The document provides a comprehensive overview of automotive engineering, including the classification and components of engines, types of vehicles, fuel properties, and power transmission systems. It discusses internal combustion engines, their construction, and various ignition types, as well as features of two-stroke and four-stroke engines. Additionally, it covers transmission methods like belt, chain, and gear drives, detailing their mechanics and applications in automobiles.

1. UNIT -04
AUTOMOBILES

2. Syllabus
 Basics of automotive engg.
 Types if engines and engine classification
 Engine terminology and major components
 Types of automobiles
 Fuels
 Power transmission drives
 Belt
 Chain
 Rope
 Gear
 Clutch and brake
 Recent innovations
 CRDI , MPFI and HYBRID

3. Basics of automotive engg.
 An automobile is, that has the ability to move or propel by itself
 OR
 Motorized Self propelled vehicle powered by an internal engine used to
transport people and items from one location to another location.
 Classified into
 Internal combustion engine and external combustion engine

4. COMBUSTION ENGINES
The heat engine is an engine in which chemical energy of the fuel is converted to thermal energy by
burning and is again converted to mechanical energy to produce power to propel
types of heat engines
external
combustion
internal combustion
steam engines
turbines
Stirling engine
Otto engine
Diesel engine
Vankel engine

5. External Combustion Engines
An engine, such as a steam engine, in which fuel
is burned outside the engine
Fuel is burned to produce heat to make steam
Fuel burning can take place within a few feet of
the engine to several miles away
Bulky in size and require big boilers

6. Internal Combustion Engines
Designed to be run on any fuel that
vaporizes easily or on any flammable gas
The internal combustion engine is an engine in which
chemical energy of the fuel is converted to thermal
energy by burning and is again converted to mechanical
energy to produce power to propel
Here, the combustion of fuel-oxidizer mixture occurs
in a confined space
applied in:
1. automotive
2. rail transportation
3. power generation
4. aviation
5. garden appliances

7. Components of automobiles
 ENGINES / power units
 FRAME { box tubular, channel }and chassis separate and monocoque (wheels,
brakes,suspension steering, fuel tank, exhaust, battery etc..)
 TRANSMISSION SYSTEMS ( clutch, gears, belts, axles, differentials etc..)
 CONTROL DEVICES – steering , wheel, brakes
 BODY
 ACCESSORIES

8. Engine Classification based on
• Number of working stroke
• Type of fuel used
• No of cylinders
• Cooling system type
• Method of ignition
• Engine speed
• Field of application
• Thermo dynamic cycles
• Lubrication method

9. TYPES OF AUTOMOBILES
 Purpose
 1. Passenger vehicles: Car, Bus, Jeep, Auto-
rickshaw.
 2. Goods vehicles: Truck
 Capacity
 1. Light motor vehicles: Motorcycle,
Car, Scooter.
 2. Heavy motor vehicles: Bus, Tractor, Truck.
 Fuel used
 1. Petrol vehicles: Car, Motorcycle, Jeep,
Scooter.
 2. Diesel vehicles: Truck, Bus, Tractor, Car.
 3. Electric cab: Fork lift, Battery truck.
 4. Steam carriages: Steam road roller.
 5. Gas vehicles: CNG vehicles.
 Number of wheels
 1. Two -wheeler: Motorcycles, Scooter,
Moped.
 2. Three -wheeler: Tempo, Road roller.
 3. Four -wheeler: Car, Bus, Jeep, Tractor.
 4. Six- wheeler: Truck, Bus, Gun carriage
vehicle.
 5. Eight- or more wheelers: Car transporting
vehicle, Rocket transporter.
 Drive of the vehicles
 1. Single-wheel drive vehicle.
 2. Two-wheel drive vehicle.
 3. Four- wheel drive vehicle.
 4. Six-wheel drive vehicle.

