carb. fuel injection
TRANSCRIPT
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BY MELODIAS BEN HUR
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Functions of CarburetorsFunctions of Carburetors
• A Mixing ValveA Mixing Valve
• Mixes Fuel & AirMixes Fuel & Air
• Meters Fuel FlowMeters Fuel Flow
• Atomizes Fuel for UseAtomizes Fuel for Use
• Controls Air FlowControls Air Flow
– Engine SpeedEngine Speed
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Ways to Classify CarburetorsWays to Classify Carburetors
• Size: (2)Size: (2)
• Air Flow Direction: (3)Air Flow Direction: (3)
• Fuel Type: (4)Fuel Type: (4)
• Barrels: (3)Barrels: (3)
• General: (3)General: (3)
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Carburetor Parts & Their FunctionsCarburetor Parts & Their Functions
• In order to understandIn order to understand
how each part of ahow each part of a
carburetor works youcarburetor works youshould first build one.should first build one.
• Building a carburetor onBuilding a carburetor on
paper will allow you topaper will allow you tosee how each part workssee how each part works
and why it is needed.and why it is needed.
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Step #1: Air HornStep #1: Air Horn
• Simple RoundSimple Round
Metal TubeMetal Tube
• Flange Bolts toFlange Bolts to
Intake ManifoldIntake Manifold
• Serves as an AirServes as an Air
Passage for AirPassage for Air
Entering the EngineEntering the Engine
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Step #2: Fuel BowlStep #2: Fuel Bowl
• Attached to Air HornAttached to Air Horn
• Holds a Supply ofHolds a Supply of
GasGas• Float Inside Bowl: (3)Float Inside Bowl: (3)
• Vent: (2)Vent: (2)
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Step #3: Main Discharge TubeStep #3: Main Discharge Tube
• Allows Fuel to beAllows Fuel to beTransfered from theTransfered from the
Fuel Bowl to theFuel Bowl to the
Air Horn.Air Horn.
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Step #4: The VenturiStep #4: The Venturi
• A vacuum is neededA vacuum is needed
to transport the fuel.to transport the fuel.
• The engine doesn’tThe engine doesn’tcreate enoughcreate enough
vacuum by itself.vacuum by itself.
• The Venturi increasesThe Venturi increasesair speed: (4)air speed: (4)
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Step #5: Secondary VenturiStep #5: Secondary Venturi
• Creates more vacuum.Creates more vacuum.
• Position: (2)Position: (2)
• Multiples the vacuum.Multiples the vacuum.
• ““Booster Venturi”Booster Venturi”
• Some carburetors haveSome carburetors have
a 3rd venturi.a 3rd venturi.
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Step #6: Air BleedStep #6: Air Bleed
• Reduces droplet sizeReduces droplet size• Introduces a stream of air into the fuel traveling upIntroduces a stream of air into the fuel traveling up
the main discharge tube.the main discharge tube.
• Smaller droplets carry into the engine properly.Smaller droplets carry into the engine properly.
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Step #7: JetsStep #7: Jets
• Introduction: (1)Introduction: (1)
• Purpose &Purpose &
Operation: (4)Operation: (4)
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Step #8: Choke ValveStep #8: Choke Valve
• Purpose: (2)Purpose: (2)
• Placement: (1)Placement: (1)
• Operation: (2)Operation: (2)
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Step #9: Throttle ValveStep #9: Throttle Valve
• The Engine Will NowThe Engine Will Now
Start!Start!
– How will it Run?How will it Run?• Throttle ButterflyThrottle Butterfly
Controls the Engine’sControls the Engine’s
Speed: (3)Speed: (3)
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CircuitsCircuits
• The carburetor is complete but it still farThe carburetor is complete but it still far
from perfect!from perfect!
• What are Circuits?What are Circuits?
