Disclosed herein is a method for controlling a bypass air split for a gas turbine combustor, the method comprising determining a target exhaust temperature, wherein the target exhaust temperature is based on at least one parameter of a group of parameters consisting of low pressure turbine speed, high pressure turbine speed, inlet guide vane angle, and bypass valve air split. Using the target exhaust temperature to calculate a required percentage of bypass air split based on maintaining maximum CO levels or minimum NOx levels. And, applying the required percentage of bypass air split to control a position of the bypass air valve.