Piston Engine (MIDTERM) 2

Question 1

device that mixes air and fuel for internal combustion engines in a proper
air-fuel ratio for combustion.

Answer 1

Carburetors

Question 2

Each one of the engine’s cylinders should receive the same quantity of fuel/air
mixture and at the same fuel/air ratio.

Answer 2

Carburetors

Question 3

The air measuring unit is the
venturi, which makes use of a
basic law of physics: as the
velocity of a gas or liquid
increases, the pressure
decreases.

Answer 3

Venturi principle

Question 4

Carburetors tyoe

Answer 4

• The float-type and
• The pressure-type.

Question 5

Float type
• Incomplete vaporization
and difficulty in
discharging fuel into some
types of supercharged
systems
• Icing tendency

Pressure type
• Better vaporization and
permits the discharge of
fuel
• Danger of fuel
vaporization icing is
practically eliminated.

Question 6

Characteristics of a float carburetor

Answer 6

• Prone to carburetor icing
• A float carburetor must remain upright or under a positive force of gravity to
properly function.
• Another short coming of the float carburetor involves fuel distribution.

Question 7

The purpose of the inlet
screen is to filter the fuel
and ensure that the fuel that
goes inside the carburetor is
free from dust, dirt and
other harmful components.

Answer 7

Fuel inlet and filtering

Question 8

The ____ maintains the required
amount of gas on the float chamber or float
bowl

Answer 8

Needle valve

Question 9

The purpose of the ____ is to maintain the
proper fuel level within the bowl or float
chamber.

Answer 9

Float mechanism

Question 10

In a carburetor, a small air bleed is bled
into the fuel nozzle slightly below the
fuel level.
• The open end of the air bleed is in the
space behind the venturi wall where the
air is relatively motionless and at
approximately atmospheric pressure.
• low pressure at the tip of the nozzle not
only draws fuel from
• the float chamber but also draws air
from behind the venturi.

Answer 10

Main bleed air

Question 11

With the throttle valve closed at idling
speeds, air velocity through the venturi
is so low that it cannot draw enough
fuel from the main discharge nozzle; in
fact, the spray of fuel may stop
altogether

Answer 11

Idling jet

Question 12

•A separate ____
known as the idle air
bleed, is included as
part of the idling
system. It functions in
the same manner as
the main air bleed

Answer 12

Idle air bleed

Question 13

The primary purpose of the ____ is to tailor the fuel flow to the engine
so that the fuel/air ratio remains suitable for the engine at various altitudes

Answer 13

Mixture control

Question 14

The primary purpose of the ____ is to tailor the fuel flow to the engine
so that the fuel/air ratio remains suitable for the engine at various altitudes

Answer 14

Mixture control

Question 15

Two types of manual mixture control

Answer 15

• Mechanical Mixture Control
• Back-Suction Mixture Control