A carburetor mixes air and fuel for combustion in internal combustion engines. It has several main components including venturis, jets, floats, valves and levers that work together to provide the optimal air-fuel ratio for different engine speeds and loads. There are several types of carburetors including updraft, downdraft and horizontal, as well as constant vacuum, multiple venturi and multi-jet varieties. Common modern carburetor brands discussed include Zenith, Solex and Carter.
6. FUNCTION OF CARBURETOR
Functions of it include,
A. Setting the ratio of air and fuel mixture.
B. Making the mixture into the mist.
C. Increase or decrease the amount of the mixture according to
engine speed and load changing
7. BASIC FORMS OF CARBURETORS
There are three general types of carburetors depending on the
direction of flow of air.
1. UP DRAUGHT CARBURETOR
2. DOWNDRAUGHT CARBURETOR
3. HORIZONTAL CARBURETOR
8. UP DRAUGHT CARBURETOR
The up draught type shown in figure in
which the air enters at the bottom and leaves
at the top so that the direction of its flow is
upwards.
The disadvantage of the up draught carburetor
is that it must lift the sprayed fuel droplet by
air friction.
9. DOWNDRAUGHT CARBURETOR
It is placed at a level higher than the inlet
manifold and in which the air and mixture
generally follow a downward course.
Here the fuel does not have to be lifted by air
friction as in the up draught carburetors but
move into the cylinders by gravity even if the
air velocity is low.
10. HORIZONTAL CARBURETOR
A cross-draught or horizontal carburetor
consists of a horizontal mixing tube with a
float chamber on one side of it figure.
By using across-draught carburetor in
engines, one right-angled turn in the inlet
passage is eliminated and the resistance to
flow is reduced.
11. CONSTANT CHOKE CARBURETOR
• Air and fuel flow area are
always maintained constant.
• But the depression or
difference which causes the
flow of fuel and air to be
maintained as per demand.
• The solex and Zenith
carburetors belong to these
class.
12. CONSTANT VACUUM CARBURETOR
• Its called variable choke
carburetor.
• Air and fuel flow areas are
varied as per demand, vacuum
is constant always same.
• The S.U and Carter carburetors
belong to this class.
13. MULTIPLE VENTURE CARBURETOR
• The boost venture is located concentrically within the main
venture.
• The discharge edge of the boost venture is located at the throat
of the main venture.
• Only fraction of air passes through boost venture.
• This result following:
• High depression is created at the region of nozzle.
• At boost venture throat velocity of air is as high as 200 m/s
• Excellent low speed full throttle operation is possible.
• More efficient mixing of the air and fuel is obtained without
incurring an avveptable reduction in volumetric efficiency.
14. MULTIJET CARBURETORS
• A single barrel carburetor has only one
barrel, whereas a dual carburetor has two
barrels.
• Each of these two barrels has different
fuel jet, choke, throttle, idling system etc.
• Passenger cars with six or more cylinders
are provided with dual carburetors.
• Each venture supplies the air-fuel
mixture to half of cylinders.
15. DIFFERENT MODERN CARBURETORS
There are mainly two type of carburetors.
• Open choke
• Vacuum type.
S.V carburetor are constant venture type.
Zenith, solex, carter and Stromberg
carburetors are constant venture type.
16. TYPES OF DIFFERENT MODERN
CARBURETORS
• Zenith Carburetor
• Solex Carburetor
• Carter Carburetor
17. ZENITH CARBURETOR
• This is the oldest type of carburetor.
• It was used in all automobile engines
before 25 years.
• It consist of all components which basic
carburetor have.
A. Starting jet
B. Main Jet
C. Compensating Jet
D. Float chamber
E. Choke and throttle valve.
18. SOLEX CARBURETOR
• This is most common type of carburetor used
in Fiat and Standard cars.
• It is famous for good and easy starting
• Performance and reliability.
• Its also runs on starting jet for starting
purpose.
• In addition it contains starting jet,
compensating jet and accelerating jet.
19. CARTER CARBURETOR
• It was founded by William Carter.
• Carter Carburetor Company in was
established in 1909, and ceased
operation in 1985.
• A carter carburetor is an American make
carburettor and is used in jeeps. It is a
standard equipment on chevorolet and
Pontiac series of cars.
20. ADVANTAGES OF CARBURETOR
• Carburetor parts are not expensive as that of fuel injectors, especially EFI,
which would give you large savings.
• With the use of carburetor you get more air and fuel mixture.
• In terms of road test, carburetors have more power and precision.
• Carburetors are not restricted by the amount of gas pumped from the fuel tank
which means that cylinders may pull more fuel through the carburetor that
would lead to denser mixture in the chamber and greater power as well.
21. DISADVANTAGES OF CARBURETOR
• At a very low speed, the mixture supplied by a carburetor is so weak that it
will not ignite properly and for its enrichment, at such conditions some
arrangement in the carburetor is required.
• The working of carburetor is affected by changes of atmospheric pressure.
• It gives the proper mixture at only one engine speed and load, therefore,
suitable only for engines running at constant speed increase or decrease.
• More fuels are consumed since carburetors are heavier than fuel injectors.
• More air emissions than fuel injectors.
• Maintenance costs of carburetor is higher than with fuel injection system
