Automotive Engine Mechanics Quiz

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Questions and Answers

What angle are valve seat inserts typically ground to?

30 degrees

45 degrees

80 degrees (correct)

90 degrees

What is the purpose of the narrow seat between the valve and valve seat?

To reduce the chance of being lifted open by foreign materials (correct)

To enhance heat dissipation

To widen the gas flow opening

To increase the valve's lifting force

For what reason are the cylinder heads hydraulically tested?

To determine their thermal conductivity

To ensure they can withstand high pressure (correct)

To assess corrosion resistance

To check for dimensional accuracy

Which material is primarily used for the valve head to provide heat resistance?

Austenitic steel Signup and view all the answers

What percentage of heat generated from combustion does the piston absorb?

18% Signup and view all the answers

What primarily occurs during the third stroke of the four-stroke cycle?

The piston is moved downward generating power. Signup and view all the answers

What is the purpose of the exhaust valves opening before TDC during the fourth stroke?

To allow burnt gases to exit the cylinder efficiently. Signup and view all the answers

How does multi-cylinder arrangement benefit engine performance?

It smooths out power output by spacing firing intervals. Signup and view all the answers

What is a characteristic of naturally aspirated engines?

They rely on atmospheric pressure to fill the cylinder. Signup and view all the answers

Why is a flywheel necessary in a four-stroke engine?

To store energy and smooth out power delivery. Signup and view all the answers

Which cylinder arrangement is typically used for engines requiring higher horsepower?

V-engines. Signup and view all the answers

What happens when exhaust pressure decreases during the fourth stroke?

Inlet air pressure aids in clearing the burnt gases. Signup and view all the answers

What is one method of pressure charging inlet air for engines?

Exhaust gas driven turbocharger Signup and view all the answers

What characterizes low speed engines in terms of application?

Too heavy and bulky for traction Signup and view all the answers

How is the firing order in a 16-cylinder engine arranged?

At 7200/16=450 intervals for even firing Signup and view all the answers

What is indicated by TDC in engine terminology?

The position of the piston at the top dead center Signup and view all the answers

What describes the correct crankshaft rotation direction when viewed from the power take-off end?

Counter clockwise Signup and view all the answers

Which part of the engine is responsible for supporting important fittings like the crankshaft and camshaft?

Engine block Signup and view all the answers

What is the purpose of vibration dampers on a crankshaft?

To prevent damage from vibrations Signup and view all the answers

How are the cylinders numbered in an engine?

From the free end, starting with No. 1 right and left Signup and view all the answers

What may occur if the firing order of an engine is not correctly arranged?

Vibrations leading to potential damage Signup and view all the answers

What indicates that the crankshaft may be bent or misaligned?

Variation in the distance between crank web faces Signup and view all the answers

What is the maximum permissible crankshaft deflection in locomotives of Indian Railways?

+0.008" Signup and view all the answers

What is the primary function of the cam shaft in an engine?

To open and close inlet and exhaust valves Signup and view all the answers

How many cams are typically associated with each cylinder in an engine?

3 Signup and view all the answers

What materials comprise the metallurgical composition of cam shafts?

Carbon and Manganese Signup and view all the answers

Which component is responsible for lubricating the cam bearings?

Valve lever mechanism oil via the push rod Signup and view all the answers

What is the purpose of valve seat inserts in cylinder heads?

To act as replaceable wearing parts Signup and view all the answers

How is the lower face of the cylinder head designed?

Complex casting forming a combustion chamber Signup and view all the answers

How is the reliable assembly of cam shafts ensured?

Through punched catalogue numbers Signup and view all the answers

What process is applied to cam lobes after profile killing?

Grinding Signup and view all the answers

What is the primary purpose of stress relieving and shot blasting in the fabrication process?

To improve the mechanical properties and reduce internal stresses Signup and view all the answers

Which material is primarily used for manufacturing crankshafts?

Chrome-molybdenum steel equivalent to SAE 4140 Signup and view all the answers

What is the maximum allowable horizontal misalignment between adjacent bores?

0.002" Signup and view all the answers

Which process is preferred for low HP engines due to its ability to grind down crank journals?

Induction hardening Signup and view all the answers

What is the purpose of ultrasonic and mechanical testing in crankshaft manufacturing?

