Readings Automotive Mechanics 4

8/2/2019 Readings Automotive Mechanics 4

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INSTITUTO TECNOLGICO SUPERIOR CENTRAL TCNICO

NIVEL TECNOLGICO

TECHNICAL ENGLISH

MAS DE UN SIGLO DE CIENCIA Y TCNICA AL SERVICIO DE LA PATRIA

I. TECHNICAL WORDS

BORE: is used to express the width of a circular hole in a cylindrical

object, especially the inside of a gun, barrel.

DENSITY: is the relationship between the mass of a substance and its size.

INJECTION: is the putting of a liquid.

INJECTOR: a mechanical device used to inject something.

LOAD: the amount of weight carried, especially by a vehicle, a structuresuch as a bridge, or an animal.

PRESSURE: is the force that a liquid or gas produces when it pressesagainst something.

RELAY: a device that reacts to a small change in an electrical current by

moving switches or other devices in an electrical circuit.

SENSOR: a device which is used to record the presence of something orchanges in something.

VALVE: a device which allows air or liquid to enter, or be prevented fromentering, a container.

II. VOCABULARY

Look up these words in your dictionary

accurate ____________________________________________________

although ____________________________________________________

core ____________________________________________________

improvement ____________________________________________________

input ____________________________________________________

UNIT 6


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intake ____________________________________________________

loop ____________________________________________________

mist ____________________________________________________

mostly ____________________________________________________

pintle ____________________________________________________

puddle ____________________________________________________

rate ____________________________________________________

to accomplish ____________________________________________________

to comprise ____________________________________________________

to contend ____________________________________________________

to deliver ____________________________________________________

to find ____________________________________________________

to improve ____________________________________________________

to spray ____________________________________________________

while ____________________________________________________


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IV. PRESENTATION

Any improvement in fuel control is beneficial to emission levels. Probablythe most effective means of controlling air/fuel ratios and fuel deliveryrates is through the use of electronic fuel injection. Although not a trueengine modification, it is an important change in basic engine design.

There are two basic types of electronic fuel injection in use today: portinjection and throttle body injection. Port fuel injection is more efficient ofthe two, mostly because the fuel is injected at or very near to the intake

valve. By injecting the fuel close to the intake valve, the problemsassociated with intake runner design are eliminated. Additionally,

computers used with most modern fuel injection systems allow veryaccurate control of the air/fuel ratio. With port fuel injection systemsinjecting fuel at the intake valves, variations in actual air/fuel ratio areeliminated.

Although throttle body fuel injection still contends with intake manifolddesign, computer control improves the efficiency of this type of systembeyond that of the carburetor. Pressurized injection of fuel also improvesatomization and reduces puddling in the intake manifold. To gain bettercontrol of air/fuel mixtures, manufactures are equipping most new carswith electronic fuel injection. Fuel injection sprays a metered amount of

fuel directly into the airstream. Through the years, many different fuelinjection systems have been used, some were mechanically operatedwhile others used electronic controls. See Fig. 1. Todays fuel injection

systems use a throttle to regulate the amount of air that enters theengine and a computer or electronic control module to regulate theamount of fuel that will be sprayed into that air.

Fig. 1: Typical Port Fuel Injection System

FUEL INJECTION


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TECHNICAL ENGLISH


The computer bases the required amount of fuel on a number of factors:

engine temperature, air density, engine speed and load, throttleposition, and others. The main component for delivering the fuel into the

airstream is the fuel injector. See Fig. 2. An injector is a device whichreceives fuel under high pressure and releases it into the airstreamthrough a small orifice normally positioned immediately before the intakevalve. A fuel injector is actually a solenoid with a plunger as its centercore. When the injector is activated, the plunger moves to allow fuel

flow. Fuel leaves the injector in the form of a mist and readily mixes withthe incoming air. Control of the air/fuel mixture is accomplished bychanging the pressure of the fuel delivered to the injector or by

changing the length of time the injector is spraying fuel. These changesoccur in response to changes in the operating conditions of the engine.