10. FUELS
A fuel is a substance which produces heat when burned in the
presence of air
Classification
SOLID FUEL- natural wood, coal,etc
LIQUID FUELS- derived from natural crude oils contain C,N,O
GASEOUS FUEL- from natural gas and prepared gas contains
methane, and other hydro carbons

11. Properties of fuels
 VISCOSITY- resistance offered by fuel itself against flow
 VOLATILITY- ability to evaporate if it evaporates at low temp, it has high volatility
 FLASH POINT- minimum temperature when the fuel gives a momentary flame or flash
 FIRE POINT- minimum temperature of fuel when starts continuous burning
 POUR POINT- its freezing point, it should be less
 CALORFIC VALUE- the amount of heat generated when one kilo gram of fuel is completely burned is
called calorific value of the fuel.
 High calorific value
 Low calorific value
 OCTANE NUMBER
 CETANE NUMBER
 Cetane number (diesel fuel) and octane number (gasoline) both measure the tendency of the fuel to
ignite spontaneously.
 In the cetane number scale, high values represent fuels that ignite readily and, therefore, perform
better in a diesel engine.
 In the octane number scale, high values represent fuels that resist spontaneous ignition and, therefore,
have less tendency to knock in a gasoline engine.

12. Internal Combustion
Engines
-construction and
major components

13. Internal combustion Engine Components:
• Block : Body of the engine containing cylinders,
made of cast iron or aluminium.
• Cylinder : The circular cylinders in the engine
block in which the pistons reciprocate back and
forth.
• Head : The piece which closes the end of the
cylinders, usually containing part of the clearance
volume of the combustion chamber.
• Combustion chamber: The end of the cylinder
between the head and the piston face where
combustion occurs.
• The size of combustion chamber continuously changes from
minimum volume when the piston is at TDC to a maximum
volume when the piston at BDC.
• Connecting rod : Rod connecting the piston with
the rotating crankshaft, usually made of steel or
alloy forging in most engines but may be aluminum
in some small engines
.

14. • Crankshaft : Rotating shaft through which engine
work output is supplied to external systems.
– The crankshaft is connected to the engine block
with the main bearings.
– It is rotated by the reciprocating pistons through the
connecting rods connected to the crankshaft, offset
from the axis of rotation. This offset is sometimes
called crank throw or crank radius.
• Piston rings: Metal rings that fit into
circumferential grooves around the piston and form
a sliding surface against the cylinder walls.
• Camshaft : Rotating shaft used to push open
valves at the proper time in the engine cycle,
either directly or through mechanical or hydraulic
linkage (push rods, rocker arms, tappets) .
• Push rods : The mechanical linkage between the
camshaft and valves on overhead valve engines
with the camshaft in the crankcase.

15. • Crankcase : Part of the engine block surrounding the
crankshaft.
– In many engines the oil pan makes up part of the
crankcase housing.
• Exhaust manifold : Piping system which carries exhaust
gases away from the engine cylinders, usually made of
cast iron .
• Intake manifold :Piping system which delivers
incoming air to the cylinders, usually made of cast metal,
plastic, or composite material.
– In most SI engines, fuel is added to the air in the
intake manifold system either by fuel injectors or
with a carburetor.
– The individual pipe to a single cylinder is called
runner.
• Carburetor : A device which meters the proper amount
of fuel into the air flow by means of pressure differential.
– For many decades it was the basic fuel metering
system on all automobile (and other) engines.
• Spark plug : Electrical device used to initiate
combustion in an SI engine by creating high voltage
discharge across an electrode gap.

16. • Exhaust System: Flow system for removing exhaust
gases from the cylinders, treating them, and
exhausting them to the surroundings.
– It consists of an exhaust manifold which
carries the exhaust gases away from the
engine, a thermal or catalytic converter to
reduce emissions, a muffler to reduce engine
noise, and a tailpipe to carry the exhaust gases
away from the passenger compartment.
• Flywheel : Rotating mass with a large moment of
inertia connected to the crank shaft of the engine.
– The purpose of the flywheel is to store energy
and furnish large angular momentum that
keeps the engine rotating between power
strokes and smooths out engine operation.
I.C. Engine components apart from
components shown in the figure:

17. • Fuel injector : A pressurized nozzle that
sprays fuel into the incoming air (SI
engines)or into the cylinder (CI engines).
• Fuel pump : Electrically or mechanically
driven pump to supply fuel from the fuel tank
(reservoir) to the engine.
• Glow plug : Small electrical resistance heater
mounted inside the combustion chamber of
many CI engines, used to preheat the chamber
enough so that combustion will occur when
first starting a cold engine.
– The glow plug is turn off after the engine is
started.
• Starter : Several methods are used to start IC
engines. Most are started by use of an electric
motor (starter) geared to the engine flywheel.
Energy is supplied from an electric battery.

