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Modern Automotive

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Title: Modern Automotive


1
PowerPoint for
Modern Automotive Technology
by Russell Krick
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
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
L-Head Engine
  • Both the intake and exhaust valves are in the
    block

21
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
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
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
Horizontally Opposed
  • Provides the lowest center of gravity of any
    piston engine

70
Overhead Cam V-8
  • Features four chain-driven camshaftsand 32 valves

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

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

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

74
V-8 Engine
  • Note the reciprocating assemblyand the valve
    train

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

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