轿车的一些英文资料

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Engine Fuel System and Engine Troubleshooting
Introduction
The fuel system has the job of supplying a combustible mixture of air and fuel to the engine. The conventional fuel system consists of the fuel tank, fuel pump, fuel filter, carburetor and fuel lines. All automobile engine fuel systems have some forms of fuel supply system .The purpose of the supply system is to store and then to supply a clean, continuous, and adequate amount of fuel under sufficient pressure to the carburetor. Moreover, the system must perform these functions regardless of the outside temperature, altitude, and speed of the vehicle.
The fuel tank stores a supply of fuel. The function of fuel pump is to deliver fuel from the tank to the carburetor. The fuel filter prevents sediment and water that settle to the bottom of the tank from entering through the fuel line to the fuel pump. The carburetor is a metering device that mixes fuel with air in the correct proportion and delivers this mixture to the intake manifold, where it delivers the air/fuel mixture to the various combustion chambers. Most carburetor contains six basic system: the float system, idle system, main metering system, power system, pump system, and choke system. The fuel lines and hoses carry the fuel from the tank to the fuel pump, from the pump to the carburetor, return excess fuel to the tank, and carry fuel vapors.;  
Electronic Fuel Injection System
A carburetor is a mechanical device that is neither totally accurate nor particularly fast in responding to changing engine requirements. Adding feedback controls and other emission-related devices in recent years has resulted in very complex carburetors. The solution to the problems posed by a carbureted fuel system is electronic fuel injection (EFI)
Electronic Fuel injection system can be divided into three basic sub-system. These are the fuel delivery system, the air induction system, and the electronic control system. There are different types of gasoline fuel injection system used in automobiles. The two basic arrangements are port fuel injection and throttle body injection (TBI). Port fuel injection is also called multiple-point injection.
The Fuel Delivery System
The fuel delivery system consists of the fuel tank, fuel pump, fuel filter, fuel delivery pipe, fuel injector, fuel pressure regulator, and fuel return pipe. Fuel is delivered from the tank to the injector by means of an electric fuel pump. Contaminants are filtered out by a high capacity in line fuel filter. Fuel is maintained at a constant pressure by means of a fuel pressure regulator. Any fuel that is not delivered to the intake manifold by the injector is returned to the tank through a fuel return pipe. The fuel injectors, which directly control fuel metering to the intake manifold, are pulsed by the ECU. The ECU determines which air/fuel ratio the engine runs at based upon engine conditions monitored by input sensors and a program stored in its memory. During cold engines starting, many engines incorporate a cold star injector designed to improve startability below a specified coolant temperature.
Fuel Pump
There are two types of fuel pumps; the early conventional EFI system used an externally mounted in-line pump. Later engines utilize an in-tank pump integrated with the fuel sender unit.
Fuel Filter
The fuel filter, which is installed between the pump and the fuel deliver pipe, removes dirt and contaminants from the fuel before it is delivered to the injectors and pressure regulator.
Fuel Delivery Pipe
The fuel delivery pipe is designed to hold the injector in place on the intake manifold. Mounted to the fuel deliver pipe are the pulsation damper and the fuel pressure regulator. The fuel delivery pipe acts as a reservoir for fuel that is held under pressure prior to delivery by the fuel injector.
Fuel Pressure Regulator
To maintain precise fuel metering, the fuel pressure regulator maintains a constant fuel pressure. This means that the pressure in fuel delivery pipe will always be at a constant value above manifold absolute pressure.
Pulsation Damper
Although fuel pressure is maintained at a constant value by the pressure regulator, the pulsing of the injectors causes minor fluctuations in rail pressure. The pulsation damper acts as an accumulator to smooth out these pulsations, ensuring accurate fuel metering.
Fuel Injector
In older vehicles, the sensing, control, and fuel metering functions were all performed by the carburetor. In EFI-equipped engines fuel delivery is done with injectors, which are small on/off valves controlled by an electric signal. The fuel delivery pipe serves to secure the injector in place. To reduce the possibility of vapor lock, which tends to during high temperature operation, a side feed injector is used in engines.
