Exhaust modulator

An exhaust modulator for an exhaust system of an internal combustion engine, comprising a body defining a flowpath therethrough for engine exhaust gases, a gate in the exhaust flowpath movable between an open and a closed position and at least one bleed flowpath communicating between opposite sides of the gate, and a flow control means operable to control the flow of exhaust gases along said at least one bleed flowpath so as to limit the increase of back pressure applied to the engine to different predetermined increasing rates as engine r.p.m. increases, as required for operation of the modulator in selected modes, said flow control means being operable in response to at least one operating parameter.

A method of operating an exhaust modulator comprising a body defining a flowpath therethrough for engine exhaust gases, a gate in the exhaust flowpath which is movable between an open and a closed position;

• at least one bleed flowpath communicating between opposite sides of the gate, and flow control means operable to control the flow of exhaust gases along said at least one bleed flowpath the method comprising sensing at least one operating parameter and operating the flow control means in response to said at least one operating parameter to change the rate of increase of back pressure imposed on the engine with increasing engine r.p.m.