US Patent 7793495 Engine gas temperature reduction

An exhaust system for a motor vehicle engine includes mixing vent flaps in the exhaust pipe which open responsive to exhaust temperature. The vent flap forms a portion of the exhaust pipe when closed and is pivotally attached along one edge to the exhaust pipe to open inwardly into the exhaust pipe to constrict and accelerate flow in the pipe to allow outside air to be drawn into the exhaust pipe. A magnetic catch latches the vent flap in its closed position and a magnetic release responsive to increased temperature of the exhaust stream releases the vent flap.