MODULE III

SUSPENSION SYSTEM Components

The automobile chassis is mounted on the axle, not 1. Springs

directly but through some form of springs. This is 2. Shock absorbers
done to isolate the vehicle body from the road shocks
which may be in the form of bounce, pitch, roll or
sway. All the parts which perform the function of Springs
isolating the automobile from the road shocks are
Springs are mechanical device, used for absorb the
collectively called a suspension system.
energy of shocks, vibrations of the irregularities
The objectives of suspension system are as follows:
present on the road surface.
To prevent the road shocks from being transmitted
to the vehicle components. Functions of suspension springs
To safeguard the occupants from road shocks.
To preserve the stability of the vehicle in pitching Springs are placed between the road wheels and the
or rolling, while in motion. body. When the wheel comes across bump on the road,
it rises and deflects the springs, thereby storing energy
BASIC CONSIDERATION therein. On realising, due to the elasticity of the spring
material, it rebounds thereby expanding the stored
Vertical Loading energy. In this way the spring starts vibrating, of
When the road wheels comes across a bump or pit on course, with amplitude decreasing gradually on
the road, it is subjected to vertical forces, tensile or account of internal friction of the spring material
compressive, depending upon the nature of the road and friction of the suspension joints, till vibrations die
irregularity. These are absorbed by the elastic down.
compression, shear, bending or twisting of the spring
Types of springs
Rolling
The C.O.G. of the vehicles is considerably above the Leaf spring
ground. Due to this reason, while taking the turns, the
centrifugal force acts outwards on the C.O.G. of
vehicle, while the road resistance acts inward at the
wheels. This gives rise to a couple turning the vehicle
about a longitudinal axis. This is called rolling.

Side thrust
Centrifugal force during cornering, cross-winds,
Leaf spring
cambering of the road etc., cause a side thrust to be
Semi elliptic leaf springs are almost universally used for
applied to the vehicle. Such forces are usually
absorbed by the rigidity of the leaf springs or by fitting suspension in light and heavy commercial vehicles. For car
panhard rods. also, these are widely used for rear suspension. The spring
consists of a number of leaves called blades. The blades
Road holdling
The degree to which a vehicle maintains contact with vary in length and the longest blade has eyes on its ends,
the road surface in various types of directional called as master leaf.
changes, e.g. dip, squat, cornering, etc., and in a
straight line motion is called road holding.

Ride and handling

Ride is the qualitative ability of a vehicle to provide a
smooth, comfortable drive on a bumpy road. Handling
is the ability of a vehicle to safety accelerate, brake
and corner. Helper spring
Helper springs are provided on many commercial vehicles This type has additional advantages that the damping is
in addition to the main leaf springs. They allow for a wide proportional to the square of the speed. In this type of shock
range of loading. absorber the tubular shape of early telescopes used in
ancient times. Thus it is called as telescopic type shock
absorber
Coil Spring

Coil Spring
Mainly used with independent suspension system, as they
can be well accommodated in restricted spaces. Coil
Telescopic Shock Absorber
springs don‗t have noise problems nor do they have static
friction causing harshness of ride as in case of leaf springs. Torsion Bar
It takes the shear as well as bending stresses. A helper
spring is also sometimes used to provide progressive A long spring steel rod or flat bar that is attached in the
suspension system in such a way that one end is
stiffness against increasing load.
anchored while the other is free to twist. One end of a
long metal bar is mounted firmly to the vehicle chassis
Shock absorbers
and the opposite end to a lever, the torsion key that is
mounted perpendicular to the bar and bolted to a
suspension arm, a spindle, or the axle. Vertical motion
of the wheel causes the bar to twist around its axis and is
resisted by the bar's torsion resistance. The effective
spring rate of the bar is determined by its length, cross
section, shape and material. If an arm is attached at right
angles, to the free end, any movement of the arm will
cause the rod or bar to twist the bars resistance to
twisting provides a spring action.
Hydraulic shock absorber Torsion bar is commonly used on high performance
vehicles and on SUVs and trucks. With the help of
A springing device must be compromise between
torsion bar, ride height can also be adjusted. However,
flexibility and stiffness. If it is more rigid, it will not too much height increase could give rise to rough ride as
absorb road shocks efficiently and if is more flexible it will the suspension can hit the bump-stop. Torsion bars are
continue to vibrate even after bump has passed. So we must advantageous for a vehicle in many ways. It not only
have a damping of the spring to prevent excessive flexing. provides easy adjustments in the ride heights, but is also
highly durable and takes less vehicle space compared to
Telescopic Shock Absorber coil springs. However, torsion bars are not as efficient as
coil springs and cannot provide consistent spring rate.
The principle of operation of a hydraulic shock absorber is
that when a piston forces the fluid in a cylinder to pass
through some hole, a high resistance to the movement of
piston is developed, which provides damping effect.
 INDEPENDENT SUSPENSION SYSTEM

This system means that the suspension is set-up in such

a way that allows the wheel on the left and right side of
the vehicle to move vertically independent up and down
while driving on uneven surface. A force acting on the
single wheel does not affect the other as there is no
mechanical linkage present between the two hubs of the
same vehicle. In most of the vehicle it is employed in
front wheels.

This types of suspension usually offers better ride

quality and handling due to less unsprung weight. The
main advantage of independent suspension are that they
require less space, they provide easier steer ability, low
weight etc.. Examples of Independent suspension are

 Double Wishbones
Air Spring  MacPherson Strut

Air suspension is a type of Double Wishbone Suspension system

vehicle suspension powered by an electric or engine- A double wishbone suspension is an
driven air pump or compressor. This compressor independent suspension design using two
parallel wishbone-shaped arms to locate the wheel. Each
pumps the air into a flexible bellows, usually made wishbone (or arm) has two mounting positions to
from textile-reinforced rubber. The air pressure the chassis and one joint at the knuckle. The shock
inflates the bellows, and raises the chassis from the absorber and coil spring mount to the wishbones to
control vertical movement. Double-wishbone designs
axle.
allow the engineer to carefully control the motion of
the wheel throughout suspension travel, controlling such
parameters as camber angle, caster angle, toe pattern,
roll center height, scrub radius, scuff and many more.
The suspension consists of a pair of upper and lower
lateral arms, roughly horizontal and of similar length.
The upper arm is usually slightly shorter to induce more
negative camber on the outside wheel as the vehicle
body rolls in a turn. Between the arms there is a knuckle
with a spindle or hub which carries the wheel bearing
and wheel. Knuckles with an integral spindle usually do
not allow the wheel to be driven. A bolt on hub design is
commonly used if the wheel is to be driven.
In order to resist fore-aft loads such as acceleration The line from the strut's top mount to the bottom ball
and braking, the arms need two bushings or ball joints at joint on the control arm gives the steering axis
the body. inclination. The strut's axis may be angled inwards from
the steering axis at the bottom, to clear the tyre; this
The advantage of a double wishbone suspension is that it
makes the bottom follow an arc when steering.
is fairly easy to work out the effect of moving each joint,
To be really successful, the MacPherson strut required
so you can tune the kinematics of the suspension easily
the introduction of unibody (or monocoque)
and optimize wheel motion. It is also easy to work out
construction, because it needs a substantial vertical
the loads that different parts will be subjected to which
space and a strong top mount, which uni bodies can
allows more optimized lightweight parts to be designed.
provide, while benefiting them by distributing stresses.
The disadvantage is that it is slightly more complex than The strut will usually carry both the coil spring on which
other systems like a MacPherson strut. the body is suspended and the shock absorber, which is
usually in the form of a cartridge mounted within the
strut. The strut can also have the steering arm built into
the lower outer portion. The whole assembly is very
simple and can be preassembled into a unit; also by
eliminating the upper control arm, it allows for more
width in the engine compartment, which is useful for
smaller cars, particularly with transverse-mounted
engines such as most front wheel drive vehicles have. It
can be further simplified, if needed, by substituting
an anti-roll bar(torsion bar) for the radius arm. For those
reasons, it has become almost ubiquitous with low cost
manufacturers. Furthermore, it offers an easy method to
Mac Pherson Strut set suspension geometry. Many modern implementations
replace the lower control arm by a wishbone. An anti-
roll bar is optional and if present is attached by a ball-
jointed rod to the spring-damper or by a ball or elasto
merically jointed rod to the wishbone.
Advantages and disadvantages:
Although it is a popular choice, due to its simplicity and
low manufacturing cost, the design has a few
disadvantages in the quality of ride and the handling of
the car.Geometric analysis shows it cannot allow vertical
movement of the wheel without some degree of
either camber angle change, sideways movement, or
both. It is not generally considered to give as good
handling as a double wishbone or multi-link suspension,
because it allows the engineers less freedom to choose
camber change and roll center.

Non Independent suspension system

In dependent suspension there is a rigid linkage between
the two wheels of the same axle. A force acting on one
wheel will effect the opposite wheel. For each motion of
the wheel caused by road irregularities affects the
A MacPherson strut uses a wishbone, or a substantial coupled wheel as well. It is mostly employed in heavy
compression link stabilized by a secondary link, which vehicles. It can bear shocks with a great capacity than
provides a bottom mounting point for the hub carrier independent suspension. Example of this system is
or axleof the wheel. This lower arm system provides
both lateral and longitudinal location of the wheel. The  solid axle.
upper part of the hub carrier is rigidly fixed to the
Anti roll or sway or stabilizer bar
bottom of the outer part of the strut proper; this slides up
and down the inner part of it, which extends upwards Stabilizer bars are part of a car's suspension system.
directly to a mounting in the body shell of the vehicle. They are sometimes also called anti-sway bars or anti-
roll bars. Their purpose in life is to try to keep the car's
body from "rolling" in a sharp turn.
Think about what happens to a car in a sharp turn. If you
are inside the car, you know that your body gets pulled
toward the outside of the turn. The same thing is
happening to all the parts of the car. So the part of the
car on the outside of the turn gets pushed down toward
the road and the part of the car on the inside of the turn
rises up. In other words, the body of the car "rolls" 10 or
20 or 30 degrees toward the outside of the turn. If you
take a turn fast enough, the tires on the inside of the turn
actually rise off the road and the car flips over

STEERING GEOMETRY
CAMBER

STEERING SYSTEM
FRONT AXLE

The front axle is a rigid unsprung beam to which the

wheel hubs are attached by means of steering knuckles
and kingpins. With independent suspension the front
axle is replaced by a load carrying transverse frame
member to which hinged rocker arms are attached. On
four wheel drive vehicles the front axle is powered as
well as the rear axle. In this type of construction the load
carrying beam of the front axle is rigidly joined to the
transmission housing. Short semi axles are connected to
the wheels by means of special constant-velocity joints.
On rough terrain, the front axle can be connected
through a transfer case with a separate shift lever.

