21AUC202J-AUTOMOTIVE ENGINES

UNIT I

INTAKE AND EXHAUST SYSTEM

An inlet manifold is the part of an engine that supplies
the fuel/air mixture to the cylinders.
REQUIREMENTS

1. To provide a direct flow as possible to each cylinder

2. To provide equal quantity of charge to each cylinder
3. To provide uniformly distributed charge of equal
mixture strength to each cylinder
4. To provide equal aspiration intervals between branch
pipes
5. To provide the smallest possible induction tract
diameter that will maintain adequate air velocity at low
speed without impeding volumetric efficiency in the
upper speed range.
REQUIREMENTS

6. To create as little internal surface frictional resistance to

each branch pipe as possible
7. To provide sufficient pre heating for cold starting and
warm up periods
8. To provide a means for drainage of the heavier liquid
fraction of fuel
9. To provide a means to prevent charge flow interference
between cylinders as far as possible
10.To provide a measure of ram pressure charging
DIFFERENT TYPES OF MANIFOLD
DIFFERENT TYPES OF MANIFOLD
INTAKE MANIFOLD
MANIFOLD MATERIALS
 The Intake manifold is a commonly made from cast iron or
aluminum and carries the air/air-fuel mixture to the
combustion chambers.
 Modern vehicles use plastic and other composite materials to
decrease overall weight and to help optimize airflow.
 Plastic manifolds run cooler and can be cast at much lower
cost than traditional materials.
 The cooler running manifold is a big advantage in direct
injection engine designs as the cooler air is denser and can
produce more power.
MANIFOLD MATERIALS
 The only drawback to plastic manifolds is the tendency to
crack if the engine backfires.
 In approximately 70% of modern vehicles, the intake
manifold is made from special heat resistant polymers
and plastics.
 Manifolds using this type of construction lighten
manifold part weight by up to 50% and contribute to
higher fuel efficiency.
 These intake manifolds are normally molded from a glass
fiber reinforced grade of crystalline polymer that consists
of a blend a of syndiotactic polystyrene and polyamide.
MANIFOLD MATERIALS
 The polyamide nylon based materials are preferred because of
their mechanical properties and their ease of processing during
their manufacture.
 This type of material is ideally suited for replacing metal in
under-the-hood applications because of its strength, stiffness,
and chemical resistance under high temperature operating
conditions.
 Intake manifolds made of polyamide nylon have succeeded in
improving the environmental performance of cars because of
the materials ability to be recycled.
OPERATION
 The intake manifold is attached to the cylinder head. Its
construction and design depends on its application.
 On carbureted engines, the intake manifold supports or houses
the carburetor. While on EFI engines it can house or support a
throttle body.
 The intake manifold can accommodate a carburetor or a
Throttle Body Injection unit.
 In either case the mixing of the air/fuel mixture is done at the
manifold base.
 The butterfly shaft connected to the throttle cable controls the
airflow through the unit.
A diesel engine intake manifold carries air only. No fuel is
vaporized in the manifold as fuel is injected directly into the
cylinder.
MULTI-POINT THROTTLE BODY
 In multi-point EFI systems, a throttle body is attached to the
intake manifold.
 While the butterfly shaft is attached to the throttle cable, it
also has a Throttle Position Sensor (TPS) attached to it as
well.
 The TPS signals the ECU of the throttle opening position so
it can complete its fuel requirement calculations.
TURBULENCE
The carburetor or the fuel injectors spray fuel droplets into the
air in the manifold.

Due to electrostatic forces some of the fuel will form into pools
along the walls of the manifold, or may converge into larger
droplets in the air.

Both actions are undesirable because they create inconsistencies

in the air-fuel ratio.

Turbulence in the intake causes forces of uneven proportions in

varying vectors to be applied to the fuel, aiding in atomization.
TURBULENCE
Better atomization allows for a more complete burn of all the
fuel and helps reduce engine knock by enlarging the flame
front.
To achieve this turbulence it is a common practice to leave the
surfaces of the intake and intake ports in the cylinder head
rough and unpolished.
Only a certain degree of turbulence is useful in the intake. Once
the fuel is sufficiently atomized additional turbulence causes
unneeded pressure drops and a drop in engine performance.
Air Charging Methods
Maximum engine power is limited by the amount of fuel that can be burned
efficiently inside cylinder. This is limited by the amount of air that is introduced into
each cylinder as fuel system can always be designed to provide the required amount
of fuel this air flow.

