Section 2 Efi System - ZONGSHEN ZS125-80 Service Manual

The EFI system assembly mainly consists of electronic control unit (ECU), nozzle, throttle valve body
assembly, intake air temperature and pressure integrated sensor, engine temperature sensor, ignition coil,
crankshaft position sensor, oil pump assembly, oxygen sensor.
The engine EFI management system can precisely control the mixing ratio of air and fuel into the
engine cylinder, the combustion process and the exhaust gas con, so as to optimize engine performance,
improve driving performance, and strengthen the control of air pollution by exhaust emissions from the
motorcycle.
The engine control unit (ECU) is a singleship-cored microprocessor. The ECU analyzes and determines
the engine's working state and through sensors and work request switches installed on the engine and at
different locations on the main frame; and then it exerts precise control on the engine and corresponding
mechanisms through the engine and actuators.
The sensor for engine rotate speed and crank angle are magnetoelectric. The system uses it to
determine the crankshaft rotation position and speed. The crank angle sensor is mounted on the
transmission clutch housing and works with the 24x ring gear on the flywheel.
The manifold absolute pressure (MAP) sensor installed on the intake pipe to measure the pressure of
the intake pipe. ECU determines the amount of air into the engine through this signal.
The MAP sensor consists of a sealed elastic diaphragm and a ferromagnetic core. The diaphragm and
the core are precisely placed in the coil. When the pressure is sensed, a 0 to 5V output signal proportional
to the input pressure is generated.
The throttle position sensor is mounted on the throttle valve body assembly, coaxial with the throttle
lever and throttle valve. It is a linear variable resistor structure, whose sliding terminal is driven by the
throttle shaft.
Different opening degrees of the throttle valve leads to different resistance signals transmitted by
the sensor to the ECU. The system determines the real-time load and dynamic changes in the engine
according to its output signal value and its rate of change; it also exerts the timely control on the engine.
The intake air temperature sensor is mounted on the transition line of the induction system to detect
the air temperature entering the engine. It also adopts a thermistor with a negative temperature coefficient
as an sensing element.
As the air temperature changes will directly affect its density, therefore, the intake air temperature
sensor is one of the important parameters to calculate the actual amount of air into the cylinder.
The nozzle structure is an electromagnetic switch gear. The coil lead to the poles communicates with
ECU through the engine harness. The ECU exerts the control to impose voltage on the coil, resulting in the
generation of coil magnetic force to overcome the spring force. The fuel pressure and the vacuum suction
of intake pipe suck the iron core up. The fuel goes through the sealed surface of ball valve as an organic
whole with the iron core, and spray from the guiding nozzle hole to form a mist injection. After power
failure, the magnetic force disappears and the nozzle is closed.
The top of the fuel injector adopts a rubber seal ring and a fuel rail interface to form a reliable pressure
fuel seal. The lower part also uses a rubber seal ring and the engine intake pipe to form an airtight seal.
The nozzle will spray the fuel into the intake valve in a mist form.
The throttle valve body is installed in front of the intake pipe, and is composed of a valve body in itself,
a throttle position sensor and an idle control valve. The main function is to control the air intake when the
engine is working. It is the most basic channel of dialogue between the electronic control system and the
driver.

Section 2 EFI System

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