To check for defects and ensure structural integrity Signup and view all the answers

What type of crankshaft design is commonly used in Indian Railways locomotives?

Single piece forging with welded counter weights Signup and view all the answers

Which of the following is a step in the sequence of operation for crankshaft manufacturing?

Rough machining Signup and view all the answers

What distinguishes nitriding from induction hardening in terms of engine application?

Nitriding provides longer life with negligible wear rates Signup and view all the answers

What is the depth of case for induction hardening based on the provided specifications?

0.124" Signup and view all the answers

What is the significance of checking crankshaft deflection during manufacturing?

To ensure proper alignment with the engine bearings Signup and view all the answers

What was the primary modification made to overcome the dislodging issue of the ring carrier from the skirt in older piston designs?

Use a forged ring carrier shrunk onto the cast piston body. Signup and view all the answers

What disadvantage does the MAHLE piston present compared to other piston designs?

It cannot have its ring carrier replaced. Signup and view all the answers

How does the steel cap piston design manage heat dissipation more effectively than traditional aluminum pistons?

By ensuring an increased flow of lube oil and larger oil passage diameter. Signup and view all the answers

What was the consequence of reducing the skirt size of the piston to balance the increased weight?

It resulted in a decrease in the number of piston rings from 6 to 5. Signup and view all the answers

What feature differentiates the steel cap piston from other aluminum alloy pistons?

It requires more lube oil pressure and mass flow of oil. Signup and view all the answers

What is the maximum permissible vertical misalignment between any two bore holes in the engine manufacturing process?

0.003" Signup and view all the answers

Which of the following processes is completed after rough machining in crankshaft manufacturing?

Drilling of oil holes Signup and view all the answers

What is the primary reason low HP engines prefer induction hardening over nitriding?

Deeper case hardening Signup and view all the answers

Which of the following is a characteristic of the crankshaft used in locomotives of Indian Railways?

Single piece forging Signup and view all the answers

What tolerance is allowed for horizontal misalignment between adjacent bores?

0.002" Signup and view all the answers

Which step directly follows stress relieving in the sequence of crankshaft manufacturing?

Welding of counter weights Signup and view all the answers

What is the depth of the case achieved by nitriding in crankshaft manufacturing?

0.012" to 0.015" Signup and view all the answers

What aspect of crankshaft manufacturing is confirmed by checking deflection?

Alignment of crankshaft Signup and view all the answers

In crankshaft manufacturing, which material is primarily used that is equivalent to SAE 4140?

Chrome-molybdenum steel Signup and view all the answers

Which of the following operations is NOT part of the sequence of crankshaft manufacturing?

Serration milling Signup and view all the answers

What type of supercharger is specifically described as being driven by exhaust gas?

Exhaust gas driven turbocharger Signup and view all the answers

In the context of engine speed classification, which type of engine is typically not suitable for traction purposes due to weight?

Low speed engines Signup and view all the answers

What is the firing order of a 12-cylinder engine as per the provided information?

1R-1L-4R-4L-2R-2L-6R-6L-3R-3L-5R-5L Signup and view all the answers

What best describes the parameters of Top Dead Centre (TDC) in an engine?

Position of the piston closest to the crankshaft Signup and view all the answers

What angle is the crankshaft arranged for in a 16-cylinder engine to ensure even firing?

450 degrees Signup and view all the answers

What arrangement is used for numbering engine cylinders?

From the free end towards the power take-off end Signup and view all the answers

What is the effect of a poorly arranged firing order in a large engine?

Increased vibrations leading to damage Signup and view all the answers

Which term refers to the end of the engine that is nearest to the turbo supercharger?

Free end Signup and view all the answers

How is the crankshaft typically rotated when viewed from the power take-off end?

Counterclockwise Signup and view all the answers

What is a defining characteristic of Compression Ignition (CI) engines compared to Spark Ignition (SI) engines?

CI engines utilize air for combustion, while SI engines use a fuel-air mixture. Signup and view all the answers

Which of the following factors increases the performance of CI engines with respect to temperature and pressure?

Higher compression ratios allowing for better combustion efficiency. Signup and view all the answers

How does the operational cycle of a two-stroke engine differ from a four-stroke engine?

