The document provides a comprehensive overview of internal combustion (I.C.) engines, specifically focusing on 4-stroke spark ignition (SI) engines. It details the basic parts of I.C. engines, their working cycle consisting of four strokes (intake, compression, power, and exhaust), and lists advantages and disadvantages. I.C. engines are widely used in various applications, including vehicles and industrial settings, due to their efficiency and compact size.

1. GOVERNMENT ENGINEERING
COLLEGE, BILASPUR (C.G)
DEPARTMENT OF MECHANICAL ENGINEERING
A PRESENTATION ON
4 STROKE SI ENGINE
Submitted by
Girendra Kumar
Submitted to
Prof. A.R. Patnaik
Assistant
professor

3. TOPIC
 What is I.C. Engine?
 Basic parts of I.C. Engine
 Working of 4-stroke Engine
 Advantages & Disadvantages

4. WHAT IS I.C. ENGINE?
I.C. Engines means Internal Combustion
Engines.
I.C. engine is type of heat engine which
converts the heat energy released during
combustion of fuel into mechanical work.
These engines are widely used as prime
movers and also in road vehicles,
locomotives, industrial applications.
Examples: Petrol engines, Diesel engines
and Gas engines.

5. BASIC PARTS OF I.C. ENGINE
1. Cylinder
2. Cylinder head
3. Piston
4. Piston Rings
5. Spark plug
6. Combustion chamber
7. Inlet manifold

6. 8. Exhaust manifold
9. Inlet & Exhaust valve
10. Connecting rod
11. Crank shaft
12. Cam shaft
13. Fly wheel

7. BASIC PARTS OF I.C. ENGINE
1. Cylinder : It is the important part of this engine in which the piston moves up
and down in order to develop power.
2. Cylinder head : It is fitted one end of the cylinder and act as a cover to close
the cylinder
• It contains: Inlet valve & Outlet valve. Spark plug or injector.
3. Piston : It is considered as the heart of I.C engine. Whose main function is to
transmit the force exerted by the burning of charge to the connecting rod.
4. Piston Ring : It fitted slots around the piston , provide a tight and seal between
the piston and the cylinder wall thus preventing leakage of combustion gases.
5. Spark Plug: It is a component to initiate the combustion process in Spark
Ignition (SI) engines and is usually located on the cylinder head.

8. 6. Combustion chamber : The space enclosed in the upper part of the cylinder,
by the cylinder head and the piston top during the combustion process is called
the combustion chamber.
7. Inlet Manifold : The pipe which connects the intake system to the inlet valve of
the engine and through which air or air-fuel mixture is drawn into the cylinder is
called the inlet manifold.
8. Exhaust Manifold : The pipe which connects the exhaust system to the exhaust
valve of the engine and through which the products of combustion scape into the
atmosphere is called the exhaust manifold.
9. Inlet and Exhaust valve : Valves are commonly mushroom shaped poppet
type.
• Inlet valve provided either on the cylinder head or on the side of the cylinder
for regulating the charge coming into the cylinder.
• Exhaust valve is used for discharging the products of combustion from the
cylinder.

9. 10. Connecting rod : It is the link between the piston and crank shaft. Whose
main function is to transmit force from the piston to the crank shaft.
11. Crank shaft :It is considered as the backbone of an I.C Engine. Whose
function is to convert reciprocating motion of piston in to the rotary motion
with the help of connecting rod.
12. Cam shaft :The shaft which has cams for the opening and closing of
inlet & outlet valves.
13. Fly wheel : It is the big wheel mounted on the crankshaft whose function is
to maintain speed at constant.
• The constant speed is done by storing excess energy during power stroke up
to returning of other power stroke.

10. 4 STROKE PETROL ENGINE
The four stroke engine was first
demonstrated by Nikolaus Otto in 1876,
hence it is also known as the Otto cycle.
The technically correct term is actually
four stroke cycle. The four stroke engine
is probably the most common engine
type nowadays. It powers almost all cars
and trucks .
The four strokes of the cycle are intake,
compression, power, and exhaust. Each
corresponds to one full stroke of the
piston; therefore, the complete cycle
requires two revolutions of the
crankshaft to complete.

11. WORKING OF 4-STROKE ENGINE

12. WORKING OF 4-STROKE PETROL ENGINE
Suction stroke
• During the suction stroke of spark ignition
engine, the piston moves down form top end
of the cylinder to the bottom end of cylinder
and simultaneously intake valve opens.
• Due to the movement of piston low pressure
or vacuum generates inside the cylinder. Due
to this vacuum and the gravity action air fuel
mixture enter into the cylinder through the
intake valve .
• The intake valve remains open until the
piston reach the lower end of the cylinder.
After it the intake valve closes and seals the
upper end of the cylinder .

13. COMPRESSION STROKE
• After the piston passes bottom end of the
cylinder, it starts moving up. Both valves are
closed and the cylinder is sealed.
• The piston moves upward. This movement
of piston compresses the air fuel mixture
into a small space between the top of the
piston and cylinder head.
• The mixture is compressed into 1/8 or less
of its original volume. This compression
ratio decides the power of engine.
• At the end of compression stroke the piston
is at top end of the cylinder.

14. EXPANSION (POWER) STROKE
• At the end of the compression stroke when
the piston is at the top end of the cylinder an
electric spark generated by the spark plug.
• The heat of the spark ignites the compressed
air fuel mixture.
• The air fuel mixture then burn rapidly and
produces high temperature up to 3300°C.
This high temperature causes very high
pressure, which pushes down. on the top of
the piston.
• The connecting rod force to the carries this
crankshaft, which turns to move the vehicle .
• At the end of power stroke the piston reach
the bottom end of cylinder.

15. EXHAUST STROKE
• When the piston reaches the bottom end of
cylinder on the power stroke, the exhaust
valve opens .
• At this time due to the burn gases inside the
cylinder, the pressure inside the cylinder is
slightly high from atmospheric pressure. This
pressure difference allows burn gases to
escape through the exhaust port and the
piston move through the top end of the
cylinder.
• At the end of exhaust all burn gases escape
and exhaust valve closed .
• Now again intake valve opens and this process
keep on running until your vehicle remain in
starting position.

16. ADVANTAGES I.C. ENGINE
•Size of engine is very less compared to external combustion engines
•Power to weight ratio is high
•Very suitable for small power requirement applications
•Usually more portable than their counterpart external combustion engines
•Starting time is very less
•High efficiency than external combustion engine
•No chances of leakage of working fluids
•Requires less maintenance
•Lubricant consumption is less as compared to external combustion engines

17. DISADVANTAGES OF I.C. ENGINE
• Variety of fuels that can be used is limited to very fine quality gaseous and liquid
fuel
• Fuel used is very costly like gasoline or diesel
• Engine emissions are generally high compared to external combustion engine
• Not suitable of large scale power generation
• In case of reciprocating internal combustion noise is generated due to detonation
of fuel

18. THANK YOU