engine learning material

7/25/2019 Engine Learning Material

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Engine Principles

1 Paramobile Technical Service training Center

Engine Principles


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Engine Principles


indexA to Z

ABNORMAL COMBUSTION, 6

CHARACTERISTICS, 26

COMBUSTION, 4

COMBUSTION CHAMBER, 5

COMPRESSION, 3

COMPRESSION TEST, 13

CONNECTING ROD, 8

COOLING SYSTEM, 20

CRANKSHAFT, 8ENGINE BLOCK, 7

EXHAUST, 4

EXHAUST MANIFOLD, 12

FOUR STROKE CYCLE, 2

FUEL PRESSURE TEST, 19

FUNCTION OF LUBRICATION, 25

IGNITION COIL, 14

IGNITION TIMING, 15

INTAKE, 3

INTAKE MANIFOLD, 12

LUBRICATIONS, 24

NORMAL COMBUSTION, 5

Notes, 34

OIL FILTER, 29

OIL PAN, 28

OIL PUMP, 28

OIL SCREEN, 28

PCV VALVE, 30

PISTONS, 7

PISTONS, RINGS, 8

POSITIVE CRANKCASE VENTILATION, 30

POWER, 3

PRE-IGNITION, 6RADIATOR, 22

RADIATOR CAP, 23

RADIATOR FAN, 23

Spark Plug, 14

THERMO FAN SWITCH, 24

THERMOSTAT, 22

TIMING BELT ALIGNMENT, 16

VALVE CLEARANCE ADJUSTMENT, 16

VALVE GUIDES, 11

VALVE OVERLAP, 4

VALVE SEALS, 11

VALVE SPRINGS, 11

VALVES, 10

WATER PUMP, 21


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FOUR STROKE CYCLEA four stroke cycle means that the piston in each cylinder must travel the length of the cylinder

four times (2 up strokes and 2 down strokes) to complete one cycle for that cylinder.

Because the engine has 4 cylinders, each piston in the cylinder will be moving in a differentstroke. It takes 720 degrees of crankshaft rotation (2 full revolutions) to complete one four stroke

cycle for each cylinder.

INTAKE STROKE - High Pressure Attempts to Equalize Low Pressure.

COMPRESSION STROKE - Volume of Gas Decreases, Temperature and Pressure Increase.

POWER STROKE - Pressure and Temperature Increase, Volume Increases.

EXHAUST STROKE - High Pressure Gas Attempts to Equalize Low Pressure Exhaust System

INTAKEThe piston is being pulled downward by the crankshaft resulting in a

low pressure area in the cylinder and the intake manifold. Thepressure in the cylinder is lower than atmospheric. The air/-fuel mix

is "pushed" into the cylinder as the higher atmospheric pressureattempts to equalize the lower pressure area in the cylinder. Theair/fuel mix enters the cylinder past the opening intake valve, and

continues to enter the cylinder until the intake valve reaches fullclosure.

COMPRESSIONAfter the piston reaches BDC on the intake stroke, it begins to move

upward. This is the beginning of the compression stroke. As the

stroke begins the intake and exhaust valve is closed, thus sealing thecylinder. As the piston travels upward the air/fuel mix is compressed

and by the time the piston reaches TDC, the air/ fuel mix has been

compressed to approx. 1/8th of its original volume.This compression causes the molecules of the air/fuel mix to move

around in the combustion chamberThe more upward in the cylinder the piston moves, the higher the

pressure in the chamber, and the faster the molecules move. Thiscauses the molecules to "bump" into each other and the walls of the

chamber, raising the temperature inside the chamber. As the pistonnears TDC, the spark is introduced to the combustion chamber. This

causes the air/fuel mix to begin to burn, and to expand in the

chamber.


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POWERAs the piston passes TDC and begins to travel downward onthe power stroke, the burning gases exert great pressure

on the walls of the chamber and the head of the piston. This

increase in pressure drives the piston downward, thus

driving the crankshaft and the other pistons.NOTE:

It is during this stroke that the reciprocal (up-down) motionof the piston is converted to the rotary (circular) motion ofthe crankshaft that is used to drive the vehicle. As the

piston nears BDC the exhaust valve begins to open and the

high pressure, burned gases start to exit the cylinder.