Camber angle is the angle made by the wheels of a

vehicle; specifically, it is the angle between the vertical
axis of the wheels used for steering and the vertical axis
STUB AXLE of the vehicle when viewed from the front or rear. It is
used in the design of steering and suspension. If the top
A stub axle is one of the two front axles that carries of the wheel is farther out than the bottom (that is, away
a wheel in a rear wheel drive vehicle. The axle is from the axle), it is called positive camber; if the bottom
capable of limited angular movement about
of the wheel is farther out than the top, it is
the kingpin for steering the vehicle. The stub axle
consists of wheel bearings which support the wheel hub. called negative camber.

The stub axle is named so because it resembles the shape Camber angle alters the handling qualities of a particular
of a stub, like a truncated end of an axle, short in shape suspension design; in particular, negative camber
and blunt. improves grip when cornering. This is because it places
the tire at a better angle to the road, transmitting the
forces through the vertical plane of the tire rather than
through a shear force across it. Another reason for
negative camber is that a rubber tire tends to roll on
itself while cornering. The inside edge of the contact
patch would begin to lift off of the ground if the tire had
zero camber, reducing the area of the contact patch. This
effect is compensated for by applying negative camber,
maximizing the contact patch area. Note that this is only
true for the outside tire during the turn; the inside tire
would benefit most from positive camber.
KING PIN INCLINATION

Combined or included angle is calculated by adding

king pin inclination or steering axis inclination and
camber angle together.
CASTOR

The kingpin inclination is the angle, measured in

degrees, that forms the line passing through the
kingpin and the perpendicular to the ground, looking
at the vehicle from the front, Wheel camber angle was
devised to reduce the kingpin offset, which is the
distance between the projection to the ground level of
the kingpin axis and the point of contact with the tyre,
But it was noted that a marked increase in this angle
created negative effects, especially with the tyres at
low pressure, the specific need arose, to reduce the
camber angle almost to zero, this was also to achieve
regular wear on the tyre, the problem was resolved by
inclining the kingpin towards the lower part of the
wheel, With rigid-axle suspension systems, the
inclination of the kingpin does not vary under the
effect of load and the vertical jolting of the vehicle,
providing there is no axis deformation, in independent
suspension systems, however, the load and vertical
jolting of the vehicle cause both the wheel camber and
the kingpin inclination to vary to the same degree, as
the kingpin forms a single block with the wheel hub.
INCLUDED ANGLE
The caster angle or castor angle is the angular
displacement of the steering axis from the vertical axis Ackermann steering geometry is a geometric
of a steered wheel in a car, motorcycle, bicycle or arrangement of linkages in the steering of a car or
other vehicle, measured in the longitudinal direction. other vehicle designed to solve the problem of wheels
It is the angle between the pivot line (in a car an on the inside and outside of a turn needing to trace
imaginary line that runs through the centre of the out circles of different radii.
upper ball joint to the centre of the lower ball joint)
and vertical. Car racers sometimes adjust caster angle STEERING LINKAGE
to optimise their car's handling characteristics in
particular driving situations.

TOE IN

Steering linkage is a series or arms, rods, and ball

sockets that connect the steering mechanism to the
steering knuckles. The steering linkage used with most
In automotive engineering, toe, also known
as tracking, is the symmetric angle that each wheel manual and power steering mechanisms typically
makes with the longitudinal axis of the vehicle, as a includes a pitman arm, center link, idler arm, and two
function of static geometry, and kinematic and tie rod assemblies. This configuration of linkage is
compliant effects. This can be contrasted with steer,
known as parallelogram steering linkage.
which is the antisymmetric angle, i.e. both wheels
point to the left or right, in parallel (roughly). The pitman arm transfers steering mechanism motion
Negative toe, or toe out, is the front of the wheel to the steering linkage. The pitman arm is splined to
pointing away from the centerline of the vehicle.
the steering mechanisms output shaft (pitman arm
Positive toe, or toe in, is the front of the wheel
pointing towards the centerline of the vehicle. [2] Toe shaft). A large nut and lock washer secure the pitman
can be measured in linear units, at the front of the tire, arm to the output shaft. The outer end of the pitman
or as an angular deflection.
arm normally uses a ball-and-socket joint to connect
to the center link.
ACKERMANN’S PRINCIPLE
The parallelogram steering linkage uses a center link,
otherwise known as an intermediate rod, track rod,
or relay rod, which is simply a steel bar that connects
the steering arms (pitman arm, tie-rod ends,
and idler arm) together. The turning action of the
steering mechanism is transmitted to the center link
through the pitman arm.
The center link is hinged on the opposite end of the
pitman arm by means of an idler arm. The idler arm
supports the free end of the center link and allows it to teeth of the sector. To provide free play, worm is
move left and right with ease. The idler armbolts to mounted on a bearing. It is also known as “Pitman arm

the frame or subframe. shaft”

WORM AND NUT STEERING GEAR
Ball sockets are like small ball joints; they provide for
A nut is meshed with the worm and screws up and
motion in all directions between two connected
down relative to the movement of the worm.
components. Ball sockets are needed so the steering
linkage is NOT damaged or bent when the wheels turn
or move up and down over rough roads. Ball sockets
are filled with grease to reduce friction and wear.
Some have a grease fitting that allowschassis grease
to be inserted with a grease gun. Others are sealed by
the manufacturer and cannot be serviced.

STEERING GEARS

WORM AND WHEEL STEERING GEARS

RECIRCULATING BALL TYPE STEERING

GEAR

A toothed roller is mounted on a roller shaft and worm

gear is mounted on a steering shaft. Gear tooth of
worm gear meshes with that of the roller and motion is
transmitted. The roller is mounted on a ball bearing.
This mechanism has low friction compared to Worm
and Sector mechanism and is widely used on
passenger cars.
WORM AND SECTOR STEERING GEAR Recirculating-ball steering is used on many trucks and
In this type of steering mechanism, worm is connected SUVs today. The linkage that turns the wheels is slightly
different than on a rack-and-pinion system.
at the end of steering shaft and sector is mounted on
a sector shaft. The sector looks like a ball and worm The recirculating-ball steering gear contains a worm
looks like a gear. The teeth of the worm mesh with the gear. You can image the gear in two parts. The first part
is a block of metal with a threaded hole in it. This block
has gear teeth cut into the outside of it, which engage a POWER STEERING
gear that moves the pitman arm (see diagram above).
The steering wheel connects to a threaded rod, similar to
a bolt, that sticks into the hole in the block. When the
steering wheel turns, it turns the bolt. Instead of twisting
further into the block the way a regular bolt would, this
bolt is held fixed so that when it spins, it moves the
block, which moves the gear that turns the wheels.

RACK AND PINION

A rack-and-pinion gearset is enclosed in a metal tube
with each end of the rack protruding from the tube. The
gearset accomplishes two things. First, it converts the
rotational motion of the steering wheel into a linear
Hydraulic power steering systems work by using
motion needed to turn the front wheels, and secondly,
a hydraulic system to multiply force applied to the
the gearset provides gear reduction, which lessens the
steering wheel inputs to the vehicle's steered (usually
effort needed to turn the wheels. A rod called a tie rod
front) road wheels. The hydraulic pressure typically
connects to each end of the rack. The pinion gear is
comes from a gerotor or rotary vane pump driven by the
attached to the steering shaft. When you turn the steering
vehicle's engine. A double-acting hydraulic
wheel, the pinion gear spins, moving the rack. The tie
cylinder applies a force to the steering gear, which in
rod at each end of the rack connects to the steering arm
turn steers the roadwheels. The steering wheel operates
on the spindle. On a power system, part of the rack
valves to control flow to the cylinder. The more torque
contains a cylinder with a piston in the middle and this
the driver applies to the steering wheel and column, the
piston is connected to the rack. There are two fluid ports
more fluid the valves allow through to the cylinder, and
on the rack; one on either side of the piston. Supplying
so the more force is applied to steer the wheels.
higher-pressure fluid to one side of the piston forces the
One design for measuring the torque applied to the
piston to move, which in turn moves the rack providing
steering wheel has a torque sensor – a torsion bar at the
the power assist.
lower end of the steering column. As the steering wheel
Advantages of the rack-and-pinion systems are many.
rotates, so does the steering column, as well as the upper
First is its simplicity. With only two moving parts there
end of the torsion bar. Since the torsion bar is relatively
is not only less friction, but the positive engagement of
thin and flexible, and the bottom end usually resists
the system gives a very tight and responsive feel to the
being rotated, the bar will twist by an amount
steering. Secondly, the complete system has only four
proportional to the applied torque. The difference in
wear points in the linkage: the inner ball joints and outer
position between the opposite ends of the torsion bar
tie-rod ends. This simplicity and lower number of parts
controls a valve. The valve allows fluid to flow to the
is one reason why most new cars use rack-and-pinion.
cylinder which provides steering assistance; the greater
Third, a rack-and-pinion system is quite a bit lighter than
the "twist" of the torsion bar, the greater the force.
a traditional box system. Less weight off the front of the
Since the hydraulic pumps are positive-displacement
car is always a good thing to strive for. Fourth, because
type, the flow rate they deliver is directly proportional to
of its design you often gain added clearance for headers
the speed of the engine. This means that at high engine
and the rack-and-pinion is sometimes easier to package
speeds the steering would naturally operate faster than at
into the car.
low engine speeds. Because this would be undesirable, a
restricting orifice and flow-control valve direct some of
the pump's output back to the hydraulic reservoir at high
engine speeds. A pressure relief valve prevents a
dangerous build-up of pressure when the hydraulic
cylinder's piston reaches the end of its stroke.
The steering booster is arranged so that should the
booster fail, the steering will continue to work (although
the wheel will feel heavier). Loss of power steering can
significantly affect the handling of a vehicle. Each
vehicle owner's manual gives instructions for inspection
of fluid levels and regular maintenance of the power
steering system.
The working liquid, also called "hydraulic fluid" or
"oil", is the medium by which pressure is transmitted.
Common working liquids are based on mineral oil.
Some modern systems also include an electronic control
valve to reduce the hydraulic supply pressure as the
vehicle's speed increases; this is variable-assist power
steering.