BODY INJECTION

Basically, there are two major types of Electronic Fuel Injection (EFI)systems: throttle or single-point injection and port or multi-point injection.Throttle Body Injection (TBI) systems delver fuel at a throttle body. A

controlled spray of fuel enters the airstream above the throttle plates.Port injection systems deliver fuel at the individual intake ports of thecylinder head. Using one injector per cylinder, these systems provide for

equal amounts of fuel to each cylinder.

Although all EFI systems can be divided into these two groups, many

variations of these basic types are found on engines today. These

variations are the result of different computer control systems and variousmethods of controlling the injectors. Whenever working on an EFI system,

Fig. 2: Typical Fuel Injector


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always refer to the service manual for the proper testing and repairprocedures.

Throttle-body injection systems, such as General Motors TBI system, are

comprised of two major sub-systems: an electro-mechanical fuel deliverysystem and an electronic air/fuel control system consist of a fuel pumpand a fuel pump relay. The electric fuel pump and a fuel pump relay.The electric fuel pump delivers pressurized fuel to the throttle bodyassembly. The fuel pump relay allows the fuel pump to run when there is

oil pressure or whenever the ECM (Electronic Control Module) receivesan ignition signal.

The air/fuel control system includes a TBI assembly, consists of the throttleplate unit and a fuel metering assembly. The throttle plate regulates

engine speed much in the same way as the throttle of a carburetordoes. The fuel metering assembly basically consists of a fuel pressureregulator and one or two injectors.

An ECM controlled solenoid pulses the injector to obtain the desired

amount of fuel. Fuel is delivered to the injector at a constant pressure.The fuel pressure regulator maintains a pressure of 9-13 psi and returns allexcess fuel to the fuel tank through the fuel return line. When the ECMprovides an electrical ground for the injectors, the injectors turn on andspray fuel at the walls of the throttle bore, above the throttle plate. Byswitching or pulsing the ground on and off, the ECM controls the air/fuel

mixture.

The injectors are pulsed according to a program in the ECM based uponthe operating conditions. When the injectors are pulsed once for eachignition reference pulse, the injectors are said to be in the synchronizedmode. During this mode, the ECM will alter the length and timing of thepulses in response to the oxygen sensor and other inputs.

When the throttle is opened rapidly, the injector momentarily spraysmore fuel to assist in acceleration. The ECM receives a signal from theThrottle Position Sensor (TPS) that the driver desires to accelerate andcauses the injector to fire longer. Likewise, when the engine is cold and isbeing stated, the injectors will also spray additional fuel. Duringdeceleration. little or no fuel is sprayed in response to the action of TPS.

The IAC system uses a motor and a pintle located in the air by-passchannel around the throttle plate to control idle speed. The ECM sets theposition of the pintle valve according to information received more orless air into the intake manifold.


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V. EXERCISE

Translate the following sentences.

As there are many different variations of TBI systems, there are also many

different designs of multi-point systems..

.

The most constant spray type fuel injection system is the Bosch K-Jetronic..

.

The systems that pulse the injectors in sequence with the engines firingorder are commonly called Sequential Fuel Injection Systems..

.

In pulsed or time sprayed systems, the fuel pressure is constant and themixture is controlled by turning the injectors on and off. Most vehicles areequipped with this type of system..

.

.

A pressure regulator is used to provide constant pressure to the injectors..

.

Critical to the proper operation of the induction system is the fuel

delivery system..

.

Shop manuals normally list the acceptable limits for fuel pressures and

volume..

.


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Volume measurements are usually made by collecting the fuel deliveredby the system during a period of time..

.

Always follow the procedure given in the shop manual and follow allsafety rules for handling gasoline..

.

Fuel pressure is measured with a pressure gauge. The gauge is normallyplaced in the fuel line before the fuel inlet at the carburetor or injector

assembly..

.

.

Certain precautions need to be followed when testing the pressure of afuel injection system..

.

To measure the fuel pressure to the injectors, begin by removing the fuelfiller cap and fuel pump fuse..

.

At this time, all of the residual fuel pressure has been released and it is

safe to connect the fuel pressure gauge.

.

.

Be certain to tighten all connections to prevent any leaks. The fuel pumpfuse should be reinstalled and the engine is started..

.


