1. Tailpipe emissions by engine technology

Internal combustion engines are energy converters that extract mechanical energy from a heat source derived from the combustion of a hydrocarbon fuel.

Combustion is organized and takes place according to processes controlled to the best of technological ability.

The compounds produced by combustion are essentially water and carbon dioxide, but no matter how sophisticated combustion technologies are, there is still room for improvement, and these main compounds are accompanied by carbon monoxide (CO), unburned hydrocarbons (HC), nitrogen oxides (NOx) and particulate matter (PM), the regulated pollutants.

Internal combustion engines can be divided into two types, which differ in terms of how the fuel charge is ignited and the type of fuel used:

• electric spark ignition,...