An Electronic Power Steering (EPS) system‘s advantage

over a hydraulic system is if the engine stalls, you will
still have steering assist. This advantage can also be a
disadvantage if the system should shut down while the
engine is running you lose steering assist. A driver
unaware of this condition would become concerned if an
electrical or electronic failure occurred while the engine
was running, as the loss of assist would not be expected.
Electronic power steering systems eliminate the need for
a pump, hoses and a drive belt connected to the engine
using variable amounts of power. The configuration of
an EPS system can allow the entire power assist system .
to be packaged on the rack and pinion steering gear or in WHEELS AND TYRES
the steering column. The system does not drag on the Various requirement of an automobile wheel:
engine from either a power steering pump or alternator 1. Must be strong enough to take the vehicle load,
because it will not provide assist until required by driver provide cushioning effect.
input. Also, there is no hydraulic fluid. 2. Should be balanced both statically as well as
dynamically
ELECTRO HYDRUALIC POWER STEERING
3. Should be lightest possible so that the unsprung
Electro-hydraulic power steering systems, sometimes weight is least.
abbreviated EHPS, and also sometimes called 4. Should be possible to remove or mount the wheel
"hybrid" systems, use the same hydraulic assist easily.
technology as standard systems, but the hydraulic 5. Material should not deteriorate with weathering
pressure comes from a pump driven by an electric and age.
motor instead of a drive belt at the engine
Wheels can be made from cast aluminium alloy or
magnesium alloy. Alloy wheels are popular because of
their appearance and because they are lighter than
similar steel wheels. Aluminium is a better conductor of
heat, so alloy wheels can dissipate heat from brakes and
tyres more effectively than steel ones. Most wheels have
ventilation holes in the flange, so air can circulate to the
brakes. Most passenger car wheels are of well, or drop- located in board of the attachment face of the disc to the
centre design. This design allows for tyre removal and center of the rim.
fitting. The removal and fitting of tyres should be carried
out according to manufactures instructions.

TYPES OF WHEELS

There are three types of wheels

1. Pressed steel disc wheel

2. Wire or spoke wheel
3. Alloy wheels

DISC WHEEL

A zero set wheel is the one in which the rim center line
coincides with the attachment face of the disc while in
the outset wheel the center line of the rim is located out
board of the attachment face of the disc. A wheel whose
disc can be mounted on either face to provide inset or
outset thus decreasing or increasing the wheel track is
called reversible wheel. A wheel constructed in two
Passenger cars normally use rims which are of well parts, which when securely fastenend together combine
based, or drop- centre design. The drop enter is used for to form a rim having two fixed flanges is called a dived
mounting and demounting the tyre onto the rim. Wheels wheel.
must be strong enough to carry the mass of the vehicle
WIRE OR SPOKE WHEEL
and withstand the forces that are generated during use.
The wheel centre must accurately locate the wheel rim
centrally on the axle. It must also provide the required
distance from the centreline of the wheel, to the face of
the mounting flange. The rim must be accurately shaped
and dimensioned and strong enough to support the tyre
under the load of the vehicle and the forces generated by
the motion of the vehicle. When inflated, the tyre is
locked to the rim by tapering the bead seat towards the
flange, or by safety ridges or humps, close to the flange. In
the event of sudden deflation, or blow-out, safety ridges
prevent the tyre moving down into the well. This helps
maintain control of the vehicle while the brakes are
applied. Well-based rims can also be used on heavy
commercial vehicles for tubeless tyres.

A wheel may be inset, zero set or outset depending upon

the position of the rim in relation to attachment face of
the disc. In the inset wheel the center line of the rim is
Unlike the disk wheel the wire wheel has a separate hub, Alloy wheels are wheels that are made from
which is attached to the rim through a number of wire an alloy of aluminium or magnesium. Alloys are
spokes. The spokes carry the weight, transmitting the mixtures of a metal and other elements. They generally
driving and braking torques and withstand the side provide greater strength over pure metals, which are
forces while cornering, in tension. Spokes are long, thin usually much softer and more ductile. Alloys of
wires and as such these cannot take any compressive or aluminium or magnesium are typically lighter for the
bending stresses. All types of loads are sustained by the same strength, provide better heat conduction, and often
spokes in tension. The spokes are mounted in a produce improved cosmetic appearance over steel
complicated criss-crosss fasion in all the three planes. wheels. Although steel, the most common material used
The component of vehicle weight in the direction of in wheel production, is an alloy of iron and carbon, the
spokes above the hub is sustained by these spokes in term "alloy wheel" is usually reserved for wheels made
tension. Similarly, the driving and the braking torques from nonferrous alloys. Lighter wheels can improve
are taken up by the spokes forming triangular handling by reducing unsprung mass,
arrangement. Thus it is seen that the spokes have to be allowing suspension to follow the terrain more closely
mounted on the wheel in a complicated manner. The and thus improve grip, however not all alloy wheels are
initial tension of the spokes can be adjusted by means of lighter than their steel equivalents. Reduction in overall
screw nipples which also serve to secure the spokes to vehicle mass can also help to reduce fuel consumption.
the rim, the hub is provided with internal splines to
Better heat conduction can help dissipate heat from
correspond to the splines provided on the axle shaft. A
the brakes, which improves braking performance in
wing nut screws the hub on the axle shaft. The
more demanding driving conditions and reduces the
advantages of this type of wheel are light weight and
chance of diminished brake performance or even failure
high strength and above all it provides much better
due to overheating. Most alloy wheels are manufactured
cooling of the brake drum. It is also very easy to change
using casting, but some are forged. Forged wheels are
the wheel when required, because only one nut has to
usually lighter, stronger, but much more expensive than
opened. However, wire wheels are expensive due to
cast wheels. There are two types of forged wheels: one
their intricate construction. Further, because the rim of a
piece and modular. Modular forged wheels may feature
wired wheel has holes, it is not possible to fit tubeless
two- or three-piece design. Typical multi-piece wheels
tyre on wire wheels.
consist of the inner rim base, outer rim lip and wheel
ALLOY WHEEL center piece with openings for lug nuts. All parts of a
modular wheel are held with bolts. BBS RS is one of the
most famous three-piece modular forged wheels.
RIM SIZES & DESIGNATIONS
To ensure correct fit between a tyre and rim, all manufactured in stages. The casing is initially
manufacturers of wheels and tyres comply with standard formed by laying the rubber inner and the first
dimensions, as recommended by automotive
layer of textile ply cords, around a flat drum
manufactures. The width of the rim is the distance
mould. The rubber-covered bead wire and
across the rim flanges, at the bead seat. Its diameter is
the distance across the centre of the rim from bead seat sidewalls are then locked into position.
to bead seat. The shape of well-based rims is provided The rubber sidewalls protect a finished tyre from
by a letter code, such as J, K, JJ and KK. The width of the kerb damage and weathering. At the second stage-
rim and the diameter is traditionally stated in inches. A building machine, the tyre is shaped. Belts of steel
rim designated 7 JJ by 14 would refer to a rim measuring wire are guided into place. The tread is then
7 inches across the rim flanges and 14 inches in diameter
positioned and the uncured tyre is consolidated
from bead seat to bead seat, with the profile conforming
to a JJ code. by rollers, before it is placed in the mould. During
the moulding and curing stage, the tyre is
TYRES subjected to high temperature and pressure and it
takes on its final fixed identity, with its own
The tyre provides a cushion between the vehicle
distinctive tread pattern. It is then trimmed and
and the road to reduce the transmission of road
checked for balance and quality before it is
shocks. It also provides friction to allow the
inflated and run under load against a rotating
vehicle perform its normal operations. Modern
drum. This is a final check for ride uniformity.
tyres are manufactured from a range of materials.
The rubber is mainly synthetic. Two types of tyre TYRE TREAD DESIGNS
construction are common – cross-ply and radial.
Most passenger cars now use radial tyres, as do Tyres generally fall into one of the following
most 4- wheel-drives and heavy vehicles. Tube categories:
tyres require an inner tube to seal the air inside 1. Directional
the tyre. 2. Non directional
3. Symmetric and Asymmetric
CONSTRUCTION

Directional tread patterns are designed to provide a

range of functions during particular driving conditions.
The tyre can only be mounted to the wheel so that it
revolves in a particular direction to correspond with the
tread pattern. An arrow on the tyre sidewall indicates the
designed direction of forward travel. On-directional
tread patterns are designed in such a way that the tyre can be
mounted on the road wheel for any direction of rotation.
Tyre treads can be directional, non-directional,
symmetric and asymmetric.
In wet conditions, the coefficient of friction between a
smooth tyre and the road surface falls to an extremely
A tyre provides a cushion between the vehicle low value. Aquaplaning is prevented by Grooves in the
and the road, to reduce the transmission of road tread pattern clearing water away from the contact patch
shocks. The air in the tyre supports the vehicle’s area. This allows a relatively ―dry area‖ to be formed
and for road adhesion to be maintained. Static friction
mass and the tread provides frictional contact with
occurs when two objects are not moving relative to each
the road surface, so the vehicle can manoeuvre
other e.g. the tyre against the road surface while the car
for normal use. Radial ply tyres are usually
is stopped. To overcome this, a force must be applied (car hole created by the nail, thus giving substantial time
starting to move) which results in rolling friction. If between a puncture and a flat tyre.
rolling friction increases until it is greater than static
sliding friction will result.

CONVENTIONAL TUBE TYRE

It is suitable for high speed performance and

comfortable driving due to the strengthened edge
construction for better sealing with rim of tyres. Also
It consists of two main parts, the carcass and the tread. there is an improved mileage due to light weight of the
The carcass is the basic structure taking mainly the tyre compared to tube tyres.
various loads and consists of a number of plies wound in
a particular fashion from the cords of rayon or any other TYPES OF CARCASS USED IN TYRES
suitable material. Each cord in each ply is covered with
resilient rubber compounds and all the plies are insulated 1. Bias / Cross-Ply
against each other. The term ply rating which is often
used in tyre industry does not indicate exact number of 2. Radial Ply
plies in the tyre. It is only relative index of tyre strength
3. Belted Bias Ply
and load carrying capacity. In order to prevent the tyre
form being thrown off the rim the plies are attached to BIAS/CROSS PLY TYRE
two rings of bundles of bronze coated high tension steel
wire strands, insulated with rubber. A radial road tyre
normally has one such bundle in the lead whereas a
cross ply tyre for off road use may have two to three
such bundles. These rings are made to fit snugly against
the wheel rim, there by anchoring the tyre to the rim.
These rings are called bead and are considered the
foundation of the tyre.

