Carburetion

1
Carburetion Fuel Injection
2
Functions of Carburetors

• A Mixing Valve
• Mixes Fuel Air
• Meters Fuel Flow
• Atomizes Fuel for Use
• Controls Air Flow
• Engine Speed

3
Ways to Classify Carburetors

• Size (2)
• Air Flow Direction (3)
• Fuel Type (4)
• Barrels (3)
• General (3)

4
(No Transcript)
5
(No Transcript)
6
Carburetor Parts Their Functions

• In 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.

7
Step 1 Air Horn

• Simple Round Metal Tube
• Flange Bolts to Intake Manifold
• Serves as an Air Passage for Air Entering the
  Engine

8
Step 2 Fuel Bowl

• Attached to Air Horn
• Holds a Supply of Gas
• Float Inside Bowl (3)
• Vent (2)

9
Step 3 Main Discharge Tube

• Allows Fuel to be Transfered from the Fuel Bowl
  to the Air Horn.

10
Step 4 The Venturi

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

11
(No Transcript)
12
Step 5 Secondary Venturi

• Creates more vacuum.
• Position (2)
• Multiples the vacuum.
• Booster Venturi
• Some carburetors have a 3rd venturi.

13
Step 6 Air Bleed

• Reduces droplet size
• Introduces a stream of air into the fuel
  traveling up the main discharge tube.
• Smaller droplets carry into the engine properly.

14
Step 7 Jets

• Introduction (1)
• Purpose Operation (4)

15
Step 8 Choke Valve

• Purpose (2)
• Placement (1)
• Operation (2)

16
Step 9 Throttle Valve

• The Engine Will Now Start!
• How will it Run?
• Throttle Butterfly Controls the Engines Speed
  (3)

17
SUCCESS
18
Circuits

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

19
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

20
Small Engine Carburetors

• Types
• Float Type
• Suction Type
• Pulsating Suction Lift Type
• Diaphram Type

21
Float Type Carburetor

• Now Common on Briggs Stratton Engines
• Fuel Bowl Float System (6)

22
Suction Type Carburetor (Vacu-Jet)

• Common in older Briggs Stratton engines.
• Suction tubes pull the fuel up.

23
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.

24
(No Transcript)
25
Diaphram Carburetor

• Has flexible diaphrams (1)
• Allows function at any position
• Popular on 2-cycle engines

26
(No Transcript)
27
Fuel Injection

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

28
Fuel Injection Arrangements

• Direct Fuel Injection
• Throttle Body Fuel Injection
• Multi-Point (Port) Fuel Injection

29
Direct Fuel Injection

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

30
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)

31
Multi-Port (Point) Fuel Injection

• 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
• Chrysler began this in the late 70s, Ford mid
  80s, Chevy Vortex

32
(No Transcript)
33
Methods of Fuel Injection

• Mechanical (2)
• Electronic Fuel Injection (4)
• Advantages (9)

EFI
34
Carburetion Fuel Injection