What is a common contributing factor to increased nitrogen oxide (NOx) emissions?

High combustion temperatures are indeed a common contributing factor to increased nitrogen oxide (NOx) emissions. When fuels are burned at elevated temperatures, the nitrogen and oxygen in the air can react more readily. This reaction produces nitrogen oxides, which are problematic pollutants that contribute to smog and respiratory issues.

The formation of NOx is closely tied to the combustion process in vehicles. Higher temperatures create a greater likelihood of these reactions occurring, leading to increased production of nitrogen oxides. This is particularly relevant in internal combustion engines where combustion efficiency can inadvertently raise temperatures due to factors such as advanced ignition timing, lean fuel mixtures, or modifications that enhance performance.

In contrast, while low fuel quality, improper air-fuel mixtures, and excessive idling can negatively affect emissions in various ways, they do not directly correlate with the significant increase in NOx emissions resulting from high combustion temperatures. To effectively manage NOx emissions, controlling the combustion process and the associated temperatures is essential.