1. GASOLINE ENGINE OPERATION, PARTS, AND SPECIFICATIONS18
GASOLINE ENGINE OPERATION, PARTS, AND SPECIFICATIONS

2. Objectives The student should be able to:
Prepare for Engine Repair (A1) ASE certification test content area “A” (General Engine Diagnosis).
Explain how a four-stroke cycle gasoline engine operates.
List the various characteristics by which vehicle engines are classified.

3. Objectives The student should be able to:
Discuss how a compression ratio is calculated.
Explain how engine size is determined.
Describe how displacement is affected by the bore and stroke of the engine.

4. PURPOSE AND FUNCTION

5. Purpose and Function
Convert heat energy of burning fuel into mechanical energy
Mechanical energy is used to perform the following:
Propel the vehicle

6. Purpose and Function
Mechanical energy is used to perform the following:
Power the air-conditioning system and power steering
Produce electrical power for use throughout the vehicle

7. ENERGY AND POWER

8. Energy and Power Engines use energy to produce power
Combustion: fuel is burned at a controlled rate to convert chemical energy to heat energy

9. Energy and Power
Combustion occurs within the power chamber in an internal combustion engine
Engines in automobiles are internal combustion heat engines

10. Energy and Power
NOTE: An external combustion engine burns fuel outside of the engine itself, such as a steam engine.

11. ENGINE CONSTRUCTION OVERVIEW

12. Engine Construction Overview
Block
Solid frame from which all automotive and truck engines are constructed
Constructed of cast iron or aluminum

13. Engine Construction Overview
Rotating Assembly
Constructed of pistons, connecting rods and a crankshaft

14. Figure The rotating assembly for a V-8 engine that has eight pistons and connecting rods and one crankshaft.
Figure The rotating assembly for a V-8 engine that has eight pistons and connecting rods and one crankshaft.

15. Engine Construction Overview?
Engine Construction Overview
Cylinder Heads
Seal top of cylinders in the engine block
Contain both intake valves and exhaust valves
Constructed of cast iron or aluminum

16. Figure A cylinder head with four valves per cylinder, two intake valves (larger) and two exhaust valves (smaller).
Figure A cylinder head with four valves per cylinder, two intake valves (larger) and two exhaust valves (smaller).

17. ENGINE PARTS AND SYSTEMS

18. Engine Parts and Systems
Intake and Exhaust Manifolds
Air and fuel enter and exit the engine through manifolds
Intake manifolds are constructed of nylon-reinforced plastic or aluminum

19. Engine Parts and Systems
Intake and Exhaust Manifolds
Exhaust manifolds must withstand hot gases and are constructed of cast iron or steel tubing

20. Engine Parts and Systems
Cooling System
Controls engine temperature
Vehicles are cooled by circulating antifreeze coolant

21. Engine Parts and Systems
Cooling System
Coolant picks up heat and releases it through radiator

22. Figure The coolant temperature is controlled by the thermostat, which opens and allows coolant to flow to the radiator when the temperature reaches the rating temperature of the thermostat.
Figure The coolant temperature is controlled by the thermostat, which opens and allows coolant to flow to the radiator when the temperature reaches the rating temperature of the thermostat.

23. Engine Parts and Systems
Lubrication System
Oil is pumped from oil pan through oil filter, then into oil galleries to lubricate engine parts

24. Figure A typical lubrication system, showing the oil pan, oil pump, oil filter, and oil passages.
Figure A typical lubrication system, showing the oil pan, oil pump, oil filter, and oil passages.

25. Engine Parts and Systems
Fuel System and Ignition System
Fuel system includes the following components:
Fuel tank – stores fuel and contains most fuel pumps

26. Engine Parts and Systems
Fuel System and Ignition System
Fuel system includes the following components:
Fuel filter and lines - transfer fuel for the fuel tank to the engine

27. Engine Parts and Systems
Fuel System and Ignition System
Fuel system includes the following components:
Fuel injectors - spray fuel into intake manifold or directly into the cylinder

28. Engine Parts and Systems
Fuel System and Ignition System
Ignition system includes the following components:
Spark plugs - provide an air gap inside the cylinder where a spark occurs to start combustion

