This my lecture slideshow-Mr Hilmi Politeknik Sultan Mizan Zainal Abidin(PSMZA)

1. Prepared by: MUHAMMAD HILMI BIN
ZAID

2.  The topic covers basic theoretical knowledge
and understanding of engine components,
classifications and terminologies. Areas
involving engine construction, operating
principles and valve train

3.  Understand engine construction
 Explain various types of internal combustion
engines construction and operation:
 two-stroke petrol and diesel
 four-stroke petrol and diesel
 rotary/Wankel
 Understand basic engine terminologies
 Explain basic engine terminologies such as
TDC, BDC, stroke, bore, displacement,
compression ratio etc.

4.  Understand cylinder head and valve train
construction
 State the purpose of cylinder head
 Describe various type of valve train:
 OHV
 OHC
 Multivalve
 Explain typical valve timing diagram
 Explain basic operating principles of:
 VTEC
 MIVEC
 VVTI
 CPS
 DVVT

5.  Engine provides the power to drive the
vehicle’s wheel.
 Biggest part of the engine is the cylinder
block. The cylinder block is a large casting of
metal that is drilled with holes to allow for
the passage of lubricants and coolant through
the block and provide spaces for movement
of mechanical parts.
 The block contains the cylinders, which are
round passageways fitted with pistons.
 The block houses or holds the major
mechanical parts of the engine.

6.  The cylinder head fits on top of the cylinder
block to close off and seal the top of the
cylinder.
 The combustion chamber is an area into
which the air-fuel mixture is compressed and
burned.
 The cylinder head contains all or most of the
combustion chamber.
 The cylinder head also contains ports through
which the air-fuel mixture enters and burned
gases exit the cylinder and the bore for the
sparkplug.

7.  The valve train is a series of parts used to
open and close the intake and exhaust ports.
 A valve is a movable part that opens and
closes the ports.
 A camshaft controls the movement of the
valves.
 Springs are used to help close the valves.

8.  The up-and-down motion of the pistons must
be converted to rotary motion before it can
drive the wheels of a vehicle.
 This conversion is achieved by linking the
piston to a crankshaft with a connecting rod.
 The upper end of the connecting rod moves
with the piston.
 The lower end of the connecting rod is
attached to the crankshaft and moves in a
circle.
 The end of the crankshaft is connected to
the flywheel.

9.  Operational cycles. (4 stroke or 2 stroke)
 Number of cylinders. (3,4,5,6,8,10,12
cylinders)
 Cylinder arrangement. (Flat, inline, V-type)
 Valve train type. (OHC,OHV, DOHC)
 Ignition type (Spark, Compression)
 Fuel type (gasoline, natural gas, methanol,
diesel, propane, fuel cell, electric, hybrid)

10.  Types of internal combustion engines
construction:
 4 Stroke petrol and diesel
 2 Stroke petrol and diesel
 Rotary/wankel

11. Intake Stroke
Compression
Stroke
Power Stroke
Exhaust
Stroke

12.  The first stroke of the cycle is the intake stroke.
 As the piston moves away from top dead center (TDC), the
intake valve opens.
 The downward movement of the piston increases the volume of
the cylinder above it, reducing the pressure in the cylinder. Low
pressure (engine vacuum) causes the atmospheric pressure to
push a mixture of air and fuel through the open intake valve.
 As the piston reaches the bottom of its stroke, the reduction in
pressure stops, causing the intake of air-fuel mixture to slow
down. It does not stop because of the weight and movement of
the air-fuel mixture.
 It continues to enter the cylinder until the intake valve closes.
The intake valve closes after the piston has reached bottom
dead center (BDC).
 This delayed closing of the valve increases the volumetric
efficiency of the cylinder by packing as much air and fuel into it
as possible.

13.  The compression stroke begins as the piston
starts to move from BDC.
 The intake valve closes, trapping the air-fuel
mixture in the cylinder.
 The upward movement of the piston compresses
the air-fuel mixture, thus heating it up.
 At TDC, the piston and cylinder walls form a
combustion chamber in which the fuel will be
burned.
 The volume of the cylinder with the piston at
BDC compared to the volume of the cylinder
with the piston at TDC determines the
compression ratio of the engine.

14.  The power stroke begins as the compressed
fuel mixture is ignited.
 With the valves still closed, an electrical
spark across the electrodes of a spark plug
ignites the air-fuel mixture.
 The burning fuel rapidly expands, creating a
very high pressure against the top of the
piston.
 This drives the piston down toward BDC. The
downward movement of the piston is
transmitted through the connecting rod to
the crankshaft.