EXHAUST

The piston begins to travel upward in the cylinder on the

exhaust stroke. The exhaust valve fully opens, then

begins to close during the stroke.

Pressure within the cylinder when the exhaust valveopens causes the exhaust gases to rush out of the

cylinder past the valve and into the exhaust system. The

upward movement of the piston, along with the effects ofvalve overlap causes the rest of the burned gases to exit

the cylinder.

VALVE OVERLAP

Valve overlap is the amount of time between the end of theexhaust stroke and the beginning of the intake stroke when bothvalves are open simultaneously. The amount of overlap is critical

as any increase or decrease will adversely affect emissions andengine performance, especially idle quality. The purposes of valveoverlap are

1) to improve volumetric efficiency

2) to help scavenge burned exhaust gases from the cylinder.

Valve overlap improves volumetric efficiency by opening the intakevalve early enough to begin introducing a new fuel charge to the

cylinder before the down stroke of the piston. This allows the

cylinder a slightly larger charge than could be attained by openingthe valve at the beginning of the intake stroke.

Scavenging of the cylinder is improved because the incoming fuelcharge helps to push out any remaining burned gases. This actionalso helps to cool the exhaust valve.


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COMBUSTION

COMBUSTION CHAMBER

The combustion chamber of the DOHC engine is referred to as having a "pent roof" shape.

This is different than a "wedge" or "hemispherical" shaped chamber. The spark plug ispositioned in the center of the combustion chamber, in line with and along the length of theblock.

NORMAL COMBUSTION

The combustions process in the automotive engine combustion chamber goes through 3stages, sometimes termed as formation (nucleus of flame), hatching out and propagation. As

soon as the spark occurs, a small ball of flame develops in the gap. This ball is the first stage,or nucleus of the flame. It enlarges with relative slowness and, during its growth, there is nomeasurable pressure created by the heat. As the nucleus enlarges, it develops into the

hatching out stage. The nucleus is torn apart, so that it sends "fingers" of flame into themixture in the combustion chamber.


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This causes enough heat to slightly raise the temperature and pressure throughout the entire

A/F mix. During the 3rd stage propagation, the burning of the fuel begins to have the greatesteffect. The flame "front" sweeps across the chamber rapidly causing heat and a rise in

pressure. This third stage is what causes the piston to move down.

With normal combustion, the burning is progressive, and increases gradually during the first

two stages. But, during the propagation stage the flame is very strong.

ABNORMAL COMBUSTION

Although there are a number of different types of abnormal combustion that could be

discussed, two that most relate to the automotive internal combustion engine are Pre-ignition

and Detonation.

Common causes of pre-ignition include :

1. Hot carbon deposits2. Valves operating at higher than operating temperature

3. Defects in the cooling system causing hot spots in the cylinder

4. Spark plugs running too hot

5. Sharp edges in the combustion chamber6. Detonation

PRE-IGNITION

Ignition of the fuel charge before the normal ignition spark occurs.With pre-ignition the

combustion process is started too early. If the process is completed before the regular sparkoccurs there may be no identifying noise. If regular spark occurs soon after the pre-ignitioncombustion has begun, a pinging noise results from the collision of the two flame fronts.


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Pre-ignition can cause detonation and vice-versa. These two types of abnormal combustion

are closely linked, can be caused by many of the same problems and it is often hard to tellone from the other.

ENGINE BLOCKThe engine block serves as a rigid metal foundation for all partsof the engine. It contains the cylinders, the cooling system

"water jacket", and supports the crankshaft mounting points,

the oil pump, and distributor mounts. The cylinder head(s) andaccessories are usually bolted to it. The block also forms the

upper part of the crankcase.


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PISTONSThe piston is a plug driven up and down by the crankshaftresiding in the cylinder. The movement of the piston provides

the action in the cylinder. It is used to draw, compress, drive

and push. The piston alternately drives, and is driven by thecrankshaft. It changes directions at high speeds, subjected tointense heat and friction and receives tremendous pressure

from the combustion process.

PISTONS, RINGS

The piston rings must seal in compression, transfer heat, cleanthe cylinder walls, withstand high pressures, and have a longwear rate. Most piston designs incorporate three rings for two

purposes. Usually the two rings toward the top of the piston arecompression rings. The third and lowest of the rings is actuallya combination of parts making up the oil control ring.

