1. Define chassis.

Draw a neat sketch of a conventional chassis and show on it its various

components.

Ans: A chassis is the structural framework of a vehicle that supports all its components, such
as the engine, transmission, axles, wheels, suspension, and body.

2. What do you mean by scavenging ? What are in types ?

Ans: Scavenging is the process of removing exhaust gas from an internal combustion engine's
cylinder and replacing it with fresh air.

There are three type of scavenging system:

Cross flow scavenging.
Loop flow scavenging.
Uni-flow scavenging.
3. Classify fuel injection system of a diesel engine. Draw a layout of common rail injection system and
explain its working.

Ans: The fuel injection system of a diesel engine is a high-pressure system that uses a
centralized fuel pump to supply fuel to the engine's cylinders.

Fuel injection systems in diesel engines are classified into:

1. Air Injection System

2. Directly injects fuel without compressed air.

Subcategories:
a. Individual Pump and Nozzle System
b. Distributor System
c. Common Rail System

Working of Common Rail Injection System-

1. Fuel Supply: Fuel is drawn from the tank by the fuel pump.

2. Pressure Generation: The pump pressurizes the fuel and sends it to the common rail,
maintaining constant high pressure.

3. Storage: The common rail acts as an accumulator, supplying pressurized fuel to the injectors.

4. Injection Control: The ECU controls the injectors to precisely deliver fuel into the combustion
chamber at the right timing and quantity.
4. What is carburetion ? How a carburetor produces various air- fuel mixture and what are
those mixtures? What are the various circuits of a modern carburetor ?

Ans: Carburation is the process of mixing fuel with air to increase the heat potential of a fuel air
mixture.

A carburetor produces various air-fuel mixtures by adjusting the flow of air and fuel
through different circuits within the carburetor, depending on the engine's speed and load.

The main types of mixtures are:

1. Rich Mixture
2. Lean Mixture
3. Stoichiometric Mixture

The various circuits of a modern carburetor are

Idle Circuit, Main Circuit, Accelerator Pump Circuit, Choke Circuit, Power Circuit.

5. State the differences between Hotchkiss drive and Torque tube drive ?

Ans: Hotchkiss drive Torque tube drive

 Open type propeller shaft is used Propeller shaft is housed in a tube

called torque tube.
 Two universal joints is used one Only one universal joint is used at the
at front & second at rear end of the front end of the propeller shaft.
propeller shaft.
 Slip joint is used to accommodate NO slip joint is used
change in length.
 Leaf spring is shackled at the rear Both end of the leaf spring are shackled .
and bracketed at front end.
6. Why valves are necessary in an engine. In which type of engine valves are needed? Explain
overhead poppet valve mechanism with a neat sketch?

Ans: Valves are necessary in an engine to control the flow of air and fuel into the combustion
chamber, and to allow exhaust gases to exit.

Valves are needed in four-stroke engines and two stroke engine.

Overhead Poppet Valve Mechanism-

In the overhead poppet valve mechanism, the valves (intake and exhaust) are located above the
combustion chamber, typically in the cylinder head. These valves are operated by a camshaft,
which is driven by the crankshaft. The camshaft pushes the valve lifters, rocker arms, and push
rods (in some engines), causing the poppet valves to open and close at the correct timing.

Working:

Intake Valve: Opens during the intake stroke, allowing the air-fuel mixture to enter the
cylinder.

Exhaust Valve: Opens during the exhaust stroke to expel the combustion gases.
7. What are the differences between 2-stroke cycle engine and 4- stroke cycle engines.

Ans:
8. State the function of final drive. What are its types ? Discuss briefly each type.

Ans: Final drive's main function is to reduce the speed of the propeller shaft by decreasing
RPMs and increasing the torque.

Types of final drive:

1. Spiral Bevel Final Drive: Uses spiral- cut gears for smoother operation and less noise.
Often used in rear-wheel drive vehicles.

2. Straight Bevel Final Drive: Uses straight- cut gears.

Simple and robust but tends to be noisier compared to spiral bevel drives.

3. Hypoid Gear Type:A type of bevel gear where the axes of the gears do not intersect.
More efficient and quieter than spiral bevel gears, commonly used in automotive applications.

4. Worm Drive Final Drive: Uses a worm gear (a screw-like gear) to transfer power.
Typically used in low-speed applications due to its high torque multiplication and compact
design.

