Dual mode muffler

A muffler assembly for a vehicle exhaust system, comprising:

• a muffler including a primary resonator with a primary resonator chamber and a secondary resonator with a secondary resonator chamber;
• a primary muffler conduit that passes through the primary resonator chamber to define a primary exhaust flow path through the muffler;
• a secondary muffler conduit extending through at least part of the secondary resonator chamber to define a secondary exhaust flow path within the muffler, wherein an end of the secondary muffler conduit intersects and is in fluid communication with the primary muffler conduit at a location downstream from the primary resonator chamber;
• and
• a valve positioned upstream of the primary resonator that is actuatable between an open position and a closed position,
• wherein exhaust flow through both the primary muffler conduit and primary exhaust flow path and through the secondary muffler conduit and secondary exhaust flow path is permitted when the valve is in the open position to produce a first level of sound attenuation provided by the muffler in a first operating mode,
• wherein the valve is configured to restrict exhaust flow through the primary muffler conduit and primary exhaust flow path in the closed position such that more than 50 percent of the exhaust flow is directed through the secondary muffler conduit and secondary exhaust flow path when the valve is in the closed position to produce a second level of sound attenuation provided by the muffler in a second operating mode that is greater than the first level of sound attenuation provided by the muffler in the first operating mode,
• wherein the primary resonator has a primary resonator cross-sectional area (A1) and the primary muffler conduit has a primary muffler conduit cross-sectional area (a1) that is smaller than the primary resonator cross-sectional area (A1),
• wherein the secondary resonator has a secondary resonator cross-sectional area (A2) and the secondary muffler conduit has a secondary muffler conduit cross-sectional area (a2) that is smaller than the secondary resonator cross-sectional area (A2),
• wherein the primary and secondary resonators and the primary and secondary muffler conduits are sized such that a primary area ratio (A1/a1) of the primary resonator cross-sectional area (A1) divided by the primary muffler conduit cross-sectional area (a1) is smaller than a second area ratio (A2/a2) of the secondary resonator cross-sectional area (A2) divided by the secondary muffler conduit cross-sectional area (a2).