The document discusses the components and functioning of a four-stroke engine. It describes the four strokes as: 1) Suction stroke where air-fuel mixture enters the cylinder, 2) Compression stroke where the mixture is compressed, 3) Power/expansion stroke where combustion provides power to move the piston, and 4) Exhaust stroke where burnt gases are expelled. The main components that enable this four-stroke cycle are the cylinder block, cylinder head, intake/exhaust valves, piston, connecting rod, crankshaft, spark plug, and fuel injector. Each component has a specific role in the intake, combustion, power and exhaust processes of the engine.

1. ARAB ACADEMY FOR
SCIENCE, TECHNOLOGY AND
MARITIME TRANSPORT.
FOUR STOKE ENGINES
PRESENTED
BY
HABIBU JIBRIN

2. What is Stroke ?
• When piston moves from
TDC to BDC, it is called as 1
stroke. Stroke means
movement of something in
a direction. Here we mean
movement of piston. OR
the full travel of the piston
along the cylinder, in either
direction.

3. THE MAIN COMPONENT OF 4 STOKE
ENGINE.

4. 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. At the upper end of cylinder,
cylinder head and at the bottom end crank case is
bolted. The upper side of cylinder is consists of a
combustion chamber where fuel burns. To handle all
this pressure and temperature generated by
combustion of fuel, cylinder material should have
high compressive strength. So it is made by high
grade cast iron. It is made by casting and usually cast
in one piece. -

5. 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.

6. THE MAIN COMPONENT AND THERE
FUNCTION.
INTAKE VALVE - a valve in
the cylinder head of an
internal-combustion engine
that opens at the proper
moment in the cycle to
allow the fuel-air mixture to
be drawn into the cylinder.
EXHAUST VALVE- a valve
through which burnt gases
from a cylinder escape into
the Exhaust manifold.

7. SPARK PLUG
• Spark plug is a device for
delivering electric current from
an ignition system to the
combustion chamber of a
spark-ignition engine to ignite
the compressed fuel/air
mixture by an electric spark,
while containing combustion
pressure within the engine

8. PISTON
• a disk or short
cylinder that slides
back and forth
inside a larger
cylinder and is
moved by steam in
steam engines and
by the explosion of
fuel in automobiles

9. CONNECTING ROD
• a rod or link for
transmitting motion
and force between a
rotating and a
reciprocating part, as
between a piston and
a crankshaft.

10. CRANKSHAFT
• CRANKSHAFT- a shaft
having one or more cranks,
the main shaft of an
internal-combustion
engine to which the
connecting rods are
attached
Its converts the up and down
motion of the piston into a
turning, or rotating motion.

11. What is 4 Stoke Engine?
• A four-stroke engine (also known as four cycle)
is an internal combustion (IC) engine in which
the piston completes four separate strokes
while turning a crankshaft. The four stokes
includes.
1.Suction
2.Compression
3.Power
4.Exaust

12. 1.SUCTION STOKE . In suction stroke what happens, first the piston
moves from TDC to BDC. As the piston moves the inlet valve opens and the air fuel
mixture in case of petrol engine and only air in diesel engine enters into the cylinder.
The exhaust valve remains closed during this stroke.

13. • 2. compression stroke. the piston moves from BDC to TDC.
The inlet and exhaust valve remains closed during this stroke. As
the piston moves upward( from BDC to TDC) the compression of air-
fuel mixture in case of petrol engine and only air in case of diesel
engine takes place. The compression processes completes when
piston reaches to the TDC. The compression is done to increase the
temperature of the air or air-fuel mixture. The temperature is
increased so that it can easily catch fire during sparking in case of
petrol engine and spraying of diesel in case of diesel engine.

14. • 3.Power/ Expansion/Working Stroke
• Petrol engine: The air-fuel mixture is ignited by the spark plug. Due to the ignition the
burning process starts. The burning of the air-fuel mixture creates a very high pressure
burnt gases. This high pressure burnt gases exerts a thrust on the top face of the piston
and it starts to move downward from TDC to BDC. This is the power stroke of the engine.
In this stroke we get power which is utilized to run the vehicle. The intake and exhaust
valve remains closed during this stroke.
Diesel engine: As the Piston approaches TDC the injection of the diesel in the form of
spray by fuel injector takes place. As the diesel sprayed by the fuel injector come in
contact with the hot compressed gases it catches fire and burning processes starts. Due to
burning high pressure hot burnt gases originates and it puts a very high thrust on the top
face of the piston. Due the thrust impact on the piston it starts to move in downward
direction i.e. form TDC to BDC.

15. • Exhaust Stroke
• In this stroke the piston moves upward i.e. from TDC to BDC. As the piston
moves upward the exhaust valve opens and all the burnt gases left after
power stroke starts escaping out of the cylinder. The burnt gases escape
out in the environment through exhaust Valve. When the piston reaches at
TDC the exhaust process completes. And after this again all the four stroke
repeat themselves.

16. FUEL INJECTOR

17. ENGINE BLOCK