29. Engine Parts and Systems
Fuel System and Ignition System
Ignition system includes the following components:
Sensor(s) - includes crankshaft position (CKP) and camshaft position (CMP)

30. Engine Parts and Systems
Fuel System and Ignition System
Ignition system includes the following components:
Ignition coils - increase battery voltage to 5,000 to 40,000 volts

31. Engine Parts and Systems
Fuel System and Ignition System
Ignition system includes the following components:
Ignition control module (ICM) - controls when the spark plug fires

32. Engine Parts and Systems
Fuel System and Ignition System
Ignition system includes the following components:
Associated wiring - electrically connects the battery, ICM, coil, and spark plugs

33. FOUR-STROKE CYCLE OPERATION

34. Four-Stroke Cycle Operation
Principles
First four-stroke cycle engine developed by Nickolaus Otto in 1876
The process begins with the starter motor rotating the engine until combustion takes place

35. Four-Stroke Cycle Operation
Principles
The cycle is repeated for each cylinder of the engine
Piston is attached to crankshaft with a connecting rod allowing the piston to move up and down

36. Figure The downward movement of the piston draws the air-fuel mixture into the cylinder through the intake valve on the intake stroke. On the compression stroke, the mixture is compressed by the upward movement of the piston with both valves closed. Ignition occurs at the beginning of the power stroke, and combustion drives the piston downward to produce power. On the exhaust stroke, the upward-moving piston forces the burned gases out the open exhaust valve.
Figure The downward movement of the piston draws the air-fuel mixture into the cylinder through the intake valve on the intake stroke. On the compression stroke, the mixture is compressed by the upward movement of the piston with both valves closed. Ignition occurs at the beginning of the power stroke, and combustion drives the piston downward to produce power. On the exhaust stroke, the upward-moving piston forces the burned gases out the open exhaust valve.

37. Figure 18-6 Cutaway of an engine showing the cylinder, piston, connecting rod, and crankshaft.

38. Four-Stroke Cycle Operation
Engine cycles are identified by the number of piston strokes required to complete the cycle

39. Four-Stroke Cycle Operation
Piston stroke: one-way piston movement
Most engines use a four-stroke cycle

40. Four-Stroke Cycle Operation
Most engines use a four-stroke cycle
Intake stroke
Compression stroke

41. Four-Stroke Cycle Operation
Most engines use a four-stroke cycle
Power stroke
Exhaust stroke

42. Four-Stroke Cycle Operation
The 720-Degree Cycle
In each cycle, the engine crankshaft makes two complete revolutions (or 720 degrees)

43. Four-Stroke Cycle Operation
The 720-Degree Cycle
To find the angle between cylinders of an engine, divide the number of cylinders into 720 degrees

44. ENGINE CLASSIFICATION AND CONSTRUCTION

45. Engine Classification and Construction
Engines are classified by several characteristics including:
Number of strokes
Cylinder arrangement

46. Engine Classification and Construction
Engines are classified by several characteristics including:
Longitudinal and transverse mounting
Valve and camshaft number and location

47. Engine Classification and Construction
Engines are classified by several characteristics including:
Type of fuel
Cooling method
Type of induction pressure

48. Engine Classification and Construction?
Engine Classification and Construction
NOTE: Although it might be possible to mount an engine in different vehicles both longitudinally and transversely, the engine component parts may not be interchangeable. Differences can include different engine blocks and crankshafts, as well as different water pumps.

49. Figure 18-7 Automotive engine cylinder arrangements.

50. Figure 18-8 A horizontally opposed engine design helps to lower the vehicle’s center of gravity.

51. Figure A longitudinally mounted engine drives the rear wheels through a transmission, driveshaft, and differential assembly.
Figure A longitudinally mounted engine drives the rear wheels through a transmission, driveshaft, and differential assembly.

52. Figure 18-10 Two types of front-engine, front-wheel drive mountings.

53. Engine Classification and Construction
Push rod engine: camshaft is located in the block, the valves are operated by lifters, pushrods, and rocker arms
Push rod engine also called cam-in-block design and overhead valve (OHV)

54. Engine Classification and Construction
Single overhead camshaft (SOHC) design uses one overhead camshaft
Double overhead camshaft (DOHC) design uses two overhead camshafts

55. Engine Classification and Construction?
Engine Classification and Construction
NOTE: A V-type engine uses two banks or rows of cylinders. An SOHC design, therefore, uses two camshafts but only one camshaft per bank (row) of cylinders. A DOHC V-6, therefore, has four camshafts, two for each bank.

