11 | Indonesian Journal of Science & Technology, Volume 5 Issue 1, January 2020 Hal 11-19 The Effect of Spoiler Shape and Setting Angle on Racing Cars Aerodynamic Performance Hesam Eftekhari, Abdulkareem Sh. Mahdi Al-Obaidi * , Shahrooz Eftekhari School of Engineering, Taylor’s University College, No. 1 Jalan SS 15/8 47500 Subang Jaya, Selangor DE, Malaysia *Correspondence: E-mail: Abdulkareem.mahdi@taylors.edu.my Automotive racing is one of the favorite sports of human being. There have been many developments in past decades by car engineers to improve the performance of the engine and increase the aerodynamic efficiency of the race cars to achieve a better lap time and get a better placement safely. One of the ways to improve the aerodynamic performance of a race car is to use rear spoilers. This study by using ANSYS FLUENT numerically investigated the effect of the spoiler shape and setting angle on the aerodynamic characteristics of a race car and then it was validated by conducting wind tunnel experiment. Lift and drag coefficient of NACA0012, NACA4412, and S1223 are determined in Reynold’s number of 2×10 5 as an airfoil and as spoiler on ERC model which is a conceptual car model inspired by Porsche 911. It was found that ERC model with spoiler would have better aerodynamic efficiency compared to ERC model without spoiler. Also, S1223 at -6 degrees was identified as the optimized configuration as it generates the highest downforce. Even though the drag coefficient at this setting angle is slightly higher, but in terms of stability and handling IT is at its best. Overall, this study would help car manufacturers, for racing and commercial purposes, to have a better insight into the effect of spoiler configuration on the aerodynamic performance of cars. Hence, the stability, handling, and efficiency of the cars can be further improved by selecting the suitable spoiler configuration. © 2020 Tim Pengembang Jurnal UPI Keywords: Aerodynamic Performance, Spoiler, Race Car, CFD. Indonesian Journal of Science & Technology Journal homepage: http://ejournal.upi.edu/index.php/ijost/ Article History: Indonesian Journal of Science & Technology 5 (1) (2020) 11-20 ____________________ Received 02 Sep 2019 Revised 13 Dec 2019 Accepted 12 Jan 2020 Available online 22 Jan 2020