Features; Outline Of Fi System - Yamaha 2009 XP500Y TMAX Service Manual

EAS20170

FEATURES

EAS4B51038

OUTLINE OF FI SYSTEM

The main function of a fuel supply system is to provide fuel to the combustion chamber at the optimum
air-fuel ratio in accordance with the engine operating conditions. In a 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 chamber. Despite the same
volume of intake air, the fuel volume requirement varies with the engine operating conditions, such as
acceleration, deceleration, or operation 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 conditions of the engine.
As the requirements for engines 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 accom-
modate this need, this model has adopted an electronically controlled fuel injection (FI) system in place
of a 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.
Adoption of the FI system has resulted in a highly precise fuel supply, improved engine response, better
fuel economy, and reduced exhaust emissions.
4
3
2
1
1. Ignition coil
2. Air filter case
3. Intake air temperature sensor
4. Battery
5. Fuel injection system relay
6. Lean angle sensor
7. Engine trouble warning light
8. ECU (engine control unit)
9. Intake air pressure sensor
10. Throttle position sensor
11. Fuel injector
12. Fuel tank
13. Fuel hose
7 8
6
5
1-2
14
9
12 13
10
11
14. Fuel pump
15. Catalyst
16. O sensor
2
17. Crankshaft position sensor
18. Coolant temperature sensor
19. Spark plug
FEATURES