a sample chapter as seen in the textbook.
Contents
1. engine Horizontally Opposed Engine C V 8 Engine The V 8 is a popular engine when high horsepower output is required The V8 is often installed in performance vehicles full sized cars and trucks Some cars are equipped with other types of V engines with a larger number of cylinders ie Chrysler s V 10 engine and Jaguar s V 12 Page Notes Engine Classification 6 Cylinder Inline Engine Horizontally Opposed Engine 8 Engine Chapter 4 Engine Introduction Design Classification Moving Engine Parts Four Stroke Cycle Valve Timing Measurements amp Performance V8 Engine D Rotary Engine The rotary engine is unj cylinders are built into a s Another name for the rot Wankel engine after its ifivertor Wankel Mazda has built millions of RX model cars equipped with a rotary engine and had fair success with it This engine is fairly compact has few moving parts and provides considerable output Rotary Engine E V 6 Engine The V 6 is a very popular engine configuration This engine is compact and easily adapted to fit into many models of vehicles Some V6 engines are capable of fairly high horsepower output They may be mounted transversely or front to back Many diesel buses and some trucks are equipped with a large V6 Detroit Diesel engine F 4 Cylinder Inline Engine The 4 cylinder inline engine is commonly used in compact cars This engine is fairly2. It All Together Because of improved valve timing we have changed the actual length of the effective cycle from 720 to 730 as shown in this example Engine designers have tried over the last century many different ways to increase engine output Changes in valve timing were discovered at the turn of the century as a way to increase power and we still use this method especially in performance engines Engine Valve Timing A clear understanding of valve timing will enable the student to perform troubleshooting and engine improvements in A performance camshaft is designed to e actual length of the cycle hd the future In this section Mill ie incre ge actual valve timing meth internal combustion engigif a le understand how engine performance may be improved with simple valve timing changes When learning about the four stroke cycle in the previous section you were told that the valves closed and opened either at TDC or BDC and the cycle uses 720 2 turns of crankshaft rotation In real life the valves begin to open before and close after TDC or BDC is reached and uses more crankshaft degrees The valve timing is set up this way to provide the engine with more power by allowing air and fuel to enter the cylinder efficiently and by removing all traces of exhaust Valve timing is linked directly to the position of the piston and crankshaft When talking about valve opening and closing we relate the valve positi
3. generated heat Chapter 4 Design Classification Valve g Moving Engine Parts Measurements amp Performance Engine Introduction K DIAGRAM 4 5 Moving Engine Parts Piston Rings Piston rings are located in grooves at the top of the piston to seal r against pressure leakage past the piston and into the crankcase Piston The piston and connecting rod are reciprocating parts The piston is fitted into the cylinder bore and is the first part to receive the push of the burning and expanding gases in the cylinder Connecting Rod The connecting rod attaches the piston to the crankpin on the crankshaft The top end is attached to the piston by a strong piston pin wrist pin The bottom end is attached to the crankpin ES a a MSE Sample The camshaft is a rotating part The camshaft is linked to the crankshaft by a chain gears or a special cogged belt When the proper time occurs the camshaft will cause a valve to be opened in the proper sequence for engine operation The camshaft converts rotary motion into the reciprocating motion needed by the valves Crankshaft The crankshaft is a rotating part The crankshaft is sometimes made of forged steel but is usually cast It is supported in the cylinder block by split plain bearings called main bearings The crankshaft converts the reciprocating motion of the piston into rotary motion by the use of offset cranks called throws Valves Valves are reciprocatin
4. small and can easily be installed transversely or front to back Some compact cars are equipped with a 3 cylinder inline engine We aw leas 4 Cylinder Inline Engine fair success When Mazda installed the rotary engine in its RX car models it was slow in getting positive consumer response The engine had a problem with an important seal apex seal which was corrected Consumers are typically slow to purchase a vehicle with such a radically new type of engine Good marketing ideas and a winning racing program eventually proved that the rotary engine is a good engine transversely In a direction from side to side In this case it refers to the engine being mounted sideways instead of front to back Transverse engine installation is used in most front wheel drive vehicles and many city transit buses front to back In a direction following a line from front to back In this case it refers to the engine being mounted in a front to back direction This type of installation is used in most rear wheel drive vehicles 47 Chapter 4 Design Classification Valve Timing Moving Engine Parts Measurements amp Performance Engine Introduction K a as DIAGRAM 4 2 Valve Arrangements _ _ Valve arrangement has to do with the location of the valves relative to the cylinder they service See Diagrams 4 2 to view the four valve arrangements in use today L head is used in some stationary engines older
