1. Engine Components and Cycle

2. Cylinder Block Cylinder block provide rigidity and strength Contains various passages and galleries, which coolant and oil circulate During manufacture  Bored -Cylinder -crank-shaft main bearing support  machined -Cylinder head -water pump -oil filter housing -oil pan -timing covers -flywheel housing

3. Cylinder Block Air-Cooled Cylinder Block Cylinder barrels separate from each other Bolted to crankcase Constructed by cooling fins But, only fins are not enough Large volumes of air forced by fan to go around the fins

4. Cylinder Bores and Liners Engine block are expensive:  must have a long service life  use replaced cylinder liner Types  cast cylinder block  flanged dry liners  wet liners Cylinder block machined in the block Replaceable flanged dry liner Replaceable wet liner in direct contact with coolant Cast Cylinder Block Used in smaller and less expensive engine Bores are machined If cylinders are damaged:  cylinder bores can be bored out  use corresponding oversize piston and ring combination  if enlarged beyond limit  fitting straight liner

5. Cylinder Bores and Liners If too loose  poor heat conduction  rise in cylinder temperature  rings and piston to scuff the cylinder wall If too tight  a fit may break on assembly  distort the surface of the cylinder wall Flanged Dry Liners Cylinder liner are manufactured as a separate item Thin metal sleeves (2mm) fitted into the cylinder bores Do not contact with engine coolant The fit is important  amount of heat conducted Can be pressed into the cylinder bore by hand  clearance (0.025~0.04)

6. Cylinder Bores and Liners Wet Liners Surrounded by coolant Required to be sealed at the top flange and at its lower skirt At the top  metal to metal seal or copper gasket between the liner flange and the counterbore seat At the lower end sealed by  o-rings  clevis seal Clevis seal are used to:  protect the o-rings  prevent corrosion occurring adjacent to the o-ring sealing area Thickness of the wet liner is much greater  not have support of the block Weep holes  identifying cylinder liner seal leakage Wet/dry liners are designed to have protrusion above the surface of the cylinder block (0.1~0.17mm) To ensure the liner is held firmly on its seat when the cylinder head is secured to the cylinder block

7. Cylinder Head 1.Cylinder head 2.Washer 3.Capscrew- short 4.Capscew- long 5.O-ring 6.Injector sleeve 7.Crosshead guide 8.Split Ting dowel 9.Cross head 10.Adjusting screw 11.Locknut 12.Half collets 13.Spring retainer 14.Valve springs 15.Valve seal 16. Wear plate 17. Valve guide 18. Pipe plugs 19. Ring dowel 20. Pipe plug 21. Valve seat inserts 22. Valves 23. Head gasket

8. Cylinder Head Constructed of cast iron and is bolted to the cylinder block Forms the upper part of the combustion chamber Provide inlet and outlet ports Provide passages for circulation of coolant Locate injector and valves mechanism A gasket is installed between the cylinder head and the cylinder block  seal the combustion chamber and all water and oil passages Variety of size:  1 cylinder head to cover 6 cylinders  2 cylinder heads to cover 4 cylinders  1 cylinder head to cover 1 cylinder Made of special alloy steel Some intake valves having a larger head Can be ground at either of two angles (30 0 ~45 0 ) Ground at 45 0 angle (exhaust)  25% more seating force  more efficient cleaning and sealing action Ground at 30 0 angle (intake)  create less restriction to air flow When head sizes are the same, manufacturers stamp it by “EX” and “I” Standard diesel engine uses 2 valves per cylinder High performance diesel engines uses 4 valves per cylinder Detroit 2-stroke engine  4 exhaust valves

9. Crank Shaft The crankshaft, sometimes casually abbreviated to crank, is the part of an engine which translates reciprocating linear piston motion into rotation. It typically connects to a flywheel, to reduce the pulsation characteristic of the four-stroke cycle. The distance of the axis of the crank throws from the axis of the crankshaft determines the piston stroke measurement, and thus engine displacement. A common way to increase the low-speed torque of an engine is to increase the stroke. This also increases the reciprocating vibration, however, limiting the high speed capability of the engine. In compensation, it improves the low speed operation of the engine, as the longer intake stroke through smaller valve(s) results in greater turbulence and mixing of the intake charge. For this reason, even such high speed production engines as current Honda engines are classified as "under square" or long-stroke, in that the stroke is longer than the diameter of the cylinder bore. In engines other than the flat configuration, it is necessary to provide counterweights for the reciprocating mass of each piston and connecting rod to improve engine balance. These are typically cast as part of the crankshaft but, occasionally, are bolt-on pieces. This adds considerably to the weight of the crankshaft. Crankshafts from Volkswagen, Porsche, and Corvair flat engines, lacking counterweights, are easily carried around by hand, compared to crankshafts for inline or V engines, which need to be handled and transported as heavy chunks of metal.

