1. Modern Automotive Technology PowerPoint for by Russell Krick
Publisher The Goodheart-Willcox Co., Inc. Tinley Park, Illinois

2. Chapter 12
Engine Design
Classifications

3. Contents Engine classifications Alternative engines
Typical automotive engines

4. Engine Classifications
Even though basic parts are the same, design differences can change the way engines operate and how they are repaired
For this reason, you must be able to classify engines

5. Common Engine Classifications
Cylinder arrangement
Number of cylinders
Cooling system type
Valve location
Camshaft location

6. Common Engine Classifications
Combustion chamber design
Type of fuel burned
Type of ignition
Number of strokes per cycle
Number of valves per cylinder
Type of aspiration

7. Cylinder Arrangement
Refers to the position of the cylinders in relation to the crankshaft
There are five basic cylinder arrangements:
inline
V-type
slant
W-type
opposed

8. Cylinder Arrangement

9. Number of Cylinders
Most car and truck engines have either 4, 6, or 8 cylinders
Some may have 3, 5, 10, 12, or 16 cylinders
Engine power and smoothness are enhanced by using more cylinders

10. Cylinder Numbering
Engine manufacturers number each engine cylinder to help technicians make repairs
Service manual illustrations are usually provided to show the number of each cylinder
Cylinder numbers may be cast into the intake manifold

11. Firing Order Refers to the sequence in which the cylinders fire
Determined by the position of the crankshaft rod journals in relation to each other
May be cast into the intake manifold
Service manual illustrations are usually provided to show the firing order

12. Cylinder Numbering and Firing Order

13. Cooling System Type There are two types of cooling systems:
Liquid cooling system
surrounds the cylinder with coolant
coolant carries combustion heat out of the cylinder head and engine block
Air cooling system
circulates air over cooling fins on the cylinders
air removes heat from the cylinders

14. Cooling System Type
A. Air cooling
B. Liquid cooling

15. Fuel Type Engines are classified by the type of fuel used
Gasoline engines burn gasoline
Diesel engines burn diesel fuel
Liquefied petroleum gas (LPG), gasohol (10% alcohol, 90% gasoline), and pure alcohol can also be used to power an engine

16. Ignition Type
Two basic methods are used to ignite the fuel in an engine combustion chamber:
spark ignition (spark plug)
compression ignition (compressed air)

17. Uses an electric arc at the spark plug to ignite the fuel
Spark Ignition Engine
Uses an electric arc at the spark plug to ignite the fuel

18. Compression Ignition Engine
Squeezes the air in the combustion chamber until it is hot enough to ignite the fuel

19. Valve Location Engines are classified by the location of the valves:
L-head engine
also called a flat head engine
I-head engine
also called an overhead valve (OHV) engine

20. Both the intake and exhaust valves are in the block
L-Head Engine
Both the intake and exhaust valves are in the block

21. Both valves are in the cylinder head
I-Head Engine
Both valves are in the cylinder head

22. Camshaft Location
There are two basic locations for the engine camshaft:
Camshaft located in the block
cam-in-block engine
Camshaft located in the cylinder head
overhead cam (OHC) engine

23. Cam-in-Block Engine
Uses push rods to transfer motion to the rocker arms and valves
Also called an overhead valve (OHV) engine

24. Camshaft is located in the top of the cylinder head
Overhead Cam Engine
Camshaft is located in the top of the cylinder head

25. Overhead Cam Engine
OHC engines may use one or two camshafts per cylinder head
Single overhead cam (SOHC) engine
uses only one camshaft per cylinder head
Dual overhead cam (DOHC) engine
uses two camshafts per cylinder head
one cam operates the intake valves, while the other cam operates the exhaust valves

26. Combustion Chamber Shape
Four basic combustion chamber shapes are used in most automotive engines:
pancake
wedge
hemispherical
pent-roof

27. Pancake Combustion Chamber
Chamber forms a flat pocket over the piston head
Valve heads are almost parallel to the top of the piston

28. Wedge Combustion Chamber
The valves are placed side-by-side
The spark plug is located next to the valves
When the piston reaches TDC, the squish area formed on the thin side of the chamber squirts the air-fuel mixture out into the main part of the chamber
this improves air-fuel mixing at low engine speeds

29. Wedge Combustion Chamber
Provides good air-fuel mixing at low engine speeds

30. Hemispherical Combustion Chamber
Shaped like a dome
The valves are canted on each side of the combustion chamber
The spark plug is located near the center of the chamber, producing a very short flame path for combustion
The surface area is very small, reducing heat loss

31. Hemispherical Combustion Chamber
First used in high-horsepower racing engines
Excellent design for high-rpm use

32. Pent-Roof Combustion Chamber
Similar to a hemispherical chamber
Has flat, angled surfaces rather than a domed surface
Improves volumetric efficiency and reduces emissions

33. Pent-Roof Combustion Chamber

34. Other Combustion Chamber Types
In addition to the four shapes just covered, there are several less common combustion chamber classifications
Each type is designed to increase combustion efficiency, gas mileage, and power while reducing exhaust emissions

35. Swirl Combustion Chamber
Causes the air-fuel mixture to swirl as it enters the chamber, improving combustion

36. Four-Valve Combustion Chamber
Uses two exhaust valves and two intake valves to increase flow

37. Three-Valve Combustion Chamber
Uses two intake valves and one exhaust valve
Two intake valves allow ample airflow into the combustion chamber on the intake stroke
Single exhaust valve provides enough surface area to handle exhaust flow

