METHOD OF ACTUATING A BY-PASS VALVE

A method of controlling a by-pass valve in an engine system, said engine system comprising at least a low pressure turbocharger and a high pressure turbocharger, said by-pass valve being located between the compressor stages of the low and high pressure turbochargers, said by-pass valve including a movable actuator/member, arranged so as to selectively divert intake air through, or by-pass, the high pressure compressor stage, wherein in an active mode the actuator/member is controlled so as to forcibly be moved to and from open and closed positions so as to divert said flow in the valve, said method including operating said by-pass valve in a passive mode.