5. Helical Gear Drive: Uses helical gears, which have angled teeth.
Offers smooth and efficient power transfer.

9. How torque is transmitted from steering wheel to front wheel.

Ans: Torque is transmitted from the steering wheel to the front wheels through the following
components:

1. Steering Shaft: The driver applies torque to the steering wheel, which is transferred to the
steering shaft.

2. Steering Gear (Rack and Pinion or Steering Box): The torque from the steering shaft is
converted into linear motion, moving the steering rack or gearbox to steer the front wheels.

3. Tie Rods and Steering Knuckles: The motion from the steering gear is transmitted through tie
rods to the steering knuckles, causing the front wheels to turn in the desired direction.
10. What do you mean by bleeding of brakes? Compare drum type brake with disc type
brake.

Ans: The process of removing air from the hydraulic brake system is called bleeding brake.

11. Why cooling is necessary in an automobile engine and what are the types of cooling
system?

Ans: Cooling is necessary to:

1. Prevent overheating of engine parts, which can lead to damage.
2. Maintain optimal operating temperature for efficient combustion.
3. Prevent thermal stress and distortion of engine components.

The types of cooling system are:

1. Air Cooling System

2. Water Cooling System
3. Liquid cooling system
12. Discuss the construction and working principal of a differential with the help of a neat
sketch.

Ans: A differential is a gear mechanism that allows the wheels of a vehicle to rotate at different
speeds, which is essential for turning.

Construction:

The differential typically consists of the following parts:

1. Pinion Gear: Driven by the driveshaft from the engine.

2. Ring Gear: Connected to the pinion gear, which transmits rotational force.

3. Side Gears: Attached to the axle shafts and transmit power to the wheels.

4. Spider Gears: Small gears that rotate between the side gears and allow them to rotate at
different speeds.

5. Casing: Encloses the gears to keep them lubricated and protect them from debris.

Working Principle of Differential-

1. The pinion gear drives the crown wheel, rotating the differential case.

2. In straight-line motion, the bevel gears remain stationary, and both wheels rotate at the
same speed.

3. During turning, the bevel gears rotate to allow the outer wheel to move faster and the inner
wheel slower, maintaining traction.
13. Describe the clutch commonly used in a passenger cars with a suitable sketch.

Ans: SINGLE PLATE CLUTCH

Single plate clutches are one of the most commonly used types of clutches used in most
modern light vehicles. The clutch helps to transmit torque from the engine to the gearbox input
shaft. As the name states it has only one clutch plate. It consists of a clutch plate, pressure
plate, flywheel, bearings, clutch spring, and nut-bolts arrangement. The single plate clutch has
only one plate which is attached to the splines of the clutch plate. Single plate clutch is one of
the main components of the clutch. The clutch plate is simply a thin metallic disc that has both
side friction surfaces. The flywheel is attached to the engine crankshaft and rotates with it. A
pressure plate is bolted to the flywheel through the clutch spring, which provides the axial force
to keep the clutch plate in engaged position and is free to slide on the clutch shaft when the
clutch pedal is operated. The clutch plate is gripped between the flywheel and the pressure
plate when the clutch is engaged. The friction lining is provided on both sides of the clutch
plate.
14. How does live axle differ from dead axle ?

Ans: Live axle Dead axle

 Transmits power from the engine to Supports the vehicle weight but does
the wheels. not transmit power.
 Found in the drive axle (rear or front in Found in non-driving wheels (usually
case of 4WD). front axle in RWD vehicles).
 Contains differential, shafts, and wheel Simple beam with wheel hubs, no
hubs. moving parts for power transfer.
 Used in driving axles for propulsion. Used in non-driving axles for support
only.

15. Under steering and over steering:

Understeering occurs when a vehicle turns less than the amount intended by the driver. It
typically happens when the front tires lose grip, causing the car to continue straight despite
steering input, making it harder to navigate corners.

Oversteering happens when a vehicle turns more than intended by the driver.It happens when
the rear tires lose grip, causing the rear end of the car to slide out, potentially leading to a spin.

16. Shock Absorber:

A shock absorber is a vehicle's suspension system that helps control the impact and rebound
movement of the vehicle's springs and suspension.

Function:

1. Control Motion: It prevents excessive movement of the springs, reducing bouncing and
swaying.

2. Improve Comfort: Provides a smoother ride by reducing road shocks and vibrations.

3. Safety: Helps maintain tire contact with the road for better control and handling.

17. Davis steering mechanism:

The Davis steering mechanism is a steering gear mechanism that converts the rotary motion of
the steering wheel into angular motion of the front wheels. It consists of the following parts:

1. Slotted links: Attached to the front wheel axle, these links turn on pivots.

2. Cross link: Slides parallel to another link and is connected to the stub axles of the front
wheels by bell crank levers.

