four-stroke engine: components€¦ · wrist pin/piston pin • attaches the piston to the upper...

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Accompanies: Four-Stroke Engine: Components & Operation 1

Directions: Answer the following questions.

1. Which of the following are two functions of piston rings? A. Hold combustion pressure in and transfer heat from the cylinder wall to the oil B. Transfer heat from the piston to the cylinder wall and hold in combustion pressure C. Retain as little oil as possible in the crankcase and keep the piston centered in the cylinder D. Make sure the wrist pin does not fall out and keep the piston in line 2. Which of the following regulates the timing of the opening and closing of the

exhaust valve? A. Rocker arm B. Lifter C. Pushrod D. Camshaft 3. Which of the following is true about hydraulic lifters? A. Are designed to be used on any camshaft B. Require no routine maintenance C. Do not use engine oil to operate the valvetrain D. Have no moving parts 4. Which of the piston rings is located in the top groove on the piston? A. Compression ring B. Scraper ring C. Wiper ring D. Oil control ring 5. Which of the following can be used to determine the stroke of the engine? A. Speed of the camshaft multiplied by three B. Distance from the top of the piston to the bottom of the piston, multiplied by four C. Distance from the centerline of the crankshaft to the centerline of the connecting rod journal, multiplied by two D. Speed of the mechanical link, multiplied by three

Four-Stroke Engine: Components & Operation - Engine Components

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1. Overheating of a liquid-cooled engine may be caused by which of the following? A. Water mixed with antifreeze B. Internal coolant flow blockage C. Thermostat opening too early D. Having the proper level of coolant 2. A great percentage of heat generated escapes through which of the following? A. Intake B. Cylinder C. Radiator D. Exhaust 3. Overheating of an air-cooled engine is NOT likely caused by which of the

following? A. Improper mixture of coolant B. Obstructions on the flywheel fins C. Damage to the external cooler D. Blockage of air intake screen 4. Coolant is commonly known as which of the following? A. Thermal energy B. Blended mixture C. Antifreeze D. Water 5. Which of the following are used to increase the surface area in which air can act

upon in an air-cooled engine? A. Shrouds connected to the exhaust B. Thermostats with coolant C. Check valves which act as vents D. Metal fins which cover the outside of the cylinders

Four-Stroke Engine: Components & Operation - Engine Cooling

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1. Which of the following is considered the lowest part of the engine? A. Sump B. BDC C. Camshaft D. Strainer 2. The oil’s resistance to flow correctly defines which of the following? A. Net-negative B. Bypass C. Viscosity D. Conservation 3. Which of the following is NOT one of the four functions of the lubrication system? A. Cleaning B. Cooling C. Sealing D. Transferring 4. API and SAE symbols contain information about which of the following? A. Energy conservation rating B. Oil color rating C. Oil volume rating D. Speed of flow rating 5. An oil dipper in a vertical-crankshaft model is attached to which of the following? A. Connecting piston B. Rotating rocker C. Crankshaft counterweight D. Connecting rod lid

Four-Stroke Engine: Components & Operation - Engine Oil & Lubrication Systems

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1. Which piston ring is located in the middle of the engine? A. Compression ring B. Scraper/wiper ring C. Oil control ring D. Exhaust ring 2. Match each component with its corresponding function. Piston Determines when valves will open and close Valves Transfers combustion energy to the crankshaft Camshaft Allow air/fuel in and exhaust out of the cylinder Crankshaft Turns reciprocating movement into rotational movement 3. Manufacturers can require users to run their oil. A. True B. False 4. Which component of a four-stroke

engine is shown in the image? A. Piston B. Camshaft C. Pushrod D. Connecting rod 5. The code on an oil service rating indicates which of the following? A. The use of the oil in a certain engine B. The viscosity of the oil C. The thickness of the oil D. The torque the oil will present

Four-Stroke Engine: Components & Operation - Final Assessment

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6. Use the word bank to complete the sentence. The _____________from the centerline of the crankshaft to the centerline of the connecting rod _____________, multiplied by _____________, determines the _____________ of the engine.

