Features; Outline Of The Fi System - Yamaha WR450FB 2012 Owner's Service Manual

EAS20170

FEATURES

EAS1DX3016

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 me-
ter the fuel through the use of jets have been provided with various auxiliary devices, so that an op-
timum air-fuel ratio can be achieved to accommodate the constant changes in the operating
conditions 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 manner. To ac-
commodate 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. Engine trouble warning light
2. Lean angle sensor
3. Fuel pump
4. Intake air pressure sensor
5. Fuel injector
6. Battery
7. Intake air temperature sensor
8. ECU (engine control unit)
9. Throttle position sensor
10.Coolant temperature sensor
11.Crankshaft position sensor
12.Ignition coil
13.Speed sensor
1-5
FEATURES