TUBELESS TYRE

There is no tube in a tubeless tyre. The tyre and the rim

of the wheel form an airtight container to seal the air as
the tubeless tyre has an inner lining of impermeable
halobutyl. The valve is directly mounted on the rim. If a
tubeless tyre gets punctured, air escapes only through the
This type of tyre is the older form. It is also called a
bias-ply or conventional tyre. It is constructed of 2 or
Radial ply tyres have much more flexible sidewalls due
more plies or layers of textile casing cords, positioned
to their construction. They use 2 or more layers of
diagonally from bead to bead. The rubber-encased cords
casing plies, with the cord loops running radially from
run at an angle of between 30 and 38 degrees to the
bead to bead. The sidewalls are more flexible because
centreline, with each cord wrapped around the beads. A
the casing cords do not cross over each other. However,
latticed criss-crossed structure is formed, with alternate
a belt of 2 or more bracing layers must be placed under
layers crossing over each other and laid with the cord
the tread. The cords of the bracing layers may be of
angles in opposite directions. This provides a strong,
fabric, or of steel and are placed at 12, to 15 degrees to
stable casing, with relatively stiff sidewalls. However
the circumference line. This forms triangles where the
during cornering, stiff sidewalls can distort the tread and
belt cords cross over the radial cords. The stiff bracing
partially lifting it off the road surface. This reduces the
layer links the cord loops together to give fore and aft
friction between the road and the tyre. Stiff sidewalls
stability, when accelerating, or braking and it prevents
can also make tyres run at a high temperature. This is
any movement of the cords during cornering. The cord
because, as the tyre rotates, the cords in the plies flex
plies flex and deform only in the area above the road
over each other, causing friction and heat. A tyre that
contact patch.
overheats can wear prematurely.
There are no heavy plies to distort and flexing of the
RADIAL PLY TYRE
thin casing generates little heat, which is easily
dispersed. A radial ply tyre runs cooler than a
comparable cross-ply tyre and this increase tread life. A
radial tyre has less rolling resistance as it moves over the
road surface.

BELTED BIAS TYRE

The structure consist of a conventional carcass and a belt

made of two or more crossed layers. It has a ply cut at an
angle and the belt is wrapped around the circumference
of the tire over the bias ply or radial ply. The difference
between the carcass and the belt is determined by the
different goals they are designed to fulfil and
consequently different materials are used in the
construction. The belt is made mainly from Aramide and
its function is to reduce the dynamic deformation caused
by centrifugal forces, while the carcass provides the tyre
with its stiffness and load carrying capacity.
 STARTING SYSTEM

The "starting system", the heart of the electrical system

in your car, begins with the Battery. The key is inserted
into the Ignition Switch and then turned to the start
position. A small amount of current then passes through
the Neutral Safety Switch to a Starter Relay or Starter
Solenoid which allows high current to flow through
the Battery Cables to the Starter Motor. The starter
motor then cranks the engine so that the piston, moving
downward, can create a suction that will draw
a Fuel/Air mixture into the cylinder, where a spark
created by the Ignition System will ignite this mixture.
If the Compression in the engine is high enough and all
this happens at the right Time, the engine will start.

COMPONENTS IN STARTING SYSTEM

STARTER MOTOR

TYRE MATERIALS

Modern tyres are made from a range of materials.

The rubber is mostly synthetic, with carbon black
added to increase strength and toughness. When
used in the tread, this combination gives a long
life. Natural rubber is weaker than the synthetic
version. It’s used mainly in sidewalls. The plies are
made from cords of fabric, coated with rubber.
Manufacturers use a sophisticated selection
process to create combinations that provide the
required performance characteristics and
‘hysteresis level’ of the tyre.

TYRE INFORMATION

P205/65 R15 92H

 P for passenger car tyre
 205 is the section width in mm
 65 is 65% aspect ratio
 R radial ply construction
 15 inch diameter rim A starter motor converts the electrical energy stored in
 92 load index, for a maximum load of 630 kg the battery into mechanical energy to crank the engine
 H for a speed rating upto 210 KMPH for starting. A simple electric motor includes a
horseshoe-shaped soft-iron yoke with field windings
wound around each of the two pole-pieces. The armature
winding rotates between the pole-pieces with its ends STARTING DRIVES
attached to each half-segment of a split-ring. The current
from the positive terminal of the battery flows to the The starting drive is the part of the starter motor that
right-hand brush and segment, round the armature loop, engages the armature to the engine fly-wheel ring gear.
and comes out of the left-hand segment and brush. It A starter drive includes a pinion gear set that meshes
then circulates through the left-and right-hand yoke field with the flywheel ring gear on the engine‘s crankshaft.
windings and returns to the negative terminal of the So here we use Bendix drive to start an engine.
battery.
A Bendix drive is a type of engagement mechanism
When the current flows through the yoke field windings, used in starter motors of internal combustion engines.
it converts the yoke into an electromagnet due to which The device allows the pinion gear of the starter motor to
a magnetic field or flux is created between the pole- engage or disengage the flywheel of the engine
pieces. Similarly, due to the flow of current through the automatically when the starter is powered or when the
armature loop, concentric rings of magnetic flux are engine fires, respectively. The Bendix system places the
established around the two half-conductor cores. This starter drive pinion on a helical drive spring. When the
magnetic flux flows anticlockwise around the left-hand starter motor begins turning, the inertia of the drive
conductor and clockwise around the right-hand pinion assembly causes it to wind the spring forcing the
conductor. length of the spring to change and engage with the ring
The magnetic lines of force between the yoke poles and gear. When the engine starts, backdrive from the ring
those for the armature conductors travel in the same gear causes the drive pinion to exceed the rotative speed
direction, and the two sets of lines merge and strengthen of the starter, at which point the drive pinion is forced
each other. This is indicated below the left-hand back and out of mesh with the ring gear. There may be
conductor and above the right-hand conductor. inboard or outboard type. In outboard type pinion moves
Conversely, where the yoke and armature magnetic away from the starting motor to engage, in inboard it
fields travel in opposite directions, they neutralise each moves toward the starting motor.
other. Hence, the field strength above the left-hand
conductor and below the right-hand conductor is very TYPES OF BENDIX DRIVE
weak. The difference in the magnetic field strengths
STANDARD BENDIX DRIVE
above and below each conductor gives rise to a net
upward force, exerted on the left-hand conductor and a
net downward force, on the right-hand conductor so that
a clockwise-rotating torque is applied to the armature
loop.

This drive is an inboard type starting drive. There is a

thread sleeve on the armature shaft. The sleeve can slide
to turn freely over the shaft. The shaft is keyed to the
For starting, an engine is required to be turned-over (or fixed drive head which is connected torsionally to the
cranked) at a speed sufficient to cause reasonable sleeve through a coil spring and sliding dog, on the
turbulence of the incoming air-fuel mixture so that sleeve there is a pinion to which an unbalanced weight is
combustion is possible. In addition, the engine‘s attached, the purpose the weight being to prevent the
flywheel must be given sufficient momentum to keep it rotation of the pinion. When the motor starts the
rotating for the first couple of firing strokes until the armature rotates causing the sleeve to rotate and because
engine develops sufficient power to run unassisted. the pinion cannot rotate due to the unbalance weight, it
Typically, a petrol engine requires a minimum cranking moves axially towards the motor till it is engaged with
speed in the region of 50-100 rpm to ensure starting in the flywheel. As it is mesh with the engine flywheel, the
cold weather, whereas a diesel engine requires at least flywheel rotated and the engine starts. When the engine
100 rpm. starts, it is the flywheel that rotates the pinion much
faster than the armature with the result that the pinion is
backed out of mesh with the flywheel.
FOLO-THRU DRIVE SOLENOID – ACTUATED DIRECT DRIVE

This is similar in construction to the standard bendix

drive. The armature shaft is connected to the threaded
sleeve through a spring and over running clutch, the
inside of the pinion barrel fits into the sleeve threads, The main parts of a solenoid-actuated, direct- drive
toward the end of the sleeve is provided a detent, lock starter are the solenoid, the shift lever, the overrunning
clutch, and the starter pinion gear. The solenoid used to
pin and anti drift pin. The engagement of the pinion with
the pinion with the flywheel takes place in the similar actuate a starter drive has two coils: the pull-in winding
manner as in case of std bendix drive. However towards and the hold-in, or holding, winding (Figure 9-43). The
the end of the pinion travel the lock pin drips into the pull-in winding consists of few turns of a heavy wire.
detent and would not let the pinion disengage The winding is grounded through the motor armature
prematurely due to a false start. The pinion thus and grounded brushes. The hold-in winding consists of
continues driving the flywheel till engine really gets many turns of a fine wire and is grounded through the
started and attain a speed of oabout 400 rpm. solenoid case.

COMPRESSION SPRING TYPRE DRIVE

When the motor is started the sleeve rotating alongwith

the armature shaft. This cause the pinion to travel
towards the motor till its teeth engage completely with
When the ignition switch is turned to the start
the teeth on the periphery of the flywheel. By this time
position, current flows through both windings. The
the pinion also strikes against the collar which stop its
solenoid plunger is pulled in, and the contacts are
travel further. The pinion therefore tries to rotate but is
closed. This applies battery voltage to both ends of the
offered initial resistance by the flywheel which is
pull-in winding, and current through it stops. The
stationary by now. The torque of the shaft then has a
magnetic field of the hold-in winding is enough to keep
tendency to force the threaded sleeve further out against
the plunger in place. This circuitry reduces the solenoid
the spring tension, till flywheel starts rotating. The
current draw during crank- ing, when both the starter
spring tension is consequently relieved. When the engine
motor and the ignition system are drawing current from
starts, the flywheel rotating at a faster speed causes the
the battery.
pinion to be backed out mesh.
The solenoid plunger action, transferred through the
shift lever, pushes the pinion gear into mesh with the
flywheel ring gear (Figure 9-44). When the starter
motor receives current, its armature begins to turn.
This motion is transferred through the overrunning The lead acid battery is most widely used in automobiles.
clutch and pinion gear to the engine flywheel. It consists of the following components.

1. Container
2. Plates
3. Separators
4. Cell covers
5. Electrolyte

Container

It is a single piece construction and is made of hard

rubber or bitumiouns material. It is divied into
compartments by partitions for different cells.

Plates

The teeth on the pinion gear may not immediately mesh

with the flywheel ring gear. If this hap- pens, a spring
behind the pinion compresses so that the solenoid plunger
can complete its stroke. When the motor armature begins
to turn, the pinion teeth line up with the flywheel, and
spring force pushes the pinion to mesh.

BATTERY

The Battery is the main part of the electrical system in

an Automobile. The battery supplied current for
operation of the starting motor and ignition system when
the engine is being cranked for starting. It also supplies
current for light, radio, heater and several other The plates in the battery consists of perforated grids
accessories. into which lead or lead peroxide has been pressed.
There are two types of plate groups in each cell
TYPES OF BATTERIES
positive plate group and negative pate group. The
1. Lead acid battery plate group connected to the positive terminal of the
2. Alkaline battery cells consists of the grids filled with a paste of Lead
a. Nickel iron type Peroxide. The negative plate group consists of
b. Nickel cadmium type Metallic lead.
3. Zinc air battery
Seperator

LEAD ACID BATTERY

 Separators are placed between the negative and power steering, power windows, electrical system for
positive plates to keep them separate with each automobile transmission, etc. A rectifier or diode is
other. These are usually made of special treated required to convert AC to DC as all electrical
wood, hard rubber etc. equipment‘s use DC.