The compression rings must keep the pressures of combustionfrom passing into the crankcase and must create a seal againstthe cylinder walls for the cylinder to become a low-pressure

area during the intake stroke. The rings are designed to allowthe forces of compression and combustion to come in behindthem and force them out against the walls of the cylinder. The

rings not only have to seal at the cylinder walls, but also in the

ring-groove/ring-land area.

CONNECTING ROD

The connecting rod connects the piston to the crankshaft. It is

subjected to very high tensile, compression and bending stressesand carries the bearings for the piston pin and the crank pin.Upper side of connecting rod is called small end which is

connected to piston by piston pin. Lower side of connecting rod is

named big end which is connected to crank pin. The length of theconnecting rod is determined by the piston stroke and the crank

pin radius.


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CRANKSHAFTThe crankshaft is the point at which thereciprocating motion of the piston and rod is

changed to the rotary motion needed to power the

driveline of the vehicle. The crankshaft revolves in

bearings called the "main" bearings. Thesebearings are housed in the main bearing bores of

the engine block and are manufactured under veryclose tolerances to withstand extreme loads.

CAMSHAFT

The second rotating shaft in the engine is

the camshaft and its function is to

operate the valve train. Cam shape or

contour is the major factor in theoperating characteristics of the engine.

NOTE :

Camshafts are also used to drive otherengine components such as the oil pumpand fuel pump. Pushrod engines have the

cam located in the block, and operate the

valves through lifters, pushrods, rockerarms, etc. Overhead cam engines have

the cam in the cylinder head. This

eliminates the lifters and pushrods, andthere is less lost motion in the valve train.Because the valve follows the cam more

closely, the valves can operate faster,and the engine can operate with lessvalve overlap. This allows a high-speed

engine to idle more smoothly.


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The function of the cam is to open and close the valves.The closing force for the valves is applied by the valvesprings which are also responsible for maintaining contactbetween the cam and the valves.

Cam lobe shape has more control over engine

performance than any other single engine part. Theshape of the lobe determines when the valves open, howfar they open, and how long they are open. This

determines the amount of valve overlap. The camcontrols the amount of air that comes into the engine,and that goes out. Any change in the shape of a cam lobe

results in a change in engine performance.

VALVESIn most automotive engines

there are two valves per

cylinder : an intake valveand an exhaust valve. The

intake valve is the larger of

the two. When the intakevalve is opened, the onlyforce driving the mix into the

cylinder is atmosphericpressure.The exhaust valve can be smaller because the motion of the piston combined with the high

pressures in the cylinder forces the burned mix out.

The valve used today is the beveled poppet valve. Its cone shaped seating surface makes it

self-centering when it closes. This closes the valve tightly to seal in the combustion gases,and helps to transfer heat from the valve face, to the seat, to the cooling system.Temperatures at which a valve operates are extremely high.

One of the most common causes for a burned valve is poor cooling system performance atthe seat or guide area.

NOTE:

Cooling of the valve during operation is done in a number of ways. An intake valve average

running temperature will rarely get above 480 to 540 degrees. The exhaust valve commonlyoperates at 760 degrees C and higher. The cylinder head is designed to bring coolant very

near to the valve seats and guides. About 75% of valve heat is lost through the seat and 25%

through the guide. The casting of the head also incorporates "deflectors "in the waterpassages to circulate the coolant around these hot spots. Exhaust gases can reach 1650degrees C.


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VALVE GUIDESThe main function of the guide is to keep the valve centeredover the seat and secondarily it must transfer heat from the

valve to the cooling system. Because of friction and heat,the guide area is a high wear point.

VALVE SEALS

Valve seals are used to keep engine oil out of thecombustion chamber. They are attached either tothe valve stem or to the valve guide boss in the

cylinder head.

VALVE SPRINGSValve springs hold the valves against the seats. One end of thevalve spring is seated against the head. The other end is secured,

under compression to the valve stem by a valve spring retainerand a valve spring keeper. Problems associated with valve

springs include when a spring becomes weak it can cause thevalve to bounce on closure, to close too slowly, or not close at all.

In extreme cases it should be replaced, otherwise a shim can beplaced under it.Another problem is spring oscillation or surge. When the valve is

opened and closed at high speeds, a vibration can start to set up

in the spring's coils. If severe, the spring will begin to oscillate, orextend and compress on its own. It can become great enough to

open and close the valve.

