List Of 100 Automobile Interview Questions Part – 2
What is Automobile Engineering?
Automobile Engineering is a branch of engineering which deals with designing, manufacturing and operating automobiles. It is a segment of vehicle engineering which deals with motorcycles, buses, trucks, etc. It includes mechanical, electrical, electronic, software and safety elements.
How will you differentiate between two stroke engine and four stroke engines?
2-stroke piston engine has an intake and an exhaust stroke. All air, fuel, and combustion products must be moved in those 2 strokes. A 4-stroke engine has a separate stroke for moving burned (or burning) and unburned mixtures – intake, compression, expansion, and exhaust. Using 4-stroke results in cleaner emissions at the expense of specific power.
Two stroke: For each explosion in cylinder piston moves downwards and upwards (one complete cycle) (Power stroke and Exhaust stroke).
Four stroke: for each explosion in cylinder piston moves down and upwards twice (two complete cycle) (Intake , compression, power, exhaust stroke.)
Four stroke is highly efficient than two stroke.
But two stroke is powerful than four stroke.
What is the range of engine efficiency in case of two stroke engine?
The two stroke engines have very high range to be compared to the four stroke engines. Because power stroke is generated every two revolution while in four stroke, power stroke is generated every four revolutions.
Definition of Octane number & Cetane number
Octane Number – Octane number is defined as the percentage, by volume, of iso octane in the mixture of iso-octane and h-heptane. It is the measure of rating of SI engine.
Cetane Number – Cetane number is defined as the percentage, by volume, of n-cetane in the mixture of n-cetane and alpha methyl naphthalene. It is the measure of rating of CI engine.
What do you understand by CC of engine?
The meaning of CC is cubic centimeters. It represents the total volume of the engine cylinder. This reflects that the engines with more CC can generate more powers than the other engines. CC can also be related as inversely proportional to the fuel consumption.
If we use gasoline in diesel engine, what will happen?
Adding gasoline to the diesel engine may blast off the engine. Compression ratio of the petrol engine is 6 to 10 and diesel engine is 15 to 22. Thus gasoline will get very highly compressed and might result in blast off engine.
Explain the significance of governor in automobiles?
Governor is an important component of automobile engine. It is used to regulate the main speed of engine during the variations in loads. With the variations in the load, fuel supply has to be maintained. This task is performed by the governor. In the case of high load on the engine, speed decreases, hence fuel supply has to be increased and similarly when load decreases then the fuel supply has to be decreased.
What is the use of hydrogen in automobile?
Low emissions. Essentially no CO or HC in the exhaust as there is no carbon in the fuel. Most exhaust would be H₂O and N₂ Fuel availability. There are a number of different ways of making hydrogen, including electrolysis of water.
What is the use of Natural gas in automobiles?
High octane number makes it very good S.I engine fuel
Low engine emissions. Less aldehydes than with methanol
What is an automotive differential and how does it work?
The automotive differential is designed to drive a pair of wheels while allowing them to rotate at different speeds. In vehicles without a differential, such as karts, both driving wheels are forced to rotate at the same speed, usually on a common axle driven by a simple chain-drive mechanism.
What is the working principle of hydrostatic propulsion system in a tractor?
It depends on Pascal law. As the pressure in the system is the same, the force that the fluid gives to the surroundings is therefore equal to ‘pressure × area’. In such a way, a small piston feels a small force and a large piston feels a large force
What is oil grade SAE stands for?
Answer: “SAE” stands for “SOCIETY OF AUTOMOTIVE ENGINEERS” (USA).
By mixing oil in fuel of four stroke bike will it damage engine, performance? If not than what happen?
Yes, absolutely. It leads to higher wear and tear in cylinder liners, piston and damage of the piston. It even leads to knocking and detonation where abnormal combustion appears and dark smoke and harsh sound will be produced by the engine.
Why are car steering wheels round?
A steering wheel is round so that your hands locate in the same place regardless of the steering wheel’s orientation.
While turning / steering the car it is ergonomically the best design.
Also as design is circle, there are no edges to hit while turning / steering is moving as the circle position remains the same.
