Exhaust is made to make a way that guide and expel exhaust gasses far from the engine. Inside exhaust system, there are four noteworthy parts which are muffler, perforation, resonator chamber, inlet and outlet. For mechanical performance of perforated resonator can be controlled by size of holes. The aim of this paper is to analyzing internal part geometry of exhaust muffler in order to increase Modenas CT115s performance by using Ansys software as a programmed to calculate the velocity magnitude and the flow rate of exhaust muffler. Consequently, high proficiency inside the exhaust system will create a brilliant execution and high quality performance. From the simulation shows that decreasing the size of holes give ultimately impact to performance of exhaust.
