Sym Fiddle III 50 Service Manual page 123

4. ELECTRONICALLY CONTROLLED CARBURETOR SYSTEM
ECS(Electronically controlled carburetor system) Introduction
The closed-loop electronically controlled carburetor system is mainly to solve the motorcycle pollutant
emissions, reduce fuel consumption and improve performance. Transplant electronic fuel injection control
principle to carburetor, accurate control fuel air-fuel ratio and engine ignition. It satisfies the requirement
of new emission standard, it is one of the new engine fuel system technology.
Electronically controlled carburetor system is controlled by PWM signal and electromagnetic valve,
carburetor main oil system and idle oil system for real-time fill gas, to realize precision control of air-fuel
ratio.
In a closed loop system, oxygen sensor feedback signal is used to adjust PWM so as to make the air-fuel
ratio return to theory state.
After control the air-fuel ratio and ignition advance, we can use different control strategies to reduce
emissions and improve driving performance.
Electronically controlled carburetor system working principle
1. Electronically controlled carburetor
Use one or two by the ECU to control the duty ratio of magnetic air compensating valve, installed in the
carburetor idle air beside of the tao and/or main air ventilation road,
By examining the operation condition of the engine (such as engine speed, the carburetor throttle
opening, engine temperature, oxygen sensor feedback, etc.) and need to set and quantitatively fill gas for
carburetor idle air way.
So as to realize to control the air-fuel ratio and the mixture of secondary atomization. Electronic air
compensating valve on the air and fuel mixture, through accurate air-fuel ratio adjustment can indirectly
control the rate of fuel supply.
It is control solenoid valve solenoid type, driven by 10 hz frequency PWM signals. The duty ratio control
of electromagnetic valve to ensure the air into the linear measurement, so as to control the gas.
And it has allowed a wide range of air-fuel ratio and fast response, high accuracy of air-fuel ratio
control.
2. Signal input, TPS (throttle position sensor) on the carburetor with TPS sensor, for more advanced
control strategy.
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SYM