A weak or oscillating spring can contribute to "floating" the valve train. A number of devices have beeused to combat valve spring oscillation. These are called vibration dampeners. The most used method

is the closed coils. The spring is built so the last coil on each end of the spring rubs against the secon

last coils. This gives the spring a variable rate of tension. It is stronger when compressed than whenextended. Another method is the flat coiled damper inside the spring. The damper looks like a flatspring with the flat sides facing in and out. The damper rubs against the inside coils of the valve

spring. It adds some spring tension to the entire assembly, and causes a turning action in the spring

assembly when the valve is returned to its seat.This helps the valve to "wipe" the seat clean during operation. Multiple valve springs are used where

large lifts are required and one spring cannot control the valve. Multiple springs have their coils wounin opposite directions to control valve spring surge and excessive rotation.


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Engine Principles


INTAKE MANIFOLD

The intake manifold is a series of tubes for carryingthe air/fuel mix from throttle body to the cylinderintake ports. Manifold sizes are a compromise. They

must have a cross section large enough to allowenough charge to flow for maximum power andsmall enough to keep flow velocities high to keep

the droplets in suspension. Manifold heat is

necessary to evaporate the fuel droplets efficiently.The intake charge temperature must be above 38-

55 degrees C to evaporate correctly. This is why

intake manifolds have special runners throughwhich exhaust is passed to heat the manifold.Exhaust heat is only provided during engine warm-

up to prevent the manifold becoming too hot. Someengines use coolant to warm the fuel charge.Coolant is used where a uniform temperature is

needed. In today's engines there is normally an

additional opening in the intake manifold for E.G.R.purposes.

EXHAUST MANIFOLDThe exhaust manifold is designed to collect the hightemperature spent gases from the cylinder head

ports and send them to the outside air. This mustbe done with the least possible restriction or backpressure while keeping system noise to a minimum.

Exhaust gas temperature will vary according to thepower output of the engine. Severe bends have

little effect on the flow of exhaust gas. A largecross-sectional area must be maintained in the

manifold runners and the exhaust system, as thegases expand at a very high rate. Small diameter

runners and exhaust pipes will cause too much backpressure.


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COMPRESSION TESTPURPOSE

To check the condition of piston rings,

cylinder head gasket, valve seat, valves and

valve springs

CHECK CONDITIONEngine oil level, starter motor and battery arenormal

CHECK PROCEDURE

1. Remove the spark plugs

2. Attach the compression gauge to thespark plug hole

3. Depress the accelerator pedal to fully

open the throttle valve4. Crank the engine and read the gauge5. Repeat step 2 through 4 on all

cylinders and check the pressuredifferential for each cylinders

LIMIT MAX. 1.0/ BETWEEN

CYLINDERS

6. If a cylinder pressure or pressure

differential is below specification, adda small amount engine oil throughspark plug hole.

If the addition of oil brings the

compression upsuspected items : worn cylinder andpiston rings, piston or ring broken

If same compression pressure after adding oil

suspected items : valve, valve spring, valveseat, cylinder head gasket


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Engine Principles


IGNITION COIL 12 volts in 30,000 + volts out

Step up transformer

When current flows magnetic

field is developed quick clean interruption of

current field collapses themagnetic field

Spark PlugThe spark plug ignites at the compressed

mixture to fire it according to the spark arcby the high voltage generated from the

ignition coil.

spark plug is classified as 14mm, 12mm, and

10mm according to the size of attaching

screw.

The spark plug, during driving, is affected by

the various temperatures. The most affecting

temperature is the combusted amount of fuel

mixture per time. As the engine is high

speed, the temperature of plug will be high.

Even in the same driving condition, the

temperature differs according to the heat

range of the plug.


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Engine Principles


IGNITION TIMING

PURPOSE

The fuel system and ignition system should be

correctly functioning for the engine to run smoothly.Hence, proper operation of the fuel system and

ignition system must be determined prior to

troubleshooting. Therefore, the purpose of ignitiontiming is to check if the ignition system is operatingproperly.