Electrolyte Principle

The principle of working of alternator differs from that of

The electrolyte used in the lead acid battery is the
dynamo in the manner in which the conductor and
solution of sulphurice acid. It consists of 40% of
magnetic field move relative to each other. In an
sulphuric acid and 60% of distilled water . The level of
alternator the conductor remains stationary but the
electrolyte should be abount 10 mm over the tops of the
magnetic field is rotated. However, conductor rotates and
plates.
magnetic field remains stationary in case of a dynamo.
CHEMICALS USED IN BATTERY In an alternator, a rotating bar magnet produces magnetic
field which is cut by a stationary conductor. Figure 15.21
The chemicals used in a Battery are as follows shows the working principle of an alternator. This
magnet is rotated by half revolution such that North Pole
1. Sponge Lead ( Solid)
comes down and South Pole takes upper position. During
2. Lead Oxide (Paste)
this the current in the upper leg of conductor flows in one
3. Sulphuric Acid (Liquid)
direction. When the magnet is now rotated by another
BATTERY CHARGING half revolution, the direction of current in the wire is
reversed. Therefore with the revolution of magnet, the
current reverses its direction after each half revolution.
Thus, an alternating current flows. This is the principle of
working of an alternator.

REACTIONS WHILE CHARGING

The chemical reactions take place between the three

chemicals in the battery. In the presence of sulphuric
The charging system consists of generator for acid, the electrons from one group of plates collect on the
converting mechanical energy from the engine into other group of plates.
electrical energy, a regulator to control the amount of The following chemical reactions take place while
electrical energy so produced, a relay to regulate the charging and discharging.
flow of the current from the generator to the battery
relevant to the state of charge of the battery and an
ammeter or indicating lamp to whether the system is
operating or not. In the moderns vehicles the charging
system consists of an alternator.
A battery can be tested to ascertain its condition by
ALTERNATOR
specific gravity test

While the chemical reaction taking place in the battery

during discharge, the electrolyte becomes dilute to form
―An alternator generates alternating current (AC) unlike a water. The proportion of water goes on increasing as the
dynamo which generates direct current (DC)‖. discharging continues. The relative amounts of water
Modern automobiles which require more electric loads and acid is determined by the specific gravity test
are fitted with alternators instead of dynamos. These
vehicles require more electrical power because they have
MODULE IV smog produced mostly from evaporated,
unburned .fuel.
EXHAUST SYSTEM  Nitrogen oxides (NO and NO2, together called
NOx) are a contributor to smog and acid rain,
Exhaust system consist of Silencer or muffler and a which also causes irritation to human mucus
Catalytic converter. membranes.

Catalytic converter In chemistry, a catalyst is a substance that causes or

accelerates a chemical reaction without itself being
Catalytic converter are emission control devices fitted on
affected. Catalysts participate in the reactions, but are
the exhaust system. Catalytic converters convert harmful
neither reactants nor products of the reaction they
exhaust gases to un-harmful gases. Catalytic converter
catalyze. In the human body, enzymes are naturally
are coated with noble metals like platinum, palladium,
occurring catalysts responsible for many essential
rhodium.
biochemical reactions
In the catalytic converter, there are two different types of
catalyst at work, a reduction catalyst and an oxidation
catalyst. Both types consist of a ceramic structure coated
with a metal catalyst, usually platinum, rhodium and/or
palladium. The idea is to create a structure that exposes
the maximum surface area of catalyst to the exhaust
In order to reduce emissions, modern car engines stream, while also minimizing the amount of catalyst
carefully control the amount of fuel they burn. They try required, as the materials are extremely expensive. Some
to keep the air-to-fuel ratio very close to of the newest converters have even started to use gold
the stoichiometric point, which is the ideal ratio of air to mixed with the more traditional catalysts. Gold is cheaper
fuel. Theoretically, at this ratio, all of the fuel will be than the other materials and could increase oxidation, the
burned using all of the oxygen in the air. For gasoline, chemical reaction that reduces pollutants, by up to 40
the stoichiometric ratio is about 14.7:1, meaning that for percent.
each pound of gasoline, 14.7 pounds of air will be
burned. The fuel mixture actually varies from the ideal Most modern cars are equipped with three-way catalytic
ratio quite a bit during driving. Sometimes the mixture converters.
can be lean (an air-to-fuel ratio higher than 14.7), and
The reduction catalyst is the first stage of the catalytic
other times the mixture can be rich (an air-to-fuel ratio
converter. It uses platinum and rhodium to help reduce
lower than 14.7).
the NOx emissions. When an NO or NO2 molecule
The main emissions of a car engine are
contacts the catalyst, the catalyst rips the
 Nitrogen gas (N2) - Air is 78-percent nitrogen
nitrogen atom out of the molecule and holds on to it,
gas, and most of this passes right through the car
freeing the oxygen in the form of O2. The nitrogen atoms
engine.
bond with other nitrogen atoms that are also stuck to the
 Carbon dioxide (CO2) - This is one product of
catalyst, forming N2.
combustion. The carbon in the fuel bonds with
the oxygen in the air. 2NO => N2 + O2 or 2NO2 => N2 + 2O2
 Water vapor (H2O) - This is another product of
combustion. The hydrogen in the fuel bonds The oxidation catalyst is the second stage of the catalytic
with the oxygen in the air. converter. It reduces the unburned hydrocarbons and
carbon monoxide by burning (oxidizing) them over a
These emissions are mostly benign, although carbon platinum and palladium catalyst. This catalyst aids the
dioxide emissions are believed to contribute to global reaction of the CO and hydrocarbons with the remaining
warming. Because the combustion process is never oxygen in the exhaust gas. For example:
perfect, some smaller amounts of more harmful
emissions are also produced in car engines. Catalytic 2CO + O2 => 2CO2
converters are designed to reduce all three:
There are two main types of structures used in catalytic
 Carbon monoxide (CO) is a poisonous gas that converters -- honeycomb and ceramic beads. Most cars
is colorless and odorless.
today use a honeycomb structure.
 Hydrocarbons or volatile organic
compounds (VOCs) are a major component of
The third stage of conversion is a control system that to flow by the baffles. The back pressure is increased,
monitors the exhaust stream, and uses this information to thus causing loss in engine power.
control the fuel injection system. There is an oxygen
sensor mounted upstream of the catalytic converter, WAVE CANCELLATION TYPE
meaning it is closer to the engine than the converter. This
sensor tells the engine computer how much oxygen is in
the exhaust. The engine computer can increase or
decrease the amount of oxygen in the exhaust by
adjusting the air-to-fuel ratio. This control scheme allows
the engine computer to make sure that the engine is
running at close to the stoichiometric point, and also to
make sure that there is enough oxygen in the exhaust to In this type, exhaust gases are divided into two parts. The
allow the oxidization catalyst to burn the unburned lengths of these paths are so adjusted that they come out
hydrocarbons and CO. the muffler, the crests of one wave coincide with the
troughs of the second wave, thus cancelling each other
Mufflers and reducing the noise to zero theoretically. This is
achieved if the lengths of the two passeges differ by half
A muffler (silencer) is a device for decreasing the the wave length. In practice this type of muffler does not
amount of noise emitted by the exhaust of an internal eliminate noise completely, because this is possible only
combustion engine. at one frequency for which muffler is designed, whereas
the noise is combination of different frequencies.
When the exhaust valve opens high pressure exhaust gas
is released, this causes a pressure wave in the air causing RESONANCE TYPE
an explosion. Since high pressure gases are released
rapidly one after the other in an engine, this noise
consists of different notes of various frequencies. Thus
any ideal silencer for absorbing this noise must
effectively reduce both the low and high frequency notes.

Types of mufflers

1. Baffle type
2. Wave cancellation type
3. Resonance type
4. Absorber type
These are also called Helmhotlz type, after the person
5. Combined resonance and absorber type
who originated the idea. It consists of a number of
BAFFLE TYPE Helmholtz resonators in series, through which a pipe
containing access port passes. The exhaust gases flow
through this type and thus experience no resistance.
Series of resonators eliminate the fundamental and higher
harmonics of the engine noise.

COMBINED RESONANCE AND ABSORBER

TYPE

It is generally cylindrical shape with a number of baffles

spot welded inside. There are many designs of baffles,
but the principle in all case is the same, closing any direct
passage for the gas. Major drawback of the mufflers is
their low efficiency. Because of the restriction provided
It is seen that the other muffler types has a draw back in gases inert to combustion to act as absorbents of
that it is not efficient in reducing noise of low frequency. combustion heat to reduce peak in-cylinder
To obviate this defect, this is combined with resonant temperatures. NOx is produced in a narrow band of high
chamber. It has been found that this type is more cylinder temperatures and pressures.
efficient. In a gasoline engine, this inert exhaust displaces the
amount of combustible matter in the cylinder. In a diesel
DeNOx engine, the exhaust gas replaces some of the
excess oxygen in the pre-combustion mixture. Because
NOx forms primarily when a mixture of nitrogen and
oxygen is subjected to high temperature, the lower
combustion chamber temperatures caused by EGR
reduces the amount of NOx the combustion generates
(though at some loss of engine efficiency). Gasses re-
introduced from EGR systems will also contain near
equilibrium concentrations of NOx and CO; the small
fraction initially within the combustion chamber inhibits
The SCR Catalyst System is based on the addition of the total net production of these and other pollutants
ammonia (NH3) to the NOx-containing flue gas and when sampled on a time average. Most modern engines
passing the mixture over an active catalyst. This converts now require exhaust gas recirculation to meet emissions
the nitrogen oxides (NO and NO2) to naturally occurring standards. Chemical properties of different fuels limit
nitrogen (N2) and water (H2O). Together, our high- how much EGR may be used.
activity catalyst and low pressure drop result in cost-
effective NOx reduction ON-BOARD DIAGNOSTICS
Selective Catalytic Reduction (SCR) is the process of
NOx reduction, or DeNOx, that occurs when a NOx OBD stands for ―On-Board Diagnostics.‖ It is a
source is mixed with ammonia and allowed to react at the computer-based system originally designed to reduce
surface of the proper catalyst. The liquid ammonia emissions by monitoring the performance of major
engine components. A basic OBD system consists of
injected upstream immediately turns into gas, mixes with
the NOx gas and the mixture then reacts at the catalyst. an ECU (Electronic Control Unit), which uses input
The result is the conversion of the mixture to nitrogen gas from various sensors (e.g., oxygen sensors) to control
N2 and water vapor H2O, both harmless constituents of the actuators (e.g., fuel injectors) to get the desired
the atmosphere. While the process uses aqueous performance. The ―Check Engine‖ light, also known as
the MIL (Malfunction Indicator Light), provides an
ammonia, there is no wet residue or by-product
collected. All the reactants leave the system in the form early warning of malfunctions to the vehicle owner. A
of gases. modern vehicle can support hundreds of parameters,
which can be accessed via the DLC (Diagnostic Link
EXHAUST GAS RECIRCULATION SYSTEM Connector) using a device called a scan tool.

