A method of controlling an operating temperature Tx of a boost pressure device, such as a turbocharger or supercharger, for a vehicle. The method comprising: determining a pressure difference ΔP (100) between a current operating pressure Px of the boost pressure device and a target boost pressure PLIM at which the boost pressure device operates at an operating temperature limit TLIM. Further determining a pressure step size dP (110), wherein the pressure step size dP is a function of the pressure difference ΔP and a predetermined number of pressure steps N, and successively adjusting the current operating pressure Px by the pressure step size dP (120) until the operating temperature Tx of the boost pressure device is substantially equal to the operating temperature limit TLIM. The method is an iterative approach which used knowledge of the boost pressure/mass flow relationship to solve for the highest boost pressure within the operating temperature limit, allowing better use of the available computing resources, thus giving a quicker response time.