Yamaha XVS950CU 2014, Service Manual

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FEATURES
1-2
EAS20170
FEATURES
EAS5S71022
OUTLINE OF THE 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 and the atmospheric temperature. 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 con-
ditions, 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 conditions of the en-
gine.
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 accom-
modate 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.
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1. Intake air temperature sensor
2. Engine trouble warning light
3. Intake air pressure sensor
4. Rear cylinder ignition coil
5. Front cylinder ignition coil
6. Injectors
7. Throttle position sensor
8. Spark plug
9. Relay unit (fuel pump relay)
10. ECU (engine control unit)
11. Lean angle sensor
12. Rear wheel sensor (for ABS models)
13. Speed sensor (except for ABS models) 14. O
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sensor
15. ISC (idle speed control) unit
16. Crankshaft position sensor
17. Engine temperature sensor
18. Fuel pump