The document discusses the parts and functioning of a four-stroke engine. It explains the four strokes of intake, compression, power, and exhaust. The intake stroke draws fuel and air into the cylinder. In the compression stroke, the valves close and piston compresses the fuel-air mixture. The power stroke ignites the mixture, pushing the piston. Finally, in the exhaust stroke, the spent gases are pushed out. It also lists key engine parts like the piston, crankshaft, connecting rod, valves, and spark plug. The document provides steps for measuring and adjusting tappet clearance to regulate the valves.

1. Part

2. motivation

3. objectives
• At the end of the lesson the student shall be able to
a. Identify the parts and function of the engine
b. Discuss the function of engine
c. Perform valve adjustment
d. Draw the starting system diagram
e. Value the importance of engine

4. topic

5. Deferent gasoline and diesel engine
•Gasoline engines and diesel engines are both
internal combustion engines. Both types of
engines use a four-stroke combustion cycle.
However, their structure and functions vary.
Essentially, while a gasoline engine uses spark
plugs, a diesel engine utilizes compression.

6. Four stroke of an engine
•Afour-strokecycleengineisaninternalcombustion
enginethatutilizesfourdistinctpistonstrokes(intake,
compression,power,andexhaust)tocompleteone
operatingcycle.Thepistonmaketwocompletepasses
inthecylindertocompleteoneoperatingcycle.

7. Intake stroke:
•The piston moves downward to the bottom,
this increases the volume to allow a fuel-air
mixture to enter the chamber.

8. Compression stroke
• The intake valve is closed, and the piston
moves up the chamber to the top. This
compresses the fuel-air mixture. At the end
of this stroke, a spark plug provides the
compressed fuel with the activation energy
required to begin combustion.

9. Power Stroke:
As the fuel reaches the end of it’s
combustion, the heat released from
combusting hydrocarbons increases
the pressure which causes the gas to
push down on the piston and create the
power output.

10. Exhaust stroke
• As the piston reaches the bottom,
the exhaust valve opens. The
remaining exhaust gas is pushed out
by the piston as it moves back
upwards.

11. Parts of a Four Stroke Engine
• Piston
• In an engine, a piston transfers the expanding forces of gas to
the mechanical rotation of the crankshaft through a
connecting rod.
• Crankshaft
• A crankshaft is a part that converts the reciprocating motion
to rotational motion.
• Connecting Rod
• It transfers motion from a piston to a crankshaft, acting as a
lever arm

12. • Flywheel
• The flywheel is a rotating mechanical device that is used to store
energy.
• Inlet and Outlet Valves
• It allows us to enter fresh air with fuel & to exit the spent air-fuel
mixture from the cylinder.
• Spark Plug
• It is a device that delivers electric current to the combustion chamber,
which ignites the air-fuel mixture leading to the abrupt gas expansion.

13. Four stroke engine

14. question
• What is a four stroke engine?
• A four-stroke engine is an internal combustion engine that utilizes four distinct piston strokes to
complete one operating cycle.
• Q2
• What are the various parts of four stroke engine?
• Various parts of four-stroke engine are:
• Piston
• Crankshaft
• Crankshaft
• Connecting Rod
• Inlet and Outlet Valves
• Spark Plug

15. • Q3
• Which is heavier? Two-stroke engine or four-stroke engine?
• A four-stroke engine weighs 50% heavier than a two-stroke engine, and hence four-stroke engine
is heavier.
• Q4
• Which type of engine tend to wear out fast?
• The two-stroke engine tends to wear out fast since it is designed to operate at a higher RPM.
• Q5
• What are the three applications of four-stroke engines?
• Four-stroke engines are used in the following ways:
• Combustion engines
• Go-karts
• Lawn mowers

16. Valve tappet adjustment
• Tappet clearance is typically adjusted by turning an adjustment screw
located on the rocker arm or cam follower. The adjustment screw
changes the position of the rocker arm or cam follower relative to the
valve stem, which in turn changes the clearance.

17. Steps to measure the Tappet Clearance:
• Before starting, make sure that you take all the necessary safety precautions by
wearing PPE, making sure the engine is cooled, and checking if the valves are
closed.
• Ensure that the piston is set in Top Dead Centre (TDC) by using the turning gear.
• Tappet Clearance is measured using a feeler gauge of multiple thicknesses.
• Try to place them one by one between the valve clearance and rocker’s arm to
find the ideal size.
• Once you find the filler gauge that fits perfectly you will know if the distance
between the valve stem and the rocker arm is larger or smaller than it should be.
• Some common doubts or questions regarding tappet clearance may include:

18. 1.Intake: Also known as induction or suction.
This stroke of the piston begins at top dead
center (T.D.C.) and ends at bottom dead
center (B.D.C.). In this stroke the intake
valve must be in the open position while the
piston pulls an air-fuel mixture into the
cylinder by producing a partial vacuum
(negative pressure) in the cylinder through
its downward motion.

19. 1.Compression: This stroke begins at B.D.C, or
just at the end of the suction stroke, and ends at
T.D.C. In this stroke the piston compresses the air-
fuel mixture in preparation for ignition during the
power stroke (below). Both the intake and exhaust
valves are closed during this stage.

20. Combustion: Also known as power or ignition. This
is the start of the second revolution of the four
stroke cycle. At this point the crankshaft has
completed a full 360 degree revolution. While the
piston is at T.D.C. (the end of the compression
stroke) the compressed air-fuel mixture is ignited
by a spark plug (in a gasoline engine) or by heat
generated by high compression (diesel engines),
forcefully returning the piston to B.D.C. This stroke
produces mechanical work from the engine to turn
the crankshaft

21. 1.Exhaust: Also known as outlet. During
the exhaust stroke, the piston, once again,
returns from B.D.C. to T.D.C. while the
exhaust valve is open. This action expels
the spent air-fuel mixture through the
exhaust port.