Two-stroke engines complete their cycle in one revolution of the crankshaft. Signup and view all the answers

What occurs during the exhaust phase in a two-stroke engine?

The piston uncovers the exhaust port as it moves down from TDC. Signup and view all the answers

Which statement accurately describes the compression ratio in engines?

Compression ratio affects both temperature and efficiency of the engine. Signup and view all the answers

What must occur immediately after fuel is injected in a Compression Ignition engine?

The ignition of the fuel must take place promptly. Signup and view all the answers

What is one of the primary functions of pistons in an engine?

To compress air to required pressure and temperature Signup and view all the answers

Which of the following is necessary for the operation of two-stroke engines?

Compressed air for effective scavenging. Signup and view all the answers

Which type of piston is primarily used in marine or stationary engines?

Crosshead type Signup and view all the answers

What is a disadvantage of using cast iron for pistons compared to aluminum?

Heavier weight leading to increased engine load Signup and view all the answers

What material has the best heat conductivity for piston manufacturing?

Aluminum Signup and view all the answers

Which property of aluminum alloy pistons makes them favorable for high-speed modern diesel engines?

Lower weight Signup and view all the answers

Which component of the piston contains the piston rings?

Ring carrier Signup and view all the answers

What factor must be considered to prevent the seizure of the piston during operation?

Material expansion allowance Signup and view all the answers

Which of the following materials is NOT mentioned as part of the composition of aluminum alloys used in pistons?

Lead Signup and view all the answers

What characteristic of the topmost ring of the piston is highlighted?

It bears the maximum pressure of hot gases. Signup and view all the answers

What is the significance of the piston body being combined with the ring carrier through an interference fit?

It prevents gas leakage during operation. Signup and view all the answers

What is the purpose of the nickel interlayer between the bearing lining and overlay plate?

To ensure satisfactory bond and reduce wear rate Signup and view all the answers

Which characteristic of the 'flash' applied to bearings provides pre-installation protection?

Thickness of 1-2 μm Signup and view all the answers

What effect does a negative free spread in a bearing have?

Can result in the bearing being trapped against the shaft Signup and view all the answers

What is the primary role of a 'nick' in a bearing assembly?

To locate the bearing axially and ensure oil passage alignment Signup and view all the answers

What is the purpose of bore relief in medium-speed diesel engine bearings?

To address variations in wall thickness at joint faces Signup and view all the answers

What distinguishes a Compression Ignition Engine from a Spark Ignition Engine?

It injects fuel in liquid state at high pressure. Signup and view all the answers

Which type of engine uses a combustion process that occurs inside the cylinder?

Internal Combustion Engine Signup and view all the answers

What is the primary purpose of an Internal Combustion Engine?

To develop power by burning fuel. Signup and view all the answers

What is the significance of the auto-ignition temperature in a Compression Ignition Engine?

It is the temperature at which the fuel ignites without a spark. Signup and view all the answers

What is the main characteristic of a Spark Ignition Engine?

It relies on electric sparks for ignition. Signup and view all the answers

Which of the following best describes how fuel combustion occurs in a Diesel engine?

By injecting fuel into already compressed hot air. Signup and view all the answers

What are the two main categories of Internal Combustion Engines?

Spark Ignition and Compression Ignition Signup and view all the answers

Which material is commonly used for manufacturing crankshafts?

Chrome-molybdenum steel Signup and view all the answers

What is a key feature of high-speed engines that prefer nitriding for surface hardening?

Negligible wear rate during operation Signup and view all the answers

Which process is performed after rough machining in crankshaft manufacturing?

Ultrasonic testing Signup and view all the answers

What sequence of operation occurs in crankshaft manufacturing first?

Forging and forming operation Signup and view all the answers

What characteristic distinguishes the crankshaft of locomotives in Indian Railways?

Single piece with welded counterweights Signup and view all the answers

Which operation involves measuring the depth of serration and the distance between pitches?

Serration milling Signup and view all the answers

What method is applied during crankshaft manufacturing for surface hardening to provide higher endurance?

Induction hardening Signup and view all the answers

What happens after the bottom dead center (BDC) during the combustion cycle?

Both exhaust valves and inlet ports remain open. Signup and view all the answers

Which misalignment tolerance is permitted for vertical alignment between any two bore holes?

