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Carb. Fuel Inj

Carb. Fuel Inj - QuickTimeª and a GIF decompressor are...

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Unformatted text preview: QuickTimeª and a GIF decompressor are needed to see this picture. Functions of Carburetors Functions • • • • • A Mixing Valve Mixes Fuel & Air Meters Fuel Flow Atomizes Fuel for Use Controls Air Flow – Engine Speed Ways to Classify Carburetors Ways • • • • • Size: (2) Air Flow Direction: (3) Fuel Type: (4) Barrels: (3) General: (3) QuickTimeª and a GIF decompressorpicture. are needed to see this Carburetor Parts & Their Functions Carburetor • In order to understand In how each part of a carburetor works you should first build one. should • Building a carburetor Building on paper will allow you to see how each part works and why it is needed. needed. Step #1: Air Horn Step • Simple Round Simple Metal Tube Metal • Flange Bolts to Flange Intake Manifold Intake • Serves as an Air Serves Passage for Air Entering the Engine Entering Step #2: Fuel Bowl Step • Attached to Air Horn • Holds a Supply of Holds Gas Gas • Float Inside Bowl: (3) • Vent: (2) Step #3: Main Discharge Tube Step • Allows Fuel to be Allows Transfered from the Fuel Bowl to the Air Horn. Air Step #4: The Venturi Step • A vacuum is needed vacuum to transport the fuel. to • The engine doesn’t The create enough vacuum by itself. vacuum • The Venturi increases The air speed: (4) air Step #5: Secondary Venturi Step • • • • • Creates more vacuum. Position: (2) Multiples the vacuum. “Booster Venturi” Some carburetors have Some a 3rd venturi. 3rd Step #6: Air Bleed Step • Reduces droplet size • Introduces a stream of air into the fuel traveling Introduces up the main discharge tube. up • Smaller droplets carry into the engine properly. Step #7: Jets Step • Introduction: (1) • Purpose & Purpose Operation: (4) Operation: Step #8: Choke Valve Step • • • Purpose: (2) Placement: (1) Operation: (2) Step #9: Throttle Valve Step • The Engine Will Now The Start! Start! – How will it Run? • Throttle Butterfly Throttle Controls the Engine’s Speed: (3) Speed: Circuits Circuits • The carburetor is complete but it still far The from perfect! from • What are Circuits? • Types of Circuits: (7) • Purpose of Circuits: (1) Engine Problems Kept on Track By Circuits: By • • • • • • Idle: Partial Throttle Operation: QuickTimeª and a GIF decompressor High Speed Cruising: are needed to see this picture. High Speed Full Power: Acceleration Hesitation: Rich Mixture for Cold Starting: Small Engine Carburetors Small • Types: Types: – – – – Float Type Suction Type Pulsating Suction Lift Type Diaphram Type Float Type Carburetor Float • Now Common Now on Briggs & Stratton Engines Stratton • Fuel Bowl & Float System: (6) Float Suction Type Carburetor: (Vacu-Jet) (Vacu-Jet) • Common in older Common Briggs & Stratton engines. • Suction tubes pull Suction the fuel up. the Pulsating Suction Lift Carburetor: Pulsating (Pulsa-Jet) – – – – Briggs & Stratton Pulsa-Jet Has a fuel pump built in: (1) Has 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. the Diaphram Carburetor Diaphram – – – Has flexible diaphrams: (1) Has Allows function at any position Allows Popular on 2-cycle engines Despite all of it’s advances the carburetor is still a compromise of efficiency. Despite The carburetor’s limitations have pushed the industry towards fuel injection . Fuel Injection Arrangements Fuel • • • Direct Fuel Injection: Throttle Body Fuel Injection: Multi-Point (Port) Fuel Injection: Direct Fuel Injection Direct – Fuel injected directly Fuel into the combustion chamber. chamber. – Fuel injector nozzle is also located in the combustion chamber. combustion – Very common in diesel Very engines. engines. Throttle Body Fuel Injection Throttle – Injectors are located in the throttle body. throttle – Throttle body is the intake Throttle cavity or intake manifold. cavity – The Carburetor is removed from the intake manifold and simply replaced by a fuel injection system. injection – Disadvantage: (1) Multi-Port (Point) Fuel Injection Multi-Port – Uses 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 efficient Much – Chrysler began this in the Chrysler late 70’s, Ford mid 80’s, Chevy Vortex Chevy Methods of Fuel Injection Methods • Mechanical: (2) • Electronic Fuel Injection: (4) – Advantages: (9) ...
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