At present, the emissions from an internal combustion engine are reduced by catalytic treatments of the exhaust gases. Catalytic converters like SCR, however, result in added weight;high costs and rejects toxic gas like ammonia because of slip. To overcome this problem, a new combustion technique should be developed to yield improved primary combustion processes inside the engine with reduced exhaust gas emissions. This work presents the results of such a technique that is applicable to direct injection, Diesel engines. The technique is based on the porous medium combustion (PMC) technology, which is developed for steady state household and industrial combustion processes. Based on the adiabatic combustion in porous medium (PM), the porous medium engine as a combustion concept is proposed to achieve high combustion efficiency and low emissions. Using a commercial code CONVERGE the entire cycle is simulated and presented here. Temperature evolution of the PM and its effects are also discussed in detail. The study is carried out in a single cylinder, four stroke, water cooled, direct injection Diesel engine. The results show that that NOx is reduced by 77.07%. However remaining pollutants CO and HC increased by 91.6%, 86.5% which can be reduced by a simple two way catalytic converter. Also mean temperature during whole cycle is reduced by 300K which is main reason for reduction of emissions like NOx. Introducing porous medium inside piston bowl creates homogeneous mixture. The formation of homogeneous mixture and 3D thermal self-ignition in the PM-volume create a realizable condition for homogeneous combustion, which is almost independent of the engine load. Furthermore, the heat recuperation in PM may be used for heating up the compressed air and controlling the combustion temperature.