FLEXIBLE commonly used in larger diesel exhaust systems, heavy duty applications and severe service vehicles.
As a car's exhaust gases are transported along the exhaust pipes, they must pass through the muffler, which is an enclosed metal container responsible for "muffling" the sounds of the travelling exhaust gases, and the catalytic converter, which is an "after burner" responsible for igniting and burning any leftover exhaust gases not burned by the engine and exhaust manifold. A catalytic converter is a device that uses a catalyst to convert harmful compounds in car exhaust into harmless compounds
When an NO or NO2 molecule contacts the catalyst, the catalyst rips the nitrogen atom out of the molecule and holds on to it, freeing the oxygen in the form of O2. The nitrogen atoms bond with other nitrogen atoms that are also stuck to the catalyst, forming N2. When an NO or NO2 molecule contacts the catalyst, the catalyst rips the nitrogen atom out of the molecule and holds on to it, freeing the oxygen in the form of O2. The nitrogen atoms bond with other nitrogen atoms that are also stuck to the catalyst, forming N2.
When the flow of exhaust gases from the engine to the atmosphere is obstructed to any degree, back pressure arises and the engine's efficiency, and therefore power, is reduced. Performance-oriented mufflers and exhaust systems thus strive to minimize back pressure by employing numerous technologies and methods to attenuate the sound. For the majority of such systems, however, the general rule of "more power, more noise" applies.
Automobile exhaust System
STUDY OF AUTOMOBILE
MR. Dinesh Dubey
Asst. Prof. (mech)
Exhaust gas or flue gases is emitted as a result of the combustion
of fuels such as petrol, diesel or fuel oil.
A car's exhaust system is responsible for transporting the burned
exhaust, or combustion gases, from its engine and out through the
An exhaust system is usually tubing used to guide reaction 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
Components of exhaust system
The exhaust system may essentially consist of the following components:
The Tail Pipe
An Exhaust Manifold is the upper end of the
It is attached directly to the side of the engine
and is the first part of the exhaust system to
receive the burned exhaust gases from the car's
The exhaust manifold burns any fuel that was
inadequately burned by the engine and funnels
it down into the main exhaust system.
Due to high temperatures, Excellent oxidation
resistance, High-temperature strength, Thermal
fatigue properties are required.
The exhaust pipes are
responsible for transporting the
burned exhaust gases from the
engine and the exhaust manifold
and funneling them towards the
It can be metal or aluminum.
The pipes are used to create an
effectively sealed pathway.
TYPES OF PIPES
There are basically two types:
■ Regular pipe
■ Flexible pipe
Regular exhaust pipe is solid, typically available in straight lengths,
bent configurations and elbows.
Flexible exhaust pipe is flexible enough to bend with road
conditions and accommodate thermal expansion of the system.
The exhaust system may be sealed by welding joints or using
exhaust clamps as a simple, effective way to seal overlapping
A catalytic converter is a device that
uses a catalyst to convert three
harmful compounds in car exhaust
into harmless compounds.
• Hydrocarbons - in the form of
• Carbon monoxide -formed by the
• Nitrogen oxides - created when the
heat in the engine forces nitrogen in
the air to combine with oxygen .
There are two different types of
catalyst at work
• Reduction Catalyst - first stage
It uses platinum and rhodium to help
reduce the NOx
2NO => N2 + O2 or 2NO2 => N2 +
• Oxidation Catalyst -second stage
It uses platinum and palladium to help
reduce the unburned hydrocarbons
and carbon monoxide by burning
2CO + O2 => 2CO2
Pollutants from Car Exhaust
CO — carbon monoxide. The main source of CO in cities is the internal
combustion engine, where it is produced by incomplete combustion.
CO2 — carbon dioxide. The internal combustion engine contributes to the
increased concentrations of CO2 in the atmosphere.
NOx — nitrogen oxide forms when fuels are burned at high temperatures.
HC — hydrocarbons. Much of the hydrocarbon fuel passes through the
process unconsumed and is expelled into the atmosphere along with other
Other pollutants such as C6H6 — Benzene and its derivatives and
SO2 — sulphur dioxide are also present
A muffler or silencer is a device for reducing
the amount of noise emitted by
the exhaust of an internal combustion
The main muffler absorbs the noise of the
exhaust gas and is composed of an outer
shell, inner plates, inner pipes, end plates
and other components.
It contains a deceptively simple set of tubes
that are finely tuned to reflect the sound
waves produced by an engine so that they
cancel each other out.
Designs of muffler
• Vector Muffler - for larger diesel trucks, uses many concentric
• Spiral Baffle Muffler - for regular cars, uses a spiral-shaped
• The tail pipe is end of
the final length of
exhaust pipe which
ends with just a straight
or angled cut where it
vents to open air.
Importance of exhaust system
The exhaust system has three major functions:
To channel out the waste products of combustion out of the engine.
To reduce the noise generated by the engine.
To clean up the emissions that are harmful to the environment.
To reduce the pollution and to increase the efficiency of the engine.
1) “Multi objective Design Optimization of merging configuration
of an exhaust manifold of a car engine” by Masahiro kanazaki
2) “Market Delivery of ultra-low carbon vehicles in UK” by Ben
3) “Low carbon cars by reducing dissipation in hydrogen hybrids”
by Kevin Kendall et al.
4)“Present and Future Trends of Stainless Steel for
AutomotiveExhaust System” by Yoshiharu INOUE and Masao
KIKUCHI submitted in July 2003
5) Automobile engineering by Robert Siegel 2. John R. Howell