Exhaust system on cars has 3 main functions. First transfer the toxic exhaust gas from the engine to the rear of the vehicle. Second, it reduces engine noise while the car is running. Finally, it converts unburnt fuel into a non-toxic combustion product through a catalytic converter. Exhaust system includes: an exhaust manifold, exhaust duct, catalytic converter, muffler and exhaust pipe (behind the car). The speed of exhaust air circulation at the end of the system is usually very large, the exhaust system has a continuous structure to reduce the huge flow rate of exhaust gas flow, the silencer system to get enough sound, it is belongs to the driver's application and preferences Exhaust manifold An exhaust manifold is used to transfer the exhaust gas from the outlet on the cover to the exhaust pipe. Most discharge manifolds contribute from 3,4,6 ... discharge contribution depends on each engine. There are discharge manifolds with an oxygen sensor mounted on the casing of th