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Any reading outside the specified range indicates a problem in the fueldelivery system and further testing may be required..

.

After measuring fuel pressure in an injection system, the fuel system mustbe purged of any pressure prior to removing the fuel pressure gauge..

.

.

The simplest way to check a fuel injector is to listen to the noise an

injector makes while the engine is running..

.

Port fuel injection systems are more difficult to see their function, as you

must remove the fuel rail and fuel injectors from the engine and crankthe engine, watching the spray pattern of the injector..

.

.

If all of the injectors are not operating at the appropriate pulse width, thisindicates a problem with the computer or its sensors..

.

Individual faulty injectors can also be identified by comparing the pulsewidth, measured in milli-seconds, of the injectors..

.


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I. TECHNICAL WORDS

BOOST: the action of increasing.

COMPRESSOR: a part of machine which presses gas or air into less space.

CRANKSHAFT: a rod, especially one in an engine, having one or two

cranks that make the rod move around a fixed line along its center.

DEVICE: an object or machine which has been invented to fulfill a

particular purpose.

DIAPHRAGM: a thin piece of material which is stretched across an

opening.

FAILURE: the action of becoming weaker or stop working completely.

HANDLE: a part of an object designed for holding, moving or carryingthe object easily.

HORSEPOWER: a unit for measuring the power of an engine.

IMPELLER: the part of the centrifugal pump connected to the drive shaft

that moves the fluid to the circumference of the volute.

OIL: is used as a fuel and also for making the parts in a machine moveeasily without sticking.

PULLEY: a piece of equipment for moving heavy objects up, or down,consisting of a small wheel over which a rope or chain fixed to the object

can be easily pulled or releases slowly.

SHAFT: a pole or a rod which forms the handle of a tool or weapon, orwhich forms part of a machine.

TURBINE: a type of machine through which liquid or gas flows and turns a

special wheel with blades in order to produce power.

WHEEL: a circular object connected at the center to a bar, which is usedfor making vehicles or parts of machines move.

WRENCH: a sudden, violent twist or pull.

UNIT 7


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II. VOCABULARY


as soon as ____________________________________________________

belt ____________________________________________________

blade ____________________________________________________

cavitation ____________________________________________________

crack ____________________________________________________

dial ____________________________________________________

drag ____________________________________________________exhaust ____________________________________________________

gasket ____________________________________________________

gauge ____________________________________________________

handle ____________________________________________________

leakage ____________________________________________________

likely ____________________________________________________

nearby ____________________________________________________

output ____________________________________________________

passage ____________________________________________________

pipe ____________________________________________________

procedure ____________________________________________________

rebuildable ____________________________________________________

road ____________________________________________________

shield ____________________________________________________

smoothly ____________________________________________________

station ____________________________________________________

tee ____________________________________________________

therefore ____________________________________________________

to bypass ____________________________________________________

to clog ____________________________________________________

to drop ____________________________________________________


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to fit ____________________________________________________

to gain ____________________________________________________

to grind ____________________________________________________

to hiss ____________________________________________________

to let ____________________________________________________

to lift ____________________________________________________

to lower ____________________________________________________

to prevent ____________________________________________________

to reach ____________________________________________________

to rub ____________________________________________________

to shred ____________________________________________________

to squeal ____________________________________________________

to squirt ____________________________________________________

to suit ____________________________________________________


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IV. PRESENTATION

Most late model cars have relatively small engines when compared toolder cars. These engines, although much more efficient that the olderengines, have a difficult time supplying the power needed during somedriving conditions. Therefore, manufacturers have installed turbo-or

super-changers on the engines. See Fig 1. These devices increase thepower output of the engines by forcing additional amounts of air into thecylinders.

Turbochargers primarily consist of two separate units connected together

at the housing and by a shaft. Exhaust gases are routed into the turbineunit causing the turbine to spin. The compressor unit contains acompressor wheel which is connected by a shaft to the turbine. As theturbine spins, the compressor wheel spins with it. The compressor draws inoutside air and delivers the air under pressure to the cylinders. See Fig.2.

As the speed of the turbine increases , so does the pressure output(boost) of the compressor.