18. • Top Dead Center (TDC): Position of the piston
when it stops at the furthest point away from the
crankshaft.
• Bottom Dead Center (BDC): Position of the piston
when it stops at the point closest to the crankshaft.
• Stroke : Distance traveled by the piston from one
extreme position to the other : TDC to BDC or BDC
to TDC.
• Bore :It is defined as cylinder diameter or piston
face diameter; piston face diameter is same as
cylinder diameter( minus small clearance).
• Swept volume/Displacement volume : Volume
displaced by the piston as it travels through one
stroke.
Engine Terminology :

19. Internal Combustion Engines – two stroke petrol engine
1. Power / Exhaust 2. Intake / Compression
a. ignition
b. piston moves downward
compressing fuel-air mixture
in the crankcase
c. exhaust port opens
a. inlet port opens
b. compressed fuel-air mixture
rushes into the cylinder
c. piston upward movement
provides further compression

20. Internal Combustion Engines
– two stroke -
Advantages:
•lack of valves, which simplifies
construction and lowers weight
•fire once every revolution, which gives a
significant power boost
•can work in any orientation
•good power to weight ratio
Drawbacks:
•lack of a dedicated lubrication
system makes the engine to wear
faster.
•necessity of oil addition into the fuel
•low efficiency
•produce a lot of pollution

21. Internal Combustion Engines
– four stroke petrol engine -
starting position
a. piston starts moving
down
b. intake valve opens
c. air-fuel mixture
gets in
1. intake
a. piston moves up
b. both valves closed
c. air-fuel mixture
gets compressed
2. compression

22. Internal Combustion Engines
– four stroke -
ignition
a. air-fuel mixture
explodes driving the
piston down
3. power
a. piston moves up
b. exhaust valve opens
c. exhaust leaves the
cylinder
4. exhaust

23. Internal Combustion Engines
– four stroke -
Advantages:
•dedicated lubrication system makes to engine
more wear resistant
•better efficiency that 2-stroke engine
•no oil in the fuel – less pollution
Drawbacks:
•complicated constriction
•should work in horizontal position due to
lubrication

24. Internal Combustion Engines
– Diesel -

25. Internal Combustion Engines
–two stoke Diesel engine -
Advantages:
•self ignition (without electrical spark plug)
•better efficiency
•reliability
•higher durability
•supplied with worse fuels
Drawbacks:
•more NOx production
•more expensive production
•more weight
•louder
•lower revolutions

26. Internal Combustion Engines
– Diesel -
fuel injector

27. Internal Combustion Engines
– multi-cylinder -

28. S.No Petrol Engine Diesel Engine
1.
Air petrol mixture is sucked in the
engine cylinder during suction
stroke.
Only air is sucked during suction
stroke.
2. Spark Plug is used. Employs an injector.
3.
Power is produced by spark
ignition.
Power is produced by compression
ignition.
4. Thermal efficiency up to 25%. Thermal efficiency up to 40%.
5. Occupies less space. Occupies more space.
6. More running cost. Less running cost.
7. Light in weight. Heavy in weight.
8.
Petrol being volatile is
dangerous.
Diesel is non-dangerous as it is non-
volatile.
9. Pre-ignition possible. Pre-ignition not possible.
10. Works on Otto cycle. Works on Diesel cycle.
Comparison between petrol and
diesel engine
PETROL
ENGINE
DIESEL
ENGINE

30. Various systems in an IC engines
 Air intake system
 Exhaust system
 Fuel system
 Ignition system
 Lubrication system
 Cooling system
 Engine starting system

31. Air intake system
 Air filter---intake throttle manifold & valves---carburettor----intake valve

32. Exhaust system

33. Fuel system

34. Lubrication system
 Remove the heat
 Reduce friction
 Prevent leakage
Properties
Types
 Mist lubrication
 Splash sump lubrication
 Dry sump lubrication

35. Cooling system

36. Belt drive
 A belt drive offers smooth transmission of large and flexible power
between shafts at a considerable distance. Pulleys are mounted on the
driver
 Amount of power transmitted depends upon velocity, tension, design etc.
 Its flexible , long life , strength, high coefficient of friction
 Types
 Open belt, cross belt ( speed less than 15 m/s),reversing belt, twisted belt
 Flat belt ( for moderate power), V belt (larger power have short centre to
centre distance)
 Leather, nylon, rubber,fabric etc..

