Page 104 - Mechanic Diesel - TT

MECHANIC DIESEL - CITS

iii Combination muffler: - Some mufflers in vehicles combine absorbent and reactive elements, so that the
broad spectrum of sound can be easily reduced. This type of mufflers are extensively used to reduce exhaust
sound.

iv Electronic muffler: - This muffler is also called the ‘Halm Holtz’ muffler after its creator. These muffler
resonators are connected in series with a pipe in between which has ports. With the help of these ports, sound
waves come out without any obstruction. It is mainly used in electronic sound control system. This almost
eliminates exhaust sound. In this system, a microphone is used to detect sound in a computer-controlled
emitter. These exhaust sound waves are similar and opposite. Its application does not produce noise in the
exhaust system.
In this type of muffler, a pattern is taken by observing the sound waves generated by the exhaust pipes with
the help of sensors and microphones. This pattern is analyzed in a computer, generating a mirror image. This
mirror image is sent to the speaker, as a result of which waves are generated and the noise stops. In this
system, fuel saving and exhaust emission are done. Therefore, this type of muffler is used to obtain a specific
sound.

Types of catalytic converter
Passenger cars and light trucks have been equipped with catalytic converters. A Catalytic converter is located
(Fig 1) within the exhaust system and converts to convert harmful emissions as HC, CO, NOx, produced by an
internal combustion engine, to less-harmful elements: H2O(Water), CO2 (Carbon Dioxide), and N2 (Nitrogen)
Modern vehicles are fitted with three-way catalytic converters (TWC). The term ‘three-way’ is in relation to the
three regulated emissions the converter is designed to reduce:

91
CITS : Automotive - Mechanic Diesel - Lesson 25 - 28 CITS : Automotive - Mechanic Diesel - Lesson 25 - 28