15.  The exhaust valve opens just before the piston
reaches BDC on the power stroke.
 Pressure within the cylinder causes the exhaust gas to
rush past the open valve and into the exhaust system.
 Movement of the piston from BDC pushes most of the
remaining exhaust gas from the cylinder.
 As the piston nears TDC, the exhaust valve begins to
close as the intake valve starts to open.
 The exhaust stroke completes the four-stroke cycle.
 The opening of the intake valve begins the cycle
again.
 This cycle occurs in each cylinder and is repeated
over and over, as long as the engine is running.

16.  It takes two full revolutions of the crankshaft
to complete the four-stroke cycle.
 One full revolution of the crankshaft is equal
to 360 degrees of rotation; therefore, it
takes 720 degrees to complete the four-
stroke cycle.
 During one piston stroke, the crankshaft
rotates 180 degrees.

17.  The operation of a diesel engine is comparable to a gasoline
engine.
 They also have a number of components in common, (crankshaft,
pistons, valves, camshaft, and water and oil pumps.
 However, diesel engines have compression ignition systems.
Rather than relying on a spark for ignition, a diesel engine uses
the heat produced by compressing air in the combustion chamber
to ignite the fuel.
 The compression ratio of diesel engines is typically three times
(as high as 25:1) that of a gasoline engine.
 As intake air is compressed, its temperature rises to 700°C to
900°C. Just before the air is fully compressed, a fuel injector
sprays a small amount of diesel fuel into the cylinder. The high
temperature of the compressed air instantly ignites the fuel.
 The combustion causes increased heat in the cylinder and the
resulting high pressure moves the piston down on its power
stroke.

19.  This engine requires only two strokes of the
piston to complete all four operations: intake,
compression, power, and exhaust.
 This is accomplished as follows:
 Movement of the piston from BDC to TDC completes
both intake and compression.
 When the piston nears TDC, the compressed air/fuel
mixture is ignited, causing an expansion of the gases.
During this time, the intake and exhaust ports are
closed.
 Expanding gases in the cylinder force the piston
down, rotating the crankshaft.
 With the piston at BDC, the intake and exhaust ports
are both open, allowing exhaust gases to leave the
cylinder and air-fuel mixture to enter.

21.  Although the two-stroke-cycle engine is
simple in design and lightweight because it
lacks a valve train, it has not been widely
used in automobiles.
 It tends to be less fuel efficient and releases
more pollutants into the atmosphere than
four-stroke engines.

22.  The rotary engine, or Wankel engine, is
similar to the standard piston engine in that
it is a spark ignition, internal combustion
engine.
 Its design, however, is quite different. For
one thing, the rotary engine uses a rotating
motion rather than a reciprocating motion.
 In addition, it uses ports rather than valves
for controlling the intake of the air-fuel
mixture and the exhaust of the combusted
charge.

24.  The rotating combustion chamber engine is
small and light for the amount of power it
produces, which makes it attractive for use
in automobiles.
 However, the rotary engine at present cannot
compete with a piston gasoline engine in
terms of durability, exhaust emissions, and
economy.

25.  Bore – cylinder diameter measured in
inches(in) or milimeters (mm).
 Stroke – length of the piston travel between
TDC & BDC.
 TDC – Top dead center
 BDC – Bottom dead center
 If bore = stroke, the engine is called a
square engine.
 If bore > stroke, the engine is called a
oversquare engine.
 If bore < stroke, the engine is called a
undersquare engine.

26.  Cylinder Displacement – volume of the cylinder
when the piston is at BDC.
 Engine displacement – sum/total of the
displacement of each of the engine cylidners.
 Typically, an engine with a larger displacement
produces more torque than a smaller
displacement engine.
 Compression ratio – comparison of a cylinder’s
volume when the piston is at BDC to the
cylinder’s volume when the piston is at TDC.
 The higher the compression ratio, the more power an
engine theoretically can produce.

27.  Volumetric efficiency describes the engine’s
ability to have its cylinders filled with air-
fuel mixture.
 If the engine’s cylinders are able to be filled
with air-fuel mixture during its intake stroke,
the engine has a volumetric efficiency of
100%.
 Typically, engines have a volumetric
efficiency of 80% to 100%.

