Top 33 Automobile Engineering Interview Questions You Must Prepare 14.Jun.2024

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.

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.

Air conditioners are based on the principles of evaporation and condensation and then compression and expion. 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 expion.

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 X 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.

Pitching is a rocking action about a trverse 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.

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.

The basic difference of BS2 and BS3 engines is the presence of catalytic convertor. Catalytic convertor is present in BS3 engine which helps in reducing the formation of HC and CO. While in BS2 engine, no catalytic convertor 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.

When the clutch is not disengaging fully and provides some difficulty in changing the gears then this defect is called clutch drag.

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.

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 trient power fuel control system. In this type of systems constant choke carburetor is used. The salient feature of this carburetor 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.

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 2@Thus gasoline will get very highly compressed and might result in blast off engine.

In case of two stroke engine, rotation of crank shaft will be power stroke for every two rotations. During compression stroke, fuel will flow towards the crank case(suction) and during power stroke, exhaust will emit the burnt fuel through the trfer ports.

While in case of four stroke engine, rotation of crank shaft will be power stroke for every four rotation. Moreover, suction compression power and exhaust strokes are separate as there will be inlet and exhaust valves.

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.

In case of cars the torque is applied to the rear wheels, thus limiting accelerator due to front wheel drive due to weight trfer. 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.

High octane number makes it very good S.I engine fuel
Low engine emissions. Less aldehydes than with methanol

It is a seal in the radiator that maintains the selected pressure in the cooling system when the engine is hot.

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 x B.S.F.C / No. of injectors x duty cycle = lb/hr per injector

cc = lb/hr x 10.5

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.

Independent suspension refers to the mounting of the wheel on a separate axle, so that road shocks affect only the particular wheel.

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.

Three methods of heat trfer are conduction, convection and radiation.

  • Conduction: The trfer of energy by collisions between the atoms and molecules in a material.
  • Convection: Trfers heat when particles move between objects or areas that differ in temperature.
  • Radiation: The trfer of energy by waves.

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 55@Pi is 3.1416 and torque is in pounds-feet, and revolutions are revs per second.

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.

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.

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 slips from the users hands.

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.

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.

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.

Back compression me the compression capability of the engine. An diesel engine can compress at the ratio of 14:1 to as high as 25:@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 ead-gasket lead into crankcase.

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.

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.

Tyres colour 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 colour. 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.

Octane number can be 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.

While cetane number can be 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.