37. Slip and Velocity ratio
 If the frictional resistance between the driver pulley / driven pulley and the belt is insufficient then it
may cause some forward motion of the pulley without carrying the belt called SLIP
 Velocity of a belt V= ω x r
ω =angular velocity= 2ΠN / 60
N1 =driver n2 = driven
1. Neglecting belt thickness
𝑁2
𝑁1
=
𝑑1
𝑑2
2. Considering belt thickness
𝑁2
𝑁1
=
𝑑1+𝑡
𝑑2+𝑡
3. Considering slip and belt thickness
𝑁2
𝑁1
=
𝑑1+𝑡
𝑑2+𝑡
(1-
𝑠
100
)

38. Problems to find
 Length of the belt
Arc + 2 right angled triangle + arc
By solving areas with binomial theorem
Length of
Open belt : L = 1 + Π 𝑟1 + 𝑟2 +
𝑟1 −𝑟2 ²
𝑥
+ 2𝑥
Cross belt : L = 1 + Π 𝑟1 + 𝑟2 +
𝑟1 + 𝑟2 ²
𝑥
+ 2𝑥
 Tension = stress X area
Expansion ratio of belt tension :
𝑇1
𝑇2
= 𝑒 μθ
θ = angle of contact deg X
Π
180
= radian
( it should be in radians , its unit less )
μ = co efficient of friction
 Power transmitted by the belt
P = (T1 – T2 ) V
(T1 – T2 ) ω x r
(T1 – T2)
2Π 𝑁
60
x r ; 2r=d
p = (T1 – T2)
Π 𝑑 𝑁
60
Watts

39. Rope drive
 For a long distance transmission and larger power
transmission wire rope is used,
 wire made of wrought iron /cast iron/ alloy steels
 Individual wires are twisted together making strands
 A number of strands are twisted to make rope
 Regular Lay ropes: direction of twist of wires and strands
are in opposite
 Long Lay ropes: direction of twist of wires and strands are
in same
 Ex : 6 x 19 means 6 stands and each stand have 19 wires
 Groove angle 40 – 60 deg
 Made of cotton , nylon , rayon, jute etc.

40. Chain drive
 Endless chain runs over toothed gear called sprocket
 One of the sprocket is driven and other is driver. Smaller one is
called pinion
 Chains consists plates,pins,bushes made of high grade steels
 Used in cranes,hoists, elevators, conveyers
 Types : roller chain
silent inverted chain :

41. GEAR GRIVE
Terminology

42. Gear drive
 For power transmission torque converter
Two or more gear connected for meshing
together called gear train
 There are driving and driven shafts
 Gears manufactured by casting , milling or
machine cutting
 Made of metallic- cast steel, alloy steel, phosphor
bronze, etc. and non metallic- plastics and
ceramics
 Spur gear in which teeth cut is parallel to axis, slow
speed gears. They are simplicity in design,
economy of manufacture and maintenance,
 Helical gear : teeth cut is in inclined, can take
higher loads ,high speed gears.
 Bevel gears: intersect each other with right angle,
tooth-bearing faces of the gears themselves are
conically shaped
 Worm gear is a threaded screw, where teeth is
engaged between the thread, transmit power at
90° and where high reductions are required.

