An exhaust chamber system having a rotatable propeller type blade assembly at the entry to an expansion chamber which creates a vortex that swirls exhaust gas towards the outlet. The resultant action within the exhaust chamber aids in scavenging internal combustion engine exhaust gases, and in reducing system back pressure. The exhaust chamber maintains the sound level of the exhaust within acceptable limits while delivering improved horsepower, torque, and/or fuel efficiency over other known conventional mufflers.