An exhaust purification apparatus includes a connection portion that connects an exhaust manifold to a catalytic converter. The connection portion includes a diffusion portion and a coupling portion. The coupling portion is configured such that a cross-sectional area of a passage of the coupling portion increases from a connection point with the diffusion portion toward a connection point with the catalytic converter. The side surface of the diffusion portion includes a connection surface to which the exhaust manifold is connected, a collision surface with which the exhaust gas that has flowed into the diffusion portion from the exhaust manifold strikes, a first coupling surface, and a second coupling surface. Cross-sectional shapes of the first coupling surface, the second coupling surface, and the collision surface are arcuate. The cross-sectional shape of the collision surface has a smaller curvature than the cross-sectional shapes of the first and second coupling surfaces.

A tunable insert assembly for a tunable exhaust system is disclosed for use with an air intake engine of a vehicle. The tunable exhaust system may include an intake tube having first and second ends with a first flange, an exhaust tube having third and fourth ends with a second flange, and a clamp to securely affix the first flange of intake tube to the second flange of exhaust tube. The tunable insert assembly may comprise a register ring, insert, and orifice plate with an opening. The insert may be perpendicularly disposed through the opening of orifice plate, while the register ring may be disposed over and circumferentially surrounds an outermost surface of orifice plate. Lastly, the exhaust system may be configured to produce a desired range of tunable sound pressure levels and a desired tunable sound frequency range based on various predetermined diameters and lengths related to the insert(s).

A tunable insert assembly for a tunable exhaust system is disclosed for use with an air intake engine of a vehicle. The tunable exhaust system may include an intake tube having first and second ends with a first flange, an exhaust tube having third and fourth ends with a second flange, and a clamp to securely affix the first flange of intake tube to the second flange of exhaust tube. The tunable insert assembly may comprise a register ring, insert, and orifice plate with an opening. The insert may be perpendicularly disposed through the opening of orifice plate, while the register ring may be disposed over and circumferentially surrounds an outermost surface of orifice plate. Lastly, the exhaust system may be configured to produce a desired range of tunable sound pressure levels and a desired tunable sound frequency range based on various predetermined diameters and lengths related to the insert(s).

An exhaust purification apparatus includes a connection portion that connects an exhaust manifold to a catalytic converter. The connection portion includes a diffusion portion and a coupling portion. The coupling portion is configured such that a cross-sectional area of a passage of the coupling portion increases from a connection point with the diffusion portion toward a connection point with the catalytic converter. The side surface of the diffusion portion includes a connection surface to which the exhaust manifold is connected, a collision surface with which the exhaust gas that has flowed into the diffusion portion from the exhaust manifold strikes, a first coupling surface, and a second coupling surface. Cross-sectional shapes of the first coupling surface, the second coupling surface, and the collision surface are arcuate. The cross-sectional shape of the collision surface has a smaller curvature than the cross-sectional shapes of the first and second coupling surfaces.