1. Two Common Types of EFI
Chapter Lesson 3

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

3. Multiport Fuel Injection
Controls

4. Multiport Fuel Injection
Air Delivery

5. Multiport Fuel Injection
Fuel Delivery

6. 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

7. 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

8. Injection Components

9. Injection Components

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

11. 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

12. Airflow-Sensing Multiport EFI

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

14. 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

15. Pressure-Sensing Multiport EFI

16. 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

17. Cold Start Injector

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

19. TBI Overview

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

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