The document provides an overview of internal combustion engines (IC engines), detailing their definition, working principles, and main components such as cylinders, pistons, and crankshafts. It explains the four-stroke cycle, highlighting the sequence of strokes and the role of various elements in the combustion process. Additionally, it distinguishes between machines and engines while discussing applications and objectives related to IC engines.

1. Introduction:
Machine: A machine is piece of equipment which uses electricity or an engine in order to do a
particular kind of work.
Example: IC Engine, Fan, Compressor, pump, electronic computing machine etc.
Engine: An engine or motor is a machine designed to convert one form of energy into
mechanical energy.
Example: Steam engine, IC engine, Diesel Engine etc.
IC Engine: The Internal Combustion engine (IC Engine) is a heat engine that converts heat
energy (chemical energy of a fuel) into mechanical energy (usually made available on a rotating
output shaft).
Applications of IC Engines:
Mainly used as ‘prime movers’, e.g. for be the propulsion of a vehicle i.e., car, bus, truck,
locomotive, marine vessel, or airplane. Other applications include stationary saws, lawn mowers,
bull-dozers, cranes, electric generators, etc.
Objectives:
 Knowing the working principle of four stroke engine.
 Knowing the difference between machine and engine.
 Knowing the mechanism of four stroke engine/diesel engine.
 Knowing the main components of IC engine.
Working Principle of Four Stroke Engine: In four-stroke cycle engines there are four strokes
completing two revolutions of the crankshaft. These are respectively, the suction, compression,
power and exhaust strokes. The piston is shown descending on its suction stroke. Only pure air is
drawn into the cylinder during this stroke through the inlet valve, whereas, the exhaust valve is
closed. These valves can be operated by the cam, push rod and rocker arm. The next stroke is the
compression stroke in which the piston moves up with both the valves remaining closed. The
compression ratio usually varies from 14:1 to 22:1. The pressure at the end of the compression
stroke ranges from 30 to 45 kg/cm2. As the air is progressively compressed in the cylinder, its
temperature increases, until when near the end of the compression stroke, it becomes sufficiently
high (650-80O °C) to instantly ignite any fuel that is injected into the cylinder. When the piston
is near the top of its compression stroke, a liquid hydrocarbon fuel, such as diesel oil, is sprayed
into the combustion chamber under high pressure (140-160 kg/c𝑚2
), higher than that existing in
the cylinder itself. This fuel then ignites, being burnt with the oxygen of the highly compressed
air. During the fuel injection period, the piston reaches the end of its compression stroke and
commences to return on its third consecutive stroke, viz., power stroke. During this stroke the
This is only the working stroke of the cylinder.

2. Main Components of IC Engine:
.
Figure: Four Stroke Engine
Figure: Two Stroke Engine

3. 1) Engine Cylinder: Cylinder is the main
body of IC engine. Cylinder is a part in
which the intake of fuel, compression of fuel
and burning of fuel take place. The main
function of cylinder is to guide the piston. It
is in direct contact with the products of
combustion so it must be cooled. For
cooling of cylinder a water jacket (for liquid
cooling used in most of cars) or fin (for air
cooling used in most of bikes) are situated at
the outer side of cylinder.
2) Cylinder Head: The top end of cylinder
is closed by means of removable cylinder
head. There are two holes or ports at the
cylinder head, one for intake of fuel and
other for exhaust. Both the intake and
exhaust ports are closed by the two valves
known as inlet and exhaust valve. The inlet
valve, exhaust valve, spark plug, injector
etc. are bolted on the cylinder head. The
main function of cylinder head is to seal the
cylinder block and not to permit entry and
exit of gases on cover head valve engine.
Cylinder head is usually made by cast iron
or aluminum. It is made by casting or
forging and usually in one piece.
3) Piston: A cylindrical-shaped mass that
reciprocate back and forth in the cylinder
transmitting force to the crankshaft. The top
of the piston is called crown and the sides
are called skirt. The piston is made by
aluminum alloy and sometimes it is made by
cast iron because light alloy piston expands
more than cast iron so they need more
clearances to the bore
Figure: Engine Cylinder
Figure: Cylinder Head
Figure: Piston

