Air By-Pass Valve; Fuel Injector; Fuel Pump - Sym Joyride 125 Service Manual

Air By-pass Valve

Description:
ECU receives all sensors' signals to control the throttle valve openness with PWM, and adjust
airflow through the by-pass valve of the intake manifold. It can adjust idle speed for a stably
running engine.
1. When engine cold starting---the by-pass valve open for a while to increase airflow and to
stabilize engine idle speed within initial starting
2. Warm-up---when engine oil is in low temperature condition, the by-pass valve adjusts airflow
according to engine temperature (engine oil temperature), and raises idle speed.
3. Speed decreasing--- ECU controls the by-pass valve in correspondence with throttle
operation, to provide inlet pipe with proper airflow quantity. Such operation will smooth the
engine rpm reduction process, preventing the engine from stalling, excessive negative
pressure, and also reduce HC emission.

Fuel Injector

The double-hole injector provides each intake valve a fuel jet. This can reduce the pollution of
HC. The shortened version of fuel pump plate makes its size more compact, and sturdier against
shocks. ECU signal controls the regulator to maintain 2.5 bars between the fuel pressure and
the air pressure of inlet pipe. Through controlling the time length of injection under steady fuel
pressure, the system can optimize the fuel injection quantity according to different engine
workloads.

Fuel Pump

Electrical fuel pump is mounted inside the fuel tank. The power source is DC current provided
and controlled by ECU; the pump can provide 14L/hour under the pressure of 2.5 bars.
To this chapter contents
5
. Fuel Injection System
5-19