An exhaust manifold does more than link the engine exhaust ports to the rest of exhaust system. It reduces combustion noise and transfers heat downstream to promote the continued oxidation of unburned hydrocarbons and carbon monoxide. The manifold therefore supplies some emissions control before the exhaust reaches a catalytic converter that may be fitted farther downstream.
The Muffler's main function is to reduce engine noise to an acceptable level. Engine noise is a jumbled collection of its fundamental firing frequencies, which range from about 100 to 400 hertz (1 Hz = 1 cycle/sec); overtones of these, and an extended range of "white noise" caused by resonance of the various component.
A muffler attenuates noise in three ways. Interior compartments called Helmholtz tuning chambers are tuned to setup canceling resonance of specific frequencies. Others, called broadband dissipaters, are design to reduce the energy of sound pulses and thus to attenuate a wide range of frequencies. Finally the muffler's absorptive surfaces function like sound-deadening wall and ceiling panels to absorb noise. In a typical "three-pass" design, the exhaust stream changes direction twice as it passes through separate compartments, each tuned to attenuate certain frequencies. When the exhaust gases finally pass out of the exhaust system through the tail pipe, their temperature, pressure, and noise have been greatly reduced.
The exhaust system design now also consider about pollutant contain throw away is limited in order not make many contaminated emission to the air and consider about the voice pollution. Concerning this matter now have been arranged by governmental regulation and run tightly.
Part of inside exhaust system:
- High pressure waste gasses from the engine cylinder to catalytic converter
- Remove polutant from the gasses, then through a muffler
- Out of the tail pipe
- The muffler reduce noise level by allowing the gasses to expand in its perforated pipes.