A carburetor performs this function mechanically; relying on differences in air pressure inside the carburetor to regulate fuel flow. EFI (Electronic Fuel Injection) performs this function electronically using computer-controlled fuel injectors to admit pressurized fuel as required by throttle position.

1. A SIMPLE OR
ELEMENTRARY
CARBURETOR / EFI
SYSTEM
Basic Automobile
Technology
ENT 2242
Group 09

2. What is Carburetor and
How its Work ?

3. A carburetor is a device that mixes fuel
and air together and delivers the
mixture to the intake manifold of an
internal combustion engine.
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4. MAIN PARTS
OF
CARBURATOR
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5. ▸ A float chamber is a device for automatically regulating
the supply of a liquid to a system.
▸ It is most typically found in the carburettor of an
internal combustion engine, where it automatically
meters the fuel supply to the engine.
FLOAT CHAMBER
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6. ▸ Fixed venturi
▹ Fixed venturi is used to varying the air velocity, as
the venturi alters the fuel flow.
▸ Variable venturi
▹ Variable venturi is used to inject the fuel jet that
primarily differs by the slide.
▹ The needle and the slide must be directly controlled
with the help of the throttle position
Venturi
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7. VENTURI
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8. TROTTLE VALVE
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• A throttle is the mechanism by which fluid flow is
managed by the constriction or obstruction.
• An engine's power can be increased or decreased by the
restriction of inlet gases (by the use of a throttle), but
usually decreased.
• The term throttle has come to refer, informally, to any
mechanism by which the power or speed of an engine
is regulated, such as a car's accelerator pedal.

9. Choke valve
▸ In an internal combustion engine, a choke valve
modifies the air pressure in the intake manifold,
thereby altering the ratio of fuel and air quantity
entering the engine.
▸ Choke valves are generally used in naturally aspirated
engines with carburetors to supply a richer fuel
mixture when starting the engine
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10. 10

11. “▸ Provides an air-fuel mixture for
cruising or normal range at A single
speed.
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SIMPLE OR ELEMENTARY
CARBURETTOR

12. “
12
COMPLETE
CARBURETTOR

13. “
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Main Metering System

14. “
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IDLING SYSTEM System
• At idle there is not
sufficient air flow to draw
gasoline from the fuel bowl
into the main air venturi.
When air flows through a
restriction, a low pressure
is effected which draws
fuel into the venturi to mix
with the air. At idle there is
insufficient air flow to draw
fuel into the venturi.

15. “
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POWER ENRICHMENT BY
ECONOMISER SYSTEM
A carburetor or fuel
injection system for a
reciprocating engine that
enriches the fuel-air mixture
when the engine is operating
at high power settings.

16. “
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ACCELERATION PUMP SYSTEM
The accelerator pump is
responsible for providing the
momentary additional fuel
needed under heavy
acceleration conditions.
When the pedal is suddenly
pressed, the throttle will
suddenly open, immediately
adding additional air for
additional power

17. “
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CHOKE
During cold starting
period, at low cranking
speed and before the
engine has warmed up, a
mixture much richer
than usual mixtures
(almost 5 to 10 times
more fuel) must be
supplied

18. Natural draft carburettor
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TYPES OF CABURATOR ?
Updraft carburetor
Downdraft carburetor
Float type carburetor

19. 19
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.

20. 20
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.

21. “
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ELECTRONIC
FUEL INJECTOR
SYSTEM

22. What is EFI system?

23. 23

24. “▸ The ECU determines precisely how much fuel
needs to be delivered by the injector based on the
engine SENSORS output. Injector is turned On for
the precise amount of time to deliver proper
air/fuel ratio to the engine.
▸ This system consist of the,
▸ ❖ Electronic Control Unit (ECU),
▸ ❖ Various engine SENSORS,
▸ ❖ Fuel injector assemblies, and related wiring
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Basic Operation of EFI System ?

25. “Demerits of electronic fuel
injection (EFI) system
▸ High maintenance cost.
▸ Difficulty in servicing.
▸ Possibility of malfunction of
some sensors
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26. DIFFERENT BETWEEN CARBURETOR
AND FUEL INJECTION
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CARBURETOR
• The air and fuel(petrol) enters the carburetor
through separate ports assigned for them.
• If undisturbed, they get mixed inside the carburetor
at stoichiometric ratio can get rich mixture by
opening the choke valve.
• After mixing, the air-fuel mixture enters the
cylinder through inlet valve during suction stroke.

27. DIFFERENT BETWEEN CARBURETOR
AND FUEL INJECTION
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Fuel Injector
• The fuel injection system consists of a fuel injector
(nozzle) whose operation is controlled by electric circuits
through sensors. The Electronic Control Unit (ECU) is used
for the control.
• The air from the air filter enters the cylinder through inlet
valve during suction stroke.
• The fuel injection begins at the end of compression
stroke.
• The fuel is sprayed like moist.
• Due to atomization, the air and fuel get mixed inside the
cylinder.

28. THANKS!
Any questions?
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