3. Sliders: Slide on the arms and are pin jointed to the cross link at its ends.

18. Torsion Bar and stabilizer:

A torsion bar is a type of spring used in the suspension system of vehicles. It works by twisting
along its length when the vehicle encounters bumps or uneven surfaces.

Function: It acts as a spring, storing and releasing energy to absorb shocks.

Advantages : Provides a compact and adjustable suspension solution, often used in heavy-duty
vehicles.

A stabilizer is a component used to reduce body roll during cornering and improve vehicle
stability.

Function: It links the left and right sides of the suspension, transferring forces from one side to
the other to balance the vehicle.

Advantages : Enhances vehicle handling, reduces body roll, and improves safety during sharp
turns.

19. Supercharger:

A supercharger is a mechanical device used to increase the air intake pressure into an internal
combustion engine, thereby enhancing its power output.
Working:
1.A supercharger is typically powered by the engine's crankshaft through a belt, gear, or chain.
2. It forces compressed air into the engine, increasing the air density and improving combustion
efficiency.
3. This leads to more power without the need for larger engine displacement.
Types : 1.Roots Supercharger
2.Centrifugal Supercharger
3.Twin-Screw Supercharger

20. 2-stroke petrol engine

A 2-stroke petrol engine is an internal combustion engine that completes a power cycle (intake,
compression, power, and exhaust) in just two strokes of the piston (one crankshaft revolution).

Working:

1. Compression Stroke: The piston moves up, compressing the fuel-air mixture, and the spark
plug ignites the mixture.

2. Power Stroke: The combustion forces the piston down, while exhaust gases are expelled, and
a fresh fuel-air mixture is drawn in for the next cycle.

Advantages:

1. More power output for the same engine size.

2. Simpler design with fewer components.
3. Lighter and more compact.

Disadvantages:
1.Less fuel efficiency.
2. Higher emissions due to incomplete combustion.

21. Discuss the working of a four-stroke petrol engine with suitable diagram.

Ans: Working of a Four-Stroke Petrol Engine:

A four-stroke petrol engine completes one power cycle in four strokes of the piston (two
revolutions of the crankshaft). The four strokes are:

1. Intake Stroke:
- The intake valve opens, and the piston moves down.
- The air-fuel mixture is drawn into the cylinder from the carburetor or fuel injectors.

2. Compression Stroke:
- The intake valve closes, and the piston moves up.
- The air-fuel mixture is compressed, raising its pressure and temperature.

3. Power Stroke:
- At the top of the compression stroke, the spark plug ignites the compressed fuel-air mixture.
- The combustion pushes the piston down, generating power that turns the crankshaft.

4. Exhaust Stroke:
- The exhaust valve opens, and the piston moves up again.
- The exhaust gases are expelled from the cylinder, preparing it for the next intake stroke.
22. Write the various sections used in a frame along with the suitable types of load each
frame section can carry.

Ans: Sections Used in a Frame and Types of Loads:

1. Chassis Frame (Main Frame):

- Load: Bending Load and Shear Load
2. Cross Members:
- Load: Shear Load and Torsional Load.
3. Longitudinal Members (Side Members):
- Load: Tensile and Compressive Loads
4. Front and Rear Rails:
- Load: Bending and Shear Loads.

23. Draw the theoretical and actual valve timing diagram of 4 stroke otto cycle engines. Show
the valve overlap on the diagram.

Ans: A valve timing diagram serves as a visual depiction that illustrates the precise moments
when the intake and exhaust valves of an engine open and close. The timing of these valve
actions is intricately tied to the movement of the piston as it travels from the top dead center
(TDC) to the bottom dead center (BDC) within the combustion chamber. This crucial
correlation between the piston and valves is established by creating a graphical representation
known as the valve timing diagram. This diagram provides a valuable tool for understanding
and controlling the interplay between the piston and valves, enabling engineers and
technicians to optimize engine performance and efficiency.
24. Briefly explain the working principle of a simple carburetor with the support of a neat
sketch.

Ans: A simple carburetor works by mixing fuel and air in the right proportions to create a
combustible fuel-air mixture for an engine. The carburetor's main working principle is based on
Bernoulli's principle, which states that as the velocity of a fluid increases, its pressure
decreases.
25. Write the differences between dry sump and wet sump lubrication system.