CHECK CONDITION

Warming up temperature

All electrical loads off A/T : "P" or "N" Idle rpm is normal

CHECK PROCEDURE

1. Install a timing light

2. Ground the ignition timing adjust terminal

3. Check the ignition timing through timing light4. Adjust the ignition timing if the ignition timing

is out of specification

If the timing can not be adjusted(some of engineignition timing can not be adjusted), please check therelevant component

NOTICE !

Do not use the scan tool to check the ignition timing .The ignition timing shown in current data on the scantool is not actual ignition timing but it is electrical

timing.


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VALVE CLEARANCE ADJUSTMENT

MECHANICAL LASH ADJUSTER

VALVE CLEARANCE CAN BE ADJUSTED BY SHIM.

PROCEDURE

1. Set no1 cylinder to TDC

2. compression3. Check TDC position of camshaft

4. Measure the clearance for

#1 intake valve, exhaust valve#2 intake valve,#3 exhaust valve

5. Turn the crankshaft one revolution

6. Measure the clearance for#2 exhaust valve,

#3 intake valve#4 intake valve, exhaust valve

7. If the valve clearance is not within the specification, replace the adjusting shim

Specification (20c)Intake 0.12 ~ 0.28mmExhaust 0.2 ~ 0.36mmUse special tools to replace adjusting shim

See the adjusting shim selection chart See page 32-33


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Engine Principles


BETA ENGINE - ELANTRA(96MY) SONATA DOHC

EF SONATA 2.5L XG 3.0L

TIMING BELT ALIGNMENT -OMEGA 4.5

1. Align the camshaft timing mark on camshaftcap timing mark

2. Align the sprocket timing mark and camshafttiming mark


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3. Align timing markbetween sprocket andhead(Left bank)

4. Align timing mark

between sprocket and

head(Right bank)

5. Align timing markbetween crankshaft

sprocket and front case

6. Install the timing belt as

following order

Check the timing mark after 8 rotation of crankshaft


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Checking the timing mark on the vehicle

Checking the timing mark on the vehicle


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FUEL PRESSURE TEST

CHECK PROCEDURE

1. Reduce the internalpressure of the fuel pipes

and hoses(disconnect the fuel pumpconnector start the engine

and turn the ignition switch

"off" after it stops by2. Itself connect the fuel

pump connector)

3.

Install a fuel pressuregauge and a fuel pressuregauge adapter

4. Start the engine and check

that there is no fuelleakage

5. Disconnect the vacuumhose from the pressure

regulator and plug thehose end. Measure the fuel

pressure

6. Measure the fuel pressurewhen the vacuum hose is

connected to the pressureregulator

SUSPECTED ITEMS

Fuel pressure too low -

Fuel filter, fuel pressure regulator, fuel pump Fuel pressure too high -

Fuel pressure regulator, return hose or pipe

Fuel pressure drops slowly after engine has stopped -

Injector leakage Fuel pressure drops immediately after engine has stopped -

Check valve of the fuel pump


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Engine Principles


COOLING SYSTEM

INLET CONTROL TYPEDIAGRAM

OUTLET CONTROL TYPEGENERAL DIAGRAM

WATER PUMP

For a cooling system to operate effectively, it must have the ability to circulate the coolant.Engine temperature needs to be controlled to maximize engine tolerances and to insure good


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lubricating conditions.

If oil is too cool or too hot, inadequate lubricating conditions exist that could result in scuffingand other wear problems. Water pumps are usually belt driven off a crankshaft pulley. Waterpumps are die cast housing construction with a stamped steel impeller. The pump has an inlet

that leads to the center of the impeller. The water pumps of the centrifugal-type will pump

the water outwards to the impeller tips. This flow of water is then discharged through anoutlet in the pump and into the cylinder block. Once in the engine block it will circulate overthe outside of the cylinders and then flow upward into the cylinder head, intake manifold and

heater core.

THERMOSTATThe thermostat has the

responsibility of regulatingthe coolant temperature in

the engine. When the

coolant is not up to

operating temperature, thethermostat will not allow

the coolant to go on to the

radiator.Instead, the coolant will be directed back to the water pump to be recirculated through the

engine to be heated to operating temperature. Think of the thermostat as a valve that opens

when its hot and closes when its cold. When the engine water does reach the ratedtemperature of the thermostat, the valve will open and direct water to the radiator forcooling.