4. 4) Piston Rings: Metal ring that fixed into a
circumferential groove around the piston.
Made up of highly polished chromed steel. It
makes a seal between piston and cylinder
walls. It also used for lubrication purpose.
5) Crank Shaft: The crankshaft of an
internal combustion engine receives the
efforts or thrust supplied by piston to the
connecting rod and converts the
reciprocating motion of piston into rotary
motion of crankshaft. The crankshaft mounts
in bearing so it can rotate freely. The shape
and size of crankshaft depends on the
number and arrangement of cylinders. It is
usually made by steel forging, but some
makers use special types of cast-iron.
6) Gudgeon Pin: These are hardened steel
parallel spindles fitted through the piston
bosses and the small end bushes or eyes to
allow the connecting rods to swivel. It
connects the piston to connecting rod. It is
made hollow for lightness. It is made of
steel.
7) Fly wheel: Fly wheel is a rotating mass
used as an energy storing device. A flywheel
is secured on the crankshaft. The main
function of flywheel is to rotate the shaft
during preparatory stroke. It also makes
crankshaft rotation more uniform. It is done
by storing excess energy during the power
strokes, which is returned during other
strokes.
Figure: Piston Rings
Figure: Crank Shaft
Figure: Gudgeon Pin
Figure: Fly Wheel

5. 8) Connecting rod: Connecting rod
connects the piston to crankshaft and
transmits the motion and thrust of piston to
crankshaft. It converts the reciprocating
motion of the piston into rotary motion of
crankshaft. There are two end of connecting
rod one is known as big end and other as
small end. Big end is connected to the
crankshaft and the small end is connected to
the piston by use of piston pin.
9) Camshaft: Camshaft is used in IC
engine to control the opening and closing of
valves at proper timing. Rotating shaft used
to push open valves at proper timing in
engine cycle. Can be control hydraulically or
mechanically.
10) Push rod: Pushrod is used when the
camshaft is situated at the bottom end of
cylinder. It carries the camshaft motion to
the valves which are situated at the cylinder
head.
11) Spark Plug: This part is used in Spark
Ignition Engine (SI Engine) only. The main
function of a spark plug is to deliver electric
current from an ignition system to the
combustion chamber. So, compressed
fuel/air mixture is ignited by an electric
spark. A spark plug consists of a metal
threaded shell which is electrically isolated
from a central electrode by a porcelain
insulator. Spark plugs usually require a
voltage of 12,000–25,000V or more to
produce spark properly.
Figure: Connecting rod
Figure: Camshaft
Figure: Push rod
Figure: Spark plug

6. 12) Engine bearing: Everywhere there is
rotary action in the engine, bearings need.
Bearings are used to support the moving
parts. The crankshaft is supported by
bearing. The connecting rod big end is
attached to the crank pin on the crank of the
crankshaft by a bearing. A piston pin at the
rod small end is used to attach the rod to the
piston, also rides in bearings. The main
function of bearings is to reduce friction
between these moving parts.
13) Carburetor: Carburetor is used for
making an air and fuel mixture . It is
replaced by EFI system. A proper mixture
is needed for proper combustion so that
carburetor used. It mixing up the fuel and
air. Making a rich or lean mixture as
requirement.
14) Spark Plug Wires: Spark plug wire are
the wire that connect distributor, ignition
coil to each of the spark plug in some types
of internal combustion engine.
15) Fuel pump: It is an important part of
fuel supply system, which supplies petrol to
the carburetor by sucking from the fuel tank.
16) Valves: To control the inlet and exhaust
of internal combustion engine, valves are
used. The number of valves in an engine
depends on the number of cylinders.
Figure: Engine Bearing
Figure: Carburetor
Figure: Spark Plug WIre
Figure: Fuel Pump
Figure: Valves

7. 17) Intake Manifold: Piping system which
delivers incoming air to the cylinder. They
made up of cast metal ,plastic or composite
materials. In IS engine fuel added to the air
in intake manifold.
18) Exhaust Manifold: Piping system
which carry exhaust gases away from the
system. Made up of cast iron.
19) Fuel Injector: Injector is usually used
in compression ignition engine. It sprays the
fuel into combustion chamber at the end of
compression stroke. It is fitted on cylinder
head. Fuel injection is a system for mixing
fuel with air in an internal combustion
engine. It has become the primary fuel
delivery system, which is used in
automotive petrol engines.
20) Governor: As the name indicates, it
controls the speed of engine by controlling
the fuel supply. It controls the speed of
engine at a different load by regulating fuel
supply in diesel engines. In petrol engines,
supplying the mixture of air-petrol and
controlling the speed at different load
conditions.
21) Head gas kit: A head gas kit is a gas kit
that sits between the engine block and
cylinder head in an internal combustion
engine.
Figure: Intake Manifold
Figure: Exhaust Manifold
Figure: Fuel Injector
Figure: Governor
Figure: Head Gas Kit