7. Which of the following is connected to the piston with the connecting rod? A. Crankshaft B. Piston rings C. Camshaft D. Lifters 8. What is the purpose of a crankcase breather system? A. To reduce the volume of the engine B. To produce coolant for the engine C. To create a vacuum to control oil consumption D. To act as an oil filter 9. Coolant exiting the engine flows through which of the following? A. Cylinder head B. Thermostat housing C. Coolant pump D. Cooling fan 10. Which of the following uses an oil dipper to throw oil onto internal engine parts? A. Viscosity oil system B. Pressure lubrication system C. Cooling oil system D. Splash lubrication system

Four-Stroke Engine: Components & Operation - Final Assessment

Journal Three Torque Stroke

Two Distance Power

Mechanical

S T U D E N T

V O C A B U L A R Y

H A N D O U T


Piston transfers combustion energy to the crankshaft Cylinder Bore diameter of the cylinder Piston Rings form a seal between the piston and the cylinder wall Crankcase case which encloses a crankshaft Wrist Pin/Piston Pin attaches the piston to the upper end of the connecting rod Connecting Rod connects the piston to the crankshaft Crankshaft converts the reciprocating movement of the piston into a rotational movement for power Torque twisting force which causes rotation Camshaft determines the time at which valves open and close in relation to each other Lifters move the pushrod up and down to move the rocker arm Valves allow air/fuel mixture in the cylinder and exhaust out of the cylinder Viscosity oil’s resistance to flow

Four-Stroke Engine: Components & Operation

Objectives

• To understand the purpose of various four-stroke engine components.

• To determine the purpose and types of cooling systems in four-stroke engines.

• To understand the uses and importance of engine oil.

• To analyze lubrication systems in four-stroke engines.

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Main Menu

Engine Components

Engine Cooling

Engine Oil & Lubrication Systems

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4ENGINE COMPONENTS

Four-Stroke Engines

• Are composed of many components, including:– piston– piston rings– wrist pin or piston pin– connecting rod– crankshaft– camshaft– lifters– valves

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Four-Stroke Engine

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1. Piston2. Piston Rings3. Wrist Pin/Piston

Pin4. Wrist Pin/Piston

Pin Retaining Clip5. Connecting Rod6. Crankshaft7. Connecting Rod

Cap

Four-Stroke Engine

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8. Oil Dipper9. Camshaft10.Lifters11.Pushrods12.Rocker Arms13.Valve Springs14.Valves

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Piston

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• Travels within the bore of the cylinder• Transfers combustion energy to the

crankshaft

Four-Stroke Fact: The cylinder wall and the piston expand at different rates, so enough clearance must be provided between them.

Piston Rings

• Are installed on the piston to form a seal between the piston and the cylinder wall

• Are typically made of high-grade cast iron and steel

• Have the following functions:– provide a seal to hold the combustion

pressure in– retain as much oil as possible in the

crankcase– transfer heat from the piston to the cylinder

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Piston Rings

• Include three common types:– compression ring– scraper/wiper ring– oil control ring

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Compression Ring

• Is installed in the top groove on the piston• Provides the seal for the cylinder by

expanding out against the cylinder wall– the compression pressure will flow in behind

the compression ring to increase pressure against the cylinder wall

• Is typically made of cast iron

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Scraper/Wiper Ring

• Is located between the compression ring and the oil ring

• Is used to further seal the combustion chamber and wipe the cylinder wall clean of excess oil

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Oil Control Ring

• Is located in the groove closest to the crankcase– toward the bottom

• Wipes excess oil from the cylinder wall and routes the oil back to the crankcase– the oil goes back to the crankcase through

holes machined in the ring and the piston ring groove

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Wrist Pin/Piston Pin

• Attaches the piston to the upper end of the connecting rod

• Allows the piston to pivot on the end of the connecting rod – while the other end of the connecting rod is

following the stroke of the crankshaft• Can be pressed in or held in place by a

wrist pin retaining clip at each end

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Connecting Rod

• Connects the piston to the crankshaft– the small end is attached to the piston with

the wrist pin– the large end is usually split across the

diameter of its opening to allow for assembly onto the crankshaft

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Four-Stroke Fact: The reciprocating movement of the piston in the cylinder is converted to the rotational movement of the crankshaft.

Connecting Rod

• Connects the piston to the crankshaft– the lower half of the large end is the

connecting rod cap and is bolted to the upper half after placing it around the connecting rod journal on the crankshaft

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Four-Stroke Fact: The connecting rod and its connecting rod cap are manufactured as a unit and must always be kept together.

Crankshaft

• Converts the reciprocating movement of the piston into a rotational movement, creating torque which powers the machine the engine is attached to

• Has a mechanical link, usually gears, to the camshaft and mechanical governor

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Four-Stroke Fact: The distance from the centerline of the crankshaft to the centerline of the connecting rod journal, multiplied by two, determines the stroke of the engine.

