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

2. Chapter 22
Gasoline Injection
Fundamentals

3. Contents Gasoline injection fundamentals
Gasoline injection classifications
Throttle body and multiport injection
Gasoline injection controls
Electronic fuel injection
Engine sensors
Injector pulse width
(Continued)

4. Contents Throttle body injection Engine idle speed control
Continuous throttle body injection
Electronic multiport injection
Air-fuel emulsion injector
Unitized multiport injection
(Continued)

5. Contents Injector resistor pack Airflow-sensing multiport EFI
Pressure-sensing multiport EFI
Hydraulic-mechanical continuous injection system
Fuel accumulator
Direct gasoline injection

6. Gasoline Injection Fundamentals
Uses pressure from an electric fuel pump to spray fuel into the engine’s intake manifold
Provides the engine with the correct air-fuel mixture for specific operating conditions

7. Advantages Improved atomization Better fuel distribution Smoother idle
Improved fuel economy
Lower emissions
Better cold-weather driveability
Increased engine power
Simpler

8. Atmospheric Pressure Formed by the air surrounding the earth
At sea level, the atmosphere exerts 14.7 psi (103 kPa)

9. Vacuum Lower than atmospheric pressure
Less than 14.7 psi (103 kPa) at sea level
Sometimes called suction

10. Differences in Pressure Cause Flow
An engine uses differences in pressure to force fuel and air into its cylinders
The engine acts as a vacuum pump, producing low pressure, or vacuum, in the intake manifold

11. Intake Manifold Vacuum
Closed throttle, high vacuum
Open throttle, reduced vacuum

12. Engine Throttle Valve
Controls airflow and gasoline engine power output
When opened, airflow, fuel flow, and power increase

13. Throttle-by-Wire System
Uses a pedal sensor, the ECU, and an actuator to operate the engine throttle valve
The ECU regulates engine speed to improve fuel economy
Some systems provide sport and comfort modes

14. Gasoline Injection Classifications
There are many types of gasoline injection systems
A gasoline injection system is commonly called a fuel injection system
A diesel injection system is also a fuel injection system

15. Throttle Body and
Multiport Injection

16. Throttle Body Injection
Injector nozzles are mounted in a throttle body assembly on top of the engine
Multiport Injection
Injectors are mounted in the intake ports going to each cylinder

17. Indirect Injection
Sprays fuel into the intake manifold. Most gasoline systems are indirect.
Direct Injection
Sprays fuel directly into the engine’s combustion chambers. Used in all diesel injection systems.

18. Gasoline Injection Controls Electronic fuel injection
Hydraulic fuel injection
Mechanical fuel injection
Injection timing
Injector opening relationship

19. Electronic Fuel Injection
Uses various engine sensors and a control module to regulate the opening and closing of the fuel injectors
This is the most common type of gasoline injection system

20. Hydraulic Fuel Injection
Uses hydraulic control devices moved by air or fuel pressure
Airflow sensor and fuel distributor meter gasoline (continuous injection)
the fuel distributor is a hydraulic valve mechanism that meters fuel into the engine

21. Mechanical Fuel Injection
Uses throttle linkage, mechanical pump, and governor to control injection volume
Old, seldom-used system
used on high-performance gasoline and diesel engine applications

22. Injection Timing Intermittent injection Timed injection
opens and closes injectors independent of engine intake valves
Timed injection
sprays fuel into the engine just before or as the intake valve opens
Continuous injection
sprays fuel into the intake manifold at all times

23. Injector Opening Relationship
Simultaneous Injection
all the injectors open at the same time
pulsed on and off together
Sequential Injection
injectors open one after the other
injection matches the firing order of the engine

24. Injector Opening Relationship
Group Injection
Several but not all injectors open at the same time
V-8 engine–one group of four injectors open at one time, another group of four open at a different time

25. Electronic Fuel Injection (EFI)
EFI system can be divided into four subsystems:
fuel delivery system
air induction system
sensor system
computer control system

26. Systems Overview

27. Fuel Delivery System Components electric fuel pump fuel filter
fuel pressure regulator
injectors

28. Fuel Delivery System

29. Electric Fuel Pump Draws gasoline out of the tank
Forces it to the fuel rail

30. Fuel Pressure Regulator
Controls the pressure entering the injector(s)
Returns excess fuel to the tank
Vacuum may be ported into the regulator
lower pressure at idle
increasing pressure at higher load

31. Fuel Pressure Regulator
Low vacuum, high load
High vacuum, low load

32. Injectors Solenoid-operated fuel valve
Electrical terminals
Armature
Injector body
Needle valve
Fuel inlet
Inlet screen
Return spring
Coil windings
Spray mist
Solenoid-operated fuel valve
When current flows, magnetism attracts the armature to open the injector valve

33. Air Induction System Air filter Throttle valve(s) Sensors Ducts
traps dust and debris
Throttle valve(s)
controls airflow through the throttle body
Sensors
sense airflow and throttle position
Ducts
route clean air to the throttle body

34. Air Induction System

35. Sensor System Inputs to the control module
Signals the following operating conditions:
temperature
position
pressure or vacuum
speed

