Spark ignition

Certainly! Let’s start by addressing each of your questions.

1. Internal Combustion Engine (ICE) and External Combustion Engine (ECE):

- Internal Combustion Engine: An engine in which the combustion of fuel takes

place inside the engine cylinder. Examples include gasoline engines and diesel
engines.

- External Combustion Engine: An engine in which the combustion of fuel takes

place outside the engine. The heat produced is then used to generate steam, which
drives the engine. Examples include steam engines and Stirling engines.

Examples:

Internal Combustion Engine: Gasoline engine, Diesel engine, Rotary engine

External Combustion Engine: Steam engine, Stirling engine, External combustion

gas turbine

2. 4-Stroke Gasoline Engines:

A 4-stroke gasoline engine completes the combustion cycle in four strokes of the
piston: intake, compression, power, and exhaust. Here’s a brief overview of the
process:

- Intake Stroke: The piston moves downward, drawing in a mixture of air and fuel.

- Compression Stroke: The piston moves upward, compressing the air-fuel

mixture.

- Power Stroke: The spark plug ignites the compressed mixture, causing an
explosion that drives the piston downward.

- Exhaust Stroke: The piston moves upward again, pushing out the spent exhaust
gases.

Diagram: [4-Stroke Gasoline Engine

Diagram](https://www.mechanicalbooster.com/2017/03/working-of-4-stroke-
petrol-engine.html)
3. V-Engine and Flat Engine:

- V-Engine: An engine with cylinders arranged in a V-shaped configuration. The V-

angle can vary, and common examples include V6 and V8 engines.

- Flat Engine: An engine with horizontally opposed cylinders, also known as a

boxer engine. The cylinders are arranged in two banks on opposite sides of the
crankshaft.

4. Firing Order:

The firing order is the sequence in which the spark plugs in the cylinders of an
internal combustion engine fire. It is determined by the engine’s design and is
crucial for smooth engine operation.

Firing Order Examples:

- Four-Cylinder Engine: 1-3-4-2

- Six-Cylinder Engine: 1-5-3-6-2-4

5. Basic Components of Petrol Engine:

The basic components of a petrol engine include the cylinder block, cylinder
head, pistons, connecting rods, crankshaft, camshaft, valves, spark plugs, fuel
injectors (in modern engines), and the intake and exhaust systems.

6. Single vs. Multi-Cylinder Engines:

- Single-Cylinder Engine: An engine with only one cylinder, typically used in small
applications such as motorcycles, lawn mowers, and small generators.

- Multi-Cylinder Engine: An engine with multiple cylinders, such as 4-cylinder, 6-

cylinder, or 8-cylinder configurations, commonly used in automobiles.

7. Crankcase Arrangement:
 The crankcase is the housing for the crankshaft in an internal combustion engine.
It also serves as a reservoir for engine oil. The arrangement can vary based on the
engine design, with options such as wet sump and dry sump systems.

8. Valve Timing of 4-Stroke Engine:

The valve timing in a 4-stroke engine controls the opening and closing of the
intake and exhaust valves in relation to the position of the piston. This timing is
critical for efficient engine operation and is typically controlled by the camshaft.

Diagram: [Valve Timing Diagram](https://www.carbibles.com/wp-

content/uploads/2019/06/valve-timing-diagram.png)

9. Variable Valve Timing:

Variable Valve Timing (VVT) is a technology that allows for the adjustment of the
valve timing, duration, and lift to optimize engine performance, fuel efficiency, and
emissions. It is achieved through the use of hydraulic, mechanical, or electronic
systems.

10. Relationship Between Valve Timing and Firing Order:

The valve timing must be synchronized with the firing order to ensure that the
intake and exhaust valves open and close at the correct times in relation to the
piston’s position. This synchronization is crucial for efficient combustion and
engine performance.

11. Differences Between 4-Stroke and 2-Stroke Engines:

- 4-Stroke Engine: Intake, compression, power, and exhaust strokes; more

complex design; better fuel efficiency; lower emissions; commonly used in
automobiles.

- 2-Stroke Engine: Intake and exhaust occur simultaneously with compression

and power strokes; simpler design; less fuel efficient; higher emissions; commonly
used in small engines, motorcycles, and some marine applications.

12. Advantages and Disadvantages of 4-Stroke Engine:

 Advantages: Better fuel efficiency, lower emissions, smoother operation, longer
lifespan, wider range of applications.

