What are the exhaust systems?

What are the exhaust systems? Automobiles are machines equipped with power – engines with convert the fuel chemical energy into mechanical energy through the combustion with air automobiles are machines equipped with power – engines with convert the fuel chemical energy into mechanical energy through the combustion with air. During this process, in addition to the main combustion products

Carbon dioxide CO2 and water H2O; atmosphere – polluting substances are also generated. Since combustion is Avery fast process and the thermodynamic balance is never reached exhaust gases contain product such a soot, carbon monoxide and hydro carbons due the high combustion temperature, nitrogen oxides are also formed as a result of the reaction of nitrogen and oxygen in the air. The main pollutants produced by the engine are : CO ( carbon monoxide ) : HC ( unburned hydrocarbons ) : NOX ( nitrogen oxides ) : PM ( particulate matter )

The reduction of polluting substances produced by motor vehicles also considering the numbers of vehicles in circulation today is an unavoidable condition for the protection is concerned which the main purpose of the exhaust gases.

Two main kinds of noise emitted by the exhaust systems are:

• Tailpipe noise.
• Shell noise.

The car maker defines the targets for each kind of noise which are related to the vehicle acoustic performances.
Many searches for innovative solutions aimed at reducing noise and emissions with optimized technologies.
These goals are pursued through specific research programs conducted with universities and research centers.
1- Low pressure ( exhaust gas re-circulation ) EGR.
2- nox abatement by means of SCR ( selective catalytic reduction of nox).
3- variable geometry mufflers

An EGR (exhaust gas re-circulation) systems consists of catalytic converter combined with anti-particulate filter where part of the exhaust gases after being filtered flows back to the combustion chamber.

Properties :

- Nox abatement in diesel engines.
- Efficiency of about 30%.
- Good mixture with intake air.
- Better turbine efficiency.
- Clean EGR the recalculated gases are particulate – free.


- Simple and compact systems (low weight and cost).
- No additives needed ( like for the SCR (selective catalytic reduction).
- System not subject to aging due to the presence of sculpture in the fuel.

The catalytic abatement of Nox through the SCR(selective catalytic reduction)consist in reducing the Nox using ammonia produced on board the vehicle containing urea (ad blue).


• Nox abatement in diesel engines.
• Efficiency of up to 80-90% depending on the complexity of the systems.
• Exhaust systems containing injector, mixing and SCR.
• System optimized for the best mixing of the additive with exhaust gases and for preventing the formation of solid deposits at the exhaust outlet.


• System complexity can be adapted to the requested Nox abatement objectives.

The variable geometry muffler adjusts its internal geometry to the caustic and performance needs of the engine systems, through a valve placed inside the silencer.


• Passive systems.
• Intel noise reduction at low engine speed reduction of the counter- pressure at high engine speed.


• Reduction in silencer volume and volume and weight.
• Low cost and high reliability.

Among the technically acceptable remedies, CATALYTIC CONVERTERS represent the most effective solution:

• They are capable of reducing by more than 90% the polluting substances 100.000 KM under any driving condition.
• The knowledge in this field is highly specialized, and the research focuses on two main objectives, the efficiency and life of catalytic converters.

• EL Zaharan group is responsible for assembling the catalytic converters for the reduction of polluting emission for vehicle-type application.