Ans: Dry sump Wet sump

 Oil is stored in a separate tank. Oil is stored in the engine sump itself.
 Uses external pumps to circulate oil. Uses an internal pump for circulation.
 More complex and expensive. Simpler and cost effective.
 Used in high performance and racing Commonly used in passenger vehicles.
engines.

26. Differentiate between battery ignition system and magneto ignition system.

27. What are the functions of frame?

Ans:

1. Vehicle structural integrity

2. The chassis supports the vehicle, providing the structural framework that determines the
collapse or deformation of the vehicle in a collision.
3. Point of attachment for other components
4. It is the attachment point for auto components like the steering system and suspension
system
and its rigidity ensures proper alignment and mounting.
5. It helps in weight distribution.
28. Describe the working of a telescopic shock absorber

Ans: A telescopic shock absorber is a hydraulic device used to dampen vibrations and absorb
shocks in a vehicle's suspension system. It consists of two main components : a cylinder (outer
tube) and a piston rod (inner tube).

Construction:
1.Outer Cylinder: Contains hydraulic fluid.
2. Inner Cylinder: Houses the piston and is connected to the vehicle's suspension.
3. Piston: Moves within the cylinder and has small valves to regulate fluid flow.
4. Hydraulic Fluid: Transfers energy from the piston to dissipate shocks.
5. Seal and Dust Cover: Prevent fluid leakage and protect the piston rod from dirt.

Working:

1. Compression Stroke:
- When the vehicle hits a bump, the piston rod moves down.
- Hydraulic fluid flows from the lower chamber to the upper chamber through small valves in
the piston.
- This flow restricts movement, absorbing energy and damping the shock.

2. Rebound Stroke:
- As the suspension expands, the piston rod moves upward.
- Fluid flows back to the lower chamber, again through restricted valves, controlling the return
movement.

Purpose:
- Damps vibrations caused by uneven road surfaces.
- Maintains tire contact with the road for better stability.
- Enhances comfort and safety during vehicle operation.
29. Describe the working of a master cylinder. What is the advantage of a tandem master
cylinder?

Ans: A master cylinder is a hydraulic device that converts a driver's foot pressure into hydraulic
pressure, which is then used to stop a vehicle:
1. Force conversion
The driver presses the brake pedal, which transmits force to the master cylinder's piston.
2. Hydraulic pressure generation
The piston pushes the brake fluid through the brake lines and into the brake calipers.
3. Braking
The brake calipers apply pressure to the brake pads, which then press against the rotors to slow
or stop the wheels.
4. Cycle completion
As the brake pads press against the rotors, the brake fluid is forced back into the master
cylinder's reservoir, completing the cycle.

Advantages of a Tandem Master Cylinder:

1. Safety: Divides the braking system into two independent circuits (front and rear or diagonal).
If one circuit fails, the other still functions.
2. Improved Reliability: Reduces the risk of complete brake failure.
3. Even Pressure Distribution: Ensures balanced braking performance between the two circuits.
4. Braking efficiency: TMCs are more efficient than single-circuit master cylinders.
5. Brake pressure: TMCs can achieve greater pressure than conventional master cylinders.
6. Compliance with Safety Standards: Meets modern safety regulations for vehicle braking
systems.

30. Draw the mechanical brake system. Show their parts.

Ans:
31. Explain the working of hydraulic brake system with suitable diagram.

Ans: The hydraulic action begins when force is applied to the brake pedal. When driver
presses the brake pedal, the pistons in the master cylinder are activated, causing pressure/
force act on the brake fluid. This force creates pressure in the master cylinder. It serves to
displace hydraulic fluid stored in master cylinder. The master cylinder converts pedal force
into hydraulic pressure to operate the brakes. The master cylinder creates oil pressure and
sent to wheel cylinder via pressurised brake lines. And then starts the brake actuation process.
The actuation of these mechanisms forces the Piston in wheel cylinder get expands due to oil
pressure, brake pads and brake shoes linings expand against the rotors/disc (front wheel) or
drums (rear wheel) and rub on it to stop the wheel so that brake will get apply. When the
brake pedal is released, return springs move the pistons back to their original positions. And
brakes are released.
32. Explain the pressure lubrication system.

Ans: In this system parts are lubricated under pressure. Oil pump takes the oil from the sump
where it stored through a strainer and delivers through a filter to the main oil gallery at a
pressure of 4-8 N/cm2. Oil from the main gallery goes to the main bearings, from where
some of it after lubricating the main bearing, falls back to the sump, some is splashed to the
cylinder walls and remaining goes through a hole to the crank pin. From the crank pin, it goes
to the piston pin through a hole in the connecting rod web, where it lubricates the piston
rings.
A separate oil line is connected from the main gallery to lubricate camshaft and timing gears.
Valve tappets are lubricated by connecting the main oil gallery to the tappet guide surfaces
through drilled holes.
33. Describe battery ignition system.