36. Computer Control System
Uses data from the sensors to control fuel injectors
Wiring harness connects computer to sensors and injectors

37. Electronic Control Module
Commonly mounted behind the instrument panel

38. Engine Sensors Oxygen (O2) Manifold absolute pressure (MAP)
Throttle position (TP)
Engine coolant temperature(ECT)
Airflow

39. Engine Sensors Intake air temperature (IAT) Crankshaft position (CKP)
Fuel pressure
Fuel temperature

40. Oxygen Sensor Measures oxygen content in the exhaust
In OBD I vehicles, the sensor is threaded into the exhaust manifold before the catalytic converter
OBD II equipped vehicles use at least two oxygen sensors
one before and one after catalytic converter
the sensor located after the converter monitors catalyst efficiency

41. Oxygen Sensor Operation
Increase in exhaust oxygen from lean mixture causes oxygen sensor voltage to decrease
Decrease in exhaust oxygen from rich mixture causes oxygen sensor voltage to increase

42. Oxygen Sensor Construction

43. Open Loop
Injection system does not use exhaust gas oxygen as an indicator of air-fuel mixture
Operation is from information stored in the computer
Cold engines operate in open loop

44. Closed Loop
Computer uses information from the oxygen sensor as a main input for air-fuel mixture control
Normally, hot engines operate in closed loop

45. Information Flow
Open Loop
Closed Loop

46. MAP Sensor
Senses engine load by measuring pressure, or vacuum, inside the intake manifold
High pressure (low vacuum) indicates high load
Low pressure (high vacuum) indicates low load

47. Often mounted on the engine or in the engine compartment
MAP Sensor
Often mounted on the engine or in the engine compartment

48. Piezo-resistor chip converts pressure change into resistance change
MAP Sensor Theory
Piezo-resistor chip converts pressure change into resistance change

49. Manifold vacuum flexes the chip, altering its resistance
MAP Sensor Side View
Manifold vacuum flexes the chip, altering its resistance

50. Throttle Position Sensor
Senses throttle position
Variable resistor connected to the throttle plate
As the throttle opens or closes, sensor resistance changes, signaling throttle position

51. Throttle Position Sensor
Variable resistor signals throttle position

52. Engine Coolant Temperature Sensor
Senses engine coolant temperature
At low temperatures, sensor resistance may be high
computer will richen mixture
At high temperatures, sensor resistance changes
computer will deliver leaner mixture

53. Airflow Sensor Measures amount of air entering engine
Air flap or door operates a variable resistor
Airflow opens the flap, changing position of the variable resistor and changing the signal voltage to the computer

54. Airflow Sensor Operation
This airflow sensor operates a variable resistor

55. Intake Air Temperature Sensor
Measures the temperature of the air entering the engine
Air temperature affects air density
Cooler air is more dense, requiring more fuel
Helps the computer compensate for changes in outside air temperature

56. Crankshaft Position Sensor
Detects engine speed and position
Information is used by computer for fuel injection operation

57. Fuel Pressure Sensor Measures fuel pressure inside the fuel rail
Signals to ECU to compensate for variations in fuel system pressure
Often used in returnless fuel injection systems

58. Fuel Temperature Sensor
Measures fuel temperature in the fuel rail
Signals to ECU to adjust fuel metering, timing, and other parameters
In some vehicles, sensor is combined with the fuel pressure sensor in a single housing

59. Other Sensors Several other sensors may be used: A/C compressor sensor
transmission sensor
EGR sensor
vehicle speed sensor
knock sensor

60. Digital Signals Signal is on or off
Voltage goes from maximum to minimum instantly
Crankshaft position sensor output may be a digital signal

61. Analog Signals Signal varies in voltage or strength
May be produced by change in resistance of a sensor as temperature, pressure, or position changes

62. Injector Pulse Width
Pulse width is the amount of time an injector is energized
At wide open throttle, computer lengthens injector pulse to richen mixture
At low load, computer shortens pulse width

63. Pulse width controls the amount of fuel injected
Injector Pulse Width
Pulse width controls the amount of fuel injected

64. Throttle Body Injection
Components:
throttle body housing
TBI injector
TBI pressure regulator
throttle positioner (idle speed control)
throttle position sensor
throttle plates

65. TBI Overview

66. Fuel enters the regulator before passing into the injector
TBI Assembly
Fuel enters the regulator before passing into the injector

67. Throttle Body Housing Bolted to the intake manifold
Holds the injector(s), throttle plates, throttle position sensor, fuel pressure regulator, and idle speed control device

68. TBI Injector Components: solenoid coil armature or plunger
ball or needle valve
seat
Injector spring

69. This injector uses a ball-type valve instead of a pointed needle valve
TBI Injector
This injector uses a ball-type valve instead of a pointed needle valve

70. Injector Operation
When the computer energizes the injector, a magnetic field is produced in the coil
Magnetism pulls the plunger and valve up to open the injector
Fuel can then squirt through the injector nozzle
Fuel is sprayed above the throttle valve