43. Gear train
 A combination of gear wheels are mounted for which
motion is transmitted from one shaft to another shaft
 Types:
 1.Simple gear train= there is only one gear is mounted on
each shaft.
 2.Compound gear train= two or more gears are mounted on
each shaft.
 3.Riverted gear train= here input and out put shafts are
collinear to each other.
 4.Epicyclic gear train= one gear is moving upon and around
another gear

44. Velocity ratio or gear ratio
 𝑉𝐸𝐿𝑂𝐶𝐼𝑇𝑌 𝑅𝐴𝑇𝐼𝑂 =
𝑆𝑃𝐸𝐸𝐷 𝑂𝐹 𝐷𝑅𝐼𝑉𝐸𝑁 𝑆𝐻𝐴𝐹𝑇
𝑆𝑃𝐸𝐸𝐷 𝑂𝐹 𝐷𝑅𝐼𝑉𝐸𝑅 𝑆𝐻𝐴𝐹𝑇
=
𝐷𝐼𝐴𝑀𝐸𝑇𝐸𝑅 𝑂𝐹 𝐷𝑅𝐼𝑉𝐸𝑅 𝑃𝐼𝐿𝐿𝐸𝑌
𝐷𝐼𝐴𝑀𝐸𝑇𝐸𝑅 𝑂𝐹 𝐷𝑅𝐼𝑉𝐸𝑁 𝑃𝑈𝐿𝐿𝐸𝑌
𝑁2
𝑁1
=
𝑑1
𝑑2
 Peripheral velocity of a gear v1 =
ω1 𝑥 𝑑1
2
 After equating both gear
𝑁2
𝑁𝑖
=
𝑑1
𝑑2
………. i
 Circular pitch p1 =
Π 𝑥 𝑑1
𝑇1
 After equating both gear
𝑇1
𝑇2
=
𝑑1
𝑑2
……………………. ii
 From i and ii velocity ratio or gear ratio
𝑁2
𝑁𝑖
=
𝑑1
𝑑2
=
𝑇1
𝑇2
 Simple gear train

𝑁3
𝑁1
=
𝑑2
𝑑3
…………………………. (i)

𝑁4
𝑁1
=
𝑑1
𝑑4
………………………… (ii)
 Compound gear train

𝑁4
𝑁1
=
𝑑1 𝑥 𝑑3
𝑑2 𝑥 𝑑4
 Reverted gear train

𝑁4
𝑁1
=
𝑑1 𝑥 𝑑3
𝑑2 𝑥 𝑑4

45. Advantages and
disadvantages

46. Clutch
 A clutch is a mechanical device that engages and disengages the power
transmission, especially from driving shaft to driven shaft.
 The sliding body creates friction. Here power transmitted via friction

47. Common working
single plate clutch
 Parts
 Flywheel: This is connected to the crankshaft and spins with the
motion of the engine.
 Pressure plate: This is bolted to the flywheel. It’s spring-loaded, so it
holds the assembly together and also releases the tension that
allows it to rotate freely. made of steel
 Disc: The clutch disc is located between the pressure plate and the
flywheel. It has friction surfaces, something like a brake pad, that
makes and break contact with the flywheel and the pressure plate.
 Throw-out bearing and release system: The throw-out bearing and
the release system work together to engage and release the clutch.
 Working
 when clutch is engaged : The spring loaded pressure plate presses
the clutch plate against flywheel
 When we disengage clutch by pressing : the pressure plate along
with clutch disc moves back breaks the connection with fly wheel,
then fly wheel rotates independent

48. Cone clutch and multiplate clutch
 Similar to the working by means of pressure
 The contact surface are a frustum of cone
 Here the male and female cones engage and disengages by means of spring force

 In multi plate clutch involves more number of plates
 decrease the moment of inertia of the clutch and increase the amount of torque
 Increased coefficient of friction, smooth gear changing.
 low force application

49. Brake
 A brake is a mechanical device that inhibits motion by
absorbing energy from a moving system.
 It is used for slowing or stopping a moving vehicle,
wheel, axle, or to prevent its motion, most often
accomplished by means of friction.
 TYPES
 Drum brakes:
an rotating drum is stopped by using a asbestos lined
mechanical lever or shoe
 Disc brakes:
• Parts: disc, caliper, brake pads.
• disc rotor attached to a caliper,
• hydraulic pressure from master cylinder presses the
caliper together makes heavy friction.

