Evolution of exhaust systems between 1990 and 2014. Euro standard

Exhaust system technology has evolved continuously as a result of European environmental requirements. The purpose of all of these requirements is to control the levels of polluting gas emissions and noise from all vehicles sold in the European Union. The way in which vehicles are checked for compliance with the standards after sale is to check them at vehicle technical inspection centres (ITV/MOT). The controls required of the manufacturers have obliged them to create new exhaust systems to reduce the amount of polluting gas emissions to the atmosphere.

Evolution table of the EURO standards for control of exhaust gas emissions.

EURO 1. The first regulation was drawn up in 1992 and required that a minimum of two or three silencers be installed and engine noise be reduced while maintaining backpressure.

EURO 2. In 1996, oxidising catalytic converters were introduced to reduce carbon monoxide (CO) emissions.

EURO 3. This standard appeared in 2000 and contained a higher number of directives for manufacturers. It required the separation of the nitrogen oxide (NOx) and unburnt hydrocarbon (HC) values resulting from combustion for the consequent reduction of carbon monoxide (CO). Solid particulate emissions to the atmosphere must be reduced. There was a change in the reading of the gases, these must now be read by the management unit immediately after starting the engine. The lambda sensor was installed from this time.

EURO 4. In 2005, another additional reduction of CO, separation of NOx and HC particulates and a reduction of solid particulate emissions were included.

 Introduction of the EOBDII system.

Gases at the catalytic converter outlet were monitored and a second lambda sensor added.

EURO 5. From 2009, the diesel particulate filter (DPF) was included with the aim of reducing solid particulates.

EURO 6. 2014. Reduction of noxious nitrogen oxides.

A system was introduced that converts nitrogen oxide molecules that are harmful to human health into water and nitrogen molecules. This is the SCR system (selective catalytic reduction). This system uses an aqueous solution of 34% urea and 66% water as a reducing agent for generating the clean molecules, this is known as AdBlue.

The evolution of these systems means that automotive professionals have to be well-trained as these are complicated and expensive repairs due to the components that may be installed in the exhaust systems, in addition to the necessary knowledge required for the diagnostic of the gas emissions.

Installation of the particulate filter system