1. Electronic Fuel Injection28
Electronic Fuel Injection
Prepared by
Martin Restoule
Algonquin College
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2. Objectives
Explain the difference between throttle body and port injection systems.
Describe the difference between a sequential fuel injection (SFI) system and a multi-port fuel injection (MFI) system.
Explain the design, purpose, and operation of major EFI components.
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3. Objectives
Describe the inputs used by the computer to control the idle air control and idle air control by-pass air motors.
Describe how the computer supplies the correct air/fuel ratio on a throttle body injection (TBI) system.
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4. Objectives Explain how the clear flood mode operates on a TBI system.
Explain why manifold vacuum is connected to the pressure regulator in an MFI system.
Describe the operation of the pressure regulator in a returnless EFI system.
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5. Objectives
Describe the operation of the central injector and poppet nozzles in a central port injection (CPI) system.
Describe the operation of direct gasoline injection systems.
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6. Electronic Fuel Injection Components
Powertrain Control Module
The heart of the fuel injection system is the computer or powertrain control module (PCM).
The PCM receives signals from all the system sensors, processes them, and transmits programmed electrical pulses to the fuel injectors.
Both incoming and outgoing signals are sent through a wiring harness and a multiple-pin connector.
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7. Electronic Fuel Injection Components
Fuel Injectors
Fuel injectors are electromechanical devices that meter and atomize fuel so it can be sprayed into the intake manifold.
When the injector is electrically energized, a fine mist of fuel sprays from the injector tip.
Two different valve designs are commonly used, a nozzle or needle valve and a ball valve.
Both operate similarly with magnetic fields unseating the valves and a spring seats or closes the valve.
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8. Electronic Fuel Injection Components
A typical fuel injector and its components
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9. Electronic Fuel Injection Components
Examples of top and bottom feed injectors
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10. Electronic Fuel Injection Components
Idle Air Control
Engine idle speed is controlled by bypassing a certain amount of airflow past the throttle valve in the throttle body housing.
Two types of air bypass systems are used; auxiliary air valves and idle air control (IAC) valves.
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11. Electronic Fuel Injection Components
Idle Air Control (concluded)
The IAC system consists of an PCM controlled stepper motor or actuator that extends or retracts the idle air control valve in the air bypass channel. around the throttle valve.
The PCM calculates the amount of air needed for smooth idling based on input data such as coolant temperature, engine load, engine speed, and battery voltage.
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12. Electronic Fuel Injection Components
An idle air control system
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13. Types of Fuel Injection Systems
Throttle Body Injection (TBI)
The throttle body unit is similar in size and shape to a carburetor, and, like a carburetor, it is mounted on the intake manifold.
The injector(s) sprays fuel down into a throttle body chamber leading to the intake manifold.
The intake manifold feeds the air/fuel mixture to all cylinders.
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14. Types of Fuel Injection Systems
Throttle Body Injection (TBI) (concluded)
Four-cylinder engines have a single
throttle body assembly with one injector and throttle, whereas V6 and V8 engines are equipped with dual injectors and 2 throttles on a common throttle shaft.
The throttle body assembly contains a pressure regulator, injector or injectors, TP sensor, idle speed control motor, and throttle shaft and linkage assembly.
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15. Types of Fuel Injection Systems
A dual throttle body assembly
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16. Types of Fuel Injection Systems
Port Fuel Injection (PFI)
PFI systems use one injector at each cylinder.
They are mounted in the intake manifold near the cylinder head, where they can inject a fine, atomized fuel mist as close as possible to the intake valve.
Fuel lines run to each cylinder from a fuel manifold, usually referred to as a fuel rail.
Since each cylinder has its own injector, fuel distribution is exactly equal.
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17. Types of Fuel Injection Systems
Port injection sprays fuel into the intake port and fills the port with fuel vapour before the valve opens
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18. Types of Fuel Injection Systems
Types of Port Fuel Injection
While all port injection systems operate using an injector at each cylinder, they do not fire the injectors in the same manner.
