Diesel engines are being extensively used in the transport sector owing to their excel-lent fuel efficiency, low emissions of carbon dioxide, unburned hydrocarbons and car-bon monoxide. However, high emissions of nitrogen oxides (NOx) and particulate mat-ter (PM) place diesel engines on the down side. It is extremely complex to reduce both emissions at the same time, because of the trade-off between NOx and PM emissions. Even though the implementation of high pressure injection and common rail system could reduce both NOx and PM emissions together, the cost involved would be high and unaffordable for many engine producers and consumers. In this research work, a new combustion technique termed, porous medium combustion, has been proven to be a proficient technique in reducing both NOx and PM emissions from the direct injection diesel engines. However, the NOx and PM emissions were found to be higher than the conventional engine at low range of part loads. {\textcopyright} 2009 WILEY-VCH Verlag GmbH {\&} Co. KGaA, Weinheim.