When the output pressure reaches a particular level, an actuator opensthe wastegate. See Fig. 3. The wastegate allows some of the exhaustgases to bypass the turbine thereby reducing its speed and boost.

Turbocharger boost pressure is controlled to prevent engine failure thatcould result from extremely high pressures and temperatures. Boostcontrol is normally accomplished in one of four ways: by a wastegate, aboost control solenoid, a MAP sensor, or by engine speed.

Fig. 1: 2.2L & 2.5L Turbo Engine Components

TURBOCHARGERS


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A wastegate is a diaphragm controlled valve which allows exhaust

gasses to bypass the turbine and enter directly into the exhaust system.Most turbocharger units have a boost limit of 7.5 to 8 psi. When that

pressure is reached, the wastegates diaphragm moves a rod whichthen opens the wastegate.

Fig. 2: Turbocharger Operation

A boost control solenoid is controlled by the ECM and operates thewastegate based upon the input it receives. The solenoid allows vacuumto pull on the wastegates diaphragm, allowing it to open. When the

boost is below the limit, the solenoid shuts off vacuum to the solenoidand the wastegate is closed. The wastegate may also be opened by thecomputer when other conditions exist that are not best suited for boost.


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Fig. 3: Turbocharger Assembly

A Manifold Absolute Pressure (MAP) sensor is commonly used on non-turbocharged engines to monitor manifold pressures. However, this

sensor is often used to monitor turbocharger boost. When the pressure inthe intake manifold reaches a particular level, the MAP sensor sends asignal to the ECM which shuts off the fuel supply to the engine causingengine speed and the resultant boost to decrease. Fuel delivery iscontinued as soon as the intake pressure falls below the limit.

Some systems rely on engine speed signals to control turbochargerboost. When the ECM receives a signal indicating that a specified

engine speed has been reached, it shuts off fuel delivery until the enginespeed has dropped below that limit.

An intercooler is used in some systems to lower the temperature of the airflowing outof the turbocharger. Although the intercooler is not a boost controldevice, it does help prevent engine failure caused by the high air

temperatures typical of turbocharger units. Cooling the air that entersthe cylinders also improves the engines efficiency and horsepoweroutput.

Because of the high speeds reached by the turbine and compressorwheel, proper oiling is critical to the unit. Engine oil is circulated through

the housing to lubricate the turbos shaft. A primary cause ofturbocharger failure is a lack of oil. Proper engine oil levels must bemaintained and if the engine oil becomes contaminated, the oil must bechanged and the turbo flushed with clean oil. Some turbocharger unitsare water cooled. In these systems, coolant is routed from the engineblock through the center housing of the turbo and then back to theblock. This additional cooling improves the efficiency of the

turbocharger.

V. EXERCISE

Translate the following sentences.

A supercharger is an air compressor driven by the engines crankshaft..

.

Connected by pulleys and a belt, the impeller blades of thesupercharger pressurize intake air in response to engine speed..

.


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Superchargers are equipped with a bypass valve which prevents

cavitation at low engine speeds and part throttle operation..

.

Supercharger units are not rebuildable and should be replacedwhenever a problem exists in the unit..

.

Intake vacuum leaks and excessive noise are the two most likely

problems that can result from a malfunctioning supercharger unit..

.

The proper procedure for removing a supercharger is given in the servicemanual and it should always be followed..

.

Like any mechanical diagnosis, you start with careful observation..

.

Are there any unusual noises, hissing sounds, grinding or squealing? Arethere any signs of exhaust gas leakage before or after the turbocharger?

Are there any air leaks on the intake and pressure side of theturbocharger?.

.

.

.

Excessive oil consumption may also be traced to the turbocharger. Theshaft seals could wear and let engine oil squirt into the turbo housing..

.


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Inspect the air cleaner for possible clogging. Look at the connectinghoses for damage, collapsing, or internal shredding. Replace or repair

any damaged components..

.

.

Deposit buildup inside the exhaust passageways can also causeproblems by restricting flow. And, of course, look for leakage; burned-outpipes and blown- out gaskets are possibilities..

.

.

The gauge is fitted on a tee into the pressure hose connecting the intakemanifold and the wastegate valve actuator. With the gauge attached,

the engine is run to around 3,000 RPM on the road..