Natural Aspiration: induction process relies solely on the pressure difference that
exists between retreating piston and air intake arrangements. Natural charging is
enhanced by utilizing:
1 Ram effect of incoming charge
2 Pressure wave tuning
Forced Induction: charge is forced to enter into the cylinder at a pressure
substantially above that of the atmosphere, although the mean gas velocities through
the intake part remain unchanged for the same engine speeds.
1. Mechanical supercharging 2. Turbocharging
Pressure Drop
Cylinder pressure variation during induction period with wide open throttle
AIR INDUCTION COMPONENTS
AIR INDUCTION COMPONENTS
 The air induction components consist of an air cleaner and
housing, solid and flexible-duct tubing, and connectors.

 The air induction system draws in ambient air from the

environment.

 The inlet opening may be located in various positions under

the hood
AIR CLEANER OR FILTER
The air cleaner on an internal combustion engine serves three
purposes:
1.It filters the air to remove dust and dirt before the air enters the
carburetor. This is very important because the engine requires
about 9,000 gallons of clean air for every gallon of fuel it burns.
2.It acts as a flame arrester to prevent fires in case the engine
backfires.
3.It acts as a muffler, reducing the hissing noises made by the air
entering the carburetor at high speed.
AIR CLEANER OR FILTER

The air cleaner element may be manufactured from pleated

paper, oil impregnated cloth or felt, or in an oil bath
configuration.

The location of the air cleaner is dependent on the available

space and the hood design
TYPES OF AIR FILTERS

All cars use some kind of air filtration system to prevent

unwanted dirt and debris from clogging the engine.

Paper filters are the standard, there are a few other air filter
options that can help improve vehicle performance under
certain driving conditions.

Air cleaners are generally classified as either wet or dry,

depending on what method is used to filter the air.
AIR FILTER - ASSEMBLY
TYPES OF AIR FILTERS – PAPER - DRY

Commonly used in factory automobile assembly, paper filters

are made from industrial grade paper folded like an accordion to
increase surface area. The greater surface area is intended to trap
more dust and debris so that it doesn't get into the engine, where
it can cause problems. Although these filters are inexpensive,
they need to be replaced more often than other types of air
filters.
DRY FILTER
Dry-type air cleaners use a metal-gauze or paper filter element.
Others use centrifugal and inertial principles: Swirling motions
and sudden changes in the direction of airflow separate the dust
from the air.
Most dry filters in use today have a replaceable paper element.
Air first enters an outer chamber around the filter element and is
then filtered through small holes in the element before entering
the carburetor.
TYPES OF AIR FILTERS – OIL BATH -
WET

Oil bath filters worked by directing airflow over a pool of oil

that would help to draw out heavier elements and air impurities
that could accumulate in the engine. Oil bath filters required
constant cleaning.
OIL BATH FILTER - EXPLANATION
 The wet type is usually called an oil bath air cleaner.
 Air enters the filter at the top outer edges and flows around
the sides over a bath of oil.
 The airflow then reverses direction and moves up through the
filter element and to the carburetor.
 Heavier dust particles are separated from the air as the air
passes the oil bath.
 As the air suddenly changes its direction of movement from
down to up, the heavier dust particles continue to move down
and are trapped in the oil.
 Lighter particles are trapped in the metal-gauze filter element.
 As the airflow reverses its direction above the oil reservoir, it
picks up an oil mist from the oil bath to keep the filter element
soaked.
TYPES OF AIR FILTERS
Foam
Composed of polyurethane foam soaked in oil, foam filters have
a very high dust absorbing capacity. This property makes them a
popular choice for vehicles that frequently drive on dirt roads or
participate in off-road motor sports.
TYPES OF AIR FILTERS
Cotton
Oil-wetted cotton gauze is used in a limited number of
aftermarket car air filters. Because they increase the air intake to
the vehicle's engine, cotton air filters have typically been
positioned as a high-performance automotive item for sport and
racing cars.
USED AND NEW FILTER
Cabin Air Filter

Charcoal Cabin Air Filter

It features a porous material and an extra carbon layer to accelerate

the absorption of any microscopic pollutant. Moreover, it tackles
gaseous toxins like exhaust fumes and smoke.

Particulate Cabin Air Filter

This also comprises a porous fibre capable of trapping particles as

tiny as 0.3 microns. It is the most basic type used in most cars.
Electrostatic Cabin Air Filter

It is the most efficient of the lot since it uses static charge to capture ultra-
fine particles. The layers of electrostatically charged material activate as the
air flows through them.

Activated Carbon Filter

It is similar to a particulate filter but has an additional layer of specially

activated carbon or charcoal. Such carbon has high absorption efficiency
for gaseous contaminants such as carbon monoxide. Additionally, it traps
bacteria and other similar micro-organisms.
USES OF INLET MANIFOLD VACUUM
Due to the downward movement of the pistons and the restriction
caused by the throttle valve, in a reciprocating spark
ignition piston engine, a partial vacuum (lower than atmospheric
pressure) exists in the intake manifold.