The inside air of coolant passage must be

vented through the jiggle valve in order toprevent the engine from overheat. The jiggle

valve opens by weight of jiggle valve when theair exists around the jiggle valve. The air canbe vented through the jiggle valve hole. Thejiggle valve closes when the water is reachedto the jiggle valve.

If the jiggle valve is installed on bottom side, it

blocks the its hole before air ventilation. Thethermostat can not open even if the coolanttemperature is over than opening temperature,

because the coolant can not be reached to the

pellet by air. Therefore, jiggle valve should belocated on top side.

RADIATORThe radiator's only function is to transfer heat from the coolant to air by radiation. The

construction of a radiator is rather simple. There are long water tanks that are connected by


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Engine Principles


thin tubes and attached to these tubes are fins for the purpose of absorbing heat to be cooledby air. The two most common types of radiator constructions are the tube-fin and the ribbon-cellular.

Radiator assemblies can be made from a variety of materials. The most common materials arecopper, brass, plastic or aluminum.

Construction of a ribbon-cellularradiator core

Construction of tube and finradiator core

RADIATOR CAP

The purpose of the radiator cap is to seal the radiator to prevent contaminants from enteringand to pressurize the cooling system.The reason for pressurizing the cooling system is to raise

the boiling point of the anti-freeze. The boiling point will increase by pressure. A pressurized

system can run hotter and dissipate heat better for improved cooling.


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Engine Principles


RADIATOR FANThe radiator has to have air flowthrough it to be able to do its job.

When the vehicle is stationary ormoving at low speeds below 60 mph,there is insufficient air flow for cooling

to be effective. Therefore, a fan isinstalled to produce adequate air flow.

The fan on some vehicles is mounted

on the water pump pulley shaft and isbelt driven off the crankshaft

pulley.The shroud acts as a suctionchamber to draw more air through theentire radiator surface. Without a

shroud, the area that the fan would

draw air through would be restrictedto the fan diameter. The fan shroudalso prevents underhood air from

recirculating behind the radiator. Bothfunctions help to increase the flow ofcool air through the radiator.

THERMO FAN SWITCH

The thermo fan switch grounds an

electromagnet in the fan relay to turn

the fan on. It is not directly connectedto the fan.

LUBRICATIONS


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Engine Principles


LUBRICATION(Elantra)

LUBRICATION(Sonata)

FUNCTION OF LUBRICATION


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Engine Principles


The power plants used in today's vehicles convert fossil fuels to mechanical power. Side

effects of this conversion process are heat and friction. Heat is created either from thecombustion process or from the friction

1.

Residual Oil Only, shaft Rests on bearing2. Oil Rotating, Journal Shaft Rotation3. Oil has wedged shaft up Bearing and journal will not touch

of the rubbing, sliding, or rotation of metal engine components against one another. It isimpossible to eliminate all of the friction but oil will eliminate most of the damaging friction.

Oil will do its best to keep the moving engine parts from coming in direct contact and creating

heat due to friction. When friction occurs, the oil will absorb much of the heat and convey it toanother area for cooling.

The oil also does a few other little favors like improving sealing of the piston rings to prevent

combustion leakage, washing away abrasive metal or dirt particles from friction surfaces, andretaining their characteristics in cold or hot operating conditions.

REDUCE WEAR AND POWER LOSS

Oil molecules can be thought of as tiny ball bearings that roll over each other to eliminate

friction in rotating or sliding parts. The primary responsibility of oil is to prevent wear ofengine parts as much as possible. Oil use in automobile engines needs two qualities to do its

job. One is to create a hydro-dynamic film of oil for parts to rotate or slide on. This eliminatesmetal contact and prolongs engine life. Two, when high pressure squeezes out the oillubricant, some sort of additive is deposited on parts when oil flows over them.

CHARACTERISTICS


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Engine Principles


COOLING

As oil flows throughout the engine, it picks up heat from engine parts it comes in contactwith. This oil will eventually find its way to the oil pan where it is cooled by air passing overthe outside of the oil pan.

It is important to have this transfer of heat from the oil to outside air in order to keep thelubricant at an ideal temperature to maintain performance.

