Exhaust emissions consisting of oxides of nitrogen (collectively known as NOx) from internal combustion engines present a serious environmental problem. Although the problem exists for both gasoline and diesel engines, the problem is more severe for the diesel engine. NOx formation in an engine depends strongly on flame temperature, and flame temperature is dependent upon the composition of the fuel and the intake air. The concept is to develop and test copolymer modules for Nitrogen Enriched Air (NEA) supply to diesel engines. The objective is to minimize NOx production from diesel engine emissions without a significant loss of fuel efficiency or a significant increase in carbon monoxide and smoke related emissions. In the present study, a module using the latest membrane technology was designed, tested and fabricated. The modules were installed in a diesel engine test stand and tests were run. The NOx level from the test engine using standard air was established. The results from the test showed that an increase of nitrogen from 79% to 81% in the intake, reduced NOx by 50-70% with no significant increase in smoke or CO. Preliminary tests with 83% nitrogen concentration shows an even higher NOx reduction but at a higher energy cost. Specifics from the proof of concept testing are given in this paper which prove the theory behind the technology. The tests demonstrated (1) the feasibility of the membrane modules for use in NOx reduction and (2) the profound effect that NEA has on NOx emissions with power losses below 5%. In addition to the use of membranes on new engines, the technology is well suited for retrofit into existing engines.