Throttle Body - Sym ATTILA RS-21 EFi 150 Service Manual

4. FUEL INJECTION SYSTEM
24-1 tooth
24 -1¾ ¦ 24 -1¾ ¦
4-10
This chapter Contents
Intake temperature and pressure sensor:
¡ E Powered by 5V DC from ECU. It has 4 terminals on the sensor.
One terminal is for power, and 2 terminals are for signal output.
And, the rest one is for ground.
¡ E The major component of the intake pressure sensor is a variable
transistor IC. Its reference voltage is DC 5V, and output voltage
range is DC 0~5V.
¡ E It is a sensor of combination by both sensing pressure and
temperature, and can measure the absolute pressure and
temperature in intake process. It also conduct fuel injection quantity
correction based on environmental temperature and position level.
Engine temperature sensor:
¡ E Powered by 5V DC from ECU, and has 2 terminals connector on the
sensor. One terminal is for voltage output and the other one for
ground.
¡ E Its major component is the thermistor of negative temperature
coefficient-NTC. (temperature up, resistance down)
¡ E It locates onto the cylinder head. Correspondence with engine
coolant temperature change, it transferred to voltage signal and sent
to ECU to calculate current temperature. Then, the ECU will correct
fuel injection time and ignition timing according to engine warm up
condition.
Throttle Valve Position sensor:
¡ E
Powered by 5V DC from ECU, and has 3-terminal connector on the
sensor. One terminal is for power, and one for voltage output, and
then the last one is for ground.
¡ E Its major component is a highly precious variable resistor. The input
voltage range: 5V DC.
¡ E
It is located on the side of throttle body. By means of the throttle
valve rotation to cause voltage change in linear, it provides ECU with
current throttle valve openness information. And also, the ECU
conducts the most properly fuel injection and ignition timing
according to the signal.

Throttle Body:

¡ E The throttle body is the air flow adjustment mechanism of the fuel
injection. (Its function is likely the carburetor.)
¡ E The throttle valve shaft is to turn the throttle valve position sensor in
synchronously so the ECU that can detect the throttle valve
openness in time.
¡ E
The guide onto the throttle body is connected to the idle speed air
by-pass valve. By means of the ECU to control the idle speed air
by-pass valve, air-flow is adjusted by the valve so that stabilizes idle
speed.
Crank position/rpm sensor:
¡ E
It does not need power supply, and has 2-signal terminals connector
on the sensor.
¡ E Its major component is the magnetic pickup coil, and its output
voltage range is ±0.8~100V.
¡ E The air gap between the sensor and flywheel must have .07~1.1mm.
¡ E
The magnetic sensor is sent an inductive voltage that is created by
cutting the magnetic field with the rotation gear (24-1 tooth) onto the
flywheel to the ECU. Then, the ECU calculates current engine
speed and crank position based on the voltage so that controls fuel
injection quantity and ignition timing in properly.