Single Point Fuel Injector and Multipoint Fuel Injection
In the EFI system, it is possible to have systems using only one per engine (single point fuel injection) or one injector per cylinder (multipoint fuel injection). In the single point fuel injection system, it combines a single (or twin) fuel injection nozzle, fuel pressure regulator, throttle valve, throttle switch and idle speed regulator into a compact throttle body unit. This unit is mounted directly on the intake manifold, in a similar manner to a conventional carburetor. This type of EFI system is more commonly called Throttle Body Fuel Injection. Fuel is injected into the area around the throttle valve, where air velocity is at a maximum; thus ensuring fuel droplets are thoroughly atomized and will be distributed throughout the air mass. While in multipoint fuel injection system, injectors deliver fuel directly onto the closed, but hot, intake valve of each cylinder. The following discussed injection system is the Multipoint Fuel Injection System.
Fuel injection volume
Fuel injection volume determination is based upon the value of input sensor signals. In addition to volume control, the ECU can pulse the injectors either synchronously or non-synchronously with ignition events.
Cold Start Injection System
To improve engine starting when coolant temperature is low, a supplementary injector is installed on many EFI engines. The cold start injection system consists of the following components: Cold Start Injector, Start Injector Time Switch, and ECU (most EFI).
Choke System
When starting a cold engine, the factors necessary for good fuel vaporization are missing or inadequate. For this reason, it is necessary to provide extremely rich mixture from the carburetor in order to provide sufficient combustible mixture to all cylinders for quick starting. The carburetor obtains this enrichment by the addition of a choke valve in the carburetor throat above the venturi and main nozzle. This chock valve, during cold engine starting, starts fuel to flow through the main system prematurely.
The Air Induction System
The purpose of the air induction system is to filter, meter, and measure intake air flow into the engine. The air induction system consists of the air cleaner, air flow meter, throttle valve, air intake chamber, intake manifold runner, and intake valve. Air, filtered by the air cleaner, passes into the intake manifold in varying volumes. The amount of air entering the engine is a function of throttle valve opening angle and engine rpm. Air velocity is increased as it passes through the long, narrow intake manifold runners, resulting in improved engine volumetric efficiency.
Power System
The main-metering system provides the leanest air/fuel mixture of any the other carburetor circuits; a richer mixture is necessary not only for extended high-speed operation but also for maximum engine power. For maximum engine power, a rich fuel mixture is mandatory in order for the combustion process to consume all the oxygen in the air entering the combustion chamber. To accomplish this action, the carburetor has some type of power system used to supplement the main-metering system. This power system provides an increase in fuel mixture flow from the nozzle tip, according to the amount of throttle opening and engine load. In other words this additional system functions to enrich the total air/fuel mixture during any phase of main-metering system operation, depending on throttle position and engine-load requirements.
Electronic Control System
The electronic control system consists of various engine sensors, Electronic Control Unit (ECU), fuel injector assemblies, and related wiring. The ECU determines precisely how much fuel needs to be delivered by the injector by monitoring the engine sensors.
Basic System Operation
Air enters the engine through the air induction system where it is measured by the air flow meter. As the air flows into the cylinder, fuel is mixed into the air by the fuel injector. Fuel injectors are arranged in the intake manifold behind each intake valve. The ECU signals the injector to deliver just enough fuel to achieve an ideal air/fuel ratio of 14.7:1. The ECU determines the basic injection quantity based upon measured intake air volume and engine rpm. Depending on engine operating conditions, injection quantity will vary. The ECU monitors variables such as coolant temperature, engine speed, throttle angle, and exhaust oxygen content.
