Section 2 Efi System - ZONGSHEN ZS250GY-3 Service Manual

The main effect of EFI system is to convert the fuel which is supplied from fuel tank into a mist, then
mixture of the mist and air import into the combustion chamber.
1 The Structure and Working Principle of EFI system
EFI system consists of ECU,nozzle,throttle valve,intake air temperature,integrated pressure
sensor,engine temperature sensor,ignition coil,CKP,fuel pump,oxygen sensor.
EFI system could control the ratio of fuel-air mixture which import into the engine cylinder, combustion
process and exhaust gas conversion accurately .So as to optimize engine performance and driveability ,and
control the exhaust emission strictly.
ECU is a microprocessor as a core of SCM. By sensor and working request switch installed in the
engine and body of motorcycle, ECM could analyse mode of operation and estimate operating conditions.
Finally,controlling engine and relevant mechanisms accurately through actuator in the engine and body of
motorcycle.
The type of engine speed and crankshaft angle sensor is magnetoelectricity. The function of this sensor
is to determine the position of the rotating and revolving speed for crankshaft.
Crankshaft angle sensor is installed on the clutch housing and it works with 24x gear ring from
flywheel.
MAP sensor is installed in the intake manifold to measure the pressure,so ECU could judge air enter
into the engine from this signal.
MAP sensor consists of an elastic diaphragm seal and a magneticcore. Diaphragm seal and
magneticcore is placed in the coil accurately.When they sense pressure, they could produce a 0～5v
output signal in direct proportion to input pressure.
Throttle position sensor is installed on the throttle body and has a same axle with throttle lever and
throttle valve. The structure is a linear variable resistor and its sliding terminal is drived by throttle axle.
Resistance signal,which is passed to the ECU through this sensor, depends on the opening of throttle.
EFI could judge the real-time load of engine and dynamic variation according to the signal and its rate of
changes which output from the sensor.
Sensor of intake air temperature is installed on the pipe of intake system. The function of it is to test air
temperature enter into the engine. It also use thermistor of NTC coefficient as a sensing element.
The change of gas temperature directly affects its density fluctuation, therefore, intake air temperature is
one of the importance parameters for computing actual amount of air,which enters into the cylinder.
Nozzle is an electromagnetic switch device.Two poles elicite from coil connect with ECU through
engine wires. Voltage is applied to coil under the control of ECU, and the coil produces magnetic force to
overcome spring force, fuel pressures and a vacuum suction of intake manifold, suck up iron core, that
could enables fuel to traverse the seal surface of ball valve which is the one with the iron core ,then the
fuel sprays from nozzle and forms a mist spray; After interruption of power supply, magnetic disappears
and nozzle shuts.
The top of fuel injector adopts rubber sealing for forming a reliable leakproofness of fuel pressure with
the port of fuel channel;The bottom of it adopts rubber sealing for forming a aeroseal with engine intake
manifold. Nozzle spray the fuel as mist into the inlet valve.
Throttle body is installed in the front of the intake manifold. It consists of valve body,throttle position
sensor and ISCV. The main function is to control air inflow when engine is working.
Oxygen sensor is installed on the exhaust pipe of engine.It is a important part of closed-loop fuel control
system.
The main sensitive materials of oxygen sensor is zirconia. Zirconia is heated to 300℃ by exhaust
and is activated, then oxygen ion traverses the zirconia part and gets to its external electrode. Ultimately,
zirconia part induct content of oxygen from engine exhaust emission and change the output voltage value.
Oxygen sensor adopts Teflon insulated wires and stainless steel materials of component.Air for reference
is imported through wire,so it is non-blocking.
When AFR becomes thin， oxygen content of exhaust increases and the output voltage of oxygen
sensor reduces;Otherwise, the output voltage valve rises, it provide feedback of the real-time condition of
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AFR to ECU.

Section 2 EFI system