Section-A
a) Define idling.
Idling is the condition when the engine runs without driving the vehicle, i.e., the engine is on,
but the vehicle is stationary, and no power is transmitted to the wheels.
b) What are the various advantages of independent suspension systems?
• Better ride comfort
• Improved handling and stability
• Reduces unsprung mass
• Wheels move independently over bumps
• Less stress on chassis
c) Explain the functions of radiator.
• Removes excess heat from engine coolant
• Maintains optimum engine temperature
• Prevents engine overheating
• Ensures continuous engine operation
d) Explain the functions of propeller shaft.
• Transmits torque from gearbox to differential
• Accommodates changes in length due to suspension movement
• Allows angular movement via universal joints
e) Explain the functions of a clutch in the transmission system.
• Engages/disengages engine from transmission
• Allows smooth gear shifting
• Helps in starting/stopping the vehicle without stalling the engine
f) Explain the term weight transfer during braking.
Weight transfer is the shift of vehicle weight from rear to front wheels during braking due to
inertia, increasing load on front wheels and reducing it on rear wheels.
g) What are the causes of stiff steering?
• Low power steering fluid
• Faulty steering rack or pump
• Misaligned wheels
• Worn-out suspension or tires
• Excessive friction in steering components
h) What are the advantages of tubeless tyres?
• Better safety (slow air loss in puncture)
• Reduced weight
• Improved fuel efficiency
• No tube friction
• Can run for short distances even when punctured
i) What are the advantages of anti-lock braking systems (ABS)?
• Prevents wheel lock during braking
• Enhances vehicle control
• Reduces stopping distance on slippery roads
• Improves safety
j) What do you understand by toe-in of front wheels?
Toe-in is the slight inward angle of the front wheels when viewed from above. It improves
straight-line stability and reduces tire wear.
Section-B:
SECTION-B
2. Merits and Demerits of AT, AMT, CVT, DCT/DSG:
Type Merits Demerits
AT (Automatic Transmission) Easy to use, smooth drive Less fuel efficient
AMT (Automated Manual Cost-effective, manual-like
Jerky shifts
Transmission) mileage
CVT (Continuously Variable Smooth acceleration, Rubber-band effect, costly
Transmission) efficient repair
Very quick gear changes, Complex and expensive
DCT/DSG (Dual Clutch)
sporty feel maintenance
3. Tractive Effort and Vehicle Performance Curve:
• Tractive effort is the force available at the wheels to move the vehicle.
• Factors influencing it: engine torque, gear ratio, transmission efficiency, and tire
radius.
• Performance curve plots tractive effort vs. vehicle speed.
• Shows max effort at low speeds, reducing with higher speed due to gear ratios.
4. Preventive Maintenance Schedule for Passenger Car:
Task Frequency
Engine oil check/change Every 5,000–10,000 km
Air filter replacement 15,000–20,000 km
Brake fluid level Monthly
Tire pressure Weekly
Battery electrolyte Monthly
Coolant level Every 3 months
5. Why Multi-Cylinder Engines Over Single Cylinder (Same Displacement):
• Smoother operation: less vibration
• Better cooling: heat distributed among more cylinders
• Higher RPM: improves power output
• Compact design possible
• Better balancing and power strokes
6. Water Cooling System in Diesel Engines:
Main components:
• Radiator
• Water pump
• Thermostat
• Hoses
• Fan
• Coolant
Working:
• Pump circulates coolant through engine
• Heat absorbed is released through radiator
• Thermostat regulates coolant flow based on temperature
SECTION-C
7. Short Notes (Fuel Injection Systems):
a. Individual Pump and Nozzle System:
• Each cylinder has its own pump and injector.
• Accurate but complex.
b. Unit Injector System:
• Combines pump and injector in one unit.
• Placed directly on cylinder head.
• High pressure; better atomization.
c. Common Rail System:
• Single high-pressure rail feeds all injectors.
• Controlled electronically.
• Precise, cleaner combustion.
d. Distributor System:
• One pump distributes fuel to all cylinders.
• Simple but limited precision.
8. a) Construction and Working of Telescopic Shock Absorber (With Diagram):
• Construction: Outer cylinder (reservoir), inner cylinder (working tube), piston, and
valves.
• Working:
o As wheel moves, piston slides in oil-filled tube.
o Fluid is forced through valves creating resistance (damping).
o Converts kinetic energy to heat, absorbs shocks.
8. b) Hotchkiss Drive (With Diagram):
• Rear-wheel-drive system.
• Leaf spring and propeller shaft carry torque and suspension loads.
• Universal joints allow movement.
9. Constant Mesh and Synchromesh Gearbox:
• Constant Mesh Gearbox:
o All gears always in mesh.
o Uses dog clutches for engagement.
o Requires skill to shift.
• Synchromesh Gearbox:
o Uses synchronizers for smooth gear engagement.
o Reduces gear clash.
o Standard in modern cars.
Differences:
Feature Constant Mesh Synchromesh
Gear Engagement Dog clutch Synchronizer
Shifting Smoothness Less More
Used in Trucks, older vehicles Cars, modern vehicles
