Abstract: An internal combustion engine and a method of operation are described involving: supplying intake gas from an intake manifold (18) to an air intake port of a combustion chamber in a cylinder (11); selectively operating an air intake valve using a first operating profile (30) and, on demand, switching selective operation of the air intake valve to a second operating profile (31) in which the closing of the air intake valve is delayed compared to the closing of the air intake valve using the first operating profile; wherein at the point (43) of or prior to switching from the first operating profile to the second operating profile the pressure of the intake gas in the intake manifold is increased.

Abstract: This disclosure is directed to a turbocharger arrangement having a high pressure turbocharger and a low pressure turbocharger connected in series. The low pressure turbine has first and second volutes and the arrangement includes a control valve which controls the proportion of exhaust gas which is directed through the first and second passages to the first and second volutes.