5. the highest point of travel the piston will get to inside the cylinder BDC Bottom Dead Centre is the lowest point of travel the piston will get to inside the cylinder Intake Stroke At the start of the intake stroke the intake valve is opened Z The piston travels downward from TDC to BDC This creates a partial vacuum in the cylinder P Atmospheric pressure forces air through the carburetor to pick up some fuel This air fuel mixture enters the cylinder past the open intake valve and through the open intake port The exhaust valve stays closed during this operation ttakes the crankGhaftfalf oll 180 complete this operon Intake Stroke ol s tro Power Stroke 2 The highly compressed and heated mixture in the cylinder is now ready to be ignited This is done electrically by a sparkplug or in the case of a diesel engine by the high temperature of the compressed air into which fuel is sprayed Combustion is immediate The mixture as it burns expands rapidly and greatly increases the pressure inside the cylinder The high pressure forces the piston downward from TDC to BDC amp At this point the crankshaft has completed one and one half revolutions 540 from the cycle starting point and the piston ends up at BDC Compression Stroke P Now the intake valve closes the intake port and the piston moves upward from BDC to TDC The mixture of air and fuel in the cylin
6. Chapter 4 Design Classification Valve Timing Moving Engine Parts Measurements amp Performance Engine Introduction K MidnightSpecial Enterprises Hugh Hunter 2006 2013 Chapter 4 Engine Introduction mm Design Classification Moving Engine Parts Four Stroke Cycle Valve g Measurements amp Performance Chapter 4 Engine Introduction Engine Design and Classification Piston type engines are divided into categories in a number of ways according to different mechanical or operational features Keep in mind that not all engines are used in cars and trucks Each engine is designed with a set of operational features in mind some are very specialized and some are commonplace A 6 Cylinder Inline Engine The 6 cylinder inline effing us some pick up trucks and ghidygiz r Mercedes and Audi use a 5 cylinder inline engine in some models Some diesel trucks are equipped with a large 6 cylinder Detroit Diesel inline engine 6 Cylinder Inline Engine 46 B Horizontally Opposed Engine The horizontally opposed 4 cylinder was a very popular engine installed in the Volkswagen Beetle Porsche still uses this type of engine The horizontally opposed engine is often installed in light aircraft and this like many other opposed engines is air cooled The opposed engine is lightweight and compact with reasonable output Other names for the horizontally opposed engine are pancake engine boxer engine and flat
7. Cycle the valves open longer and also to open the ports wider by lifting the valve higher off its seat The greater the amount of air and fuel that can be put into the cylinder during the intake stroke the higher the volumetric efficiency of the engine An engine with good volumetric efficiency will produce more horsepower Can you think of any more ways to increase the volumetric efficiency of an engine by using the following items DIAGRAM 4 7 Valve Timing Chart Valve Lead is when a valve is opened before TDC BDC Valve lead increases tl time that the valve stays open let more air fuel into the cylinder and all traces of exhaust out SE Top Dead Centre Valve Overlap Intake Valve Opens Valve Lead Intake stroke starts at 5 BTDC and continues until 45 ABDC Duration 230 of crankshaft rotation a larger valves b supercharger c turbocharger d intake manifolds e exhaust system modifications etc Engine Valve Timing Nalve Timing Chart Visit an engine performance shop or talk to someone who does performance work Find out at least five different ways to increase the volumetric efficiency of an engine Explain on page two of your worksheet how each improvement will work toward this end valves open longer A performance camshaft will in most cases open the valves for a longer period of time more degrees of crankshaft rotation This is done to increase the
