适温度条件下运行，发动机管理系统会通过负载和发动机转速从映射中取得正确的点火时刻，然而也有发动机管理系统需要修改点火时刻的情况。

归结起来，通常为4种情形，发动机/冷却液温度，空气温度，爆震和起动。

Engine temperature
When the engine temperature is low，the burn times within the cylinders are longer than with a fully warmed up engine and the ignition timing will normally need to be advanced a little to adjust．The EMS usually has a small map of ignition timing adjustments graded by engine temperature that are added to the base timing figures．The engine temperature information is relayed to the EMS by an engine temperature sensor attached to the engine．
发动机处于低温时，气缸内的（混合气）燃烧时间会比它完全加热时要长，因此点火时刻需要提前调整。

发动机管理系统通常有一个小的按照发动机温度分级的点火时刻调整映射被添加到基本点火时刻图中。

发动机温度信息通过附着在发动机上的温度传感器传送到发动机管理系统。

Air temperature
When air temperature varies so does burn time of the inducted mixture，again a small map of ignition adjustments graded by air temperature are added to the base timing figures. The engine temperature information is relayed to the EMS by an air temperature sensor located near to the air inlet．
当空气温度改变时，吸入混合气的燃烧时间也跟着改变，一个小的按照空气温度分级的点火时刻调整映射也被添加到基本点火时刻图中。

发动机温度信息通过位于进气口附近的空气温度传感器传送到发动机
管理系统。

Knock sensing
There may be times during the operation of the engine，even after adjustments have been applied when the timing calculated does not meet the engines requirements．Sometimes this may result in ‘pinking’（‘knocking’ or ‘pinging’）where the mixture burns so fast that it meets the piston just before TDC while it is still on the compression stroke rather than meeting the piston just after TDC on the power stroke．This is very harmful to the engine．Some EMS systems have an acoustic sensor called a‘knock sensor’which listens for knocking and will inform the EMS when this occurs．The EMS is then able to make adjustments to the timing to prevent knocking from occurring．
在发动机运转期间，也许会发生这样的情况：虽然已经修正了点火时刻，但是修正后的点火时刻仍不能满足发动机的要求。

这有时也会导致“轻微爆震”现象出现。

出现这种情况时，混合气燃烧得如此之快，以至于燃烧膨胀的混合气体撞向活塞时，活塞还处在上止点前的压缩冲程中，而不是在上止点后的做功冲程中。

句中，where为“在这场合”，while为“然而，却”。

这对发动机有损害。

一些发动机管理系统有一个声敏元件（声响传感器）称为爆震传感器用来监听爆震现象，并在其发生时通知发动机管理系统。

这时发动机管理系统会调整点火时刻来阻止（发生）爆震。

Start-up or cranking
When starting an engine its effective RPM is quite low，around 200RPM or so ．If the ignition timing used at idle is set to around 25 degrees（which is about average for a mapped engine）the chances are that the piston will hit the ignited mixture while still on the compression stroke．This will have the effect of pushing the piston down against its normal rotation，effectively this is ‘knocking’ at cranking speeds．This is known as ‘kicking back’ and is normally characterized by the starter motor ‘straining’ and slowing right down，this makes the engine difficult to start and can easily destroy a starter motor in short order．
当发动机起动有效转速非常低，大约200转/分。

如果怠速时点火时刻设在25度左右（大约是映射发动机的平均值），大概是活塞仍处于压缩冲程，但将要撞到点燃混合气的时候。

其结果将推动活塞朝着与正常运动方向相反的方向运动，实际上这就是起动时的爆震现象。

这也被称为“逆转现象”，其特征通常表现为起动电机的负荷增加，转速明显下降，使发动机起动困难，在短期内易破坏起动机。

the chances are大概是，很可能是straining张紧，拉紧right down非常in short order在短期内，迅速地
This is a common problem on engines equipped with mechanical ignition systems and more extreme cams since the engine needs plenty of ignition advance at idle to ran properly．Unfortunately this extra advance can also cause ‘kick back’ and there is no way with a mechanical system to differentiate the timing between cranking and idle．
这在装有机械式点火系统和过量凸轮的发动机上是一个常见问题，因为发动机在怠速时需要很大的点火提前角度，以使运转正常。

不幸的是这个额外的点火提前角度也会造成逆转现象，因此采用机械式点火系统不可能区分起动和怠速时的点火时刻。

EMS based systems solve this problem by having a separate timing value for cranking/start-up which is normally set to around 5-8 degrees．This is low enough to prevent kickback but is high enough to start the engine；the moment the engine fires the appropriate ignition setting from the base map is used．
发动机管理系统的基本系统是通过一个为起动单独设置的（点火）时刻值来解决这个问题，这个时刻通常设在5－8度。

这是对阻止爆震来说，是最低的，但对起动发动机来说够高了。

一旦发动机点火，就会采用基本映射图中合适的点火设置值。