This document discusses the four stroke petrol engine. It describes the four strokes of the engine cycle: intake, compression, power, and exhaust. During intake, the piston moves down and air-fuel mixture enters the combustion chamber. In compression, the piston moves up and compresses the mixture. In power stroke, ignition occurs and the expanding gases push the piston down. Finally, in exhaust stroke, the piston moves up to push out the exhaust gases. The four strokes complete one cycle requiring two revolutions of the crankshaft.

1. FOUR STROKE PETROL ENGINE
SUBMITTED BY
WILSON G,
YOGANATH S.
KONGUNADUCOLLEGE OF ENGINEERING AND TECHNOLOGY
THOTTIYAM

2. INTRODUCTION OF FOUR STROKE ENGINE
 Engine:
An engine is motor which converts chemical energy into mechanical
energy
 Fuel/petrol engine:
A petrol engine (known as a gasoline engine in North America) is
an internal combustion engine with spark-ignition, designed to run on
petrol (gasoline) and similar volatile fuels.
 Four stroke engine:
A four-stroke engine (also known as four-cycle) is an internal
combustion engine in which the piston completes four separate strokes
which comprise a single thermodynamic cycle. A stroke refers to the full
travel of the piston along the cylinder, in either direction.

3. FOUR STROKE ENGINE
 Four stroke cycle engine s is working at completed four stroke of the
piston or two revoluation of the crank shaft it is called as four stroke
engine
 It is two types of valves is presented these are
 Inlet valve
 Exhaust valve
 Four stroke petrol engine working at the four types of stroke
 Suction stroke
 Compression stroke
 Power stroke or expansion stroke
 Exhaust stroke

4. OTTO CYCLE
In 1862 a German engineer Nikolaus
Augustus Otto began experimenting
with different kinds of engines.
His first experiment was conducted on a
4-stroke engine. 10 years later he
introduced to the world the Otto engine.
The 4-stroke engine consists of a 4-
stroke cycle better known as the Otto
cycle.

5. OTTO CYCLE PROCESS
OTTO CYCLE
Each movement of the cylinder up or down the cylinder
is one stroke of
the four stroke combustion cycle or Otto cycle.
The four stroke cycle consists of
- induction stroke
- compression stroke
- ignition/power stroke
- exhaust stroke
A single cycle requires two revolutions of the crankshaft
to complete.

6. SUCTION STROKE
Suction Stroke (Intake) : During a suction
stroke the piston moves downward by the
engine crankshaft either by the
momentum of flywheel and or the electric
motor or the starter motor. During this
stroke piston moves downward and
creates a vaccum inside the combustion
chamber. Inlet valve (Intake valve)
opens during this stoke allowing the air
fuel mixture to enter the combustion
chamber. Here the fuel is petrol mixed
with air broken up into a mist and
partially vaporized in the carburettor

7. COMPRESSION STROKE
Compression Stroke : During this
stroke piston moves upward and
compresses the charge. The heat
produced by the compression makes
more homogeneous mixture of air and
petrol inside the cylinder. This heat
makes it easier to burn. During this
stroke both valves remain closed.

8. POWER OR EXHAUST STROKE
During this stroke the mixture
under compression is ignited
by the spark that is produced
by a spark plug. The expansion
of the gases due to heat of the
combustion creates a pressure
on the piston and the cylinder
walls. During this stroke piston
moves downward. Both valves
remain closed during this
stroke.

9. EXHAUST STROKE
During this stroke the inlet valve remains closed
and the exhaust valve remains open. During this
stroke piston moves upward and pushes the burnt
gases out through exhaust valve. Only a small
amount of exhaust gases remain in the clearance
space which gets diluted with the fresh incoming
charge during a next suction stroke.
In this type of engine four strokes of piston are
required to complete the cycle.. Four strokes make
two revolutions of the crankshaft. Each alternative
revolution of the crankshaft has one power stroke.
A power stroke consist of above mentioned cycles.

10. THERMODYNAMIC PROCESS ANALYSIS

11. ADVANTAGES OF
FOUR STROKE
PETROL ENGINE
• Less fuel consumption.
• Thermal efficiency is more.
• More volumetric efficiency.
• Less wear and tear.
DISADVANTAGES OF
FOUR STROKE PETROL
ENGINE
• More components.
• Separate valve mechanism is required.
• More cost.
• More complicated design.

12. APPLICATIONS OF FOUR STROKE
PETROL ENGINE:
 The four stroke version is generally used for larger applications and is
the most common type of engine used in automobiles today.
 This type of engine is an ingenious and practical design that has
powered millions of vehicles. It produces a large amount of power in
an efficient and effective manner. It also generally produces less
pollution and lasts longer than a two stroke engine. The engine was
created by Nikolas Otto in the mid 1800s, and in his honor, it's
sometimes known as the Otto Engine. The four main strokes or steps
that make up the cycle are intake, compression, combustion, and
exhaust, which is sometimes called the Otto cycle.

13. LUBRICATION OF FOUR STROKE
PETROL ENGINE:
 Four-stroke engines are lubricated by oil held in an oil sump. The oil
is distributed through the engine by splash lubrication or a
pressurized lubrication pump system; these systems may be used
alone or together

15. DIFFERENCE BETWEEN 4 STROKE AND
2 STROKE PETROL ENGINE
FOUR STROKE ENGINE
 One cycle completed in every 2
revolution of crankshaft
 More moving parts
 More maintenance
 Heavy in weight
 More expensive
 Produce more pollution
 Long engine life
 Not required
 Complex design
TWO STROKE ENGINE
 One cycle completed in every
revolution of crankshaft
 Less moving parts
 Less maintenance
 Light in weight
 Less expensive
 Less pollution
 Short engine life
 Required a mix of oil to lubricate
the crankshaft
 Simpler design