From Design view, it should be able to give uniform force i.e. torque, by varying the distance from center will vary the torque provided.
How Trains take turns, though there is no any differential?
Purpose of the differential is to enable vehicles to take turn, by allowing both the wheel to rotate with different speed. This is required when wheels, like in car, are connected with same axle. Interestingly, wheel in trains are not connected with the axle, they are independent and hence can take turns without ant differential. This is same as how the bullock cart takes turns, without any differential.
What is the difference between BS2 & BS3 engine?
IN BS2 there is No catalytic converter to reduce formation of co and HC whereas in BS3 catalytic converter is available to reduce the formation of HC and CO. So less emission of HC and co will take place in BS3
Why big tyre used in rear of Tractors?
Tractors have big rear tires because, the larger the surface area of the tractor’s wheels touching the ground, the more pulling power you have. Like how tractor pullers have large tires.
Another reason is that the tractor doesn’t have to operate at a higher speed to get the same ground speed with larger tires. Gear ratios don’t have to be as high b/c of the larger tires.
What will happen if someone adds oil to the fuel of four stroke bike engine?
This will result in damaging of the engine faster. Adding oil will lead to the higher wear and tear of the cylinder liner, piston and damage to the piston. It will lead to abnormal combustion and knocking and detonation. Dark smoke and abnormal sounds will be generated by the engine. One should not mix oil with the fuel of four stroke engine.
How air conditioners work in cars?
Air conditioners are based on the principles of evaporation and condensation and then compression and expansion. The hot air of the car is removed by the process of evaporation and then the condensation of the evaporated air takes places which is then further compressed by the compressor and then finally expanded to us in the form of cold breeze. Somehow, Air conditioning reduces the average of the car, as the energy is required to remove the hot air and then compression and expansion.
Why entropy decreases with the increase in temperature?
The relation is ds = dQ/T
Entropy is inversely proportional to the temperature so as temperature increases, entropy decreases.
What is SAE? Mention the importance of SAE to the automobile domain.
SAE stands for society of automotive engineers. This society is responsible for developing the standards for the engineering of powered vehicles of all kind. The vehicles may include car, boat, truck and even aircraft. SAE has developed standards for ground vehicles and aerospace vehicles. SAE also encourages students of engineering, technology, science and math’s disciplines. This society has been publishing technical information since 1906.
How does the thermostat work?
When the engine is too cold the thermostat closes the main valve, thus stopping the flow to the radiator. When the engine is too hot, it opens the main valve for normal circulation through the radiator.
Why involute curve used in gear?
It’s smooth to drive the gear.
In gears contact is only point, this type is curve take the more load than normal one
What does it mean when your car emits white smoke?
White smoke is a sign of a coolant leak as is milky brownish oil. This could be due to bad head gasket or cracked block. Burning oil smoke is usually more bluish in color. White smoke is usually associated with a coolant leak, but burning oil can also look like white smoke
What happens if gasoline is used in a Diesel engine? Diesel engine will work?
No, it will not work, as the Compression ratio of Petrol engine is 6 to 10 & that of Diesel engine is 15 to 22. Thus on such high compression, gasoline gets highly compressed & it may blast.
What is the range of the engine efficiency for two stroke engine? Why you don’t see two stroke engines in car? What are problem with two stroke engine?
The range of two stroke engine is too high compare to the four stroke engine because of each revolution one power in two stroke engine. I cannot see the 2 stroke engine in car. Power loss is more.
What is the formula for calculating BHP in SI units?
Boiler horse power (BHP) is a power unit used for measuring the power output of boilers, widely used in the past, but now confined to North America. The boiler horsepower conversion formula is as follows.
1 Boiler Horsepower = 9,809.5 Watts
What is the meaning of CC engine?
CC stands for Cubic centimeter. CC represents the total volume of an engine cylinder. The engine which has more CC can produce more power than others.
Why freezer in the fridge is placed in top level?
Because density of cold air is higher than warm air, hence it is placed at top. Cold air comes downward & cool the bottom part.
Poisons ratio is higher in (rubber/steel/wood)
When a material is compressed in one direction, it usually tends to expand in the other two directions perpendicular to the direction of compression. This phenomenon is called the Poisson effect. Poisson’s ratio is a measure of the Poisson effect.
