An innovative Diffusive Air Jet (DAJ) Combustion Chamber concept has been introduced in the present work. The DAJ Combustion Chamber design is based on the study of rate of heat release (ROHR) curve and its correlation with emission generation. The objective is to lower the trade-off between NOx and soot without sacrificing fuel economy of Direct Injection (DI) diesel engine. DAJ Combustion Chamber modifies ROHR curve to the desired one so that it lowers engine out emissions. To study its effect, a large bore, six cylinder engine with mechanical fuel injection system has been used. Three dimensional simulation software is used for the model calibration of basic reentrant cavity. Local emissions and ROHR curve have been studied using reentrant cavity shape. It has been modified to DAJ Combustion Chamber using Air Jet Chambers (AJCs). AJCs are positioned in the three dimensional model in such a way that they affect local in-cylinder emissions. Combustion in the DAJ combustion chamber has been studied at two different load conditions at the same engine speed. The results obtained with DAJ Combustion Chamber have been validated experimentally for the selected multi cylinder engine. In this paper simulation and experimental results with basic reentrant cavity and DAJ Combustion Chamber have been discussed in detail. Effectiveness of DAJ combustion chamber is further explored during experimentation which has been covered in this paper.