Methods and systems for individual cylinder fuel-air ratio adaptation
Systems and methods for determining normalized fuel-air ratio error for a cylinder of an engine an engine are disclosed. In one example, the engine is operated in a four-cylinder mode to generate a first normalized fuel-air ratio error for a first cylinder and operated in an eight-cylinder mode to generate a second normalized fuel-air ratio error for a second cylinder.
1 . A method for operating an engine, comprising:
operating the engine in a four-cylinder mode and generating a first normalized fuel-air ratio error for a first cylinder via a first feedback correction value generated from an oxygen sensor output produced while operating the engine in the four-cylinder mode;
operating the engine in an eight-cylinder mode and generating a second normalized fuel-air ratio error for a second cylinder via the first normalized fuel-air ratio error and a second feedback correction value generated from the oxygen sensor output produced while operating the engine the eight-cylinder mode; and
adjusting output of one or more fuel injectors in response to the first normalized fuel-air ratio error or the second normalized fuel-air ratio error.
2 . The method of claim 1 , where the engine is a direct fuel injection engine.
3 . The method of claim 1 , where the engine is a port fuel injected engine.
4 . The method of claim 1 , where the engine is port fuel injected engine and a direct fuel injected engine.
5 . The method of claim 4 , further comprising generating the first normalized fuel-air ratio error for a direct fuel injector of the first cylinder via activating the direct fuel injector of the first cylinder and deactivating a port fuel injector of the first cylinder.
6 . The method of claim 4 , further comprising generating the first normalized fuel-air ratio error for a port fuel injector of the first cylinder via activating the port fuel injector of the first cylinder and deactivating a direct fuel injector of the first cylinder.
7 . The method of claim 1 , where in the eight-cylinder mode each engine oxygen sensor senses a total of two cylinders.
8 . The method of claim 1 , where the engine includes a cross plane crankshaft.
9 . The method of claim 1 , where the oxygen sensor output produced while operating the engine in four-cylinder mode is generated from a same oxygen sensor from which the second feedback correction value is generated.
10 . The method of claim 1 , where the first feedback correction value generated from the oxygen sensor output is based on a difference between a commanded fuel-air ratio and a fuel-air ratio determined via the oxygen sensor output.