8. 22) Oil Pan: Oil pan is a metal pan that is
attached to the bottom of an engine
crankcase. Remove the oil plug and drain
out all the oil from the oil pan.
23) Turbocharger: A turbocharger
increases an internal combustion engine’s
efficiency and power output by forcing extra
air into the combustion chamber.
24) Starter: A starter is a device used to
rotate an internal combustion engine so as to
initiate the engine’s operation under its own
power.
25) Radiator: It is an heat exchanger. It is
usually mounted in front of the engine in the
flow of the air. Used to cool down the
engine and run proper thermodynamic cycle
.
Figure: Oil Pan
Figure: Turbocharger
Figure: Starter
Figure: Radiator
Conclusion:
i. From this lab experiment I’ve learnt about machine and engine as well as got a basic
idea about four stroke engine, two stroke engine and the main components of Internal
Combustion engine.
ii. Basic difference between machine and engine are given below:

9. Main Components of IC Engine:
Figure: Two Stroke Engine

10. Introduction:
Machine: A machine is piece of equipment which uses electricity or an engine in order to do a
particular kind of work. Example: IC Engine, Fan, Compressor, pump, electronic computing
machine etc.
Engine: An engine or motor is a machine designed to convert one form of energy into
mechanical energy. Example: Steam engine, IC engine, Diesel Engine etc.
IC Engine: The Internal Combustion engine (IC Engine) is a heat engine that converts heat
energy (chemical energy of a fuel) into mechanical energy (usually made available on a rotating
output shaft).
Applications of IC Engines:
Mainly used as ‘prime movers’, e.g. for be the propulsion of a vehicle i.e., car, bus, truck,
locomotive, marine vessel, or airplane. Other applications include stationary saws, lawn
mowers, bull-dozers, cranes, electric generators, etc.
Objectives:
 Knowing the difference between machine and engine.
 Knowing the main components of IC engine.
 Knowing the mechanism of four stroke engine/diesel engine.
 Knowing the working principle of four stroke engine.
Working Principle of Four Stroke Engine: In four-stroke cycle engines there are four strokes
completing two revolutions of the crankshaft. These are respectively, the suction, compression,
power and exhaust strokes. The piston is shown descending on its suction stroke. Only pure air
is drawn into the cylinder during this stroke through the inlet valve, whereas, the exhaust valve
is closed. These valves can be operated by the cam, push rod and rocker arm. The next stroke is
the compression stroke in which the piston moves up with both the valves remaining closed.
The compression ratio usually varies from 14:1 to 22:1. The pressure at the end of the
compression stroke ranges from 30 to 45 kg/cm2. As the air is progressively compressed in the
cylinder, its temperature increases, until when near the end of the compression stroke, it
becomes sufficiently high (650-80O°C) to instantly ignite any fuel that is injected into the
cylinder. When the piston is near the top of its compression stroke, a liquid hydrocarbon fuel,
such as diesel oil, is sprayed into the combustion chamber under high pressure (140-160
kg/cm2 ), higher than that existing in the cylinder itself. This fuel then ignites, being burnt with
the oxygen of the highly compressed air. During the fuel injection period, the piston reaches the
end of its compression stroke and commences to return on its third consecutive stroke, viz.,
power stroke. During this stroke the This is only the working stroke of the cylinder.

11. 1) Cylinder Block: Cylinder is the main body of IC engine. Cylinder is a part in which the intake
of fuel, compression of fuel and burning of fuel take place. The main function of cylinder is to
guide the piston. It is in direct contact with the products of combustion so it must be cooled.
For cooling of cylinder a water jacket (for liquid cooling used in most of cars) or fin (for air
cooling used in most of bikes) are situated at the outer side of cylinder.
2) Cylinder head: The top end of the cylinder is covered by cylinder head over which inlet and
exhaust valve, spark plug or injectors are mounted. A copper or asbestos gasket is provided
between the engine cylinder and cylinder head to make an air tight joint.
3) Piston: A piston is fitted to each cylinder as a face to receive gas pressure and transmit the
thrust to the connecting rod. It is the prime mover in the engine. The main function of piston is
to give tight seal to the cylinder through bore and slide freely inside of cylinder.
4) Piston Rings: A piston must be a fairly loose fit in the cylinder so it can move freely inside the
cylinder. If the piston is too tight fit, it would expand as it got hot and might stick tight in the
Figure: Two Stroke Engine
Figure: Cylinder Block
Figure: Cylinder Head
Figure: Piston

