Automobile Engineering Diploma Interview Questions & Answers | EngineerX
Automobile Engineering (Diploma / Polytechnic) Interview Questions & Answers — commonly asked polytechnic diploma interview and campus placement questions with clear, practical answers. Tap any question to open its answer.
Showing the first 50 questions free. The complete 250-question bank is available as a PDF below.
Automobile Engineering — Diploma Interview Q&A
Q1What is Automobile Engineering?
AnswerAutomobile Engineering is a branch of engineering concerned with the design, development, manufacturing, operation, maintenance, testing, and servicing of automobiles and their systems.
Q2What is an automobile?
AnswerAn automobile is a self-propelled road vehicle designed primarily for transporting people, goods, or both from one place to another.
Q3What are the main systems of an automobile?
AnswerThe major systems include the engine or powertrain, transmission, clutch, braking, steering, suspension, electrical/electronic, cooling, lubrication, fuel or energy supply, and exhaust systems.
Q4What is an engine?
AnswerAn engine is a machine that converts the energy available in fuel or another energy source into mechanical power to perform useful work, such as driving a vehicle.
Q5What is the difference between an engine and a motor?
AnswerAn engine generally converts thermal or chemical energy into mechanical energy, while a motor typically converts electrical energy into mechanical energy. In automobiles, the terms are also used more broadly depending on the powertrain.
Q6What are the main types of automobile powertrains?
AnswerAutomobile powertrains include petrol engines, diesel engines, CNG/LPG engines, hybrid powertrains, battery-electric powertrains, and fuel-cell systems. Internal combustion engines can also be classified based on cylinder arrangement, cooling method, and operating cycle.
Q7What is an IC engine?
AnswerIC stands for Internal Combustion. An IC engine is an engine in which fuel combustion takes place inside the engine cylinder or combustion chamber, producing high-pressure gases that generate mechanical power.
Q8What is the difference between a petrol engine and a diesel engine?
AnswerA petrol engine generally uses spark ignition, while a diesel engine uses compression ignition. Diesel engines normally operate at higher compression ratios and inject fuel into highly compressed air.
Q9What is an SI engine?
AnswerSI stands for Spark Ignition. In an SI engine, the air-fuel mixture is ignited by an electric spark produced by a spark plug.
Q10What is a CI engine?
AnswerCI stands for Compression Ignition. In a CI engine, air is highly compressed to raise its temperature, and fuel injected into the hot compressed air ignites without the need for a spark plug.
Q11What is a four-stroke engine?
AnswerA four-stroke engine completes one complete operating cycle in four piston strokes: intake, compression, power, and exhaust. The cycle requires two complete crankshaft revolutions.
Q12What is a two-stroke engine?
AnswerA two-stroke engine completes one operating cycle in two piston strokes, requiring one complete revolution of the crankshaft. It is generally simpler and has a higher power-to-weight ratio than a comparable four-stroke engine.
Q13What are the four strokes of a four-stroke engine?
AnswerThe four strokes are intake or suction, compression, power or expansion, and exhaust. These strokes together complete one operating cycle.
Q14What happens during the intake stroke?
AnswerDuring the intake stroke, the piston moves from TDC toward BDC. The intake valve is open, allowing fresh air or an air-fuel mixture to enter the cylinder depending on the engine type.
Q15What happens during the compression stroke?
AnswerDuring the compression stroke, the piston moves from BDC toward TDC with the valves closed. The charge or air is compressed, increasing its pressure and temperature.
Q16What happens during the power stroke?
AnswerDuring the power stroke, combustion produces high-pressure gases that push the piston from TDC toward BDC. This piston movement is converted into rotary motion by the crankshaft.
Q17What happens during the exhaust stroke?
AnswerDuring the exhaust stroke, the exhaust valve is open and the piston moves from BDC toward TDC, forcing the burnt gases out of the cylinder.
Q18How many revolutions does the crankshaft make during one cycle of a four-stroke engine?
AnswerThe crankshaft makes two complete revolutions, or 720°, during one complete operating cycle of a four-stroke engine.
Q19What is the function of a piston?
AnswerThe piston reciprocates inside the cylinder and receives the force produced by combustion. It transfers this force to the connecting rod and also helps perform the intake, compression, and exhaust processes.
Q20What is a cylinder?
AnswerA cylinder is a precisely machined passage or chamber in which the piston moves. In an IC engine, it forms the main working space where compression and combustion-related processes occur.
Q21What is a connecting rod?
AnswerA connecting rod connects the piston to the crankshaft. It transmits the force from the piston and converts the reciprocating motion of the piston into the rotary motion of the crankshaft.
Q22What is a crankshaft?
AnswerA crankshaft is a rotating engine component that converts the reciprocating motion of the piston into rotary motion. It transmits the generated mechanical power to the flywheel and transmission system.
Q23What is a camshaft?
AnswerA camshaft is a rotating shaft fitted with cams that control the opening and closing of the engine's intake and exhaust valves at the required timing.
Q24What is the function of a flywheel?
