Fi System - Yamaha WR450FB 2012 Owner's Service Manual

EAS1DX3017

FI SYSTEM

The fuel pump delivers fuel to the fuel injector via the fuel filter. The pressure regulator maintains the
fuel pressure that is applied to the fuel injector at a certain level. Accordingly, when the energizing
signal from the ECU energizes the fuel injector, the fuel passage opens, causing the fuel to be inject-
ed into the intake manifold only during the time the passage remains open. Therefore, the longer the
length of time the fuel injector is energized (injection duration), the greater the volume of fuel that is
supplied. Conversely, the shorter the length of time the fuel injector is energized (injection duration),
the lesser the volume of fuel that is supplied.
The injection duration and the injection timing are controlled by the ECU. Signals that are input from
the throttle position sensor, coolant temperature sensor, atmospheric pressure sensor, lean angle
sensor, crankshaft position sensor, intake air pressure sensor and intake air temperature sensor en-
able the ECU to determine the injection duration. The injection timing is determined through the sig-
nals from the crankshaft position sensor. As a result, the volume of fuel that is required by the engine
can be supplied at all times in accordance with the driving conditions.
10
9
1. Fuel pump
2. Fuel injector
3. ECU (engine control unit)
4. Throttle position sensor
5. Coolant temperature sensor
6. Crankshaft position sensor
7. Intake air pressure sensor
8. Throttle body
9. Intake air temperature sensor
10.Air filter case
A. Fuel system
B. Intake system
C. Control system
1
A
2
B
7
8
1-6
4
C
3
5
6
FEATURES