CARBURETOR CIRCUITS AND COMPONENTS

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CARBURETOR CIRCUITS AND COMPONENTS

• CBC AUTOMOTIVE TECHNOLOGY

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BASIC CARB DESIGN

• Conventional Design
• Computer Control for Better Fuel Metering
• 1,2,3,4 barrel carbs

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CARBURETOR SYSTEMS
Pg 7

• FLOAT SYSTEMS
• Float Material
• Maintains Level
• Float setting
• Viton Needle and Seat
• Dampening Spring
• Float Bowl Construction
• Float Drop

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FLOAT BOWL VENT

• Vented to outside atmosphere
• Vapor Seperator
• Mechanical Vent
• Dirty air filters affect pressure in bowl
• Usually located near center of bowl

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IDLE SYSTEM
Pg 8

• 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

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TRANSFER CIRCUIT
Pg 8

• Transfers fuel off in Off idle mode
• Adds fuel to mixture as throttle plate opens to
  cover sag

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MAIN SYSTEM

• Fuel supplied by main jets
• Operates under high venturi vacuum
• Atmospheric Pressure pushes fuel out discharge
  nozzel

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ACCELERATOR PUMP SYSTEM
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HOT IDLE COMPENSATOR

• Allows mixture to be lean out during hot idle
  conditions caused by excessive fuel vapor

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CHOKE TYPES

• Automatic Chokes
• Manual Hot Air
• Electric
• Integeral Choke
• Divorced Choke

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CHOKE SYSTEM
Pg 10

• Operates when cold and low rpm
• Sometimes fuel extracted from air bleed holes
• Allows 51 mixture
• Vacuum Break or Choke Pull Off

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CHOKE SYSTEM
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CHOKE COIL OPERATION
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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!

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POWER CIRCUITS

• Mechanical Power Valve
• Adjustable
• Sometimes combination with metering rods
• Flows through a circuit into main metering system

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VACUUM POWER VALVE
Pg 8

• Different locations on carbs. Usually in bowl
  area.
• Supplies Extra fuel under heavy loads
• Operated by Manifold Vacuum

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BAROMETRIC PRESSURE COMPENSATOR

• Compensates for altitude
• Fairly troublefree

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THROTTLE POSITION SENSOR
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IDLE SPEED CONTROL
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A/C IDLE SOLENOID

• Used with A/C
• Compensates for drag on engine caused by
  Compressor
• Adjustment is usually seperate from Curb Idle rpm.

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TYPES OF CARBURETORS
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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