In internal combustion engines, exhaust gas

recirculation (EGR) is a nitrogen oxide (NO x) emissions
reduction technique used in petrol/gasoline and diesel There are two kinds of on-board diagnostic
engines. EGR works by recirculating a portion of an systems: OBD-I and OBD-II.
engine's exhaust gas back to the engine cylinders. This
dilutes the O2 in the incoming air stream and provides
OBD-I important safety features -- the cruise control will
OBD-I refers to the first generation OBD disengage as soon as you hit the brake pedal, and it
systems which were developed throughout the 1980s. won't engage at speeds less than 25 mph (40 kph).
These early systems use proprietary connectors,
hardware interfaces, and protocols. A mechanic who
wanted to access diagnostic information typically had to
buy a tool for every different vehicle make. OBD-I scan
tools that support multiple protocols are supplied with an
array of different adapter cables.

OBD-II
In the early 1990s, Society of Automotive
Engineers (SAE) and International Standardization
Organization (ISO) issued a set of standards which
described the interchange of digital information between
ECUs and a diagnostic scan tool. All OBD-II compliant
vehicles were required to use a standard diagnostic
connector (SAE J1962), and communicate via one of the
standard OBD-II communication protocols.
The primary purpose of the OBD-II connection
is for emissions testing, but one of the first and most
widespread applications available to consumers is the
scan tool or code reader. These devices are sometimes
battery powered, but newer units may be powered by the
electricity provided by the OBD connection itself. When
a Check Engine light is illuminated, these handheld
devices connect to the OBD-II port and simply record
and display any trouble code that the vehicle is sending.
Users can then use the code to see what's wrong with the
car and, once the problem has been fixed, clear the code
from the vehicle's memory, deactivating the Check
Engine light until the next issue arises.
These devices often just display the raw code, so
you'll need some sort of code reference to know the
difference between a P0302 and a P0455 (for the
curious, the first means that your engine's second
cylinder is misfiring and the second simply means that
you've probably left your gas cap off). The most-
advanced units may actually store the trouble codes in
the device's memory to be retrieved later via USB and The system pictured above has buttons: On, Off,
cross-referenced against Internet databases of code Set/Accel, Resume and Coast. It also has a sixth control
values and known issues. -- the brake pedal, and if your car has a manual
transmission the clutch pedal is also hooked up to the
CRUISE CONTROL cruise control.
Cruise control is an invaluable feature on
American cars. Without cruise control, long road trips  The on and off buttons don't actually do much.
would be more tiring, for the driver at least, and those of Hitting the on button does not do anything except tell
us suffering from lead-foot syndrome would probably the car that you might be hitting another button soon.
get a lot more speeding tickets. The cruise control The off button turns the cruise control off even if it is
system actually has a lot of functions other than engaged. Some cruise controls don't have these
controlling the speed of your car. For instance, the cruise buttons; instead, they turn off when the driver hits the
control pictured below can accelerate or decelerate the brakes, and turn on when the driver hits the set
car by 1 mph with the tap of a button. Hit the button five button.
times to go 5 mph faster. There are also several
 The set/accel button tells the car to maintain the When the cruise control is engaged, the actuator moves
speed you are currently driving. If you hit the set the cable connected to the pivot, which adjusts the
button at 45 mph, the car will maintain your speed at throttle; but it also pulls on the cable that is connected to
45 mph. Holding down the set/accel button will make the gas pedal -- this is why your pedal moves up and
the car accelerate; and on this car, tapping it once down when the cruise control is engaged.
will make the car go 1 mph faster. The brain of a cruise control system is a small computer
 If you recently disengaged the cruise control by that is normally found under the hood or behind the
hitting the brake pedal, hitting the resume button will dashboard. It connects to the throttle control seen in the
command the car to accelerate back to the most previous section, as well as several sensors. The diagram
recent speed setting. below shows the inputs and outputs of a typical cruise
 Holding down the coast button will cause the car to control system.
decelerate, just as if you took your foot completely A good cruise control system accelerates aggressively to
off the gas. On this car, tapping the coast button once the desired speed without overshooting, and then
will cause the car to slow down by 1 mph. maintains that speed with little deviation no matter how
 The brake pedal and clutch pedal each have a switch much weight is in the car, or how steep the hill you drive
that disengages the cruise control as soon as the pedal up. Controlling the speed of a car is a classic application
is pressed, so you can shut off the cruise control with of control system theory. The cruise control system
a light tap on the brake or clutch. controls the speed of the car by adjusting the throttle
position, so it needs sensors to tell it the speed and
The cruise control system controls the speed of your car throttle position. It also needs to monitor the controls so
the same way you do -- by adjusting the throttle it can tell what the desired speed is and when to
position. But cruise control actuates the throttle valve by disengage.
a cable connected to an actuator, instead of by pressing a
pedal. The throttle valve controls the power and speed of EURO AND BHARAT EMISSION NORMS
the engine by limiting how much air the engine takes in.
Table 1
Indian emission standards (4-wheel vehicles)

Standard Reference Date Region

India Euro 1 2000 Nationwide
2000
Bharat Euro 2 2001 NCR*, Mumbai,
Stage II Kolkata, Chennai
2003.04 NCR*, 11 cities†
2005.04 Nationwide
Bharat Euro 3 2005.04 NCR*, 11 cities†
Stage III 2010.04 Nationwide
Bharat Euro 4 2010.04 NCR*, 13 cities‡
Stage IV 2015.07 Above plus 29 cities
mainly in the states of
Haryana, Uttar
Pradesh, Rajasthan
and
Maharastra [3231]
2015.10 North India plus
bordering districts of
Rajasthan (9
States) [3232]
2016.04 Western India plus
parts of South and
East India (10 States
In the picture above, you can see two cables connected and
to a pivot that moves the throttle valve. One cable comes Territories) [3232]
from the accelerator pedal, and one from the actuator.
 2017.04 Nationwide [3232] In its May 2014 report, Auto Fuel Vision and Policy
2025, the Expert Committee recommended that Bharat
Bharat Euro 5 n/a a
Stage V Stage IV fuel be required nationwide from April 2017
followed by a further step up to the BS V in April 2020
Bharat Euro 6 2020.04 Nationwide [3349]
and BS VI in April 2024. Draft recommendations
Stage VI
discussed prior to the report‘s release included a national
* National Capital Region (Delhi) Bharat Phase IV+ stage (40 ppm sulfur) starting in 2017
and a national Bharat Stage V fuel standard staring in
2021. The Oil Ministry supported proceeding directly
The foundation for automotive emission standards in
from BS IV to BS VI but this was opposed by the
India since the early 2000s is contained in two reports
automotive industry. In November 2015, a draft notice
from the Indian Planning Commission. The National
was published by the Ministry of Road Transport and
Auto Fuel Policy, announced on October 6, 2003,
Highways announcing that BS V would be implemented
envisioned a phased program for introducing Euro 2-4
across the country starting 2019 and BS VI starting
emission and fuel regulations by 2010. In order to
2021. While the automotive industry was supportive of
establish limits beyond Bharat Stage IV, the Indian
the dates for BS V, they claimed advancing the dates for
Planning Commission established an Expert Committee
BS VI by more than 1 year from those recommended by
in 2013 to draft an updated Auto Fuel Policy, Auto Fuel
the Expert Committee would not leave sufficient time
Vision and Policy 2025, that was published in May
for testing and validation and were unrealistic.
2014. While legislators are not required to adhere strictly
Severe air pollution episodes at the end of 2015 in
to the recommendations contained in these reports, they
Delhi-NCR lead to a number of Supreme Court rulings
serve as a starting point for subsequent legislative action
that would have significant impacts on the automotive
to establish the implementation schedule and other
industry. One ruling in late 2015 banned the sale of
details of automotive emission standards. The
diesel cars in the NCR with engine displacements
implementation schedule of EU emission standards in
greater than 2.0 L from January 1 to April 1, 2016.
India is summarized in Table.
Another ruling in early January 2016 asked the
The above standards apply to all new 4-wheel vehicles
government to advance the implementation of BS VI
sold and registered in the respective regions. In addition,
emission standards from those contained in the
the National Auto Fuel Policy 2003 introduced certain
November 2015 proposals. The government responded
emission requirements for interstate buses with routes
by withdrawing its November 2015 BS V/VI proposal
originating or terminating in Delhi or the other
and announcing that they would move the
mentioned cities.
implementation date for BS VI to April 1, 2020 for all
For 2-and 3-wheelers, Bharat Stage II applied from April
models and skip over BS V standards. A new draft
1, 2005 and Stage III standards came into force in April
proposal was published in February 2016.
1, 2010. Bharat Stage IV standards for gasoline fueled 2-
wheelers came into force April 1, 2016. Bharat Stage VI
AIR BAGS
standards for SI and CI 2- and 3-wheelers were proposed
in February 2016.
The roll out of Bharat Stage IV limits nationwide was
An airbag is more correctly known as
delayed by the challenge of convincing fuel producers to
a supplementary restraint system
make the necessary investments required to supply 50
(SRS) or supplementary inflatable restraint (SIR).
ppm sulfur fuel nationwide. Potential solutions that have
The word "supplementary" here means that the airbag is
been suggested include deregulation of diesel prices, an
designed to help the seatbelts protect you rather than
environment compensation charge on diesel vehicles and
replace them (relying on an airbag to protect you without
an additional levy on diesel fuel.
fastening your seatbelt is extremely dangerous).
Even in cities with Bharat Stage IV limits, there have
The basic idea is that the airbag inflates as soon
been challenges ensuring the dominance of compliant
as the car starts to slow down in an accident and deflates
vehicles. Some of these challenges include: exemptions
as your head presses against it. That's important: if the
granted to some specialty vehicle (e.g., taxis)
bag didn't deflate, your head would just bounce back off
manufacturers, registration of Bharat Stage III vehicles
it and you'd be no better off.
by vehicle owners outside of their place residence due to
The idea behind the airbag is to take advantage
loopholes in residential proof, registration of commercial
of the physics of a crash. In the case of a head-on
vehicles outside of the Bharat Stage IV zones and
collision, a car usually stops fast. The body of the driver,
insufficient availability of some specialty vehicles (e.g.,
of course, doesn't. It follows Newton‘s second law: its
garbage trucks) in Bharat Stage IV configurations.
momentum continues until an outside force (usually the There are six main parts of an airbag system: an
steering wheel, dash board or windshield) brings it to a accelerometer; a circuit; a heating element; an explosive
stop. An airbag doesn't just soften the blow. It actually charge; and the bag itself.
lowers the impact by stretching it out over a longer The accelerometer keeps track of how quickly the speed
period of time. It also spreads the impact over a larger of your vehicle is changing. When your car hits another
area of the body. That way, no single area (forehead, car—or wall or telephone pole or deer—the
chin, neck) bears the brunt of it. That's why airbags accelerometer triggers the circuit. The circuit then sends
inflate and then quickly deflate—to gradually bring the an electrical current through the heating element, which
driver‘s momentum from 60 mph to zero. is kind of like the ones in your toaster, except it heats up
a whole lot quicker.
This ignites the charge, often solid pellets of sodium
azide (NaN3), which explodes. The explosion produces
nitrogen gas (N2~) that fills the deflated nylon airbag
(packed in your steering column, dashboard or car door)
at about 200 miles per hour. The whole reaction takes a
mere 1/25 of a second.
The bag itself has tiny holes that begin releasing the gas
as soon as it‘s filled. The goal is for the bag to be
deflating by time your head hits it. That way it absorbs
the impact, rather than your head bouncing back off the
fully inflated airbag and causing you the sort of whiplash
that could break your neck.

