Chapter I Electronic Injection System
Section I Introduction
I. Fundamentals
The electronic injection system is a multi-point fuel injection system with electronic control unit
(ECU). With various sensors installed on different parts of the engine to measure each working
parameter of the engine, the ECU can precisely control the fuel injection volume by controlling the
fuel injector according to the pre-set control program in the computer, and achieve the most
favorable air-fuel mixture for the engine under any working condition. With the control program in
the ECU and relevant actuator, such functions as fuel increase at start, fuel increase at warm-up,
fuel increase at acceleration, fuel increase at full load, fuel decrease at deceleration, fuel cut at
idle speed, and automatic idle speed control are available in this system, which can achieve
special air-fuel mixture for the engine under the special working condition. Therefore, the engine
enjoys good performances in fuel efficiency and exhaust emission, and the service performance of
the vehicle is improved at the same time. Besides, the trouble diagnostic mode in the ECU can
make the researching of troubles much easier.
II. Structure of electronic control system
The electronic control system is divided into the following three parts:
(1) Sensor---Convert various non-electrics physical quantities of the engine into electrics physical
quantities, and then send them to the ECU. The sensors on the engine include: ① Intake
pressure/temperature sensor, ② Throttle position sensor, ③ Coolant temperature sensor, ④
Heated oxygen sensor (front and rear oxygen sensor, only front oxygen senor available under
National III Emission Standard, front and rear oxygen sensor available under National III Emission
Standard+EOBD and in National IV Emission Standard), ⑤ Knock sensor, ⑥ Crankshaft position
sensor, ⑦ Weak acceleration sensor (unavailable under National III Emission Standard
(Simplified), available under National III Emission Standard +EOBD and under National IV
Emission Standard).
(2) Electronic control unit (ECU) is the “brain” for the whole electronic control system, which
analyses and processes all the information from sensors, sends orders to actuator, and makes the
engine work under the best condition.
(3) Actuator is to perform the orders from the ECU. The actuator is the “hand” and “leg” of the
electronic control system, which include: ① Fuel pump, ② Fuel injector, ③ Ignition coil, ④ Idle
speed actuator with stepper motor, ⑤ Canister control valve.
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