For rubber = 0.5
For steel = 0.288
For wood < 0.2
Thus Poisson’s ratio is higher in RUBBER.
What type of gears is used in small cars?
A gear in a car is used mainly in the transmission system, the steering system and the differential system. In the transmission system the gears used are helical gears these provide better efficiency, better safety and durability at high speeds, steering system uses rack and pinion type of gear system. While differential uses bevel gears. As the torque is to be transmitted perpendicularly.
How is power generated from fuel?
Fuel generates power by being burned, oxidized is the technical term. In the process of burning, heat is released. The energy of the heat is used to do work. Exactly what kind of work depends on what kind of energy absorbing device the energy is put into.
Steam power can be generated by burning the fuel under a container with water in it and using the steam for some purpose.
What are the different type’s sun gears and planet gears used in differential?
A differential is a particular type of simple planetary gear train that has the property that the angular velocity of its carrier is the average of the angular velocities of its sun and annular gears. This is accomplished by packaging the gear train so it has a fixed carrier train ratio R = -1, which means the gears corresponding to the sun and annular gears are the same size.
This can be done by engaging the planet gears of two identical and coaxial epicyclic gear trains to form a spur gear differential. Another approach is to use bevel gears for the sun and annular gears and a bevel gear as the planet, which is known as a bevel gear differential
What is pan hard rod or track bar?
A pan hard rod is a bar or tube running from one side of the axle to the frame on the other side of the vehicle. It helps the leaf spring in keeping the axle centered under the body during turning a corner.
What is DTSI? Why this technology is used in motor bikes?
DTSI stands for Digital Twin Spark Ignition. This is used to get better combustion in the combustion chamber. In this technique double spark plugs are used to obtain better combustion of fuel in cylinder head. Through this technique fuel is ignited properly. Moreover it provides better efficiency and it is economical in fuel consumption.
What is the reason for emitting the white exhaust smoke during start of the vehicle? How will you prevent this?
The main cause of white smoke is water or anti-freeze entering the cylinder, so the engine starts to burn it with the fuel. That white smoke is nothing but steam.
Prevention measures: There are special gaskets i.e. head gaskets and primary gaskets that prevent the anti-freeze from entering into the cylinder area. This anti-freeze will produce a white steam which will accumulate at the tailpipe area.
What are three methods of heat transfer?
Three methods of heat transfer are conduction, convection and radiation.
Conduction: The transfer of energy by collisions between the atoms and molecules in a material.
Convection: Transfers heat when particles move between objects or areas that differ in temperature.
Radiation: The transfer of energy by waves.
What is BHP? How can you measure BHP?
Answer: BHP is ‘Brake Horsepower’. It reflects the powerfulness of the brakes of the vehicles. BHP stands for how much power will be required to make the engine stop working i.e. to stop the rotation of the engine.
BHP = 2 times pi times torque times revolutions; all this divided by 550.
π (Pi) is 3.1416 and torque is in pounds-feet, and revolutions are revs per second
During the drive torque, what will be the weight shift?
In case of cars the torque is applied to the rear wheels, thus limiting accelerator due to front wheel drive due to weight transfer. This drive is bolted to the chassis of the car. Modern manufacturers therefore design rear wheel drive to have similar handling to front wheel drive wherever possible via suspension tuning.
Explain the reason that why big tyres are used in rear of vehicles.
Large tyres provide larger surface area touching the ground, thus providing the more pulling power. Basically tractors have larger rear tyres because tractors don’t have to operate at higher speeds, thus getting the same ground speed with larger tyres. Moreover gear ratios don’t have to be as high as b/c of the tyres.
When we start a vehicle, exhaust smoke appears white. Why?
When you start, the mixture is rich, and the exhaust will be cold, so any unburned hydrocarbons and water vapor will condense out into a cloudy mist and appear white.
Once the engine is warmed up, the exhaust system gets hot enough that the vapor is invisible.
What is an injector pressure in heavy vehicles? Why it is used?