In multiport injection (MPI) systems, the injectors are arranged and turned on in pairs or groups.
When the injectors are split into 2 equal groups, the groups are fired alternately (one group firing during each engine revolution).
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19. Types of Fuel Injection Systems
Types of Port Fuel Injection
Sequential fuel injection (SFI) systems control each injector individually so that it is opened just before the intake valve opens.
This means that the mixture is never static in the intake manifold and mixture adjustments can be made almost instantaneously between the firing of one injector and the next.
Sequential firing is the most accurate and desirable method of regulating port injection.
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20. Types of Fuel Injection Systems
Grouped injectors in multiport injection
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21. Types of Fuel Injection Systems
Central Port Injection (CPI)
In a central port (CPI) or central multiport fuel injection (CMFI) system, a central injector assembly is mounted in the lower half of the intake manifold.
This system uses one injector to control the fuel flow to 6 (on six cylinder engines) individual poppet nozzles.
Each nozzle contains a check ball and extension spring that regulates the injector discharge.
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22. Types of Fuel Injection Systems
Central multiport fuel injection components in the lower half of the intake manifold
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23. Types of Fuel Injection Systems
Gasoline direct injection (GDI)
With gasoline direct-injection, the gasoline is injected directly into the combustion chamber.
To prevent the heat from igniting the fuel in the injector, the injectors are designed to completely seal after the fuel is sprayed.
The injectors must also be able to spray the fuel at a much higher pressure than what is in the cylinder.
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24. Types of Fuel Injection Systems
Gasoline direct injection (GDI) (concluded)
GDI allows for very lean operation (as much as 35:1) during cruising.
Under heavy loads, the system provides near-stoichiometric air/fuel ratios.
With these lean ratios, the engine’s fuel economy is increased by nearly 30% and the emission levels are substantially decreased.
Volumetric efficiency is improved because the intake manifold and port only deliver air to the cylinders.
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25. Types of Fuel Injection Systems
Component layout for a GDI system
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26. Common Input Sensors Volume Airflow Sensors
The airflow sensor (commonly called an airflow meter or vane airflow sensor), measures airflow, or air volume.
As air is drawn into the engine, a flap is deflected against a spring.
A potentiometer attached to the flap shaft monitors the flap movement and produces a voltage signal.
Signal strength increases as the flap opens.
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27. Common Input Sensors Volume Airflow Sensors (concluded)
A Karman Vortex sensor is another design of airflow sensor.
Air entering the airflow sensor passes through vanes arranged around the inside of a tube and begins to swirl.
The swirling air exerts high pressure against the outside of the housing and a low-pressure area in the centre of the intake tube.
Two pressure-sensing tubes and an electronic sensor counts how many times the low-pressure area is sensed.
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28. A typical airflow sensor
Common Input Sensors
A typical airflow sensor
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29. Common Input Sensors Intake Air Temperature (IAT) Sensor
Cold, dense air can burn more fuel than the same volume of warm air because it contains more oxygen.
Airflow sensors that only measure air volume must have their readings adjusted to account for air temperature.
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30. Common Input Sensors Intake Air Temperature (IAT) sensor
An air temperature sensor mounted in the induction system can measure air temperature and send an electronic signal to the control computer.
The computer uses this input along with the air volume input in determining the amount of oxygen entering the engine.
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31. Common Input Sensors Mass Airflow Sensor (MAF)
By measuring air mass, a mass airflow sensor does the job of a volume airflow sensor and an air temperature sensor.
The mass of a given amount of air is calculated by multiplying its volume by its density.
From a measurement of mass, the electronic control unit adjusts the fuel delivery for the oxygen content in a given volume of air.
The accuracy of air/fuel ratios is greatly enhanced when matching fuel to air mass.
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32. Common Input Sensors
A Mass Airflow Sensor
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33. Common Input Sensors Mass Airflow Sensor (MAF) (concluded)
The mass airflow sensor converts air flowing past a heated sensing element into an electronic signal.
The strength of this signal is determined by the energy needed to keep the element at a constant temperature.