71. TBI Pressure Regulator
Contains a fuel valve, diaphragm, and spring
Spring holds the fuel valve closed, causing pressure increase as fuel flows in from the electric fuel pump
When preset pressure is reached, fuel pressure acting on the diaphragm forces the fuel valve open, allowing fuel to flow back to the tank

72. TBI System Cutaway

73. Engine Idle Speed Control
There are several different types of idle speed control devices:
fast idle thermo valve
idle air control motor
throttle positioner

74. Fast Idle Thermo Valve
Thermowax plunger contracts when cold to allow more airflow at idle
Plunger expands when the engine warms, closing valve and reducing airflow

75. Fast Idle Thermo Valve
Idle air control valve and the thermo valve affect air that bypasses the throttle valve to alter idle speed

76. Computer controlled solenoid- or servomotor-operated air bypass valve
Idle Air Control Motor
Computer controlled solenoid- or servomotor-operated air bypass valve

77. Throttle Positioner
Computer controlled motor opens or closes the throttle plates
In this way, the computer can maintain a precise idle speed with changes in temperature, load, and other conditions

78. Continuous Throttle Body Injection (CTBI)
Sprays a solid stream of fuel into the air horn
Does not pulse the injectors on and off to control the air-fuel mixture
System alters pressure applied to the throttle body nozzles to control mixture

79. Electronic Multiport Injection
Uses a computer, sensors, and one solenoid injector for each cylinder
Components:
multiport throttle body
multiport pressure regulator
fuel rail

80. Multiport Fuel Injection
Controls

81. Multiport Fuel Injection
Air Delivery

82. Multiport Fuel Injection
Fuel Delivery

83. Injection Components Throttle body Multiport pressure regulator
contains throttle plates and a throttle position sensor
Multiport pressure regulator
mounted on the fuel rail, maintains pressure at the inlet to the injectors by acting as a bypass

84. Injection Components Fuel rail Multiport fuel Injector
connects the main fuel line to the inlet of each injector
Multiport fuel Injector
sprays fuel into the intake port, below the throttle valve

85. Injection Components

86. Injection Components

87. Multiport Fuel Injector
Solenoid opens the injector when current flows through the coil

88. Air-Fuel Emulsion Injector
Mixes air with the fuel creating a slurry
Slurry is injected into the intake manifold
Atomizes the fuel and improves combustion
Low pressure air from the air injection pump may be used

89. Air-Fuel Emulsion Injector

90. Unitized Multiport Injection
Mounts all of the injectors into a single assembly
A multi-pin terminal connects each injector to the control module

91. Unitized Multiport Injection Components

92. Unitized Multiport Injection Components
Fuel injection transfer lines
connect each injector to its poppet valve
Fuel injection poppet valve
spring loaded valve that prevents fuel leakage between injector pulses
when the fuel injector opens, fuel pressure forces the poppet valve open, spraying fuel into the intake port

93. Note the fitting for the plastic transfer line
Unitized Injector
Note the fitting for the plastic transfer line

94. Injector Resistor Pack
Set of low-ohm resistors
Resistors control current flow to each injector coil
Resistors protect windings from excess current
Usually 5-7 ohms
Often mounted in the engine compartment

95. Injector Circuit Circuit contains resistor pack
Each pin corresponds to a resistor

96. Airflow-Sensing Multiport EFI Uses an airflow sensor as a main control
Airflow sensor is placed at the inlet to the intake manifold
Sensor converts airflow into an electrical signal for the computer

97. Airflow-Sensing Multiport EFI

98. Airflow Sensor Operation
Throttle moved open for more power, increased flow pushes sensor flap open
Throttle almost closed, sensor detects little airflow

99. Pressure-Sensing Multiport EFI
Uses intake manifold pressure (vacuum) as a primary control
Pressure sensor is connected to the intake manifold
Sensor converts changes in manifold pressure into changes in resistance
Computer uses this data

100. Pressure-Sensing Multiport EFI

101. Hydraulic-Mechanical
Continuous Injection
System

102. Continuous Injection System (CIS)
Hydraulic-mechanical system
Uses a mechanical airflow sensor to operate a hydraulic fuel distributor
Continuous injectors spray fuel anytime the engine is running

103. Continuous Injection System (CIS)

104. Continuous Fuel Injector

105. Cold Start Injector Extra fuel injector
Sprays fuel into the intake plenum for cold engine starting and running
Improves cold operation by enriching the air-fuel mixture
Controlled by a thermo-time switch or control module

106. Cold Start Injector

107. Fuel Accumulator Damps pressure pulses
May maintain pressure when shut down to aid restarting

108. Fuel Accumulator Components and Operation
Engine running, fuel pressure compresses diaphragm spring
Engine off, spring pressure on diaphragm maintains system pressure

109. Direct Gasoline Injection
Used in high-efficiency engines
Fuel injector sprays fuel directly into combustion chamber
Permits more precise control over fuel economy

110. Piezo Gasoline Injectors
Crystalline ceramic material used instead of an electromagnet to open injector valve
Piezo crystal converts electrical energy directly into motion
Smaller, lighter construction allows for quick and accurate operation

111. Direct Gasoline Injection System