Injector pressure i s the pressure at which the fuel can be injected into the vehicle. In heavy vehicles, injector pressure is 220 kg/cm square. It is used to set up the standard fuel injection in the vehicles. With the help of injector pressure we can calculate the amount of fuel needed, through the following formula:
Est. Horsepower × B.S.F.C / No. of injectors × duty cycle = lb/hr per injector
cc = lb/hr × 10.5
What is the size of the recommended compressor CFM? Where it can be used?
It is generally used in spray painting of very small areas. It can be used where painting with brush is very difficult. Thus to improve the rate of painting the spray painting is used as this method is very fast and efficient. Usually reciprocating compressors are used but size depends on requirements.
What is a pressure cap in the radiator?
It is a seal in the radiator that maintains the selected pressure in the cooling system when the engine is hot.
How to generate power from differential gear?
Differential Gear comes under the category of Power transmitting mechanisms called Gears. Gears can’t generate power; they can only transmit the power from one source to the receiver.
A Differential Gear has three jobs.
It directs engine power to the wheels. It’s the connecting link between the drive shaft and the wheel axles.
It acts as the final gear reduction in the vehicle, slowing the rotational speed of the transmission before it hits the wheels.
The differential also transmits the power to the wheels while allowing them to rotate at different speeds.
How to calculate bearing number to diameter of the inner and outer?
Divide the shaft diameter size by 5, it will give last two digit of the bearing no. and according to type of load we have to choose the type of bearing and that will give prior no. of the bearing.
Fit is defined as the degree of tightness and looseness between two meeting parts.
What is transverse weight shift due to drive torque?
It is weight of drive torque which is bolted to chassis of the car.
Why tractor rear wheel is big then front wheel?
For maximum torque provide
Does the design & fittings vary on the type of the vehicle engine? Why they use petrol for engines only & vice versa?
No, the type of fitting & design does not vary for automotive segment. It’s the same. However, it’s different in case of aerospace & other sector.
In the fittings, usually of hole/shaft one of those is made at the basic size so that it can accommodate the other one.
What is kingpin offset? State some of its application.
The kingpin offset is the part, basically called as pivot used in the steering of the vehicles. This offset helps in rotating of the steering and thus it’s very useful in steering mechanism of the cars.
Applications: This is also used to measure scrub radius with the help of geometric parameters of wheel plane above and below ground level. It provides directional stability to the vehicles when it i combined with the caster.
Explain the basic difference between BS2 and BS3 engine.
The basic difference of BS2 and BS3 engines is the presence of catalytic converter. Catalytic converter is present in BS3 engine which helps in reducing the formation of HC and CO. While in BS2 engine, no catalytic converter is present which forms HC and CO. Thus in BS3 engine there is no emission of harmful CO and HC. The full form of BS is bharat stage, which is a standard of emission in India.
In a tractor, how the hydrostatic propulsion systems work?
This system is based on Pascal’s law. In a tractor the pressure is same, so the force given by the liquid to the surrounding is equal to the pressure × area. Thus, obeying the Pascal’s law hydrostatic propulsion system is designed, similarly small piston feels small force and the large piston feels larger area.
Explain the reason that why the tyres are always black in color. Is this phenomena related to the heat conduction?
Tyres color is black due to the proportion of carbon mixed in it during the vulcanization of the rubber, to make the tyre shear resistant. Without vulcanization tyres won’t be able to bear the friction heat and stress of the road. Thus carbon is responsible for giving tyres the prominent black color. Adding of carbon prevents tyres from rapidly deteriorating because when ozone combines with the ultraviolet light from the sun. It attacks the polymer of the tyre.
What is back compressor in engines?
Back compression means the compression capability of the engine. A diesel engine can compress at the ratio of 14:1 to as high as 25:1. Thus the higher compression leads to better efficiency of the engine. Thick black smoke is emitted when the engine’s compression is reduced which leads to the deformed head-gasket lead into crankcase.
Why the plastic materials used in the screwdriver’s handles?
Due to non-conducting nature of plastic, it is widely used for the electricity purposes. Moreover, plastic is cheap and strong so it is less prone to damage. Furthermore, plastic does not bend and does not slip from the users hands.