Advantages of EFI (Multipoint Fuel Injection)
Each cylinder has its own injector that delivers fuel directly to the intake valve. This eliminates the need for fuel to travel through the intake manifold, improving cylinder to cylinder distribution. EFI supplies an accurate air/fuel ratio to the engine no matter what operating conditions are encountered. This provides better drivability, fuel economy, and emissions control. By delivering fuel directly at the back of the intake valve, the intake manifold design can be optimized to improve air velocity at the intake valve. This improves torque and throttle response. Cold engine and wide-open throttle enrichment can be reduced with an EFI engine because fuel pudding in the intake manifold is not a problem. This results in better overall fuel economy and improves emissions control. The combination of better fuel atomization and injection directly at the intake valve improves ability to start and run a cold engine. The EFI system does not rely on any major adjustments for cold enrichment or fuel metering. Because the system is mechanically simple, maintenance requirements are reduced.
Engine Troubleshooting
Engine Overheating
There are many conditions of the automobile that result in overheating, and the degree of overheating is indicated by the temperature gauge on the instrument panel. Some conditions will cause only a slight change in the recorded temperature, other causes will result in a rapid rise in temperature and violent boiling of the coolant. Still other while causing only a slight increase in recorded temperature, while will be more noticeable in engine performance.
When troubleshooting the cause for overheating and consequent loss coolant, the first step is to make careful visual inspection to see if there is any evidence of external leakage. All surfaces of the radiator and its hose connection should be carefully inspected. Leaks generally cause corrosion, which is easily seen. The visual inspection also must include the cooling fan and its drive belt. It is not too unusual for cracks to from in the engine water jacket. When cracks occur, the condition is usually indicated by extreme overheating. The crack is often difficult to locate, because it is not always visible to the naked eye. The condition is also complicated by the fact that the crack usually will close when the engine is cold, and open only when the engine is at operating temperature.
Cleaning the Cooling System
Unless very severely clogged with rust and hard scale, cooling systems can be cleaned with special chemicals designed for the purpose. The procedure is to fill the system with water, then put in the chemical. The chemical, after dissolving the rust and scale, is flushed from the system. In severe cases of clogged radiators, it is necessary to remove them and have them cleaned by specialized equipment.
High Oil Consumption
Quite often high oil consumption is blamed on the piston ring. While worn piston rings and cylinder walls do cause increased oil consumption, there are a great number of other things that could be at fault, either singly or in combination. Worn valve guides are also a frequent cause of high oil consumption. When oil is being consumed by passing through the engine, it usually will cause heavy blue smoke to come from the exhaust, particularly after the engine has idled for several minutes.
Low Oil Pressure
In most cause of low oil presser, the presser is satisfactory when the engine is first started up, then it drops as the engine warms up. This condition is almost positive proof that excessive clearance exists at some point, or point, such as connecting rod bearings, main bearings, camshaft bearings, etc. When cold, the oil has thickened and does not flow as readily through the clearance. When the oil heats up and thins out, it flows through the worn bearings so fast that the pump cannot maintain sufficient pressure.
Chassis and Engine Vibration
Consider the case where there is a pronounced vibration in the car at a certain speed range. First of all it is necessary to determine whether the unbalance is in the engine or the chassis, or both. If it is in the engine, or the parts that rotate with the engine, the vibration should occur at the critical engine speed when the car is not in motion. If it is in the chassis, it will occur only when the car is operated at the critical speed. It is most likely to be fount in the chassis, because the engine assembly is carefully balanced at the factory. Out-of-balance tries and propeller shafts are the most common causes of chassis vibration.
Abnormal Engine Noises and their Causes
The following listing will point out the most common causes of sound itself and what must be done to eliminate them.
1.        Piston slap is a very common noise most noticeable when an engine is cold. A piston that slaps against the cylinder wall produces a hollow, muffled, bell-like sound, quite audible when an engine is operating under load at low rpm. Piston slap results from worn pistons or cylinders, collapsed piston skirts, excessive piston-to-cylinder wall clearance, misaligned connecting rods, or a lack of lubricating oil. Therefore, in order to correct piston slap, it will be necessary to replaced or resize the piston, reborn the cylinder or replace the sleeves, replace or realign the rods, or add oil to the engine.