50.  Anti lock brakes:
• parts: sensor, ecu, pump
• ABS prevents wheel from skidding and locking ,
• a wheel sensor and ECU helps to make pressure pulses,
• decreases stopping distance, and makes stability
Emergency brakes,
• service brakes ,
• mechanically applicable,
• helps to park vehicle

51. Common Rail Direct Injection (CRDi):
 Introduction
 Its an advanced technology
 In conventional diesel engine low pressure, less
precise control of fuel delivery, spray is relatively
coarse, thus combustion is inefficient Sluggish and
noisy
 To overcome the above disadvantages and to
increase the efficiency
 We increases the pressure of fuel by a high pressure
fuel pump
 A common rail with several branches of nozzled
edge and plunger controlled by a computer
 CRDI system consists of
 High pressure pump, common rail, injectors, engine
control units

52.  Principle
 ECU gets input from various sensors
 In CRDI system the fuel rail constantly stores and supplies the
fuel to the solenoid valves at regulated pressure.
 Solenoid or piezoelectric valves make possible fine electronic
control over the fuel injection time and quantity,
 The higher pressure that the common rail technology makes
available provides better fuel atomization.
 To lower engine noise, the engine's electronic control
unit can inject a small amount of diesel just before the main
injection event ("pilot" injection), thus reducing its
explosiveness and vibration, as well as optimizing injection
timing , fuel quality, cold starting and so on.
 advantages
 Common rail engines require a very short to no heating-up
time,
 depending on the ambient temperature, and produce lower
engine noise and emissions than older systems
 better combustion at low speed,
 Better power balance
 Compact

53. MPFi, Electronic Fuel injection (EFi), Gasoline Direct
Injection (GDi ).
 This technology consists of following parts:
1. Injectors
2. Fuel Pump
3. Fuel Rail
4. Fuel Pressure Sensor
5. Engine Control Unit
6. Fuel Pressure Regulator
7. Various Sensors – Crank/Cam Position Sensor, Manifold Pressure sensor,
Oxygen Sensor

54.  These are the types of MODERN fuel injection systems,
which are used; mainly in the gasoline or petrol
fuel engines.
 The carburetor, being a mechanical device, was just
not fully capable of controlling an accurate air-fuel
ratio to meet the growing demands for better emission
control and power delivery
 Hence, it was replaced with Fuel Injection technology.
 In this method, the petrol fuel is atomized by spraying
it thru’ an injector;
 It uses multiple individual injectors to insert fuel in each
cylinder
 The fuel pressure regulator, connected to the fuel rail by
means of an inlet and outlet, directs the flow of the fuel.
 While the control diaphragm and pressure spring
controls the outlet valve opening and the amount of fuel
that can return.
 The pressure in the intake manifold significantly changes
with the engine speed and load
 This is the fundamental difference between the earlier
generation carburetor & newer generation Fuel
Injection (EFi) system.

55. ADVANTAGES
 Improves fuel efficiency
 reduces the fuel consumption and makes the
vehicle more efficient and economical.
 reduces the emission
 improves the engine performance.
 The MPFI automobile technology improves
the engine response during sudden
acceleration and deceleration.
 The MPFI engines vibrate less and don’t
require to be cranked twice or thrice in cold
weather.
 It improves functionality and durability of the
engine components.

56. HYBRID
 The rise of petroleum price, high fuel consumption,
unavailability of fuel, to reduce pollution leds to the
invention of hybrid vehicles
 A hybrid vehicle uses two or more distinct types of
power, such as internal combustion engine+electric motor
 hybrid car features a small fuel-efficient gas engine
combined with an electric motor that assists the engine
when accelerating.
 The electric motor is powered by batteries that recharge
automatically while you drive.
 Smaller and more efficient engines.
 Motor-generator:
 Regenerative braking:
 Electric drive:
 Stop-start:


57.  ADVANTAGES

Regenerative braking - the electric motor that drives
the hybrid can also slow the car. In this mode, the
electric motor acts as a generator and charges the
batteries while the car is slowing down.
 Periodic engine shut off - when a hybrid car is
stopped in traffic, the engine is temporarily shut off. It
restarts automatically when put back into gear.

Advanced aerodynamics - to reduce drag

Low-rolling resistance (LRR) tires - narrow, stiffer tires
have less drag

Lightweight materials - increases the efficiency of
hybrid cars.
 LESS FUEL CONSUMPTION- BETTER MILEGE
 LOW NOISE