Does diesel engine powered automobile use unit pump and unit injector?
In the case of the engines powered by diesel fuel supply systems, unit pump & unit injector are operated by camshaft & thus pressure of injected fuel depends on engine speed. Whereas, in common rail systems it is independent of engine speed.
What are MPFI and TPFC systems?
MPFI stands for Multi Point Fuel Injection. In this system fuel is injected into the intake ports which is situated just upstream of each cylinder’s intake valve. These systems are sequential systems, in which injection is timed to coincide with intake stroke of each cylinder.
TPFC stands for transient power fuel control system. In this type of systems constant choke carburettor is used. The salient feature of this carburettor is that it provides jerk less engine raise. In these systems, throttle valve creates vacuum which opens the slide which controls the air fuel ratio through a tapered jet.
Why does a compression engine use high octane fuel?
The property of a fuel, which describes how fuel will or will not self-ignite, is called the octane number or just octane. Engines with low compression ratios can use fuels with lower octane number, but high compression engines must use high-octane fuels to avoid self-ignition and knock.
What is pitching in the suspension system?
Pitching is a rocking action about a transverse axis through the vehicle, parallel to the ground. The front suspension moves out of phase with the rear, experiencing the rocking effect due to pitching.
What do you mean by Independent suspension?
Independent suspension refers to the mounting of the wheel on a separate axle, so that road shocks affect only the particular wheel.
What is clutch drag?
When the clutch is not disengaging fully and provides some difficulty in changing the gears then this defect is called clutch drag.
What is the cause of black smoke from the exhaust?
There are various possible causes of black exhaust smoke, almost all of which should let you know that your engine is burning too much fuel. Check all of your vehicle’s intake components, including your air filter, sensors, fuel injectors, and fuel-pressure regulator. One other cause could be a clogged fuel line.
What type gear is used for sun gear?
Most commonly used gears as Sun gears are Spur gears and Helical gears. In some cases Epicyclic Gear trains with Bevel Gears are also used.
Why don’t auto-rickshaws have differential gears?
Auto-Rikshaws have engine directly connected to rare end wheels. There is no need of differential gears.
But some Auto-Rikshaws are not driven by the engine directly instead they use a differential gear. The entire differential mechanism is inside the gearbox unlike other vehicles.
Which type of gears is used in motorcycle gearbox?
Spur gears in sequential arrangement are used inside a gear box of a motorcycle. While chain and sprocket are engaged to transmit power from engine to the rear wheel.
How many differential gears are used in a car?
There is only one differential working in a car, however in a differential 5 bevel gears are used, one is mounted upon the shaft, the 2 are mounted upon the 2 shafts connecting to the rear wheels, the other 2 gears are so arranged so that they mess with the gears upon the wheel shafts.
Which Mechanism is used in Automobile gearing system?
1 hp is how much watt?
Explain Bicycle rear wheel Sprocket working?
Rear wheel sprocket works under the principle of ratchet and pawl.
The Fatigue life of a part can be improved by?
Improving the surface finish by Polishing & providing residual stress by Shot peening.
When crude oil heated Which Hydro carbon comes first?
Natural gas (Gasoline) at 20 degree Celsius
What type of metal is used in a propeller?
Aluminium, stainless steel, magnesium bronze, NIBRAL (nickel, brass, aluminium)
What is more dangerous longitudinal stress or Hoop stress and why?
Hoop stress is more dangerous than longitudinal stress, because the dangerous area coming under the hoop stress is circumferential, while in longitudinal, the axial area will come under dangerous area will be less than circumferential area. So the hoop stress is more dangerous than longitudinal stress.
For the purpose of inflating car tyres, spray painting, etc. i.e. say a small workshop, what size of a compressor (CFM) is recommended? It will be generally for a hobby use and not commercial use?
Spray painting it is generally used for painting in a very smaller area of any part and where it is very hard to paint in a brush and to improve faster rate of painting, spray painting r used. Usually reciprocating compressor r used but size depends upon requirement.
What is king pin offset?
A geometric parameter which is positive if the kingpin axis intersects the wheel plane at or below ground level, or is negative if the point of intersection is above ground level. Also called scrub radius.