With the existing emission norms, automotive industries are struggling to achieve the concentrations of CO, HC, Oxides of Nitrogen and Particulate Matter emissions; especially NOx and PM emissions with direct injection of fuel in both gasoline and diesel engines. Minimizing NOx and PM emissions in diesel engines is much complication than gasoline engines due to low vaporization rate of diesel fuel. Selective catalytic reactor with aqueous ammonia solution and titanium oxide catalyst reduces the concentrations of NOx from an engine exhaust. Due to high cost of selective catalytic reactor for NOx emissions control, the cost of vehicles was huge. Effective and cost operative selective catalytic converter was designed, fabricated and tested with GDI engine; an average about 27% of NOx concentration was reduced. Expecting the high percentage reduction of NOx emissions in diesel engines also. © 2023 Elsevier B.V., All rights reserved.