SHOCK ABSORPTION

The shock load of the piston and connecting rod assembly as it bottoms out on the powerstroke is absorbed by the film of oil on the connecting rod and crankshaft main bearings. Thisshock force can be upwards of two tons and can cause a pounding noise which is cushionedand quieted by the film of oil.

COMBUSTION CHAMBER SEALING

Oil sprayed on cylinder walls not only provides lubrication, but it also improves cylinder

sealing. This improved sealing helps prevent combustion gases from escaping past the piston

compression rings. The oil compensates for small unevenness between the piston ring andcylinder wall by filling in the gaps.

CLEANSING

As the oil circulates, it picks up particles of dirt, carbon, metal particles, and various otherforeign particles. As the oil finds its way back to the pan, the heavier particles will go to the

bottom where they could be picked up and circulated through the lube system. The pick-up

screen prevents the large contaminants from going into the lube system and the oil filterblocks out the small particles that could potentially cause engine damage.


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Engine Principles


COMPONENTS

OIL PAN

The oil pan seals the crankcase ofthe engine and is also the engine

oil reservoir. The pan has anadded responsibility of cooling theengine oil. Air passing over the

outside of the pan will cool the oil

(radiator) and help keep it withinoperating temperature range of

about 220F. Baffles are

sometimes added to the oil pan tohelp prevent oil from washing

away from oil pickup underextreme turns, acceleration ordeceleration conditions.

OIL SCREEN

The oil screen is a tube assembly attached to the suction side of the oil pump. The other endof the oil screen tube has an integral screen filter to help filter out large particles that could

damage the oil pump.

The screen sits on the bottom of the oil pan and ideally should be submersed in the oil at alltimes to prevent air from entering the lubrication system.

OIL PUMP

The oil pump is the heart of the lubricating system. The pump draws oil from the oil pan,

through the pickup tube, pressurizes the oil and sends it on to the oil filter.


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Engine Principles


An integral part of most oil pumps is a pressure relief valve. This valve will control high

pressure so the oil filter or other engine components would not be damaged. The pressure is

determined by the spring tension. Any additional pressure would not be beneficial and wouldinstead result in parasitic losses because of the extra engine power used to drive the pump.

Oil pumps are usually driven off the camshaft, but there are cases when the pump will bedriven off an intermediate shaft or crankshaft. The two most commonly used styles of pumpsare the gear pump and the rotor pump. Both are positive displacement pumps which arenecessary to insure lube pressure at low engine speeds.

OIL FILTER

Although the oil pickup tub has a screen that

filters out large particles, the oil filter is stillresponsible for the bulk of the filteringduties. Most filters today filter out particles

between 20-30 microns or 0.008 to 0.0012

inch. The filtering medium in the filter is

pleated paper or fibrous material that isenclosed in a spin-on, throw-away type

assembly.Oil enters the filter on the outside of thefiltering element and flow towards the center.

The reason it flows that way is because there

is more filtering area exposed to the oil, andit is able to hold increased amounts of

contaminant also resulting in longer life. Ifthe filter ever becomes plugged and unable

to flow a sufficient supply of oil, a by passvalve will open.

This is a built-in safety feature that will

prevent an engine catastrophe. This by-pass

will open when there is a pressure differentialof 5 to 15 psi between the outside and inside

of the filtering element.


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Engine Principles


FILTER ADAPTER

The filter adapter is mounted on the engine block or oil pump, if the pump is externallymounted. The adapter has two functions. One is to retain the oil filter. The second purpose isto prevent the oil filter from draining back through the engine galleries when the engine is notrunning. To do this function, it has a spring loaded check valve that comes unseated at

approximately 1-2 psi. This is to keep the oil filter filled at all times so when the engine isstarted there will be an almost instantaneous supply of oil to the engine.

POSITIVE CRANKCASE VENTILATION

COMPONENTS


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Engine Principles


PCV VALVENo Vacuum

Engine :Not running

PCV Valve :Notperating

Vacuum Passage :Restricted

High Vacuum

Engine :Idling ordecelerating

PCV Valve :Fullyoperating

Vacuum Passage :

Small

Moderate Vacuum

Engine :Normal

Operation

PCV Valve :

Properly Operating

Vacuum Passage :

Large

Low Vacuum

Engine :Accelerating

PCV Valve :Slightly

Operating

Vacuum Passage :

MuchLarger


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Notes


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Engine Principles

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