.

.

Never lift the turbocharger using the wastegate actuating rod as a

handle. When access is gained to the compressor wheel, turn it by handand see if it rotates freely and smoothly. If it turns hard or drags, theturbocharger will have to be replaced..

.

.

.

Inspect the compressor wheel for deposits, cracks, and rubbing areas..

.

Deposits on the turbine usually mean that the engine is burning excessiveoil..

.


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It may be necessary to rebuild the valve guides or replace the piston

rings. A dial gauge is stationed against the end of the shaft..

.

A few precautions are necessary with regard to removing theturbocharger from the engine. Be very careful with heat shields..

.

They are often fragile. Damage to a heat shield will cause nearby engine

component damage in a very short time..

.

Coolant and oil lines must be removed in order to remove theturbocharger. To prevent damage, use tubing wrenches for these fittings..

.

You want the turbocharger bearings lubricated when the engine starts.Look for oil or coolant leaks as soon as the engine is restarted..

.

Not much actual repair is done to turbocharger components. Damaged

parts are simply replaced. Problems in this area are not cheap..

.


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I. TECHNICAL WORDS

CHAMBER: an enclose space in a machine. The combustion chamber is

the part of an engine where the fuel burns.

DRAFT: plan.

EXHAUST: the waste gas from an engine, especially a cars, or the pipe

the gas flows through.

FUMES: strong, unpleasant and sometimes dangerous gas or smoke.

PICK: in combinations, a sharp pointed tool.

TUBE: a long thin container made of a soft metal or plastic, which isclosed at one end and has a small hole at the other, usually with acover, and which is used for storing thick liquids.

VENT: a small opening which allows air, smoke or gas to enter or escape

from an enclosed space.

VENTILATION: causing fresh air to enter and move around an enclosedspace.

II. VOCABULARY


bottom ____________________________________________________

chamber ____________________________________________________

cover ____________________________________________________

drawback ____________________________________________________

either ____________________________________________________

mostly ____________________________________________________

peak ____________________________________________________

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reliable ____________________________________________________

scrutiny ____________________________________________________

sludge ____________________________________________________

source ____________________________________________________

spring ____________________________________________________

to attach ____________________________________________________

to be aware ____________________________________________________

to blow ____________________________________________________

to create ____________________________________________________

to dilute ____________________________________________________

to drain ____________________________________________________

to draw out ____________________________________________________

to ensure ____________________________________________________

to gather ____________________________________________________

to lead ____________________________________________________

to remain ____________________________________________________

to remove ____________________________________________________

to widespread ____________________________________________________

top ____________________________________________________

unstable ____________________________________________________


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IV. PRESENTATION

HISTORY & DEVELOPMENT

Engines create blow-by fumes and vapors as products of normal

combustion. Early engine designers were aware of the damage whichthese gases cause. Gathering in the crankcase, diluting andcontaminating the oil these impurities could not be allowed to remain

there. Early designers took the easy way out, and simply vented thecrankcase to the atmosphere. Today, we dont want these vapors

floating around outside the crankcase either. The result is thedevelopment and widespread use of modern Positive Crankcaseventilation systems.

Various vapors and gases are produced during normal engine

operation. Some of these by-products of combustion are forced past thepiston rings into the crankcase. If these gases and vapors are not ventedthe engine oil will become contaminated and sludge will form.Additionally, pressure in the crankcase will increase at higher RPMs andif not vented, could force engine oil past seals and gaskets. To avoidthese problems, crankcase ventilation systems were installed on all

internal combustion engines.

The first method of crankcase ventilation was the road draft tube. Onvehicles using this system, the crankcase is fitted with a vent. This vent isusually located in the valve cover, but it may be at any point on the

engine open to crankcase vapors and pressure. A tube is attached tothis vent which runs to the bottom of the engine (or in front of a

Fig.1: By-Productsof CombustionEnter CrankcaseDuring NormalEngine Operation

CRANKCASE VENTILATION


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carburetor intake). Airflow past the end of the tube creates a vacuumwhich draws gases out of the crankcase. As these gases are removed,

fresh air enters the crankcase through a vented oil filler cap or breather.The fresh air not only replaces vented gases, but helps to keep fumes

and vapors suspended until they are removed.

