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CARBURETOR CIRCUITS AND COMPONENTS CBC AUTOMOTIVE TECHNOLOGY Slide 2 BASIC CARB DESIGN Conventional Design Computer Control for Better Fuel Metering 1,2,3,4 barrel carbs Slide 3 CARBURETOR SYSTEMS FLOAT SYSTEMS Float Material Maintains Level Float setting Viton Needle and Seat Dampening Spring Float Bowl Construction Float Drop Pg 7 Slide 4 FLOAT BOWL VENT Vented to outside atmosphere Vapor Seperator Mechanical Vent Dirty air filters affect pressure in bowl Usually located near center of bowl Slide 5 IDLE SYSTEM Not enough airflow at idle to allow main system to operate Manifold vacuum is high to draw fuel out idle ports Usually adjustable Idle air bleed helps atomize fuel and prevents siphoning Pg 8 Slide 6 TRANSFER CIRCUIT Transfers fuel off in Off idle mode Adds fuel to mixture as throttle plate opens to cover sag Pg 8 Slide 7 MAIN SYSTEM Fuel supplied by main jets Operates under high venturi vacuum Atmospheric Pressure pushes fuel out discharge nozzel Slide 8 ACCELERATOR PUMP SYSTEM Slide 9 HOT IDLE COMPENSATOR Allows mixture to be lean out during hot idle conditions caused by excessive fuel vapor Slide 10 CHOKE TYPES Automatic Chokes Manual Hot Air Electric Integeral Choke Divorced Choke Slide 11 CHOKE SYSTEM Operates when cold and low rpm Sometimes fuel extracted from air bleed holes Allows 5:1 mixture Vacuum Break or Choke Pull Off Pg 10 Slide 12 CHOKE SYSTEM Slide 13 CHOKE COIL OPERATION Slide 14 CHOKE PULLOFF Forces the choke open slightly just after engine starts. Position determined by torque of coil air velocity on blade vacuum on piston must adjust correctly! Slide 15 POWER CIRCUITS Mechanical Power Valve Adjustable Sometimes combination with metering rods Flows through a circuit into main metering system Slide 16 VACUUM POWER VALVE Different locations on carbs. Usually in bowl area. Supplies Extra fuel under heavy loads Operated by Manifold Vacuum Pg 8 Slide 17 BAROMETRIC PRESSURE COMPENSATOR Compensates for altitude Fairly troublefree Slide 18 THROTTLE POSITION SENSOR Slide 19 IDLE SPEED CONTROL Slide 20 A/C IDLE SOLENOID Used with A/C Compensates for drag on engine caused by Compressor Adjustment is usually seperate from Curb Idle rpm. Slide 21 TYPES OF CARBURETORS Slide 22 TERMINOLOGY Emulsion Float Circuit Lean Metering Metering Rod Power Valve Rich Stoichiometric ratio Throttle Kicker Throttle stop solenoid Transfer slot Vaporization variable venturi Venturi Air Bleed