Automotive Diesel engines delivers more energy than gasoline because it burns the fuel more efficiently by compression process. Diesel engine piston plays an important role in delivering more power with the same volume of air-fuel mixture. To achieve this we need to have a better swirl (rotation of air inside the cylinder along the cylinder axis) to ignite the fuel by proper air-fuel ratio. In this project we target to improve the swirl motion for the proper mixing of fuel and air inside the combustion chamber by making tangential groves on the piston bowl. Different bowl designs are targeted to compare and analyse the effects of piston bowl by using CFD code (Commercial CFD code for engine specific).The intake port, combustion chamber roof, cylinder liner, piston bowl, intake valves and exhaust vales are considered for the 3D CFD modelling. The in-cylinder flow are measured numerically on different planes at various crank angles to see the effect of air motion caused by the tangential swirl groves created on the piston bowl. Different types of piston bowls by varying the number of groves, increasing the width of the groves are studied numerically and compared to identify the better swirl generating piston bowl.