The charge system follows the Variable Twin Turbo principle and is made up of two turbochargers of various size perfectly matched to one another and therefore operating either individually or together as a team, depending on the driver's power and performance requirements. (press.bmwgroup.com)
Following the variable rate is not as common as it used to be since the Treasury now focuses on the CPI - U / Inflation rate and the fixed rates instead. (ibonds.info)
For example, let's say your average response rate is 1 % and you test the following variables — each giving you a slight lift in response: (simpson-direct.com)