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
(18 Topics)
Gasoline injection fundamentals
Gasoline injection classifications
Throttle body and multiport injection
Gasoline injection controls
Electronic fuel injection
Engine sensors

4. Contents Injector pulse width Throttle body injection
Engine idle speed control
Continuous throttle body injection
Electronic multiport injection
Air-fuel emulsion injector

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

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
Engines use differences in pressure to force fuel and air into its cylinders
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. Drive-by-Wire System
Uses a pedal sensor, control module and an actuator to operate the throttle valve on a gasoline engine
When the pedal is pressed, it moves a variable resistor
Control module senses pedal position by measuring current flow through the resistor, and sends a signal to the actuator, controlling engine speed

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. Injector nozzles in a throttle body assembly on top of the engine
Throttle Body Injection
Injector nozzles in a throttle body assembly on top of the engine
Multiport Injection
Gasoline is sprayed into each intake port, toward each intake valve

17. Sprays fuel into intake manifold. Most gasoline systems are indirect
Indirect Injection
Sprays fuel into intake manifold. Most gasoline systems are indirect
Direct Injection
Sprays fuel directly into engine 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 injection
Most common type of gasoline injection system
Hydraulic Fuel Injection
Uses hydraulic control devices moved by air of fuel pressure
Airflow sensor and fuel distributor meter gasoline (continuous injection)

20. Intermittent Injection
Mechanical Injection
Uses throttle linkage, mechanical pump, and governor to control injection
Used on older, high-performance, and diesel applications
Intermittent Injection
Opens and closes injectors independently of engine intake valves
Also known as modulated injection

21. Timed Injection Continuous Injection
Sprays fuel just before, or as the intake valves open
A good example is diesel Injection
Continuous Injection
Sprays fuel into intake manifold at all times
Air-fuel ratio is controlled by increasing or decreasing fuel pressure at the injectors

22. 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

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

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

25. Systems Overview

26. Fuel Delivery System Components Electric fuel pump Fuel filter
Fuel pressure regulator
Injectors

27. Fuel Delivery System

28. Electric Fuel Pump Draws gasoline out of the tank
Forces it to the fuel rail
Unused fuel returns to the tank

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

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

31. 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 armature to open injector

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

33. Throttle plates control airflow
Air Induction System
Throttle plates control airflow

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

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

36. Electronic Control Module
Commonly mounted behind the instrument panel

37. Engine Sensors Exhaust gas oxygen Manifold absolute pressure (MAP)
Throttle position (TP)
Engine coolant temperature(ECT)
Airflow
Inlet air temperature (IAT)
Crankshaft position (CKP)

38. Oxygen Sensor Measures oxygen content in the exhaust
Threaded into exhaust manifold before the catalytic converter
OBDII equipped vehicles also use a second sensor after the catalytic converter to monitor converter efficiency

39. Signals air-fuel mixture
Oxygen Sensor
Signals air-fuel mixture

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

41. Oxygen Sensor Construction

42. 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
Closed Loop
Computer uses exhaust oxygen as a main input for air-fuel mixture control
Normally, hot engines operate in closed loop

43. Information Flow
Open Loop
Closed Loop

44. 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

45. Often mounted on the engine or in the engine compartment
Map Sensor
Often mounted on the engine or in the engine compartment

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

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

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

49. Throttle Position Sensor
Variable resistor signals throttle position

50. Engine Coolant Temperature Sensor
Senses engine coolant temperature
At low temperature, sensor resistance may be high, signal voltage high, computer will richen mixture
At high temperature, sensor resistance may be low, signal voltage low, computer will deliver leaner mixture

51. 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, changing the signal voltage to the computer

52. Airflow Sensor Operation
Airflow sensor operates a variable resistor

53. Inlet Air Temperature Sensor
Measures temperature of air entering the engine
Air temperature affects air density
Cooler air is more dense, requiring more fuel
Operation is similar to engine coolant temperature sensor

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

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

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

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

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

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

60. Throttle Body Injection
Components:
throttle body housing
TBI injector
TBI pressure regulator
idle speed control
throttle position sensor
throttle plates

61. TBI Overview

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

63. Throttle Body Housing Bolted to the intake manifold
Injector(s) are in the upper housing
Throttle plates are in the lower housing
Holds the throttle position sensor, fuel pressure regulator and idle speed control device

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

65. 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

66. 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 is sprayed above the throttle valve

67. 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

68. TBI System Cutaway

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

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

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

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

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

74. 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

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

76. Multiport Fuel Injection
Controls

77. Multiport Fuel Injection
Air Delivery

78. Multiport Fuel Injection
Fuel Delivery

79. 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

80. 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

81. Injection Components

82. Injection Components

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

84. 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

85. Air-Fuel Emulsion Injector

86. Unitized Multiport Injection
Mounts all of the injectors into a single assembly
Plastic transfer lines carry fuel from each injector to a poppet valve located in the intake port

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

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

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

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

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

92. 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 a signal for the computer

93. System Overview

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

95. 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

96. System Overview

97. Hydraulic-Mechanical
Continuous Injection
System

98. Continuous Injection System (CSI)
Hydraulic-mechanical system
Mixture control unit senses airflow with an airflow sensor plate and distributes fuel
Operates the injectors with a fuel distributor

99. Continuous Injection System (CSI)

100. Airflow Sensor Disc-shaped plate, hinged in the air horn
Plate operates a lever arm
Lever arm pushes up a fuel control plunger in the fuel distributor when air flows
Plunger opens fuel passages to the injectors

101. CIS Fuel Distributor Hydraulically-operated valve mechanism
Controls fuel flow or pressure to each injector
Whenever air flows to the engine, the fuel distributor sends fuel to the injectors, causing them to spray continuously

102. CIS Operation Airflow sensor Partial load, more airflow
Idle, low airflow
Full load, airflow pushes plate up high

103. Continuous Fuel Injector
Spring-loaded valve
One injector for each cylinder
Injects fuel continuously when the engine is running
Spring holds the valve closed
Fuel pressure forces it open, spraying fuel into the intake port
Fuel pressure forces the valve open

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