Ans: The system consists of two circuits, the primary and the secondary circuit. The primary
circuit contains a battery of 6 or 12 volts, ammeter, ignition switch, primary winding of the
ignition coil, contact breaker and condenser. The secondary circuit contains secondary
winding of the ignition coil, distributor and the spark plugs.
Referring to the figure below, when the contact breaker points are in closed position then the
current passing through the primary circuit develops a magnetic field in the ignition coil.
As soon as the contact breaker point are opened by means of cam system, the magnetic field
developed in the ignition coil is collapsed suddenly, thereby producing a high voltage in the
secondary winding. This high voltage is led to the spark plug by means of distributor to
produce spark at the electrodes as per setting of the ignition timing.

34. Define the terms

a. Compression ratio
Ans: The compression ratio is the ratio between the volume of the cylinder and
combustion chamber in an internal combustion engine at their maximum and
minimum values.
b. Valve overlap
Ans: Valve overlap is the period during engine operation when both intake and
exhaust valves are open at the same time. Valve overlap occurs when the piston nears
TDC between the exhaust event and the intake event.
35. What is the functions of the given engine parts
1. Crankshaft
Ans:
1. The crankshaft is essentially the backbone of the internal combustion engine.
2. The crankshaft is responsible for the proper operation of the engine and
converting a linear motion to a rotational motion.
3. Crankshafts should have very high fatigue strength and wear resistance to
ensure long service life.
4. The crankshaft experiences high levels of cyclical loading.
2. Piston rings
Ans:
1. Sealing of the combustion chamber, in order to maintain the pressure of the
combustion gas. The combustion gas must not enter the crankcase, and oil
must not reach the combustion chamber.
2. Transfer of heat built up in the piston to the cylinder surface.
3. Controlling the oil balance, where a minimum of oil is needed on the cylinder
surface to create a hydrodynamic situation, while oil consumption needs to be
kept as low as possible.
3. Fly wheel
Ans: 1. Saving Mechanical Power
2. Connecting Components to the Clutch
3. Balancing the Engine Speed
4. Connecting rod
Ans: 1. The connecting rod creates the link between the piston and crankshaft and
thus transmits power.
2. It converts the linear up and down movement of the piston into the circular motion
of the crankshaft and is therefore subject to tension, compression, bending and
buckling.

36. What is the function of clutch in an automobile?

Ans: The function of a clutch is to engage and disengage the power between the engine and
gearbox.
1. The clutch helps the engine run in a stationary position.
2. It can be used to reduce engine speed.
it enables easy changing of gears.
3. Smooth vehicle control is achieved.
37. Why the differential is needed in automobile ?

Ans: The primary functions of differential are:

1.Distributes power between the wheels.
2. Allows for smooth turns.
3. Prevents wheel slippage.
4. Enhances traction and stability.
5. Reduces stress on tires and drivetrain.
6. Helps improve fuel efficiency.
6. Enhances overall vehicle performance and safety.

38. What are the main components of steering system.

Ans: The components of a steering system which are as follows:

1. Steering wheel
2. Steering column
3. Steering box
4. Pitman Arm
5. Pull & Push rod
6. Steering knuckle arm
7. Tie-rod
8. Tie rod arm
9. King-pin.

39. Distinguish between fuel system in SI and CI engines.

Ans: SI engine CI engine

 The fuel used here is gasoline or petrol. In CI engine the fuel used is diesel.
 The compression ratio is 6 to 9. The compression ratio is high
around 15 to 20.
 Low vibration and noise here. More vibration and noise here.
 SI engine works on the Otto cycle. CI engine works on the diesel cycle.
 Thermal efficiency is low. Thermal efficiency is high.
40. Differentiate clearly between the motion of spring and shock absorber.

Ans: Spring Shock absorber

 The spring supports the vehicle’s weight The shock absorber controls the
and absorbs energy from road bumps. movement of the spring.
 To store and release energy, providing To control the rate of spring
a cushion to the vehicle. Compression and rebound, preventing
excessive bouncing.
 Primarily undergoes compression and Primarily absorbs and dampens the
tension. compression of the spring.
 Provides basic cushioning and prevents Smooths out the ride by preventing
bottoming out. the vehicle from continuing to bounce.

41.