REVISION MECHANICAL - 2-06-2025

By WINCENTRE CLASSES

Multiple Choice

Low octane number in petrol may cause:

• Slow combustion
• Detonation/knocking
• Better mileage
• Lower emissions

Explanation Slide...

Low octane fuels can cause detonation or knocking.

Multiple Choice

Which component in a carburetor maintains the fuel level constant?

• Venturi
• Float chamber
• Main jet
• Choke

Explanation Slide...

The float chamber uses a float and needle valve to maintain a steady fuel level in the carburetor.

Multiple Choice

The purpose of the venturi in a carburetor is to:

• Filter the air
• Increase fuel pressure
• Decrease air velocity
• Create suction to draw fuel

Explanation Slide...

The venturi causes low pressure due to high air velocity, drawing fuel into the airstream from the jet.

Multiple Choice

The choke in a carburetor is used to:

• Stop the engine
• Lean the mixture
• Enrich the fuel-air mixture during starting
• Control throttle

Explanation Slide...

Choke enriches the air-fuel mixture by restricting air during engine start-up, especially in cold conditions.

Multiple Choice

The part of the carburetor that controls engine speed is:

• Choke valve
• Float
• Venturi
• Throttle valve

Explanation Slide...

The throttle valve adjusts the air-fuel flow into the engine, controlling power and speed.

Multiple Choice

The .......... Number is an

important factor in determining the quality of diesel fuel

• Octane

• Cetane

• Cracking

• Combustion

Multiple Choice

Valve is closed when the spring is ________

• compressed

• released

Fill in the Blanks

Multiple Choice

What is number 5 pointing to?

• choke

• throttle

• fuel

• air / fuel mixture

Multiple Choice

The Chemically Correct Mixture (CCM) ratio of Fuel to AIr is

• 1:15

• 15:1

• 12:1

• 1:12

Multiple Choice

How many degrees of rotation does the crankshaft rotate to complete all the 4 stroke engine cycle.

• 180
• 360 
• 540
• 720

Multiple Choice

Mixture requirements during starting of SI engine is

• Rich

• Lean

• Stoichiometry

• Best power

Multiple Choice

A 150 cc engine has following parameter as 150 cc

• fuel tank capacity

• swept volume

• cylinder volume

• clearance volume.

Multiple Choice

Which of the following is not an internal combustion engine?

• 2-stroke petrol engine

• 4-stroke petrol engine

• diesel engine

• steam turbine

Multiple Choice

A stoichiometric air fuel ratio is

• chemically correct mixture

• lean mixture

• rich mixture for idling

• rich mixture for over loads

Multiple Choice

Octane number of iso-octane is:

• 0
• 50
• 100
• 150

Explanation Slide...

Iso-octane is the reference fuel with an octane number of 100.

Multiple Choice

Cetane number of cetane is:

• 0
• 50
• 100
• 150

Explanation Slide...

Cetane (hexadecane) is the reference fuel with a cetane number of 100.

Multiple Choice

Fuel with a high cetane number has:

• Higher ignition delay
• Lower ignition delay
• High knocking
• More smoke

Explanation Slide...

High cetane number leads to shorter ignition delay and smooth operation.

Multiple Choice

Cetane number is a measure of:

• Knock resistance of diesel
• Fuel calorific value
• Flash point
• Lubricating ability

Explanation Slide...

Cetane number indicates ignition quality of diesel fuel.