Over the past century, need and development of micro-power devices have necessitated the need for studies to look further into mediums that can enhance combustion processes of fuels by optimizing system parameters. This is essential so as to utilize the high specific energy content of liquid hydrocarbon fuels. As we know that main source of pollution is oxides nitrogen (NOx) so method or apparatus is develop which is used as pre-processing unit for the automobile mainly. This method and apparatus for reducing the emissions and improving the performance of an internal combustion engine. An input air stream is separated into an oxygen-enriched air stream and a nitrogen-enriched air stream. The nitrogen-enriched air stream is received by a holding chamber. The oxygen-enriched air and a combustible fuel are provided to a combustion chamber of the internal combustion engine and a combustion process is initiated. After a predefined time delay, a volume of nitrogen-enriched air is provided from the holding chamber to the combustion chamber to be used during the rest of the combustion process or we can also used separated nitrogen for other useful application such as air-conditioning or cooling purpose.