Modern Automotive

1
PowerPoint for
Modern Automotive Technology
by Russell Krick
2
Chapter 12
Engine Design Classifications
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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

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Pancake Combustion Chamber

• Chamber forms a flat pocket over the piston head
• Valve heads are almost parallel to the top of the
  piston

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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

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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

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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

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Two-Stroke-Cycle Engine Operation
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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

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Two-Stroke-Cycle Engine Operation
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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

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Miller-Cycle Engine
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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
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Horizontally Opposed

• Provides the lowest center of gravity of any
  piston engine

70
Overhead Cam V-8

• Features four chain-driven camshaftsand 32 valves

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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