8. amount of air fuel that can enter the cylinder and to allow the exhaust to leave the cylinder faster The term given to how long the valve is held open is Valve Duration It is given in degrees of camshaft rotation or crankshaft rotation EE Power Stroke 135 E Exhaust Stroke 230 E Intake Stroke 230 amp t Valve Lag is when a val is closed after TDC or BDC Valve lag increases the time that the valve stays open to let more air fuel into the cylinder and all traces of exhaust out S Exhaust Valve Closes Valve Lag lifting the valve Lifting the valve higher off its seat will allow more air fuel to enter the cylinder and make it easier for quick exhaust removal Most performance camshafts will lift the valve more and for a longer period of time that a stock camshaft Power stroke starts at TDC The term given to the amount and continues until 45 BBDC Compression stroke starts at 45 ABDC and continues until TDC Duration 135 of crankshaft rotation Intake Valve Closes Bottom Dead Centre Exhaust stroke starts at 45 BBDC and continues until 5 ATDC Duration 230 of crankshaft rotation a valve is lifted off its seat is Duration 135 of crankshaft Valve Lift degrees Volumetric efficiency Compares how much air fuel can be placed in an engine cylinder when the engine is stopped with the piston at BDC to how much air fuel is placed in an engine cylinder during
9. der is compressed The air and fuel are mixed together very well and heated up during this stroke Both valves remain closed during this stroke P By now the crankshaft has completed one complete revolution 360 and the piston is back at TDC ample Exhaust Stroke 2 The cylinder is now full of burnt gases that must be removed amp The exhaust valve opens the exhaust port and the piston moves upward from BDC to TDC This forces the exhaust gases out of the cylinder P During this stroke the intake valve is closed The exhaust stroke is the last one in the Four Stroke Cycle At the end of the Four Stroke Cycle the crankshaft has completed two complete revolutions 720 52 Design Classification Chapter 4 Moving Engine Parts Four Stroke Cycle Engine Introduction Valve Timing Measurements amp Performance Keeping the Engine Running Smoothly of explaining valve timing Every model of engine has different timing specifications Did you notice in Diagram 4 6 that there depending on what it will be used for is only one stroke that actually supplies power to the engine through the two revolutions of the crankshaft This situation will cause the engine to supply power in surges which is unacceptable Attaching a heavy flywheel to the crankshaft will reduce this problem The momentum of the flywheel carries the engine crankshaft smoothly from one power stroke to the next Putting
10. e cylinder and is measured in millimetres or inches Crankshaft Throw This is the distance from the center of the crankshaft main bearing journal to the center of the crankpin The stroke of the piston is equal to twice the length of the throw It is measured in millimetres or inches Top Dead Centre TDC This is the farthest point of upward travel of the piston in the cylinder Bore Bottom Dead Centre BDC This is the lowest point of downward travel of the piston in the cylinder Page Notes Engine Measurements and Performance Definitions Bore Stroke Crankshaft Throw Top Dead Centre TDC Bottom Dead Centre BDC DID YOU KNOW An engine that has a bore and stroke that are identical in size is often called square So if the bore is 90mm and the stroke is 90mm the engine is square When the stroke is larger than the bore the engine is referred to as under square When the bore is bigger than the stroke the engine is over square 55 Chapter 4 Design Classification Valve Timing Moving Engine Parts mm Measurements amp Performance _ Engine Introduction Bek acu 3 RPM Revolutions Per Minute more accurate indicator of the possible Page Notes performance of an engine High torque This is the unit of measurement used to engines generally have lower horsepower RPM determine the speed of a rotating part If an because they have a longer stro
11. g parts They are used to open and close a port in the cylinder head or block and each cylinder must have an intake and exhaust valve The intake valve usually has a larger head than the exhaust valve and it allows air and fuel to enter the cylinder at the correct time The exhaust valve allows the burnt air and fuel to leave the cylinder at the correct time 50 Chapter 4 Engine Introduction Design Classification Valve g Moving Engine Parts Measurements amp Performance Four Stroke Cycle Four Stroke Cycle A good knowledge of the four stroke cycle is the main point of understanding the operation of the internal combustion engine and this information can be used in making accurate assessments and repairs to engine problems You will learn the operation of the four stroke cycle and how the stationary and moving parts work together to produce an efficient and environmentally friendly engine Requirements for Engine Operation In order to have the engine run we must meet four requirements 1 Supply the engine with fiir ang fi 2 Prepare the air fuel migftur jto combustion 3 Ignite the air fuel mixture at the correct time 4 Get rid of the burnt gases These four operations are known as four strokes The strokes are called the Intake Stroke Compression Stroke Power Stroke and Exhaust Stroke Engine Valve Operation In order to accomplish these four strokes we must open and close openings called p