Camshaft

• Is at half speed of the crankshaft, usually through direct gear contact

• Will have a teardrop lobe to open each intake and exhaust valve

• Determines the timing when valves open and close in relation to each other

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Lifters

• Are also known as tappets• Are located on the camshaft lobes

– as the camshaft rotates, the lifter follows the profile of the camshaft lobe and moves the pushrod up and down to move the rocker arm

• Include two types– hydraulic– mechanical

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Hydraulic Lifters

• Have multiple parts and are usually replaced as a unit– through the use of a spring, inner and outer

cylinders, and engine oil, the hydraulic lifter will be maintenance free

• Allow for constant contact between the cam, lifter, pushrod, rocker arm and valve

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Mechanical Lifters

• Are solid, without moving parts– these lifters typically require some adjustment

regularly as components wear• the most common form of adjustment is at the

rocker arm• Are typically made of solid metal

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Valves

• Are components which allow the air/fuel mixture in and exhaust out

• Are made of heat resistant materials– the exhaust valve is usually made from a

separate alloy metal• Include the use of valve seats

– valve seats are inserted into the cylinder head for the valves to seal and transfer heat

– valve seats are grounded to an angle which mates with the valve face, so a tight seal is created when the valve is closed

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Engine Cooling

23ENGINE COOLING

Air-Cooled Engines

• Generate heat which is released directly into the air

• Rely on the circulation of air to cool hot engine components– heat must be removed from the engine to

prevent permanent damage

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Air-Cooled Engines

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1. Hot Air2. Shroud3. Warm Air

4. Cool Air5. Flywheel Fins6. Intake Screen

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Air

• Is brought in through an air intake screen by fins on the flywheel and distributed through a shroud and then across the fins on the cylinder(s)– metal fins covering the outside of the

cylinders are used to increase the surface area air can act on

– the air movement across the cooling fin draws away excess heat

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Four-Stroke Fact: In all combustion engines, a great percentage of the heat generated escapes through the exhaust.

Heat Energy

• May find its way into the oil, which although primarily meant for lubrication, also plays a role in heat dissipation– on an air-cooled engine, the addition of an oil

cooler may greatly help in the dissipation of heat

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Engine Overheating

• May occur if any part of the air flow is restricted by debris

• May also be caused by one or more of the following:– obstructions or blockage of air intake screen– obstructions on or in the flywheel fins– obstructions or damage to the shroud– obstructions or damage to the cylinder cooling

fins– obstructions or damage to the external cooler

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Liquid-Cooled Engines

• Utilize a radiator, coolant pump, thermostat, engine coolant passages, and the correct blend of coolant and water to regulate and dissipate engine heat

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Four-Stroke Fact: Coolant, commonly called antifreeze, is a mixture of ethylene or propylene glycol and water.

Liquid-Cooled Engine

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1. Radiator2. Hot Coolant3. Thermostat4. Coolant Pump

5. Cylinder Head6. Coolant Passage7. Cooled Coolant8. Cooling Fan

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• Operate in the following manner:– coolant is circulated from the coolant pump to

the cylinders, engine block, cylinder head, valves and combustion chambers through a series of coolant passages

• coolant exiting the engine flows through the thermostat housing

– coolant flows through a check valve opening in the thermostat, enabling a fast warm-up period

• the check valve also acts as a vent to allow air to escape while filling the cooling system

• before engine warm-up, the thermostat is closed

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• Operate in the following manner:– once the engine has reached full operating

temperature, the thermostat will completely open, allowing maximum coolant flow through the upper radiator hose to the radiator top tank

– coolant circulates through the radiator, dissipates heat and flows out the lower radiator hose back to the coolant pump

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Excessive Temperatures

• Will trigger the pressure cap to open to allow excess coolant to flow into the expansion tank– when the coolant temperature drops, the

pressure cap will close– as the coolant continues to cool, a vacuum

will form in the radiator, opening a valve in the pressure cap, allowing coolant to be siphoned from the expansion tank back into the radiator

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Engine Coolant

• Will continue circulating throughout the system until the coolant temperature drops below the thermostat temperature rating, at which the thermostat begins to close and the sequence starts again

• Allows the engine to operate at an optimal temperature, facilitating clean, efficient operation

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Engine Overheating

• May be caused by one or more of the following:– improper mixture of water and coolant/antifreeze– improper level of coolant– improper fan belt tension– internally clogged radiator– externally clogged cooling fins on radiator– thermostat opening slowly or not at all– collapsed hoses– faulty water pump– blockage of water flow in the block or cylinder

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Engine Oil & Lubrication Systems

36ENGINE OIL & LUBRICATION SYSTEMS

Pressure-Lubricated Engines

• Typically utilize a wet sump lubrication system in which the oil pump is driven by the crankshaft

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Four-Stroke Fact: Most systems include a pressure regulation system which maintains a working pressure.