12. cylinder and if it is too loose it would leaks the vapor pressure. To provide a good sealing fit and
less friction resistance between the piston and cylinder, pistons are equipped with piston rings.
5) Connecting rod: Connecting rod connects the piston to crankshaft and transmits the motion
and thrust of piston to crankshaft. It converts the reciprocating motion of the piston into rotary
motion of crankshaft. There are two end of connecting rod one is known as big end and other
as small end.
6) Valves: To control the inlet and exhaust of internal combustion engine, valves are used. The
number of valves in an engine depends on the number of cylinders. Two valves are used for
each cylinder one for inlet of air-fuel mixture inside the cylinder and other for exhaust of
combustion gases. The valves are fitted in the port at the cylinder head by use of strong spring.
This spring keep them closed. Both valves usually open inwards.
7) Turbocharger: A turbocharger increases an internal combustion engine’s efficiency and
power output by forcing extra air into the combustion chamber.
Figure: Piston Rings
Figure: Connecting rod
Figure: Valves
Figure: Turbocharger

13. 8) Carburetor: The main function of the carburetor is to blends air and fuel in the proper ratio
for combustion in internal combustion engine. It converts petrol in a fine spray and mixes with
air in the proper ratio as per requirement of the engine.
9) Crank Case: The main body of the engine to which the cylinder are attached and which
contains the crankshaft and crankshaft bearing is called crankcase. It serves as the lubricating
system too and sometime it is called oil sump. All the oil for lubrication is placed in it.
10) Cam Shaft: Camshaft is used in IC engine to control the opening and closing of valves at
proper timing. For proper engine output inlet valve should open at the end of exhaust stroke
and closed at the end of intake stroke. So to regulate its timing, a cam is use which is oval in
shape and it exerts a pressure on the valve to open and release to close. It is driven by the
timing belt which drives by crankshaft.
11) Fly Wheel: It is big wheel mounted on the crankshaft, whose function is to maintain its
speed constant. It is done by storing excess energy during the power stroke, which is returned
during other stroke.
Figure: Carburetor
Figure: Crank Case
Figure: Cam shaft

14. 12) Spark plug:This part is used in Spark Ignition Engine (SI Engine) only. The main function of a
spark plug is to deliver electric current from an ignition system to the combustion chamber. So,
compressed fuel/air mixture is ignited by an electric spark. A spark plug consists of a metal
threaded shell which is electrically isolated from a central electrode by a porcelain insulator.
13) Piston Pin: The piston pin connects the piston with connecting rod. It is subjected to a
combination of shearing and bending loads. Piston pin has to operate under some of the
highest temperatures experienced in the engine. The piston-pins are in tubular shape, which
provides adequate strength with minimum weight.
14) Engine Governor: As the name indicates, it controls the speed of the engine by controlling
the fuel supply. Diesel engine speed control will be achieved by the governor at a different load
by regulating fuel supply. The upward motion of governor sleeve operates the throttle valve to
decrease the supply of the fuel. Hence the speed of an engine is governed.
Figure: Fly Wheel
Figure: Spark plug
Figure: Piston Pin
Figure: Engine Governor

15. 15) Push rod: Pushrod is used when the camshaft is situated at the bottom end of cylinder. It
carries the camshaft motion to the valves which are situated at the cylinder head.
16) Fuel Injector: Injector is usually used in compression ignition engine. It sprays the fuel into
combustion chamber at the end of compression stroke. It is fitted on cylinder head. Fuel
injection is a system for mixing fuel with air in an internal combustion engine. It has become the
primary fuel delivery system, which is used in automotive petrol engines. The primary
difference between carburetors and fuel injection is that fuel injection atomizes the fuel by
forcibly pumping it through a small nozzle under high pressure, while a carburetor relies on low
pressure created by intake air rushing through it to add the fuel to the airstream.
17) Oil Pan: Oil pan is a metal pan that is attached to the bottom of an engine crankcase.
Remove the oil plug and drain out all the oil from the oil pan.
18) Oil pump: It is an important part of fuel supply system, which supplies petrol to the
carburetor by sucking from the fuel tank.
19) Spark Plug Wires: Spark plug wire are the wire that connect distributor, ignition coil to each
of the spark plug in some types of internal combustion engine.
Figure: Push rod
Figure: Fuel Injector
Figure: Oil Pan
Figure: Oil pump