0.003" Signup and view all the answers

What leads to peak pressure being reached during the combustion process?

Compression of air continues until after TDC. Signup and view all the answers

During the suction phase of the four-stroke cycle, what occurs as the piston moves down?

Fresh air is sucked in through the inlet valves. Signup and view all the answers

How does the air inlet valve operate after BDC?

It remains closed until the next cycle. Signup and view all the answers

What occurs during the second stroke of a four-stroke engine compression phase?

The trapped air gets compressed as the piston moves upwards. Signup and view all the answers

Why is combustion initiated after the top dead center (TDC)?

To ensure complete compression and heating of the air. Signup and view all the answers

What advantage does keeping the exhaust valve open after BDC provide?

It helps in scavenging the remaining gases. Signup and view all the answers

What is the result of incomplete combustion in the four-stroke cycle?

Increased emissions and soot formation. Signup and view all the answers

What is the purpose of drawing in extra air after BDC during the suction phase?

To ensure a complete purge of stale gas. Signup and view all the answers

What happens at the end of the compression stroke before TDC?

Fuel is injected into the highly compressed air. Signup and view all the answers

What principle do diesel engines operate on that differentiates them from petrol engines?

Compression ignition principle Signup and view all the answers

What does the compression ratio indicate in an engine?

The degree of compression of trapped air Signup and view all the answers

In a four-stroke engine, how many strokes are required to complete one full cycle of operation?

Four strokes Signup and view all the answers

What is required for scavenging in two-stroke engines?

Compressed air Signup and view all the answers

At what point does fuel injection begin in relation to the top dead center (TDC) in a two-stroke cycle?

Just before TDC Signup and view all the answers

What does a higher compression ratio lead to in an engine's operation?

Higher compression pressure and temperature Signup and view all the answers

Which stage follows the compression stage in the operation of a compression ignition engine?

Power stroke Signup and view all the answers

What is crucial for the proper function during the exhaust phase of an engine cycle?

Allowing exhaust gases to escape Signup and view all the answers

Which of the following ratios is typically lower in a Spark Ignition engine compared to a Compression Ignition engine?

8:1 Signup and view all the answers

Study Notes

Diesel Engine Fundamentals and Working Principles

Diesel engines are Internal Combustion engines where fuel burns inside the cylinder.
External combustion engines burn fuel outside the cylinder.
Examples of external combustion engines include coal or oil fired steam engines.
Examples of internal combustion engines include petrol, diesel, and gas engines.
The basic purpose of an Internal Combustion (IC) engine is to develop power by burning fuel.
Complete and quick burning of fuel is crucial for good engine performance. This chemical process (oxidation) is called combustion.
Spark ignition engines require an electrical spark to ignite the fuel-air mixture.
Diesel engines use compression ignition.

Compression Ignition Engine

The process of combustion in a diesel engine is different from a petrol engine.
Diesel engines inject fuel into highly heated and compressed air, igniting the fuel by the heat.
Compression Ignition Engine is where the air drawn in the suction stroke is compressed to such a degree, in the compression stroke, that the heat generated due to compression goes much above the self-ignition or auto-ignition temperature of the liquid fuel.
The compression ratio of a Spark Ignition (SI) engine is lesser (around 8:1), whereas the compression ratio of a Compression Ignition (CI) engine is 12:1 or above.

Cycle of Operation

Suction or Induction: Fresh cool air is drawn into the cylinder to provide oxygen for combustion.
Compression: The trapped air is compressed raising the temperature.
Injection: Fuel is injected.
Combustion: Fuel burns producing heat.
Expansion: The expanding gases drive the piston, creating power.
Exhaust: The burnt gases are pushed out.

Two Stroke Cycle

In two-stroke engines, all the events are completed in two strokes or one revolution of the crankshaft.
Compressed air is essential for the purpose of scavenging

Four Stroke Cycle

In four-stroke engines, the events are completed in four strokes ( or two revolutions of the crankshaft).
Suction, Compression, Fuel Injection, exhaust and scavenging are events of four stroke cycle
Compressed air is essential for the purpose of scavenging, especially at lower power ranges

Valve Timing Diagram

Valve timing describes the opening and closing times of the inlet and exhaust valves.
Timing is critical for proper engine performance.
Different valve timing diagrams depict the timing for 2 stroke and 4 stroke cycles.