Disadvantages: More complex design, heavier, higher manufacturing cost.

13. Four-Stroke Cycle Engine and Two-Stroke Cycle Engine:

- Four-Stroke Cycle Engine: Completes the combustion cycle in four strokes of the
piston, with separate intake, compression, power, and exhaust strokes.

- Two-Stroke Cycle Engine: Completes the combustion cycle in two strokes of the
piston, with intake and exhaust occurring simultaneously with compression and
power strokes.

Q1b. Two groups of heat engines are:

- Internal combustion engines

- External combustion engines

Q1c. Two ways automobile engines can be categorized are:

- Based on fuel type (e.g., petrol, diesel, electric)

- Based on the number of strokes (e.g., two-stroke, four-stroke)

Q1d. Merits and demerits of a two-stroke petrol engine:

Merits:

- Simple design

- Lighter weight

- Higher power output

Demerits:

- Higher fuel consumption

- More pollution

- Less efficient combustion

Q2b. The main purposes of a flywheel in an engine are:

- Energy storage: It stores rotational energy to smooth out the power delivery from
the engine.

- Dampening vibrations: It reduces vibrations and torsional fluctuations in the

engine.

Q2c. The teeth cut on the outer circumference of a flywheel are for engaging with
the starter motor to start the engine.

1. Service Procedure for Installing a New Flywheel Ring Gear:

a. Disconnect the battery to ensure safety during the procedure.

b. Remove the transmission or gearbox to access the flywheel.

c. Secure the flywheel in place using a flywheel holder tool to prevent it from
rotating.

d. Remove the old ring gear from the flywheel using appropriate tools.

e. Clean the mounting surface of the flywheel to ensure proper adhesion for the
new ring gear.

f. Heat the new ring gear to expand it slightly for easier installation.

g. Carefully place the new ring gear onto the flywheel and ensure it is properly
aligned.

h. Use a press or appropriate tools to press the new ring gear onto the flywheel.

i. Reinstall the transmission or gearbox and reconnect the battery.

j. Test the vehicle to ensure proper functionality of the new flywheel ring gear.

Q3a. Briefly define the following terms as they relate to automobile engines:

(i) Engine capacity: Engine capacity refers to the total volume of all the
cylinders in an engine. It is usually measured in liters or cubic
centimeters and indicates the total amount of air and fuel the engine can
intake and combust in one complete cycle.
 (ii) Compression ratio: Compression ratio is the ratio of the maximum
volume of the combustion chamber to the minimum volume. It indicates
how much the air-fuel mixture is compressed before ignition and affects
the engine’s efficiency and performance.

(iii) Stroke: Stroke refers to the distance traveled by the piston in the cylinder
from top dead center (TDC) to bottom dead center (BDC) or vice versa. It
is a crucial parameter in determining the engine’s displacement and
performance characteristics.

(iv) Thermal efficiency: Thermal efficiency measures how effectively an

engine converts the heat from fuel combustion into mechanical work. It
is a measure of the engine’s ability to utilize energy from the fuel.

(v) Displacement: Displacement refers to the total volume swept by all the
pistons in the engine during one complete cycle. It is a key factor in
determining the engine’s power output and is usually measured in liters
or cubic centimeters.

Q3b. Name two types of piston rings commonly used in an internal combustion
engine and explain their functions:

The two common types of piston rings are:

- Compression Rings: These rings seal the combustion chamber by preventing the
leakage of air-fuel mixture from the combustion chamber into the crankcase and
also prevent the entry of oil from the crankcase into the combustion chamber.

- Oil Control Rings: These rings regulate the amount of oil that reaches the cylinder
wall, preventing excessive oil from entering the combustion chamber while
ensuring proper lubrication of the cylinder wall.

Q3c. State the four functions of an automobile cooling system:

The four functions of an automobile cooling system are:

1. Regulating Engine Temperature: The cooling system helps maintain the engine at
an optimal operating temperature to ensure efficient combustion and prevent
overheating.

2. Heat Dissipation: It dissipates the excess heat generated during engine operation
to prevent damage to engine components.

3. Consistent Temperature Control: The cooling system ensures that the engine
operates within a consistent temperature range under varying conditions.

4. Preventing Corrosion: It helps prevent corrosion and rust formation within the
engine by maintaining the proper temperature and preventing the formation of
condensation.