This Small Business Innovative Research Phase I project will establish a novel diesel engine concept in combination with catalyst technology. This will dramatically reduce diesel engine emissions while maintaining the enhanced fuel efficiency. In this program we will demonstrate that the best features of spark engines (low emissions) and diesel engines (enhanced fuel efficiency) can be combined to produce a high fuel efficiency, low emissions diesel engine consistent with the 80 mpg goals of the Partnership For Next Generation Vehicle Program (PNGV). The key to this program is the use of modest levels of oxygen enriched air (22-25% oxygen) to a diesel engine in combination with other after treatment procedures. In Phase I we will demonstrate the needed enhancements from oxygen enriched air (OEA) and simulate overall system performance based on our after treatment model. These results should demonstrate the engines ability to meet the PNGV mileage and emissions objective for passenger cars (hybrid vehicle) and/or meet the 2002 diesel engine emissions goal. In Phase II we will integrate both OEA and after treatment systems into overall engine package for full scale demonstration.