10. Cam Shaft The camshaft is an apparatus often used in piston engines to operate poppet valves. It consists of a cylindrical rod running the length of the cylinder bank with a number of oblong lobes or cams protruding from it, one for each valve. The cams force the valves open by pressing on the valve, or on some intermediate mechanism, as they rotate. Since the valves control the flow of air/fuel mixture intake and exhaust gases, they must be opened and closed at the appropriate time during the stroke of the piston. For this reason, the camshaft is connected to the crankshaft either directly, via a gear mechanism, or indirectly via a belt or chain called a timing belt or timing chain. Depending on the location of the camshaft, the cams operate the valves either directly or through a linkage of pushrods and rockers. Direct operation involves a simpler mechanism and leads to fewer failures, but requires the camshaft to be positioned at the top of the cylinders. In the past when engines were not as reliable as today this was seen as too much bother, but in modern gasoline engines the overhead cam system, where the camshaft is on top of the cylinder head, is quite common. Some engines use two camshafts each for the intake and exhaust valves; such an arrangement is known as a double or dual overhead cam (DOHC), thus, a V engine may have four camshafts.

11. Cam Shaft

12. Concept question The bus exerts greater amount of force on the car than the car exerts on the bus; The car exerts a greater amount of force on the bus than the bus exerts on the car; Neither exerts a force on the other, the car gets smashed simply because it gets in the way of the bus; The bus exerts the same amount of force on the car as the car exerts on the bus. A bus collides with a small car. During the collision:

13. Piston Function: 1.To create a seal within the cylinder 2. To transmit the forces of combustion via the connecting rod to the crankshaft 3. to acts as a pump on the intake and exhaust strokes Characteristics: 1.Light weight (cast from aluminium alloy) 2.Good strength 3.High heat conductivity Types of piston: 1.Trunk type piston 2.Two-piece design

14. Piston Type Trunk type piston: 1.Piston crown (combustion chamber) 2.Compression ring grooves 3.Oil ring groove 4.Skirt Two-piece Piston Allows for easy access to the crown and top of the skirt area to construct more efficient oil galleries. Steel crown being a stronger material Top ring position is higher  reducing the diad air volume  reduce HC 4. Skirt more isolated from the high temperature piston crown 5. Skirt-to-cylinder wall clearance can be smaller  minimizing piston slap and engine noise 6. Piston more stable in bore  prevent the piston crown and rings form tilting in the bore

15. Cam-ground Shape Greater amount of metal in the piston pin boss area Uneven expansion of metal Constructed oval in shape to ensure piston will expand into round shape from heat of combustion Engine must run at correct operating temperature  if not, resulting in piston slap and accelerated engine wear

16. Piston Pin Made from hardened alloy steel Pin is hollow to reduce its weight and subsequent inertia force Different methods of mounting: Located off the centre line of the piston towards the power thrust side of the piston Less tilting of the piston during the power stroke Piston slap and engine noise are kept minimum

17. Piston Ring Compression ring Function:  seal against the cylinder wall  transfer heat Compression and combustion gases help in forcing the ring to seal against the cylinder wall Many are chrome

18. Oil Ring Oil control rings: Functions:  to control the amount of oil on the cylinder walls  to provide adequate lubrication to the compression rings Too much oil left allowing the oil to enter and burnt in combustion chamber Too little oil causing scuffing and scoring

19. Engine Basic Components Camshaft Spring Air manifold Stem Guide Valve head Valve seat Piston Spark plug

20. Engine Basic Components Camshaft Intake valve Rocker arm Piston Connecting rod Crankshaft Oil pump Exhaust valve Carburetor Crank sprocket Oil pickup Timing belt Cam sprocket Air cleaner Timing belt tensor

21. Concept question Metals expand when heated. If a sheet of metal containing a circular hole is heated will the diameter of the hole increase, decrease or remain the same? ANSWER: Hole diameter increases. Imagine that there was metal in the hole, then it would expand. Alternatively imagine the perimeter of the hole; the metal here expands and therefore the hole gets bigger.

22. Four Stroke SI Cycle Four Stroke Spark Ignition (SI) Engine Stroke 1:Fuel-air mixture introduced into cylinder through intake valve Stroke 2:Fuel-air mixture compressed Stroke 3:Combustion (roughly constant volume) occurs and product gases expand doing work Stroke 4:Product gases pushed out of the cylinder through the exhaust valve Compression Stroke Power Stroke Exhaust Stroke A I R Combustion Products Ignition Intake Stroke FUEL Fuel/Air Mixture

23. P-V Graph 4-Stroke SI Cycle 1 atm Spark TDC Cylinder volume BDC Pressure Exhaust valve opens Intake valve closes Exhaust valve closes One power stroke for every two crank shaft revolutions

24. Two-Stroke SI Cycle Two Stroke Spark Ignition Engine Stroke 1:Fuel-air mixture is introduced into the cylinder and is then compressed, combustion initiated at the end of the stroke Stroke 2:Combustion products expand doing work and then exhausted * Power delivered to the crankshaft on every revolution

25. Two-Stroke SI Cycle Cont. Intake (“Scavenging”) Compression Ignition Exhaust Expansion Fuel-air-oil mixture Fuel-air-oil mixture compressed Crank shaft Check valve Exhaust port

26. Scavenging in Two-Stoke Cross Loop Uniflow

27. Scavenging in Two-Stoke Cross

28. Two-Stroke Adv. and Disadv. Advantages of the two stroke engine: Power to weight ratio is higher than the four stroke engine since there is one power stroke per crank shaft revolution. Simple valve design Most often used for small engine applications such as lawn mowers, marine outboard engines, motorcycles…. Disadvantages of the two-stroke engine: Incomplete scavenging or to much scavenging Burns oil mixed in with the fuel