This type of system has two drawbacks. The first drawback is that thesystem only works at peak efficiency when the vehicle is at speed. Eventhen, unstable airflow and vacuum lowers the efficiency. At speeds

below 20-25 MPH, vacuum at the road draft tube is to low to draw outfumes. This allows fuel vapors to remain in the crankcase, promotingsludge formation, diluting the oil and reducing its ability to properly

lubricate the engine.

These unreliable systems led to the development of the first PositiveCrankcase Ventilation (PCV) systems. Used mostly on military andcommercial vehicles, they first appeared in the 1950s. The main purposeof the system vas to ensure sludge was reduced and oil lubricatingqualities maintained.

The second drawback with this system, and for our purposes the moreimportant of the two, is that vapors drawn out of the crankcase arevented directly to the atmosphere. This creates unwanted emissions andcontributes to the air pollution problem. This was the main reason for thedevelopment of mandatory use of PCV systems on all non.-commercial

vehicles.

The automobile engine fell under scrutiny in the early 1960s as a sourceof air pollution. Research indicated that automobiles, as a group, were

responsible for a major portion of the air pollution in this country. Of the

Fig.2: A TypicalRoad Draft Tube

Ventilation System


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emissions produced by non-PCV equipped vehicles, about 20% are fromcrankcase vapors.

DESCRIPTION

A positive Crankcase Ventilation (PCV) system routes crankcase gases tothe intake system where they are drawn into the combustion chamberand burned. Actually, a PCV system is quite simple. A breather (air vent)

is placed in the valve cover or top of the engine. It allows fresh air intothe crankcase and also functions as a separator, condensing some ofthe fumes and draining them back into the crankcase. A one-way valve

(PCV valve)) is placed in the valve cover or side of the block. It isconnected by a tube to engine vacuum at the base of the carburetor or

intake manifold. As engine vacuum drops, spring tension opens the PCVvalve and crankcase vapors are drawn in and burned. The vapor flowinto the intake manifold can be adjusted by varying the strength of thespring in the PCV valve and the design of the valve itself.

V. EXERCISE

Translate the following sentences

This type of a ventilation system is beneficial in a number of ways..

.

For this reason, some manufacturers began using PCV systems in non-commercial vehicles long before they were required by law. Chevrolet,for instance, installed PCV systems as early as 1955..

.

.

Under full throttle conditions, crankcase pressures build up rapidly whilevacuum levels drop..

.

A closed PCV system solves this problem by connecting the breather

to the air cleaner.

..


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A small orifice in the valve allows a metered volume of gas to pass into

the intake manifold..

.

If the engine backfires, flames travel up the intake manifold into de PCVhose..

.

Instead, a carefully-sized hole (orifice) is placed in the system.

..

The system should be checked whenever stalling, rough. idle, or other

condition indicating a ventilation system malfunction occurs..

.

Although variations do exists, the basic design and function of all

crankcase ventilation systems is the same..

.

If the system fails any test, replace the indicated component and repeatthe test..

.

However, if a new valve is not available, clean the old one in solventand make sure the check valve rattles..

.

Position filter so excess oil drains thoroughly through the vent nipple, thenreinstall it on the engine..

.


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A clicking or rattling noise should be heard when the valve is shaken..

.

Crankcase fumes (vapors, gases) are forced out through the oil cap orbreather, through the air cleaner and into the cylinders where they areburned..

.

.

The pressure of the backfire snaps the PCV valve closed, and preventsthe flames from reaching the flammable vapors in the crankcase..

.

The hoses must be clean inside, so blow them out with compressed air ifnecessary..

.

Position filter so excess oil drains thoroughly through the vent nipple, thenreinstall it on the engine..

.

If test results are correct, system is operating properly..

.

They control the flow of crankcase fumes into the intake manifold while,at the same time, preventing gases or flames from traveling in theopposite direction..

.

.


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With the engine idling at normal operating temperature, disconnect thePCV valve from the rocker cover..

.

Readings Automotive Mechanics 4

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