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

Chapter 22 Gasoline Injection Fundamentals

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

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

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

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

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

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

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

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

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

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

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

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

Throttle Body and Multiport Injection

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

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.

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

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

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

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

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

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

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

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

Systems Overview

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

Fuel Delivery System

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

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

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

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

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

Air Induction System

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

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

Electronic Control Module Commonly mounted behind the instrument panel

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

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

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

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

Oxygen Sensor Construction

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 information from the oxygen sensor as a main input for air-fuel mixture control Normally, hot engines operate in closed loop

Information Flow Open Loop Closed Loop

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

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

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

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

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

Throttle Position Sensor Variable resistor signals throttle position

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

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

Airflow Sensor Operation This airflow sensor operates a variable resistor

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

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

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

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

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

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

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

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

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

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

TBI Overview

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

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

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

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

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

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

TBI System Cutaway

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

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

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

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

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

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

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

Multiport Fuel Injection Controls

Multiport Fuel Injection Air Delivery

Multiport Fuel Injection Fuel Delivery

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

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

Injection Components

Injection Components

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

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

Air-Fuel Emulsion Injector

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

Unitized Multiport Injection Components

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

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

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

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

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

Airflow-Sensing Multiport EFI

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

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

Pressure-Sensing Multiport EFI

Hydraulic-Mechanical Continuous Injection System

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

Continuous Injection System (CIS)

Continuous Fuel Injector

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

Cold Start Injector

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

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

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

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

Direct Gasoline Injection System