56. Figure Cutaway of an overhead valve (OHV) V-8 engine showing the lifters, pushrods, roller rocker arms, and valves.
Figure Cutaway of an overhead valve (OHV) V-8 engine showing the lifters, pushrods, roller rocker arms, and valves.

57. Figure SOHC engines usually require additional components, such as a rocker arm, to operate all of the valves. DOHC engines often operate the valves directly.
Figure SOHC engines usually require additional components, such as a rocker arm, to operate all of the valves. DOHC engines often operate the valves directly.

58. Figure A DOHC engine uses a camshaft for the intake valves and a separate camshaft for the exhaust valves in each cylinder head.
Figure A DOHC engine uses a camshaft for the intake valves and a separate camshaft for the exhaust valves in each cylinder head.

59. Figure A rotary engine operates on the four-stroke cycle but uses a rotor instead of a piston and crankshaft to achieve intake, compression, power, and exhaust stroke.
Figure A rotary engine operates on the four-stroke cycle but uses a rotor instead of a piston and crankshaft to achieve intake, compression, power, and exhaust stroke.

60. Engine Classification and Construction
Engine Rotation Direction
SAE standard for automotive engine rotation is counterclockwise (CCW)

61. Engine Classification and Construction
Engine Rotation Direction
Direction is viewed from the flywheel end (principal end) of the engine (end to which power is applied to drive vehicle)

62. Engine Classification and Construction
Engine Rotation Direction
Non-principal end is referred to as the front end and is opposite the flywheel end

63. Figure Inline 4-cylinder engine showing principal and nonprincipal ends. Normal direction of rotation is clockwise (CW) as viewed from the front or accessory belt (nonprincipal) end.
Figure Inline 4-cylinder engine showing principal and nonprincipal ends. Normal direction of rotation is clockwise (CW) as viewed from the front or accessory belt (nonprincipal) end.

64. ENGINE MEASUREMENT

65. Engine Measurement Bore The diameter of a cylinder
Pressure measured in units, such as pounds per square inch (PSI)

66. Figure 18-16 The bore and stroke of pistons are used to calculate an engine’s displacement.

67. Engine Measurement Stroke
Distance the piston travels from top dead center (TDC) to bottom dead center (BDC)

68. Engine Measurement Stroke Determined by the throw of the crankshaft
The throw is the distance from the centerline of the crankshaft to the centerline of the crankshaft rod journal

69. Engine Measurement
Stroke
The throw is one-half of the stroke

70. Engine Measurement
NOTE: Changing the connecting rod length does not change the stroke of an engine. Changing the connecting rod only changes the position of the piston in the cylinder. Only the crankshaft determines the stroke of an engine.

71. Figure The distance between the centerline of the main bearing journal and the centerline of the connecting rod journal determines the stroke of the engine. This photo is a little unusual because it shows a V-6 with a splayed crankshaft used to even out the impulses on a 90-degree, V-6 engine design.
Figure The distance between the centerline of the main bearing journal and the centerline of the connecting rod journal determines the stroke of the engine. This photo is a little unusual because it shows a V-6 with a splayed crankshaft used to even out the impulses on a 90-degree, V-6 engine design.

72. Engine Measurement Displacement
Displacement (engine size) is the cubic inch (cu. in.) or cubic centimeter (cc) volume displaced or how much air is moved by all of the pistons

73. Engine Measurement Displacement
Most engines today are identified by their displacement in liters
1 L = 1,000 cc
1 L = 61 cu. in.
1 cu. in. = 16.4 cc

74. Engine Measurement Conversion
To convert cubic inches to liters, divide cubic inches by 61.02
To convert liters into cubic inches, multiply by 61.02

75. Engine Measurement Calculating Cubic Inch Displacement
Formula: Cubic inch displacement = π (pi) × R2 × Stroke × Number of cylinders

76. Engine Measurement Calculating Cubic Inch Displacement
Applying the formula to a 6-cylinder engine:
Bore = in.
Stroke = in.

