Bypass exhaust pathway to allow gases to bypass the start catalyst of a vehicle

A system for improving the fuel economy of a vehicle, the system comprising:

• an engine having a plurality of cylinders and an output manifold coupled to the plurality of cylinders, the engine configured to produce an initial exhaust gas;
• a first exhaust pipe having a first end connected to the output manifold and a second end, the first exhaust pipe defining a first inner diameter;
• a start catalyst having an output and an input connected to the second end of the first exhaust pipe;
• a second exhaust pipe having a first end connected to the output of the start catalyst and a second end;
• a bypass exhaust pipe having a first end connected to the first exhaust pipe and a second end connected to the second exhaust pipe, the bypass exhaust pipe defining a third inner diameter that is the same or larger than the first inner diameter of the first exhaust pipe;
• a first valve positioned at the first end of the bypass exhaust pipe and configured to move between a closed position and an open position for directing the initial exhaust gas to the start catalyst or the bypass exhaust pipe;
• an engine speed sensor configured to determine a speed of the engine;
• a load sensor configured to determine an amount of torque being output by the engine;
• a vehicle speed sensor configured to determine a speed of the vehicle;
• and
• an electronic control unit for estimating a temperature of the start catalyst based on the speed of the engine, the amount of torque being output by the engine, and the speed of the vehicle and controlling the first valve to be in the closed position or the open position based on the estimated temperature of the start catalyst.