12. ke High Engine Performance engine is said to be turning at 2000 RPM it torque engines produce their rated torque at tess means that the crankshaft will make 2000 fairly low speeds A high torque vehicle is complete revolutions in one minute not very fast but will pull a lot of weight Torque Engine Performance You often see the terms Horsepower and Torque referred to in vehicle sales literature and service manual specification charts Power Power Horsepower k which the engine will do horsepower produced by according to the engine speed All engines have a peak horsepower point that occurs at a pre determined engine speed This speed is usually the point of highest operating efficiency Advertised horsepower net horsepower is greatly reduced by the time it reaches the wheels due to frictional losses and accessory loads For example a 250 net HP engine would only have approximately 150 HP available at the drive wheels High horsepower engines generally produce less torque because they have a short stroke A high horsepower vehicle will be fast but cannot pull a large amount of weight Torque Torque is the measurement of turning effort put out by the engine Torque is usually measured in N m Newton metres of lbs ft pounds feet Engine torque is a 56 Chapter 4 Engine Introduction Design Classification Valve g DIAGRAM 4 8 Engine Measurements Total Volume TV Total volume i
13. marine engines and is very popular in small engines It is not a very efficient design with regards to easy airflow through the cylinder but it is very simple and provides years of trouble free service I head is the most common arrangement used today It is very efficient as far as airflow through the cylinder goes and is very reliable Newer engines have reduced the number of parts in the valve operating system by using an overhegil calh shi F head is used in som l ine a provides reasonably good airflow through the cylinder This system is used when space is restricted in a compact engine design but fairly high output is needed T head is used in some stationary engines where space is not a problem These engines tend to be quite wide at the top Airflow is fairly good through the combustion chamber and the valve operating system is very reliable This engine has one camshaft for the exhaust valves and one for the intake valves Cooling System Classification Engines are sometimes classified according to the type of cooling system is uses In many cases it is safe to assume that highway vehicles will be equipped with a liquid cooled engine and small recreational vehicles are powered by an air cooled engine Diagrams 4 3 amp 4 4 will show you 48 Chapter 4 m Design Classification Valve g m Moving Engine Parts Measurements amp Performance 3 Fa f Engine Introduction K two types of engine cooli
14. ng systems DIAGRAM 4 3 Air Cooled Engine Moving Engine Parts Fins on the cylinder head and cylinder to increase surface area exposed to air flow Being able to understand the function of Shown over top of both cylinder heads the main moving parts in the engine will make learning the operation of the engine easier This information is also very useful for diagnosing engine problems In this section you will review the names and functions of the main moving parts in the internal combustion engine and be able to show the relationship between the different types of parts Moving Engine Parts and Their Functions N The moving parts in th integal combustion engine can bi t groups These are reciprogfatil a rotating parts Reciprocating parts move back and forth Rotating parts spin on an Large blower fan A assembly to force cool depends on the conversion of reciprocating air over all hot engine motion into a rotating motion Diagram 4 5 surfaces axis The mechanical function of the engine shows you a picture of various engine parts DIAGRAM 4 4 Liquid Cooled Engine Waterjackets Liquid moves through internal waterjackets to carry away heat from cylinder walls and cylinder head waterjacket inside cylinder head Radiator Inlet Heated coolant enters a radiator to have its heat removed by a moving airstream Radiator Outlet The cooled coolant leaves the radiator and enters the engine to remove more