16. 20) Starter: A starter is a device used to rotate an internal combustion engine so as to initiate
the engine’s operation under its own power.
21) Radiator: It is an heat exchanger. It is usually mounted in front of the engine in the flow of
the air. Used to cool down the engine and run proper thermodynamic cycle.
22) Head gas kit: A head gas kit is a gas kit that sits between the engine block and cylinder head
in an internal combustion engine.
23) Crank shaft: The crankshaft of an internal combustion engine receives the efforts or thrust
supplied by piston to the connecting rod and converts the reciprocating motion of piston into
rotary motion of crankshaft. The crankshaft mounts in bearing so it can rotate freely. The shape
and size of crankshaft depends on the number and arrangement of cylinders. It is usually made
by steel forging, but some makers use special types of cast-iron such as spheroid graphitic or
nickel alloy castings which are cheaper to produce and have good service life.
Figure: Spark plug wires
Figure: Starter
Figure: Radiators
Figure: Head gas kit

17. 24) Manifold: The main function of manifold is to supply the air fuel mixture and collects the
exhaust gases equally form all cylinder. In an internal combustion engine two manifold are
used, one for intake and other for exhaust. They are usually made by aluminum alloy.
25) Distributor: A case that enables engine’s ignition. The plug wires connected with
distributor.
Figure: Crank Shaft
Figure: Manifold
Figure: Distributor

18. Conclusion:
i. From this lab experiment I’ve learnt about the basic of machine and engine as well as
got a basic idea about four stroke engine, two stroke engine and most importantly the
main components of Internal Combustion engine.
ii. Basic difference between machine and engine are given below:
 Machine is an apparatus used for the generation of mechanical power. On the
other hand engine is a machine with moving parts that converts power into
motion.
 Machine is a static device. On the other hand engine runs the machine.
 Machine comprises of engine as one of its parts. Engine is the heart of the
machine, due to which the machine works.
 Machine is the assembly of desired equipments. Engine is one type of machine.
iii. In my opinion cylinder, piston, piston rings, piston pin, connecting rod, crankshaft,
engine bearings, valves, camshaft, flywheel etc. have more importance in an IC engine.
Discussion:
From this lab experiment I came to know about engine and machine, four stroke engine, two
stroke engine and most important part of IC engine. It is seen that each and every components
of IC engine which we’ve seen is very important to convert any form to mechanical energy.
Learnt about the working principle of four stroke engine. As we know the internal combustion
engine is an engine in which the burning of a fuel occurs in a confined space called a
combustion chamber.
Internal Combustion engine are seen mostly in transportation. Several other uses are for any
portable situation where we need an non-electric motor. The largest application in this
situation would be an Internal Combustion engine driving an electric generator. That way, we
can use standard electric tools driven by an internal combustion engine.

19. Machine Engine
1) Machine is an apparatus used for the
generation of mechanical power. It has
many parts, each with a definite
function, together performing a
particular task.
1. Engine is a machine with moving parts
that converts power into motion.
2) Machine is the assembly of desired
equipments.
2. Engine is one type of machine.
3) It comprises of engine as one of its
parts.
3. It is the heart of the machine, due to
which the machine works.
4) Machine is a static device. 4. Engine runs the machine.
iii) In my opinion engine cylinder, cylinder head, piston, piston rings, gudgeon pin, connecting
rod, crankshaft, camshaft, engine bearings, valves, flywheel have more importance in an IC
engine.
Discussion:
With the analogy of human metabolism we can explain Internal Combustion engine as follows:
Human metabolism = Oxidization of food converts chemical energy into Mechanical energy.
Food = fuel,
Oxygen = air,
Optimum air fuel ratio leads to optimum engine performance = Balanced diet leads to healthy
human life.
Cooling of engine via water, air or any coolant to maintain its temperature = Human body
maintains its temperature by perspiration, sweating.
So it’s seen that each and every parts/components of an Internal Combustion engine are
important to converting any form of energy to mechanical energy.