As the volume and density (mass) of airflow across the heated element changes, the temperature of the element is affected and the current flow to the element must be adjusted.
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34. Common Input Sensors Components of a hot wire-type mass airflow sensor
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35. Common Input Sensors Manifold Air Pressure (MAP)
The MAP sensor measures changes in the intake manifold pressure that result from changes in engine load and speed.
The pressure measured by the MAP sensor is the difference between barometric and manifold pressure.
At idle, the engine produces a low MAP value.
At wide-open throttle, manifold and barometric pressure are equal and a high value is produced.
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36. Common Input Sensors
A MAP Sensor
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37. Common Input Sensors Oxygen Sensor
The signals from the exhaust gas oxygen sensor (O2S), or lambda sensor, are used by the PCM to monitor the air/fuel mixture.
The signal from an oxygen sensor is based on the amount of oxygen in the exhaust gas.
When the sensor’s signal indicates a lean mixture (more oxygen), the computer enriches the air/fuel mixture to the engine.
When the sensor reading is rich (less oxygen), the computer leans the air/fuel mixture.
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38. Common Input Sensors Coolant Temperature Sensor
The coolant temperature sensor signals the PCM when the engine needs cold enrichment, as it does during warm-up.
This adds to the base pulse, but decreases to zero as the engine warms up.
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39. Common Input Sensors Throttle Position Sensor
The PCM uses throttle position sensor information to determine throttle position, the rate of throttle opening and closing, and to determine if the throttle is closed or wide open.
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40. Common Input Sensors Crankshaft Position Sensor
The crankshaft position sensor (engine speed) can provide engine data directly to the PCM or through the ignition system.
This also times the start of the injection according to the intake stroke cycle.
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41. Common Input Sensors Cranking Enrichment
The starter circuit sends a signal for fuel enrichment during cranking operations even when the engine is warm. This is independent of any cold start fuel enrichment demands.
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42. Basic Fuel Injection System
Input sensors
Give engine operating condition information to the computer.
Control module
Determines how much fuel the engine needs and controls the fuel injectors.
Fuel injectors
Meter and atomize the fuel entering the intake manifold or intake port.
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43. Control Module Operating Modes
Open loop mode
The computer uses pre-programmed values and basic sensor information to determine injector pulse length.
Closed loop mode
In addition to the other input sensors, the computer uses signals from the exhaust oxygen sensor to determine injector pulse length.
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44. Open and Closed Loop
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45. Operating Modes Clear flood mode Acceleration enrichment mode
The computer cuts off the fuel injectors when throttle position is high (wide open) and RPM is low (cranking speed).
Acceleration enrichment mode
The computer adds extra fuel during rapid changes in throttle position and manifold vacuum or air flow.
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46. Summary
There are three types of electronic fuel injection systems: throttle body, port, and central multi-port.
Port injection systems use one of four firing systems: grounded single fire, grouped double fire, simultaneous double fire, or sequential fire.
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47. Summary
The airflow sensor determines the amount of air entering the engine.
The heart of the fuel injection system is the electronic control unit.
Two types of fuel injectors are currently in use: top feed and bottom feed.
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48. Summary
In a speed-density EFI system, the computer uses manifold pressure and engine rpm inputs to calculate the amount of air entering the engine.
In an EFI system, the computer supplies the proper air/fuel ratio by controlling injector pulse width.
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49. Summary
In an SFI system, each injector is controlled individually by the computer.
The pressure regulator maintains the specified fuel system pressure and returns excess fuel to the fuel tank.
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50. Summary
In a returnless fuel system, the pressure regulator and filter assembly is mounted with the fuel pump and gauge sending unit assembly in the fuel tank.
A central multi-port injection system has one central injector and a poppet nozzle in each intake port.
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51. Summary
GDI systems inject gasoline directly into the combustion chamber and allow for very lean operation.
EFI systems rely on inputs from various sensors; these include airflow, air temperature, mass airflow, manifold absolute pressure, oxygen, coolant temperature, and throttle position sensors.
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