15. on to crankshaft degrees Keep in mind that the figures given on the next screen are only for the purpose momentum Momentum is the energy stored in a moving object In this case momentum is stored in the spinning flywheel Once the flywheel is spinning it will want to continue to spin and will carry the attached crankshaft with it actual length The actual length of the four stroke cycle is controlled more by the start and finish of the strokes than it is by piston crankshaft position The start and finish of a stroke is determined by when a particular valve leaves its seat until it returns to it In other words the exhaust stroke actually lasts from the instant the exhaust valve starts to open until it is completely closed The position of the piston is secondary A longer stroke will produce more engine output up to a certain point performance camshaft A performance camshft will change various aspects of engine valve timing Some cams are designed strictly for racing while others work best for performance street driving conditions Seek expert advice when deciding on the camshft you want to install Some problems with changing the camshaft are poor idle quality increased fuel consumption breaking anti pollution laws and voiding a new vehicle warranty agreement 53 Chapter 4 Engine Introdu Design Classification Moving Engine Parts Measurements amp Performance ction Four Stroke
16. orts at the correct time These ports are located near the top of the cylinder The Intake Valve controls when the air fuel enters the cylinder The Exhaust Valve controls when the burnt gases leave the cylinder Let s review each stroke with a little more detail Diagram 4 6 shows you diagrams of the four strokes Four Stroke Cycle Requirements of Engine Operation Putting It All Together Engine Valve Operation At the end of the FOUR STROKE CYCLE the crankshaft has completed two complete revolutions Since the piston is at TDC at the end of the four strokes the cycle will repeat over and over again until the engine runs out of fuel or the operator switches off the ignition system Putting It All Together Summary of the Four Stroke Cycle Remember A Each stroke takes 1 2 of a revolution 180 of the crankshaft to complete B Fo oke e re oluo pt the cy omple C Each valve must open one time only during the four strokes so the camshaft must turn at one half the speed of the crankshaft Photo 1 1 Timing Gear This photo shows the relationship between the crankshaft sprocket bottom to the camshaft sprocket top The crankshaft turns twice to turn the camshaft once 51 Chapter 4 Engine Introduction Design Classification Valve g Moving Engine Parts Measurements amp Performance Four Stroke Cycle DIAGRAM 4 6 The Four Stroke Cycle Glossary TDC Top Dead Centre is
17. s the totalf lu gie i the cylinder above the el the piston is at BDC T fal Wlu equal to piston displacement clearance volume TV PD CV n Clearance Volume CV Clearance volume is the volume of the combustion chamber above the piston when the piston is at TDC e shape ambegi measure calculated by carefully measuring the amount of water it takes to fill it up In most situations the CV is given to you to make other calculations easier DIAGRAM 4 9 Compression Ratio of This cylinder is completely full of the air fuel mixture The air fuel mixture has now been compressed Moving Engine Parts Four Stroke Cycle Piston Displacement PD Piston cement for one s to the volume that h pi isplaces as it travels from BDC to TDC It is measured in cubic centimetres cc or cubic inches ci Piston displacement for one cylinder is calculated using this formula PD pi x r x stroke To get the displacement for a mult cylinder engine just multiply the PD x the number of cylinders Compression Ratio CR Compression ratio represents how much a completely full cylinder is compressed when the piston moves from BDC to TDC It is the ratio of the TV of a cylinder to the CV Compression ratio is calculated using this formula CR TV CV It is expressed in the form of a ratio such as 10 1 57 Measurements amp Performance
18. the intake stroke when the engine is running The closer the two situations come to a match the better the engine will perform Volumetric efficiency is sometimes called breathing efficiency Exhaust Valve 45 Opens Exhaust Valve Opens the instant that the exhaust valve opens signal the end of the power stroke and the beginning of the power stroke 54 Design Classification Chapter 4 Moving Engine Parts Four Stroke Cycle Engine Introduction Valve g mm Measurements amp Performance Engine Measurements And Performance Stroke In order to carry on an intelligent conversation regarding an engine a good knowledge of basic terminology is needed This will be useful in understanding what a technician is telling you when engine repairs are needed Also knowing this terminology will help you understand sales literature and track reports This section will teach you standard terminology used in the discussion of engine parts and power related measurements You will also learn how to calculate Total Volume Piston Displacement and Compression Ratio This is the distance in millimetres or inches travelled by the piston in its movement from TDC to BDC Two strokes of the piston is equal to one turn of the crankshaft Definitions Here are some definitions of common terms that are important tofknoygjin fi everyone to understand wA i gOgin discussed Bore This is the inside diameter of th
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