Yamaha YZFR1W 2007, Service Manual

Page: 8 / 429

FEATURES
1-2
EAS20170
FEATURES
OUTLINE OF THE FI SYSTEM
The main function of a fuel supply system is to provide fuel to the combustion chamber at the opti-
mum air-fuel ratio in accordance with the engine operating conditions and the atmospheric tempera-
ture. In the conventional carburetor system, the air-fuel ratio of the mixture that is supplied to the
combustion chamber is created by the volume of the intake air and the fuel that is metered by the jet
used in the respective carburetor.
Despite the same volume of intake air, the fuel volume requirement varies by the engine operating
conditions, such as acceleration, deceleration, or operating under a heavy load. Carburetors that
meter the fuel through the use of jets have been provided with various auxiliary devices, so that an
optimum air-fuel ratio can be achieved to accommodate the constant changes in the operating con-
ditions of the engine.
As the requirements for the engine to deliver more performance and cleaner exhaust gases
increase, it becomes necessary to control the air-fuel ratio in a more precise and finely tuned man-
ner. To accommodate this need, this model has adopted an electronically controlled fuel injection
(FI) system, in place of the conventional carburetor system. This system can achieve an optimum
air-fuel ratio required by the engine at all times by using a microprocessor that regulates the fuel
injection volume according to the engine operating conditions detected by various sensors.
The adoption of the FI system has resulted in a highly precise fuel supply, improved engine
response, better fuel economy, and reduced exhaust emissions.
1. Intake air temperature sensor
2. Engine trouble warning light
3. Air induction system solenoid
4. Atmospheric pressure sensor
5. Throttle position sensor (for throttle cable
pulley)
6. Throttle servo motor
7. Throttle position sensor (for throttle valves)
8. Intake funnel servo motor
9. Injector
10.Intake air pressure sensor
11.Fuel pump
12.Lean angle sensor
13.ECU (engine control unit)
14.Starting circuit cut-off relay
15.Speed sensor
16.EXUP servo motor
17.O
2
sensor
18.Crankshaft position sensor
19.Coolant temperature sensor
20.Spark plug
21.Ignition coil
22.Cylinder identification sensor