AnswerA flywheel stores rotational energy and helps maintain more uniform crankshaft speed by reducing speed fluctuations during the different strokes of the engine.
Q25What is the function of engine valves?
AnswerThe intake valve allows fresh air or air-fuel mixture to enter the cylinder, while the exhaust valve allows burnt gases to leave the cylinder. Their opening and closing are controlled according to engine timing.
Q26What is a spark plug?
AnswerA spark plug is an ignition device used in SI engines. It produces a high-voltage electrical spark inside the combustion chamber to ignite the compressed air-fuel mixture.
Q27Why is a spark plug generally not used in a diesel engine?
AnswerA diesel engine uses compression ignition. Air is compressed to a sufficiently high temperature, and injected diesel fuel ignites when it comes into contact with the hot compressed air.
Q28What is compression ratio?
AnswerCompression ratio is the ratio of the cylinder volume when the piston is at BDC to the clearance volume when the piston is at TDC. It indicates how much the charge or air is compressed.
Q29What is TDC?
AnswerTDC stands for Top Dead Centre. It is the position where the piston reaches its extreme upper position in the cylinder.
Q30What is BDC?
AnswerBDC stands for Bottom Dead Centre. It is the position where the piston reaches its extreme lower position in the cylinder.
Q31What is engine displacement?
AnswerEngine displacement is the total swept volume of all the cylinders in an engine. It is commonly expressed in cubic centimetres (cc) or litres.
Q32What is swept volume?
AnswerSwept volume is the volume displaced by the piston as it moves from TDC to BDC. For a multi-cylinder engine, the total displacement is the sum of the swept volumes of all cylinders.
Q33What is clearance volume?
AnswerClearance volume is the volume remaining above the piston when it is at TDC. It is the minimum volume inside the cylinder during the engine cycle.
Q34What is engine power?
AnswerEngine power is the rate at which the engine performs mechanical work. It is commonly expressed in kilowatts (kW) or horsepower (HP).
Q35What is torque?
AnswerTorque is the turning moment produced by an engine or rotating component. It is the product of force and perpendicular distance from the axis of rotation and is commonly measured in Newton-metres (N·m).
Q36What is the difference between power and torque?
AnswerTorque represents the rotational turning effect, while power represents the rate of doing work. For a rotating shaft, power depends on both torque and rotational speed.
Q37What is RPM?
AnswerRPM stands for Revolutions Per Minute. It indicates the number of complete revolutions made by a rotating component in one minute.
Q38What is the function of a clutch?
AnswerA clutch temporarily connects or disconnects the engine from the transmission. It allows smooth vehicle starting, stopping, and gear changing.
Q39Why is a clutch required in an automobile?
AnswerA clutch is required to disconnect the engine from the gearbox during vehicle starting and gear changes. It also allows the engine and transmission to be connected gradually for smooth power transfer.
Q40What is a gearbox?
AnswerA gearbox is a mechanical transmission unit containing different gear ratios. It changes the speed and torque delivered from the engine to the driving wheels according to vehicle operating conditions.
Q41Why are different gears used in an automobile?
AnswerDifferent gears provide different speed-to-torque ratios. Lower gears provide higher wheel torque for starting and climbing, while higher gears allow efficient cruising at higher vehicle speeds.
Q42What is a transmission system?
AnswerThe transmission system transfers power from the engine or other power source to the driving wheels. It also provides suitable speed, torque, and direction combinations according to driving conditions.
Q43What is a differential?
AnswerA differential is a mechanical device that allows the driving wheels on the same axle to rotate at different speeds while transmitting torque to them.
Q44Why do the wheels rotate at different speeds during a turn?
AnswerDuring a turn, the outer wheel travels a longer distance than the inner wheel. Therefore, the outer wheel must rotate faster than the inner wheel to avoid excessive tyre slip.
Q45What is the function of an axle?
AnswerAn axle supports the vehicle and wheel loads and, in a driven axle, transmits torque to the wheels. Depending on the vehicle design, it may also accommodate differential and other drivetrain components.
Q46What is the braking system?
AnswerThe braking system is a safety-critical system used to reduce vehicle speed or bring the vehicle to a controlled stop. It converts the vehicle's kinetic energy mainly into heat through friction.
Q47What is the difference between a disc brake and a drum brake?
AnswerA disc brake uses a rotating disc and brake pads, while a drum brake uses a rotating drum and brake shoes. Disc brakes generally provide better heat dissipation, while drum brakes can be simpler and economical for certain applications.
Q48What is ABS?
AnswerABS stands for Anti-lock Braking System. It prevents or reduces wheel lock-up during hard braking by automatically modulating brake pressure, helping maintain steering control.
Q49What is the function of a suspension system?
AnswerThe suspension system supports the vehicle body, absorbs road shocks, maintains tyre contact with the road, and contributes to ride comfort, handling, and vehicle stability.
Q50What is the function of the steering system?
AnswerThe steering system allows the driver to control the direction of the vehicle by changing the steering angle of the road wheels. It also helps provide directional stability and controlled manoeuvring.
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