Cylinder Arrangements and Engine Layout

Configurations and arrangements of cylinders in two stroke and four stroke engines, vary based on use case
V-engines and inline horizontal are examples of such configurations
Inline vertical engines are also used for lower horsepower applications.

Natural Aspiration and Supercharging

Naturally aspirated engines draw air with atmospheric pressure.
Supercharging involves pressurizing the intake air, leading to better combustion and higher power output.

Engine Sizes and Speed

Diesel engines are designed for different usage and sizes giving a wider range of use.
The engines are classified into groups depending on their speed and size.
Normally low-speed engines are not used for traction purposes.

Firing Order

The firing order determines in which sequence cylinders ignite the fuel.
This can help to reduce vibrations in the engine

Explanation of Terms (Diesel Engines)

Free End - Turbocharger end of the engine.
Generator End - Power take-off end of the engine.
Right Side/Left Side - Determined when viewing from the power take off end
Cylinder Location - Numbered from the free end.

Crankshaft

The crankshaft is one of the most expensive components in a diesel engine.
It is the medium for transforming reciprocating to rotary motion.
It can be assembled in a few types: single piece, two piece bolted, or assembled type

Cylinder Heads

Cylinder heads are very important for high-stressed structures.
They are fabricated with low carbon steel, with some parts forged from steel.

Pistons

Piston is one of the most important components.
They are generally made from cast iron or aluminum alloy forgings.
Their function is to convert heat from combustion to mechanical power.

Valves

Valves are important components in engine.
They are made of alloy steel and austenitic steel.
They are responsible for allowing and blocking the flow of air, fuel, and gases

Piston Rings

Piston rings along with cylinder liner present the major wear and maintenance problem.
Function as a seal between the piston and cylinder, preventing blow-by, and preventing excessive oil from reaching the combustion chamber.

Crankshaft Bearings

Thin wall bearings are pre-finished precision steel materials used to back components lined with bearing material that should withstand applied loads.
Bi-metal and Tri-metal bearings are common.

Bearing Lining

The lining's material type varies widely based on the engine, but are typically bonded to the steel backing using an aluminum or copper based material, or lead bronze in some cases.
A typical lining thickness for modern diesel engines is 0.5 to 1.00 mm.

Steel Cap Pistons

These pistons use an exploded metal cap as a major component, with the majority of the piston being aluminum alloy forgings.

Oil System

Correct fuel delivery, metering, and atomization are important for optimal engine performance.

Cooling System

Controlling the temperature of engine components is very important for long engine life.
Air and water cooling are used widely in diesels.

General Description of Bogie

Describes the construction and load transmission characteristics of the bogie.
Describes the pivot, load bearers and frame used for traction and braking.
Includes the specifics for specific locomotive types.

AAR Wheels (American Association of Railroads)

Classification system for locomotive axles and wheels

Defects in Wheels

Various aspects like faulty manufacture, overheating, and usage can result in defects in rims, cracks, and overall damaged conditions.

Air Dryer

A component of many diesel locomotives.
Its main function is to filter air and remove water which prevents freezing in cold weather.

Other Updates

Firing Order: The firing order assists in reducing vibrations within an engine.
Cylinder Arrangement and Engine Layout: There are various types of cylinder arrangements depending on engine type and application, including inline, V-form, and others.
Engine Sizes and Speed: The size and speed of diesel engines vary according to use cases.
Crankshaft: Crankshafts are a significant part of diesel engines and are costly. They come in different types of construction.
Crankshaft Bearings: Various types of crankshaft bearings exist, such as bi-metal and tri-metal.
Bearing Lining: The lining's material type varies widely based the engine, but are typically bonded to the steel backing using an aluminum or copper based material, or lead bronze in some cases, with certain types of alloy having specific coatings.
Steel Cap Pistons: These pistons use an exploded metal cap as a major component, with the majority of the piston being aluminum alloy forgings.
Electrical Components: Including switches, relays, and contactors.

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Description

Test your knowledge on automotive engine mechanics with this quiz focused on valve systems, cylinder head design, and engine performance. Explore questions about the functionality of components and the engineering principles behind efficient engines. Ideal for students and enthusiasts alike.