Answer: combustion causes a chemical reaction between nitrogen and oxygen in the engine.
Explanation:
Nitrogen oxides are produced in combustion processes, partly from nitrogen compounds in the fuel, but mostly by direct combination of atmospheric oxygen and nitrogen in flames. Nitrogen oxides are produced naturally by lightning, and also, to a small extent, by microbial processes in soils.
when fuels are burned in vehicle engines high temperatures are reached. at these high temperature nitrogen and oxygen from the air combine to produce nitrogen