38. Stratified Charge Combustion Chamber
Uses a small combustion chamber flame to ignite and burn the fuel in the main, large chamber
Lean mixture is admitted into the main chamber
Richer mixture is admitted into the small chamber by an extra valve

39. Stratified Charge Combustion Chamber
When the mixture in the small chamber is ignited, flames blow into the main chamber and ignite the lean mixture
Allows the engine to operate on a lean, high-efficiency air-fuel ratio
fuel economy is increased
exhaust emissions are reduced

40. Air Jet Combustion Chamber
Has a single combustion chamber fitted with an extra air valve, called a jet valve
The jet valve injects a stream of air into the combustion chamber at idle and at low engine speeds to improve fuel mixing and combustion
At higher rpm, normal air-fuel mixing is adequate for efficient combustion

41. Air Jet Combustion Chamber

42. Precombustion Chamber
Commonly used in automotive diesel engines
Used to quiet engine operation and to allow the use of a glow plug to aid cold weather starting
During combustion, fuel is injected into the prechamber, where ignition begins
As the fuel burns, the flame expands and moves into the main chamber

43. Precombustion Chamber

44. Alternative Engines
Vehicles generally use internal combustion, 4-stroke cycle, reciprocating piston engines
Alternative engines include all other engine types that may be used to power a vehicle

45. Rotary Engine Uses a triangular rotor instead of pistons
The rotor orbits a mainshaft while turning inside a specially shaped chamber
This eliminates the reciprocating motion found in piston engines

46. Rotary Engine

47. Rotary Engine Operation
Three complete power-producing cycles take place during every revolution of the rotor:
three rotor faces produce three intake, compression, power, and exhaust events per revolution

48. Rotary Engine Operation
Rotor movement produces a low-pressure area, pulling the air-fuel mixture into the engine
As the rotor turns, the mixture is compressed and ignited
As the fuel burns, it expands and pushes on the rotor
The rotor continues to turn, and burned gases are pushed out of the engine

49. Rotary Engine Operation

50. Steam Engine Heats water to produce steam
Steam pressure operates the engine pistons
Known as an external combustion engine since its fuel is burned outside the engine

51. Used on some of the first automobiles
Steam Engine
Used on some of the first automobiles

52. Gas Turbine
Uses burning and expanding fuel vapor to spin fan-type blades
Blades are connected to a shaft that can be used for power output
Expensive to manufacture because of special metals, ceramics, and precision machining required

53. Gas Turbine

54. Two-Stroke-Cycle Engine
Not used for automotive applications because of high emission levels and poor fuel efficiency
Requires only one revolution of the crankshaft for a complete power-producing cycle
Two piston strokes complete the intake, compression, power, and exhaust events

55. Two-Stroke-Cycle Engine Operation
As the piston moves upward, the air-fuel mixture is compressed
Vacuum is created in the crankcase, which draws fuel and oil into the crankcase
A reed valve or rotary valve controls flow into the crankcase

56. Two-Stroke-Cycle Engine Operation

57. Two-Stroke-Cycle Engine Operation
When the piston reaches the top of the cylinder, ignition occurs
Burning gases force the piston downward
The reed valve or rotary valve closes, compressing and pressurizing the fuel mixture in the crankcase

58. Two-Stroke-Cycle Engine Operation
As the piston moves down in the cylinder, it uncovers the exhaust port
Burned gases leave the cylinder
The piston continues downward, uncovering the transfer port
Pressure in the crankcase causes a fresh fuel charge to flow through the transfer port and into the cylinder

59. Two-Stroke-Cycle Engine Operation

60. Two-Stroke-Cycle Engine Lubrication
The crankcase is used as a storage chamber for each successive fuel charge
Lubricating oil is introduced into the crankcase along with the air-fuel charge to provide lubrication
Inside the crankcase, some of the oil separates from the fuel
The oil mist lubricates and protects the moving parts inside the engine

61. Miller-Cycle Engine Uses a modified four-stroke cycle
Designed with a shorter compression stroke and a longer power stroke to increase efficiency
The intake valve remains open longer to delay compression

62. Miller-Cycle Engine

63. Miller-Cycle Operation
The piston slides down the bore with the intake valve open

64. Miller-Cycle Operation
The intake valve remains open as the piston starts up the bore
The supercharger pressurizes the intake to prevent backflow

65. Miller-Cycle Operation
The intake valve closes and compression occurs

66. Miller-Cycle Operation
The power stroke occurs

67. Miller-Cycle Operation
The exhaust stroke occurs

68. Typical Automotive
Engines

69. Provides the lowest center of gravity of any piston engine
Horizontally Opposed
Provides the lowest center of gravity of any piston engine

70. Features four chain-driven camshafts and 32 valves
Overhead Cam V-8
Features four chain-driven camshafts and 32 valves

71. Inline SOHC
This 16-valve, four-cylinder engine has a belt-driven camshaft and a balance shaft

72. This engine uses many aluminum parts
Fuel-Injected V-8
This engine uses many aluminum parts

73. Each cylinder head contains two camshafts
DOHC V-6
Each cylinder head contains two camshafts

74. Note the reciprocating assembly and the valve train
V-8 Engine
Note the reciprocating assembly and the valve train

75. Six-cylinder engine with a rear drive belt for the injection pump
Inline Diesel
Six-cylinder engine with a rear drive belt for the injection pump

76. Two roller chains drive the overhead camshafts
V-12 Engine
Two roller chains drive the overhead camshafts