Pressure Lubrication System

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1. Crankshaft Journal Oil Passage

2. Camshaft Oil Passage

3. Main Bearing Oil Passage

4. Oil Filter5. Oil from Sump6. Pickup Strainer7. Oil Pump8. Crankshaft

Pressure-Lubricated Engines

• Operate in the following manner:– the rotation of the oil pump draws oil from the

sump through the pickup strainer• the sump is the lowest part of the engine

– the oil is pumped into passages in the engine block, which route the oil to the components requiring lubrication• oil is routed to bearings, bushings, hydraulic

lifters and rotating crankshaft assembly

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Oil Pressure Switch

• Is situated in an engine block oil passage• Alerts the operator of a low pressure

situation– the engine oil continues to a full-flow oil filter

equipped with a bypass valve• if oil flow through the filter becomes restricted,

the bypass valve opens to allow engine oil to continue to circulate through the engine

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Splash Lubrication System

• Uses an oil dipper, attached to the connecting rod cap in a horizontal-crankshaft engine

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Four-Stroke Fact: In a vertical-crankshaft model, the oil dipper will be attached to a crankshaft counterweight, or it will be a separate component driven by the cam gear.

Splash Lubrication

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1. Direction of Rotation

2. Crankshaft3. Connecting

Rod Cap4. Oil Dipper5. Oil Supply6. Crankcase

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Splash Lubrication System

• Operates in the following manner:– with each rotation of the crankshaft, the oil

dipper reaches into the engine’s oil supply like a small cup at the bottom of the crankcase, throwing oil onto the internal engine parts

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Engine Oil

• Is used in the lubrication system to perform the following four basic functions:– lubrication– sealing– cooling– cleaning

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Choosing the Correct Oil

• Requires technicians to know how lubricating oils are rated – the oil should meet the manufacturer’s

viscosity recommendations and performance classification

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Four-Stroke Fact: By law, a manufacturer cannot require users to run their oil. The manufacturer can only specify the specific oil quantity and grade.

Viscosity – resistance to flow

Choosing the Correct Oil

• Can be accomplished with the help of the American Petroleum Institute (API) and Society of Automotive Engineers (SAE) standards

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API & SAE

• Are voluntary collaborations of the automotive and oil industries to ensure certain standards

• Place a symbol on oil containers which gives technicians consistent standards of information among oil brands and formulations– a container of engine oil bearing the API and

SAE symbols conforms to the standards and specifications of each

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API & SAE Symbols

• Contain information about the following:– viscosity grade– oil performance classification– energy conservation rating

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Oil Ratings

• Include API ratings which are expressed as C for compression ignition and S for spark ignition– also includes codes which indicate the use of

the oil in a certain engine• Include SAE ratings to ensure the

standards of the oil’s viscosity– a multi-viscosity oil is commonly recommended

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Crankcase Breather System

• Is required to maintain a net-negative pressure in the crankcase– a net-negative (vacuum) is

necessary to control oil consumption and manage crankcase vapor for emissions concerns

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Four-Stroke Fact: Modern engines incorporate a closed crankcase breather system.

Resources• The Equipment & Engine Training Council Four-Stroke

Education Committee (2016) Four-Stroke Study Guide• http://courses.washington.edu/engr100/Section_Wei/engine/U

ofWindsorManual/Piston%20and%20Piston%20Rings.htm

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Acknowledgments

52CEV Multimedia, Ltd.

©MMXVII

Assistant Brand ManagerStevi Huffaker

Graphic DesignerMelody Rowell

Quality Control DirectorAngela Dehls

V.P. of Brand ManagementClayton Franklin

Special ThanksThe Equipment & Engine

Training Council

Executive ProducerGordon W. Davis, Ph.D.

four-stroke engine: components€¦ · wrist pin/piston pin • attaches the piston to the upper...

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