Automobile Engineering — Part 2 MCQs with Explanations

The self ignition temperature of Diesel as compared to petrol is lower

Highest Useful Compression Ratio (HUCR) is the compression ratio at which a fuel can be used without detonation in a specified test engine under specified operating condition and the ignition and mixture strength being adjusted to give best efficiency

When the battery is half (50%) charged, the specific gravity of acid in a battery is usually 1.19

The function of a governor in automobiles is to limit fuel to the engine to a maximum safe speed when unloaded and to maintain a relatively constant speed despite changes in loading.

Tire rotation is the practice of moving the wheels and tires of an automobile from one position to another, to ensure even tire wear. The weight on the front and rear axles differs which causes uneven wear.

In a four stroke engine for each crankshaft revolution, the camshaft revolves One half turn

scavenging is the process of pushing exhausted gas-charge out of the cylinder and drawing in a fresh draught of air or fuel/air mixture for the next cycle. This process is essential in having a smooth-running internal combustion engine.

A caster is a wheeled device typically mounted to a larger object that enables relatively easy rolling movement of the object. Caster creates stability as the geometry created forces the wheels back to straight. The front wheels are “encouraged” to stay straight as turning them involves lifting the car weight.

A feeler gauge is a tool used to measure gap widths. Feeler gauges are mostly used in engineering to measure the clearance between two parts

A connecting rod is an engine component that transfers motion from the piston to the crankshaft and functions as a lever arm. Connecting rods are commonly made from cast aluminum alloy and are designed to withstand dynamic stresses from combustion and piston movement.

The size of engine cylinder is referred in terms of its Bore and stroke

The engine oil is stored in oil pan when the engine is not running.

The major purpose of an electronically controlled automatic transmission is that this type of transmission Reduces shift shock and achieves more efficient transmission of engine torque

Instead of valves, the ports are used in case of two stroke I.C. engines

An overinflated tyre will wear the tread most near the centre

The connecting rods are generally made of I shaped cross-section.

The compression ratio in petrol engine is kept less than in Diesel engine because Higher or equivalent compression ratio in petrol engines is not possible due to pre-ignition

The purpose of the fuel injection system is to deliver fuel into the engine cylinders, while precisely controlling the injection timing, fuel atomization, and other parameters.

If the air-fuel mixture in a spark ignition engine is too rich, then air-fuel ratio is about 10 : 1.

front stabilizer bar is a part of many automobile suspensions that helps reduce the body roll of a vehicle during fast cornering or over road irregularities.

The aluminium alloy is used in cylinder blocks because It is lighter and has good heat dissipation characteristics

The firing order for an inline four cylinder I.C. engine is 1-3-4-2

The firing order for an opposed four cylinder l.C. engine is 1-4-3-2

$$\frac{{{\text{P}}{\text{.L}}{\text{.A}}{\text{.N}}{\text{.}}}}{2}$$ is the correct answer to “The indicated power of a four stroke engine (in watts) is equal to (where P = Mean effective pressure in N/m 2 , L = Length of stroke in metres, A = Cross-sectional area of the piston in m 2 and N = Speed of the engine in revolutions per second (r.p.s)”. This question is standard in competitive examination syllabi for Automobile Engineering.

Cetane number is an indicator of the combustion speed of diesel fuel and compression needed for ignition. The rating of C.I. engine fuel (Diesel) is given by cetane number.

The capacity of a battery is usually expressed in terms of Ampere hours

If clearance volume of I.C. engines is increased, the compression ratio will Decrease

The calorific value of diesel fuel is roughly 45.5 MJ/kg (megajoules per kilogram), slightly lower than petrol which is 45.8 MJ/kg. However, diesel fuel is denser than petrol and contains about 15% more energy by volume (roughly 36.9 MJ/litre compared to 33.7 MJ/litre)

The specific gravity of Diesel is about 0.85

Volume of one cylinder will be $$\frac{{2.4}}{4}$$ = 0.6 litres or 600 cubic centimeters.

The calorific value of petrol is about 42.7-43.5 MJ/kg

The specific gravity of petrol is about 0.75

The crescent shaped cavity on the piston head top surface is called as Valve recess

The formula for Iso-octane is C 8 H 18

The mechanical efficiency $$\left( {{\eta _{\text{m}}}} \right)$$ of an I.C. engine is equal to $$\frac{{{\text{B}}{\text{.P}}{\text{.}}}}{{{\text{I}}{\text{.P}}{\text{.}}}}$$ Where I.P. = Indicated power B.P. = Brake power F.P. = Frictional power

The function of a second ring is that it is a Compression ring and aids the top ring in sealing and cooling

The starting system includes A battery, a starter, and an ignition switch

The parking brake generally acts on Rear wheels

The most accurate ignition system of a spark ignition engine is Electronic control unit system

the duration between the time of injection and the time of ignition is called Delay period