Wastegate valve seat position determination

1. A method of operating a wastegate in an internal combustion engine, comprising:

at engine startup, placing a wastegate valve at a seat;

recording a position of the seat and associating the seat position with an operating temperature; and

modifying a position of a wastegate actuator based on the seat position throughout engine operation, including, each time the wastegate valve is placed at the seat, increasing a force applied by the wastegate actuator to the wastegate valve to verify contact with the seat, determining a current position of the seat and the current operating temperature, and updating a previously-recorded position of the seat with the current position of the seat at the current operating temperature, to form a plurality of seat positions each associated with respective operating temperatures.

2. The method of claim 1 , further comprising overwriting a previously-recorded position of the seat with the current position of the seat if a difference between an absolute value of the previously-recorded position of the seat and the current position of the seat exceeds a threshold.

3. The method of claim 1 , further comprising, as the wastegate valve is placed at the seat throughout engine operation, incrementing the position of the wastegate actuator by adding a current margin to a current presently supplied to the wastegate actuator, and estimating deflection in a linkage coupling the wastegate valve to the wastegate actuator based on a change in output from a wastegate actuator position sensor, the change in output resulting from incrementing the position of the wastegate actuator.

4. The method of claim 1 , wherein the plurality of seat positions is stored in a data structure in a computer-readable storage medium.

5. The method of claim 4 , wherein placing the wastegate valve at the seat includes:

retrieving a previously-recorded position of the seat from the data structure;

placing the wastegate valve at the previously-recorded position of the seat;

incrementing the position of the wastegate actuator by adding a current margin to a current presently supplied to the wastegate actuator; and

recording a current position of the seat once output from a wastegate actuator position sensor falls below a threshold.

6. The method of claim 4 , wherein modifying the position of the wastegate actuator includes retrieving a previously-recorded position of the seat associated with the current operating temperature by accessing the data structure with the current operating temperature.

7. The method of claim 4 , wherein the data structure is a lookup table.

8. The method of claim 4 , wherein the data structure comprises a plurality of positions of the seat generated offline prior to being programmed in the data structure.

9. The method of claim 4 , wherein the data structure comprises a plurality of deflection corrections each associated with the operating temperature for compensating deflection in a linkage coupling the wastegate valve to the wastegate actuator.

10. The method of claim 1 , wherein the wastegate valve is placed at the seat when maximum boost is requested.

11. The method of claim 1 , wherein the operating temperature includes a turbine inlet temperature.

12. A method for controlling a wastegate valve coupled through a linkage to an actuator for diverting gases from a turbocharger, comprising:

determining a wastegate valve lift to reduce a difference between a desired boost and an actual boost;

determining a desired wastegate actuator position to achieve the wastegate valve lift;

retrieving a position of a wastegate valve seat from a data structure, the data structure holding a plurality of positions of the wastegate valve seat each associated with respective operating temperatures;

modifying the desired wastegate actuator position based on the retrieved position of the wastegate valve seat;

upon receiving a fully closed command, placing the wastegate valve at a fully closed position;

increasing a force applied by the wastegate actuator to the wastegate valve to verify contact with the wastegate valve seat;

determining a current position of the wastegate valve seat; and

updating a previously-recorded position of the wastegate valve seat with the current position of the wastegate valve seat at a current operating temperature.

13. The method of claim 12 , further comprising, at engine startup, placing the wastegate valve at the fully closed position, and adding a current position of the wastegate valve seat corresponding to the fully closed position of the wastegate valve to the data structure, the current position of the wastegate valve seat associated with the current operating temperature.

14. The method of claim 13 , wherein placing the wastegate valve at the fully closed position includes:

retrieving a previously-recorded position of the wastegate valve seat from the data structure;

placing the wastegate valve at the previously-recorded position of the wastegate valve seat;

incrementing a current wastegate actuator position by adding a current margin to a current presently supplied to the wastegate actuator; and

adding the current position of the wastegate valve seat to the data structure once output from a wastegate actuator position sensor falls below a threshold.

15. The method of claim 12 , wherein the operating temperature comprises a turbine inlet temperature.

16. The method of claim 12 , wherein increasing the force applied by the wastegate actuator to the wastegate valve comprises incrementing a current wastegate actuator position by adding a current margin to a current presently supplied to the wastegate actuator, the method further comprising:

determining deflection in a linkage based on a change in output from a wastegate actuator position sensor, the change in output resulting from incrementing the current wastegate actuator position.

17. The method of claim 16 , further comprising adding a deflection correction to the data structure based on the determined deflection, the deflection correction for compensating deflection in the linkage and associated with the operating temperature.

18. A method of operating a wastegate valve via a wastegate actuator, comprising:

placing the wastegate valve between a fully open position and a fully closed position responsive to a desired boost;

placing the wastegate valve at the fully closed position responsive to a request of maximum boost;

increasing a force applied by the wastegate actuator to the wastegate valve to verify contact with a wastegate valve seat;

determining a current position of the wastegate valve seat; and

updating a previously-recorded position of the wastegate valve seat with the current position of the wastegate valve seat at an operating temperature.

19. The method of claim 18 , wherein the current position of the wastegate valve seat is one of a plurality of wastegate valve seat positions stored in a data structure, each of the plurality of wastegate valve seat positions associated with a respective operating temperature and a respective deflection correction.