Introduction to Fuel Injection Chapter 22 Lesson 1

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

Gasoline Injection Classifications There are many types of gasoline injection systems A gasoline injection system is commonly called a fuel injection system The two main types of gasoline injection systems used today are Throttle Body and Multiport Injection systems Some engine manufactures are developing direct fuel injection systems

Throttle Body and Multiport Injection

Injectors are mounted in the intake ports going to each cylinder 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 (Main focus) 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

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 (Bank 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