This manifold vacuum can be used as a source of automobile

ancillary power to drive auxiliary systems: power assisted brakes,
emission control devices, cruise control, ignition advance,
windshield wipers, power windows, ventilation system valves,
etc.

This vacuum can also be used to draw any piston blow-by gases
from the engine's crankcase. This is known as a
positive crankcase ventilation system. This way the gases are
burned with the fuel/air mixture.
DESIGN CONSIDERATIONS FOR
MANIFOLD
 Minimizing resistance to gas flow (back pressure) and
keeping it within the limits specified for the particular
engine model and rating to provide maximum efficiency.

 Reducing exhaust noise emission to meet local regulations

and application requirements.

 Providing adequate clearance between exhaust system

components and engine components to reduce the impact of
high exhaust temperatures on such items.
DESIGN CONSIDERATIONS

 Ensuring the system does not overstress engine components

such as turbochargers and manifolds with excess weight.
Overstressing can shorten the life of engine components.

 Ensuring the exhaust system components are able to reject

heat energy as intended by the original design.
INTAKE MANIFOLD DESIGN
CONSIDERATIONS
Runners:
• Pipes from throttle to each cylinder
Diameter
• Large enough to reduce flow resistance
• Small enough for high velocity and turbulence to keep fuel
droplets from falling out
Equal length
Equal fuel distribution to cylinders
EXHAUST SYSTEM
An exhaust system is usually the piping used to guide the exhaust
gases away from a controlled combustion inside an engine.
The entire system conveys burnt gases from the engine and includes
one or more exhaust pipes.
Depending on the overall system design, the exhaust gas may flow
through one or more of:
Cylinder head and exhaust manifold
A turbocharger to increase engine power.
A catalytic converter to reduce air pollution.
A muffler or silencer to reduce noise.
EXHAUST SYSTEM COMPONENTS

The primary components of the automotive exhaust

system are:
1.Exhaust manifold,
2.Engine pipe,
3.Catalytic converter,
4.Exhaust brackets,
5.Muffler and components such as the resonator and tail
pipe.
EXHAUST SYSTEM
EXHAUST MANIFOLD
 The exhaust manifold is an assembly designed to collect the exhaust gas
from two or more cylinders into one pipe.
 The exhaust manifold is the beginning portion of the exhaust system
located at the engine.
 It funnels the exhaust gases from the combustion chamber down into the
piping underneath the vehicle.
 The fumes are expelled through the piping and dispersed into the air.
 Due to the extreme temperatures generated at the exhaust manifold, heat
shields can be installed to protect other vehicle components from heat
damage.
 The manifold is designed to give minimum backpressure and turbulence.
MATERIALS FOR EXHAUST MANIFOLD

Manifolds are often made of cast iron and may have material-
saving design features such as to use the least metal, to occupy
the least space necessary, or have the lowest production cost.

Cast iron is the material of choice for 60 - 70 percent of

today's exhaust manifold

Ni resist iron maintains adequate strength at temperatures up

to 1000 °C
Stainless Steel with Polish finish
CAST IRON VS STAINLESS STEEL

Stainless steel does not rust like cast iron, but react to heat by
expanding more than iron.
This heat expansion and contraction makes stainless steel
prone to loosening exhaust joints, as well as possible
cracking within the exhaust manifold.
Though cast iron is not as visually appealing as stainless
steel, it is an inexpensive material that is durable, as long as it
is not subjected to water.
Cast and SS Manifolds
HEAT SHIELD

Heat shielding may be used as a means of shielding hot

surfaces and protecting components or operators from
excessive heat
ENGINE PIPE

The engine pipe is attached to the exhaust manifold. It takes

the gases away through the catalytic converter, then through
the muffler system to the outside environment.
CATALYTIC CONVERTER

The catalytic converter is attached to the engine pipe, between

the engine and the muffler. It converts the harmful by-
products of combustion to relatively harmless gases.
EXHAUST BRACKETS

The exhaust components are supported along the length of the

vehicle by brackets suspended from the underbody. These are
usually rubber-mounted supports that help isolate the
vibrations of the exhaust from the main body of the vehicle.
Rubber is preferred because of its natural dampening effect.
MUFFLER & COMPONENTS

Muffler
The muffler is located between the Resonator
engine and the exhaust outlet. It is Many manufacturers use a resonator
designed to reduce the noise levels in the exhaust system. It is located
of the exhaust by breaking up the between the muffler and the exhaust
sound frequencies of the gases. outlet. Its function is to reduce any
Mufflers can be of various designs resonance levels that the muffler
but their function is common to all. could not adequately suppress.
TAIL PIPE

The tail pipe takes the exhaust gases away from the vehicle.
Its exit point must not allow any of the exhaust gases to
enter the vehicle.