2.        An abnormal sound origination from some form of piston-ring problem is audible during engine acceleration. To correct the cause of ring noise, it may be necessary, therefore, to replace the rings, the pistons, or the sleeves or reborn the cylinders.
3.        A sound not frequently heard in an engine is that of a piston ring striking the ring ridge at the top of the cylinder. This particular problem causes a very distinct and high-pitched, metallic rapping or clicking noise audible at all engine speeds but particularly on deceleration. To repair the cause of this sound, it will be necessary to replace the piston pin or connecting rod bearings.
4.        A piston-pin knock is noticeable most of the time when an engine is idling. Piston pin noise is usually the result of a worn piston pin, piston-pin boss, pin bushing, or a lack of oil. To correct this problem, install oversize pins, replace the bushings and pins, or service the engine with oil.
5.        An abnormal noise that is audible when the engine is running at speeds above 35 miles per hour (mph) without a load is usually the result of loose connecting-rod bearings. Loose rod bearings cause a light to heavy knock or pound, depending on how badly the bearings are worn. Connecting-rod bearing noise can be due to a worn bearing, crankpin, misaligned rod, or lack of oil. To correct the noise, it will be necessary to replace the bearings, service or replace the crankshaft, realign or replace the rod, or service the engine with oil.
6.        An abnormal noise that is audible upon engine acceleration under load is usually the result of a loose crankshaft main or thrust bearing. Main or thrust bearing noise is usually the result of worn bearings, crankshaft journals, or a lack of oil. To correct this noise, it will be necessary to replace the bearings, crankshaft, or service the engine with oil.
7.        A loose vibration damper or flywheel can also cause abnormal engine noises. This sound is more noticeable during engine acceleration from idle under load or at an uneven idles, but it is less apparent at higher engine rpm or during smoother engine operation. A loose flywheel, on the other hand, sets up either a heavy thump or a light knock at the back of the engine, depending upon the amount of play the flywheel has and the type pf engine. You can detect a loose flywheel by shutting off the ignition switch at idle and then turning it on again just before the engine stops rotating. Also, operating the clutch pedal, at the same time the noise is audible at running speeds, will vary the sound enough so that it is easier to identify and then locate its source.
8.        Excessive clearance in the valve train produces a noise that is usually more apparent during engine idle rpm than any other time. Valve-train noise is brought about by improper valve adjustment, worn or damaged parts, dirty hydraulic lifter, or lack of clean lubricating oil. In order to correct the cause of the noise, it will be necessary to adjust the valves, replace worn or damaged parts, clean or replace the lifters, or service the engine’s lubrication system.
9.        The one abnormal sound unrelated to worn, damaged, loose, or maladjusted engine parts is detonation knock. The noise is most noticeable during acceleration with the engine under load and operating at normal temperature. Excessive detonation is very harmful to the engine, and you should do everything possible to correct the cause as soon as possible. Detonation knock in an engine is usually the product of advanced ignition timing, excessive carbon buildup in the combustion chambers, or use of too low an octane fuel. T o correct this malfunction, check the distributor’s advance mechanisms, check and reset the ignition timing, decarbonizes the engine, or recommend a change in fuel to one with a higher octane rating.

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关于轿车英文资料的回复：

尊敬的提问者，

我作为一名汽车工程师，对于轿车的英文资料有着深入了解。这些资料通常涵盖了车辆设计、性能参数、技术特点等方面。如果您需要这些资料，我可以为您提供专业的指导。

您可以先明确所需的具体内容，如发动机参数、车身结构、底盘设计等。随后，我会为您提供相应的英文专业术语和资料链接，确保您能够准确获取所需信息。如有需要，我还可以对关键内容进行中文解释。请随时告知您的具体需求，以便为您提供更专业的帮助。