Carburetor

Feedback Carburetor System (FBC):

The Feedback System controls the air/fuel mixture to about the stoichiometric ratio (14.7:1), reduces emissions and minimizes fuel consumption.

The system is composed of the ignition coil, neutral switch, idle switch, water thermosensor, water temperature switch, intake air thermosensor, oxygen sensor, vacuum sensor, A/C switch as a sensor (input), air/fuel solenoid valve as an actuator (output) and the ECU as a processor.

The ECU controls the opening duration of the air/fuel solenoid valve to maintain the mixture at the stoichiometric air-fuel ratio and be suitable for current driving conditions.

The air/fuel solenoid valve controls the amount of fuel added to the primary main circuit through the solenoid-controlled fuel jet. It also controls the air added to the primary slow circuit through the solenoid-controlled air-bleed.

The ECU controls the Feedback System by utilizing input from various sensors and switches:

1. Ignition coil negative terminal for engine speed.
2. Neutral switch detects in-gear operation.
3. Idle switch detects throttle opening. The switch is "OFF" at idle and "ON" between 1,000 and 1,200 rpm.
4. Water thermosensor detects intake manifold coolant temperature. The switch is "ON" at 15° - 19°C (59° - 66°F) or cooler.
5. Water temperature switch detects radiator coolant temperature.
6. Intake air thermosensor detects intake air temperature. The ECU uses this input to fix the duty of the air/fuel mixture solenoid valve at air temperatures of 67°C (153°F) or higher.
7. Oxygen sensor detects rich/lean condition of exhaust gas.
8. Vacuum sensor detects intake manifold vacuum.
9. A/C switch signals the ECU when turned "ON."