77. Engine Measurement Calculating Cubic Inch Displacement
Applying the formula to a 6-cylinder engine:
π = 3.14
R = 2 inches

78. Engine Measurement Calculating Cubic Inch Displacement
Applying the formula to a 6-cylinder engine:
R2 = 4 (22 or 2 × 2)
Cubic inches = 3.14 × 4 (R2) × 3 (stroke) × 6 (number of cylinders)

79. Engine Measurement Calculating Cubic Inch Displacement
Applying the formula to a 6-cylinder engine:
Cubic inches = 226 cubic inches

80. Chart To find the cubic inch displacement, find the bore that is closest to the actual value, then go across to the closest stroke value.
Chart To find the cubic inch displacement, find the bore that is closest to the actual value, then go across to the closest stroke value.

81. Chart 18-1 (continued) To find the cubic inch displacement, find the bore that is closest to the actual value, then go across to the closest stroke value.
Chart 18-1 (continued) To find the cubic inch displacement, find the bore that is closest to the actual value, then go across to the closest stroke value.

82. Chart 18-1 (continued) To find the cubic inch displacement, find the bore that is closest to the actual value, then go across to the closest stroke value.
Chart 18-1 (continued) To find the cubic inch displacement, find the bore that is closest to the actual value, then go across to the closest stroke value.

83. Engine Measurement Engine Size Conversion
Many vehicle manufacturers will round the displacement so the calculated cubic inch displacement may not agree with the published displacement value

84. Chart Liters to cubic inches is often not exact and can result in representing several different engine sizes based on their advertised size in liters.
Chart Liters to cubic inches is often not exact and can result in representing several different engine sizes based on their advertised size in liters.

85. COMPRESSION RATIO

86. Compression Ratio Definition
Ratio of the difference in the cylinder volume when the piston is at the bottom of the stroke to the volume in the cylinder above the piston when the piston is at the top of the stroke

87. Figure Compression ratio is the ratio of the total cylinder volume (when the piston is at the bottom of its stroke) to the clearance volume (when the piston is at the top of its stroke).
Figure Compression ratio is the ratio of the total cylinder volume (when the piston is at the bottom of its stroke) to the clearance volume (when the piston is at the top of its stroke).

88. Compression Ratio Calculating Compression Ratio Formula: CR =
Volume in cylinder with piston at bottom of cylinder
Volume in cylinder with piston at top center

89. Compression Ratio Calculating Compression Ratio
Example: What is the compression ratio of an engine with 50.3 cu. in. displacement in one cylinder and a combustion chamber volume of 6.7 cu. in.?
CR = cu. in. = = 8.5
6.7 cu. in

90. Figure Combustion chamber volume is the volume above the piston when the piston is at top dead center.
Figure Combustion chamber volume is the volume above the piston when the piston is at top dead center.

91. Compression Ratio Changing Compression Ratio
Factors that can affect compression ratio include:
Head gasket thickness

92. Compression Ratio Changing Compression Ratio
Factors that can affect compression ratio include:
Increasing cylinder size

93. TORQUE AND HORSEPOWER

94. Torque and Horsepower Definition of Torque
Rotating force that may or may not result in motion
Measured as the amount of force multiplied by the length of the lever through which it acts

95. Torque and Horsepower Definition of Torque
Twisting force measured at the end of the crankshaft and measured on a dynamometer

96. Torque and Horsepower Definition of Torque?
Torque and Horsepower
Definition of Torque
Engine torque is always expressed at a specific engine speed (RPM) or range of engine speeds
Metric unit for torque is newton-meters

97. Torque and Horsepower Definition of Power Rate of doing work
Power equals work divided by time

98. Torque and Horsepower Definition of Power
Power is expressed in units of foot-pounds per minute and power also includes the engine speed (RPM) where the maximum power is achieved

99. Torque and Horsepower Horsepower and Altitude
Power that a normal engine can develop is greatly reduced at high altitude

100. Torque and Horsepower Horsepower and Altitude
According to SAE conversion factors, a nonsupercharged or nonturbocharged engine loses about 3% of its power for every 1,000 ft (300 m) of altitude