Carb. Fuel Inj_2

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Carb. Fuel Inj_2 PPT

Transcript of Carb. Fuel Inj_2

  • Functions of CarburetorsA Mixing ValveMixes Fuel & AirMeters Fuel FlowAtomizes Fuel for UseControls Air FlowEngine Speed

  • Ways to Classify CarburetorsSize: (2)Air Flow Direction: (3)Fuel Type: (4)Barrels: (3)General: (3)

  • Carburetor Parts & Their FunctionsIn order to understand how each part of a carburetor works you should first build one.Building a carburetor on paper will allow you to see how each part works and why it is needed.

  • Step #1: Air HornSimple Round Metal TubeFlange Bolts to Intake ManifoldServes as an Air Passage for Air Entering the Engine

  • Step #2: Fuel BowlAttached to Air HornHolds a Supply of GasFloat Inside Bowl: (3)Vent: (2)

  • Step #3: Main Discharge TubeAllows Fuel to be Transfered from the Fuel Bowl to the Air Horn.

  • Step #4: The VenturiA vacuum is needed to transport the fuel.The engine doesnt create enough vacuum by itself.The Venturi increases air speed: (4)

  • Step #5: Secondary VenturiCreates more vacuum.Position: (2)Multiples the vacuum.Booster VenturiSome carburetors have a 3rd venturi.

  • Step #6: Air BleedReduces droplet sizeIntroduces a stream of air into the fuel traveling up the main discharge tube.Smaller droplets carry into the engine properly.

  • Step #7: JetsIntroduction: (1)Purpose & Operation: (4)

  • Step #8: Choke ValvePurpose: (2)Placement: (1)Operation: (2)

  • Step #9: Throttle ValveThe Engine Will Now Start!How will it Run?Throttle Butterfly Controls the Engines Speed: (3)

  • CircuitsThe carburetor is complete but it still far from perfect!What are Circuits?Types of Circuits: (7)Purpose of Circuits: (1)

  • Engine Problems Kept on Track By Circuits:Idle:Partial Throttle Operation:High Speed Cruising:High Speed Full Power:Acceleration Hesitation:Rich Mixture for Cold Starting:

  • Small Engine CarburetorsTypes: Float TypeSuction TypePulsating Suction Lift TypeDiaphram Type

  • Float Type CarburetorNow Common on Briggs & Stratton Engines Fuel Bowl & Float System: (6)

  • Suction Type Carburetor: (Vacu-Jet)Common in older Briggs & Stratton engines. Suction tubes pull the fuel up.

  • Pulsating Suction Lift Carburetor:(Pulsa-Jet)Briggs & Stratton Pulsa-Jet Has a fuel pump built in: (1)Provides more Hp than a suction type: (2) Allows the air tube in the carb. to be larger b/c the fuel does not have to be lifted so far.

  • Diaphram Carburetor Has flexible diaphrams: (1) Allows function at any positionPopular on 2-cycle engines

  • Despite all of its advances the carburetor is still a compromise of efficiency.The carburetors limitations have pushed the industry towards fuel injection.

  • Fuel Injection ArrangementsDirect Fuel Injection:Throttle Body Fuel Injection:Multi-Point (Port) Fuel Injection:

  • Direct Fuel InjectionFuel injected directly into the combustion chamber. Fuel injector nozzle is also located in the combustion chamber.Very common in diesel engines.

  • Throttle Body Fuel Injection Injectors are located in the throttle body.Throttle body is the intake cavity or intake manifold. The Carburetor is removed from the intake manifold and simply replaced by a fuel injection system.Disadvantage: (1)

  • Multi-Port (Point) Fuel InjectionUses one injector located: At the mouth of the intake valve -or- At the mouth of an individual intake port that is connected to only one intake valve. Much more efficientChrysler began this in the late 70s, Ford mid 80s, Chevy Vortex

  • Methods of Fuel InjectionMechanical: (2)Electronic Fuel Injection: (4)Advantages: (9)