SEAT BELTS

Seat belts are responsible for saving

hundreds of thousands of lives since they were
first implemented in vehicles. The belts stop a
person‘s forward movement in the case of an
accident or sudden stop, and prevent the wearer
from being thrown into a windshield or ejected
from the vehicle. While there are many different
types of seat belts that are used in cars, aircraft,
boats and other powered vehicles, there are six
primary types of safety restraints that are us ed in
passenger vehicles.

COMMON SEAT BELT DESIGNS

LAP STYLE
These seat belts were the first type of safety
restraint created. The belt wraps across the waist
of the occupant, and usually have an adjustment
mechanism which allows them to be tightened or
loosened. Today, they are most commonly found
in airplanes.
SASH TYPE continuous length of webbing, and helps to spread
out the force of a collision through the shoulders,
The sash type of seat belt is worn over the chest and pelvis. One known problem with this
occupants shoulder and is generally fastened at the design is that it can allow occupants to slide out of
waist, on the ―B‖ pillar of the vehicle. Used the seatbelt in the event of a rollover collision.
mainly throughout the 1960‘s, this style was found
to have a design flaw that enabled occupants to BELT IN SEAT
slide out of it under certain accident conditions .
The BIS, or belt-in-seat type of restraint,
LAP / SLASH (NON – AUTOMATIC) was created in an attempt to remedy the sliding
problems associated with the inertia reel style
restraints. While still essentially a three-point
system, the shoulder attachment location is
actually moved to the backrest of the seat. Some
claim that this type of restrain is safer in rollover
crashes.

FIVE – POINT HARNESS

The Five-Point Harness is commonly found

in child safety seats, race cars and other high-
performance vehicles. While it is somewhat
restrictive when compared to most other seat
belts, these belts are acknowledged as one of the
safer types of seat belt designs currently available.
As the name implies, this design is a combination An important design of these restraints is that each
of the lap style and sash type of seat belt. This side of the ―lap‖ section connects into a center
design secures passengers from each side of the belt and lock located between the legs of the
waist, as well as over the shoulder . occupant (which prevents vertical movement in
the event of a rollover), while there are a separate
INERTIA REEL (AUTOMATIC)
belt for each shoulder. Another important design
feature is that these belts are generally never
fastened to the seat – they are bolted into the
vehicle itself.

ELECTRONIC STABILITY CONTROL

SYSTEM
Electronic Stability Control (ESC) helps drivers
to avoid crashes by reducing the danger of skidding, or
losing control as a result of over-steering. ESC becomes
active when a driver loses control of their car. It uses
computer controlled technology to apply individual
brakes and help bring the car safely back on track,
without the danger of fish-tailing.
Driving safety took a big step forward in the mid-1990s
when electronic stability control was introduced. The
German auto supplier Bosch developed the first system,
and the Mercedes-Benz S-Class and BMW 7-series were
This version of the seat belt is the type
the first cars to use the new safety and regulatory
most often found in vehicles. A more developed
devices.
version of the lap/sash design, the inertia reel
It's been more than a decade since electronic stability
seatbelt also uses a geared mechanism which locks
control was first introduced, and it goes by many names,
in tension when a certain amount of force is pulled
depending on the company. Audi calls it the Electronic
on the belt. Also considered a ―three-point‖
Stability Program, or ESP; at Ford, it goes by Advance
design, this belt is made up of one single,
Trac. GM has Stabilitrak, and Porsche puts its stamp on Before the 1990s, drivers were taught to pump the brake
the system by dubbing it Porsche Stability Management. pedal to keep the brakes from locking up and causing a
slide. With the invention of anti-lock brakes, driving
But all of these systems, no matter their names, use
safely became much easier. ABS electronically pumped
high-tech sensors, the car's central computer and
the brakes faster than the driver could, which kept them
mechanical actions to assist in driving safely. We often
from locking and causing understeer or oversteer. ESC
read about high-performance cars having a tendency to
uses this system to correct the problem almost before it
understeer or oversteer; but the truth is, any car can veer
can start by activating the ABS for as many wheels as
off course, especially if the road is slippery.
needed, from one individual wheel to all four. The
Understeer happens when the front wheels don't have nature of ABS keeps the over- or understeer from getting
enough traction and the car continues moving forward worse while slowing the car to a controllable speed.
rather than turning. Oversteer is just the opposite: the car
ESC also uses traction control for driving safety. If ESC
turns farther than the driver intended causing the rear
is in charge of monitoring side-to-side motion around a
wheels to slide and the car to spin. ESC, as electronic
vertical axis, traction control is in charge of front-to-
stability control is often known, can help correct both of
back motion. If the traction control system is detecting
these situations. The electronic stability control system
wheel slippage, the electronic stability control sensor
doesn't work all alone -- it uses the car's other safety and
will pick up on the direction of the slide. If there's a
regulatory devices, like anti-lock braking and traction
difference between the angle of the steering wheel and
control, to correct problems before they become
the direction the car is sliding, the ESC will work with
accidents.
the traction control system to engage the ABS at the
The center of the ESC system is also the center of the proper wheel (or wheels) and control the throttle to
car: the yaw control sensor. It's almost always located as reduce the speed of the vehicle, too.
close to the very center of the car as possible. If you
ESC information is fed into the car's central computer
were sitting in the driver's seat, the yaw control sensor
via three types of sensor:
would be under your right elbow, somewhere between
you and the passenger.  Wheel-speed sensors: One wheel-speed sensor
at each wheel measures the speed of the wheel
But what the heck is "yaw?" If it sounds like something
which the computer can then compare to the
a pirate would say, that's because they probably would.
speed of the engine.
Ships and cars both experience yaw, which is a
 Steering-angle sensors:This sensor, in the
movement around a vertical, or z, axis. It's as if the car
steering column, measures the direction the
were pinned like a butterfly in a display case, where the
driver intends to aim the car. If it's different than
pin is the z axis. The yaw sensor is right at the center of
the direction the car is actually traveling, the
the pin. If the ESC system detects that the car is
ESC system will kick in.
swinging too far (or not far enough) around that up-and-
 Rotational-speed sensor:This is also known as
down axis, it springs into action to assist.
the yaw sensor. It's the one in the middle of the
Using all the modern electronic systems at its disposal, car that measures the side-to-side motion of the
the ESC can activate one or more individual brakes, vehicle.
depending on which wheel can increase driving safety
the most, and control the throttle to lessen the speed at The most important role ESC plays in driving safety is
which the car is traveling. The sensor is looking for reducing the number and severity of crashes. Almost
differences between the direction of the steering wheel everyone ends up in nasty, slippery driving conditions at
and the direction the car is headed; the car's computer some point, whether it's a rainstorm, a sudden patch of
then makes the necessary corrections to bring the ice or a snowy road. Electronic stability control, along
vehicle's direction of travel in line with what the driver with the other safety and regulatory devices on-board
wanted. today's vehicles, can help drivers maintain control on the
road.
Here are lots of safety and regulatory devices in cars
these days, and they all work together to keep the wheels SIDE IMPACT PROTECTION SYSTEM
on the road and the passengers safe. Electronic stability
control, in particular, takes advantage of two other SIPS or Side Impact Protection System is the
systems, ABS and traction control, plus a few special name of a system to protect against injury in a side
collision, developed by Volvo.
sensors, to do its job
 SIPS was first introduced in 1991[1] for STEER BY WIRE
the Volvo 700, 900 and 850 series cars of model year
1992. It has been standard on every new Volvo since. The aim of steer-by-wire technology is to
completely do away with as many mechanical
The SIPS system works by having a reinforced components (steering shaft, column, gear reduction
lower sill, b-pillar and energy absorbing honeycomb
mechanism, etc.) as possible. Completely replacing
materials inside the doors. The idea is to more widely
distribute the energy in a side collision across the whole conventional steering system with steer-by-wire
side of the car rather than having the b-pillar absorb it holds several advantages, like:
all. Driver and passenger seat are mounted on transverse
steel rails, not bolted to the floor as per the standard  The absence of steering column
configuration. In a side impact these transverse rails simplifies the car interior design.
allow the seats to crush a reinforced center console  The absence of steering shaft, column
designed to absorb additional energy. and gear reduction mechanism allows
much better space utilization in the
DRIVE BY WIRE engine compartment.
 The steering mechanism can be designed
Drive by wire, DbW, by-wire, Steer-by-wire, or x-by- and installed as a modular unit.
wire technology in the automotive industry is the use of  Without mechanical connection between
electrical or electro-mechanical systems for performing the steering wheel and the road wheel, it
vehicle functions traditionally achieved by mechanical is less likely that the impact of a frontal
linkages. This technology replaces the traditional crash will force the steering wheel to
mechanical control systems with electronic control intrude into the driver‘s survival space.
systems using electromechanical actuators and human-  Steering system characteristics can easily
machine interfaces such as pedal and steering feel and infinitely be adjusted to optimize the
emulators. Components such as the steering column, steering response and feel.
intermediate shafts, pumps, hoses, belts, coolers
and vacuum servos and master cylinders are eliminated ANTI-COLLISION SYYSTEM
from the vehicle.
A collision avoidance system is an automobile
THROTTLE BY WIRE safety system designed to reduce the severity of a
collision. It is also known as a precrash system, forward
This system helps accomplish vehicle propulsion by collision warning system, or collision mitigating system.
means of an electronic throttle without any cables from It uses radar (all-weather) and sometimes laser (LIDAR)
the accelerator pedal to the throttle valve of the engine. and camera (employing image recognition) to detect an
In electric vehicles, this system controls the electric imminent crash. GPS sensors can detect fixed dangers
motors by sensing the accelerator pedal input and such as approaching stop signs through a location
sending commands to the power inverter modules. database.