28.  Purpose of cylinder head
 The cylinder head fits on top of the cylinder
block to close off and seal the top of the
cylinder.
 The cylinder head also contains ports through
which the air-fuel mixture enters and burned
gases exit the cylinder and the bore for the
sparkplug.

29.  Overhead Valve (OHV)
 Overhead Cam (OHC)
 Multivalve

30.  The intake and exhaust valves in an OHV engine
are mounted in the cylinder head and are
operated by a camshaft located in the cylinder
block.
 This arrangement requires the use of valve
lifters, pushrods, and rocker arms to transfer
camshaft rotation to valve movement.

32.  An OHC engine also has the intake and exhaust
valves located in the cylinder head.
 But the cam is located in the cylinder head.
 In an OHC engine, the valves are operated directly
by the camshaft or through cam followers or
tappets.
 Engines with one camshaft above a cylinder are
often referred to as single overhead camshaft
(SOHC) engines.

34.  A multivalve design typically has three, four, or
five valves per cylinder to achieve improved
performance.
 Any four-stroke internal combustion engine
needs at least two valves per cylinder: one for
intake of air and fuel, and another for exhaust
of combustion gases.
 Multi-valve engines tend to have smaller valves
 have lower reciprocating mass,
 can reduce wear on each cam lobe,
 more power from higher RPM without the danger of
valve bounce.

35.  Three-valve cylinder head
 This has a single large exhaust valve and two
smaller intake valves
 Four-valve cylinder head
 This is the most common type of multi-valve
head, with two exhaust valves and two similar
(or slightly larger) inlet valves.
 Five-valve cylinder head
 Less common is the five-valve head, with two
exhaust valves and three inlet valves. All five
valves are similar in size.

36.  Valve timing is the precise timing of the opening and closing of
the valves.
 One way to look at this diagram is to think of these events in
terms of the position of the crankshaft and 360 degrees rotation.

37.  With traditional fixed valve timing, an engine will have a period
of valve overlap at the end of the exhaust stroke, when both
the intake and exhaust valves are open.
 The intake valve is opened BTDC because to give enough time for
air-fuel mixture to get into the cylinder.
 The intake valve is allowed open ABDC because to get advantages
of inertia created by velocity assists in drawing in the fresh
charge.
 The exhaust valve is opened BBDC because the gases inside the
cylinder posses a higher pressure even after the expansion
stroke. This higher pressure enables it to reduce the work that
needs to be done by the engine piston in pushing out these gases.
 The exhaust valve close ATDC because to give sufficient time for
exhaust gas exit through the exhaust valve. If the exhaust valve
is closed like in actual timing diagram, a certain amount of
exhaust gases will get compressed and remain inside the cylinder
and will be carried to the next cycle also.

38.  At low speed, a little valve lift already sufficient
for air/fuel to enter the cylinder.
 The fuel consumption is better and enough for
cruising and low speed.
 But at high speed, the valve need to open and
close very fast and need more longer time for
air/fuel to enter the cylinder.
 Therefore, the valve lift must be higher and the
timing is longer.
 If the engine has fixed valve lift and valve
timing, the performance will be bad.
 To increase the performance of the engine and
better fuel consumption, variable valve timing is
introduced.

39.  How it works?
 As the camshaft spins, the lobes open and close
the intake and exhaust valves in time with the
motion of the piston.
 VVT is the process of altering the timing of a
valve lift event, and is often used to improve
performance, fuel economy or emissions.
 Some cars use a device that can advance the
valve timing. This does not keep the valves open
longer; instead, it opens them later and closes
them later.
 VIDEO

40.  Type of variables valve timing
 VTEC (Honda)
 MIVEC (Mitsubishi)
 VVTI (Toyota)
 CPS (Proton)
 DVVT (Perodua)

41.  How an Engine Works - Comprehensive
Tutorial Animation featuring Toyota Engine
Technologies

42. 1. Explain how 4-stroke engine works?
2. Compare 2-stroke and 4-stroke engines.
3. Compare petrol and diesel engine.
4. Sketch and explain 4 process in the rotary
engine.
5. An engine has 4 cylinders. Each cylinder has
a bore of 5.15cm and its stroke is 6cm.
Calculate the engine displacements.
6. Draw and explain a typical valve timing
diagram for 4-stroke petrol engine.
7. What is ‘valve overlap’?

43. Chapter 1
9 July 2013 (Tuesday)