• Types of Circuits: (7)Types of Circuits: (7)
• Purpose of Circuits: (1)Purpose of Circuits: (1)
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Engine Problems Kept on TrackEngine Problems Kept on Track
By Circuits:By Circuits:• Idle:Idle:
• Partial Throttle Operation:Partial Throttle Operation:
• High Speed Cruising:High Speed Cruising:
• High Speed Full Power:High Speed Full Power:
• Acceleration Hesitation:Acceleration Hesitation:• Rich Mixture for Cold Starting:Rich Mixture for Cold Starting:
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Small Engine CarburetorsSmall Engine Carburetors
• Types:Types:
– Float TypeFloat Type
– Suction TypeSuction Type
– Pulsating Suction Lift TypePulsating Suction Lift Type
– Diaphram TypeDiaphram Type
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Float Type CarburetorFloat Type Carburetor
• Now CommonNow Common
on Briggs &on Briggs &
Stratton EnginesStratton Engines
• Fuel Bowl &Fuel Bowl &
Float System: (6)Float System: (6)
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Suction Type Carburetor:Suction Type Carburetor: (Vacu-Jet)(Vacu-Jet)
• Common in olderCommon in older
Briggs & StrattonBriggs & Stratton
engines.engines.• Suction tubes pullSuction tubes pull
the fuel up.the fuel up.
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Pulsating Suction Lift Carburetor:Pulsating Suction Lift Carburetor:
(Pulsa-Jet)(Pulsa-Jet)– Briggs & Stratton Pulsa-JetBriggs & Stratton Pulsa-Jet
– Has a fuel pump built in: (1)Has a fuel pump built in: (1)
– Provides more Hp than a suction type: (2)Provides more Hp than a suction type: (2)
– Allows the air tube in the carb. to be larger b/cAllows the air tube in the carb. to be larger b/c
the fuel does not have to be lifted so far.the fuel does not have to be lifted so far.
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Diaphram CarburetorDiaphram Carburetor
– Has flexible diaphrams: (1)Has flexible diaphrams: (1)
– Allows function at any positionAllows function at any position
– Popular on 2-cycle enginesPopular on 2-cycle engines
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Despite all of it’s advances the carburetor is still a compromise of efficiency.Despite all of it’s advances the carburetor is still a compromise of efficiency.
The carburetor’s limitations have pushed the industry towards fuel injectionThe carburetor’s limitations have pushed the industry towards fuel injection.
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Fuel Injection ArrangementsFuel Injection Arrangements
•Direct Fuel Injection:Direct Fuel Injection:
• Throttle Body Fuel Injection:Throttle Body Fuel Injection:
• Multi-Point (Port) Fuel Injection:Multi-Point (Port) Fuel Injection:
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Direct Fuel InjectionDirect Fuel Injection
– Fuel injected directlyFuel injected directlyinto the combustioninto the combustion
chamber.chamber.
– Fuel injector nozzle isFuel injector nozzle is
also located in thealso located in the
combustion chamber.combustion chamber.
– Very common in dieselVery common in diesel
engines.engines.
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Throttle Body Fuel InjectionThrottle Body Fuel Injection
– Injectors are located in theInjectors are located in the
throttle body.throttle body.
– Throttle body is the intakeThrottle body is the intake
cavity or intake manifold.cavity or intake manifold.
– The Carburetor is removedThe Carburetor is removed
from the intake manifold andfrom the intake manifold and
simply replaced by a fuelsimply replaced by a fuel
injection system.injection system.
– Disadvantage: (1)Disadvantage: (1)
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Multi-Port (Point) Fuel InjectionMulti-Port (Point) Fuel Injection
– Uses one injector located:Uses one injector located:
• At the mouth of the intake
valve -or-
• At the mouth of an individualintake port that is connected to
only one intake valve.
– Much more efficientMuch more efficient
– Chrysler began this in theChrysler began this in thelate 70’s, Ford mid 80’s,late 70’s, Ford mid 80’s,
Chevy VortexChevy Vortex
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Methods of Fuel InjectionMethods of Fuel Injection
• Mechanical: (2)Mechanical: (2)
• Electronic Fuel Injection: (4)Electronic Fuel Injection: (4)
– Advantages: (9)Advantages: (9)
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