BRAKE BY WIRE Once the detection is done, these systems either provide
a warning to the driver when there is an imminent
A pure brake by wire system would eliminate the need collision or take action autonomously without any driver
for hydraulics completely by using motors to actuate input (by braking or steering or both). Collision
calipers, in comparison to the currently existing avoidance by braking is appropriate at low vehicle
technology where the system is designed to provide speeds (e.g. below 50 km/h), while collision avoidance
braking effort by building hydraulic pressure in the by steering is appropriate at higher vehicle speeds. Cars
brake lines. with collision avoidance may also be equipped
with adaptive cruise control, and use the same forward-
SHIFT BY WIRE looking sensors.
VISIBILTY ASSISTANCE
The direction of motion of the vehicle (Forward,
Reverse) is set by commanding the actuators inside the HEAD UP DISPLAY
transmission through electronic commands based on the
A HUD is a digital transparent image that is projected
current input from the driver (Park, Reverse, Neutral or
onto the windshield of a car, displaying the same
Drive).
information you would get from the dashboard. This can
include everything from your current speed to the revs
on your engine, and even various temperature gauges.
The idea behind it is that by displaying this vital data in These displays are becoming increasingly available in
the same place a driver should be keeping their eyes on, production cars, and usually
HUDs can reduce the amount of time that people‘s offer speedometer, tachometer, and navigation
attention is spent looking around the car for their phones system displays. Night vision information is also
or checking the radio. More time with their eyes on the displayed via HUD on certain automobiles.
road means lesser accidents, and safer drivers all around.
NIGHT VISION SYSTEM
A typical HUD contains three primary components:
a projector unit, a combiner, and a video generation
computer.
The projection unit in a typical HUD is an optical
collimator setup: a convex lens or concave mirror with
a Cathode Ray Tube, light emitting diode, or liquid
crystal display at its focus. This setup (a design that has
been around since the invention of the reflector sight in
1900) produces an image where the light is collimated,
i.e. the focal point is perceived to be at infinity.
The combiner is typically an angled flat piece of glass
(a beam splitter) located directly in front of the viewer,
that redirects the projected image from projector in such
a way as to see the field of view and the projected
infinity image at the same time. Combiners may have
special coatings that reflect the monochromatic light
projected onto it from the projector unit while allowing
all other wavelengths of light to pass through. In some
optical layouts combiners may also have a curved
surface to refocus the image from the projector.
The computer provides the interface between the HUD
(i.e. the projection unit) and the systems/data to be
displayed and generates the imagery and symbology to
be displayed by the projection unit.
Types
Other than fixed mounted HUD, there are also head-
mounted displays (HMDs). Including helmet mounted
displays (both abbreviated HMD), forms of HUD that
features a display element that moves with the
orientation of the user's head.
Generations The term ―automotive night vision‖ refers to a number
HUDs are split into four generations reflecting the of systems that help increase driver awareness when it‘s
technology used to generate the images. dark out. These systems extend the perception of the
driver beyond the limited reach of the headlights through
 First Generation—Use a CRT to generate an image
the use of thermographic cameras, infrared lights, heads
on a phosphor screen, having the disadvantage of
the phosphor screen coating degrading over time. up displays, and other technologies. Since automotive
The majority of HUDs in operation today are of this night vision can alert drivers to the presence of potential
type. hazards before they become visible, these systems can
 Second Generation—Use a solid state light source, help prevent accidents.
for example LED, which is modulated by an LCD
screen to display an image. These systems do not Automotive night vision systems are broken into two
fade or require the high voltages of first generation basic categories, which are referred to as active and
systems. These systems are on commercial aircraft. passive. Active night vision systems uses infrared light
 Third Generation—Use optical waveguides to sources to illuminate the darkness, and passive systems
produce images directly in the combiner rather than rely on the thermal radiation that is emitted from cars,
use a projection system. animals, and other potential hazards. The systems both
 Fourth Generation—Use a scanning laser to display rely on infrared data, but each one has its own benefits
images and even video imagery on a clear
and drawbacks.
transparent medium.
Active Automotive Night Vision System light from the headlights according to driving
circumstances. Depending on vehicle speed and steering
Active systems are more complex than passive systems input, the system points the low-beams headlights in the
because they use infrared light sources. Since the direction the driver intends to travel.
infrared band falls outside the visible spectrum, these In combination with discharge headlights, the system
light sources don‘t cause oncoming drivers to suffer
illuminates a greater distance and more brightly
from temporary night blindness like high beam
headlights can. That allows the infrared lights to compared to halogen headlights, improving the driver's
illuminate objects that are significantly further away field of vision and visibility around curves and at
than headlights are able to reach. Since infrared light intersections during night driving. Mated with the auto-
isn‘t visible to the human eye, active night vision leveling function, the system offers a stable distribution
systems use special cameras to relay the extra visual of light unaffected by the vehicle's position. Maintaining
data. Some systems use pulsed infrared lights, and others the illumination axis, the system helps to prevent drivers
use a constant light source. These systems don‘t work
of oncoming vehicles from getting blinded when many
very well in adverse weather conditions, but they do
provide high contrast images of vehicles, animals, and people or a lot of luggage weighs down the back of the
even inanimate objects. car, or when the vehicle position changes going over a
bump or driving up a slope.
Passive Automotive Night Vision System

Passive systems don‘t use their own light sources, so

they rely on thermo graphic cameras to detect thermal
radiation. This tends to work very well with animals and
other vehicles since they emit a lot of thermal radiation.
However, passive systems have trouble picking up
inanimate objects that are about the same temperature as
the surrounding environment. The range of passive night
vision tends to be significantly higher than the range of
active night vision, which is due to the limited power of
the light sources used by the latter systems. The image
quality produced by the thermographic cameras also
tends to be poor when compared to active systems, and
they don‘t work very well in warm weather.

How does infrared or thermo graphic information

Help to see? HEATING VENTILATION AND
There are a number of types of night vision displays that AIRCONDITIONING IN VEHICLES
can relay infrared or thermo graphic information to the
Heating Ventilation and Air Conditioning (HVAC) is the
driver. The earliest night vision systems used heads up
technology for indoor and automotive ambient comfort.
displays, which projected warnings and alerts on the
HVAC facilitates in managing the pleasant climate
windshield within the driver‘s field of vision. Other
inside the cabin by controlling the degree of
systems use an LCD that's mounted on the dash, in the
hotness/coolness.
instrument cluster, or integrated into the head unit. Night
There were times when having an air conditioner in a car
vision systems can detect objects that are more than 500
was considered one of the big features, but today air
feet away, but traditional headlights typically only
conditioners have become standard equipment even in
illuminate objects that are about 180 feet away. Since
entry-level automobiles.
the stopping distance of a car can easily be longer than
180 feet, it‘s clear that the proper use of a night vision
The basic principle behind the operation of HVAC unit
system can help an alert driver avoid certain collisions.
is conduction and convection. Heat is transferred from a
ADVANCED FRONTLINE SYSYTEM / low-temperature region to a high-temperature region in
ADAPTIVE FRONT LIGHTING SYSYTEM the vehicle, due to the pressure difference. This process
Concept of intelligent lighting, according to curves, of heat transfer is called Refrigeration
weather and speed.
An air conditioning system comprises five major
One of the most important factors in mitigating driver
components:
fatigue and increasing safety during night driving is
1. Evaporator
providing a well-illuminated field of view. The Adaptive
2. Compressor
Front-lighting System (AFS) optimizes distribution of
 3. Condenser The condensed and pressurized liquid refrigerant is next
4. Receiver/Drier routed through a thermal expansion valve where it
5. Expansion device undergoes an abrupt reduction in pressure. That pressure
The five major components are divided into two reduction results in flash evaporation of a part of the
pressure regions: the high-pressure side is the condenser liquid refrigerant, lowering its temperature. The cold
and receiver/drier unit, and the low-pressure side is the refrigerant is then routed through the evaporator coil in
air conditioning evaporator. The dividing point between the passenger compartment. The air (which is to be
high and low pressure cuts through the compressor and cooled) blows across the evaporator, causing the liquid
the expansion valve. part of the cold refrigerant mixture to evaporate as well,
further lowering the temperature. The warm air is
therefore cooled. To complete the refrigeration cycle, the
refrigerant vapor is routed back into the compressor.
The compressor can be driven by the car's engine (e.g.
via a belt) or by an electric motor. It is possible, indeed
very likely, that the refrigerant over time, will leak from
the system, resulting in poor air conditioning
performance and potentially expensive part replacement.
So it's vital that every 2 or 3 years you have your car air
con recharged.
AUTOMATIC CLIMATE CONTROL
Automatic climate control is the ability to monitor and
influence the temperature of a specified space without
manual intervention. This climate control capability can
be found in many cars, boats, and airplanes. Its primary
purpose is to manage the temperature of a given area
based on settings by a user of the system. Climate
control devices were first introduced into automobiles in
the early 1960s, and are available in many vehicles
today. The benefit of automatic climate control is that it
enables the occupants of a vehicle to set a specified
temperature for one area within the automobile. This
temperature is then regulated by the climate control
system, which determines how best to maintain the
current environment.
Prior to climate control, a heating and cooling system
could only be engaged by manually selecting one of the
In the refrigeration cycle, heat is transported from the mechanisms. While a user could select a general
passenger compartment to the environment. temperature via a sliding warmer or cooler control, the
A refrigerator is an example of such a system, as it system would not automatically switch from air
transports the heat out of the interior and into its conditioning to heating without manual intervention.
environment. Circulating refrigerant gas vapor enters The creation of the automatic system has advanced the
the gas compressor in the engine bay and is compressed overall comfort for automobiles, as users are not forced
to a higher pressure, resulting in a higher temperature as to constantly move the controls to adjust the temperature
well. The hot, compressed refrigerant vapor is now at a of the compartment. The mechanics of automated
temperature and pressure at which it can climate control require sensors to be placed into the
be condensed and is routed through a condenser, usually compartment of the area to be managed. These sensors
in front of the car's radiator. Here the refrigerant is read the current temperature of the area. The readings
cooled by air flowing across the condenser coils and are then matched to the setting defined by the occupants
condensed into a liquid. Thus, the circulating refrigerant through the computer system within the vehicle, and the
rejects heat from the system and the heat is carried away heating and cooling are adjusted appropriately.
by the air Advances in automatic climate control in automobiles
have evolved into zoned climate control. In this type of
implementation, each occupant can adjust the
temperature of the seating area in which he or she is
seated. Each area within the defined zones has a separate
climate control sensor that reads the current temperature
of the specified area.

This type of system also includes a computer that

regulates the entire air system within the compartment.
The computer regulates the fan speed, engagement of air
conditioning compressor, and overall air temperature to
be disbursed. Typically, these processes are integrated
into the overall computer system within modern
automobiles.