Adjusting the specificity of an engine map based on the sensitivity of an engine control parameter relative to a performance variable

1. A method of engine control optimization, the method comprising:

detecting a plurality of operating conditions of a vehicle engine, the plurality of operating conditions including a first operating condition and a second operating condition;

identifying an initial value for a first engine control parameter that corresponds to a combination of the detected first operating condition and the detected second operating condition in a first engine map look-up table, the first engine map look-up table defining a plurality of operating sub-regions each corresponding to a range of values for the first operating condition and a range of values for the second operating condition and defining a first engine control parameter value corresponding to each operating sub-region;

adjusting the initial value for the first engine control parameter based on a detected engine performance variable to cause the engine performance variable to approach a target value;

identifying an initial value for a second engine control parameter that corresponds to the combination of the detected first operating condition and the detected second operating condition in a second engine map look-up table, the second engine map look-up table defining a plurality of operating sub-regions each corresponding to a range of values for the first operating condition and a range of values for the second operating condition and defining a second engine control parameter value corresponding to each operating sub-region;

adjusting the initial value for the second engine control parameter based on the detected engine performance variable to cause the engine performance variable to approach the target value;

determining a first sensitivity of the engine performance variable in response to changes in the first engine control parameter when the detected first operating condition and the detected second operating condition are within a first operating sub-region of the first engine map look-up table;

adjusting the first engine map look-up table by dividing the first operating sub-region of the first engine map look-up table into a plurality of new operating sub-regions within the first operating sub-region of the first engine map look-up table when the first sensitivity is greater than a threshold;

determining a second sensitivity of the engine performance variable in response to changes in the second engine control parameter when the first operating condition and the second operating condition are within a first operating sub-region of the second engine map look-up table; and

adjusting the second engine map look-up table by dividing the first operating sub-region of the second engine map look-up table into a plurality of new operating sub-regions within the first operating sub-region of the second engine map look-up table when the second sensitivity is greater than a threshold.

2. The method of claim 1 , wherein the acts of adjusting the initial value for the first engine control parameter and adjusting the initial value for the second engine control parameter are performed only when an engine controller is operating in an engine optimization mode.

3. The method of claim 2 , further comprising:

repeating the acts of detecting the plurality of operating conditions of the vehicle engine, identifying the initial value for the first engine control parameter, adjusting the initial value for the first engine control parameter, identifying the initial value for the second engine control parameter, and adjusting the initial value for the second engine control parameter until the engine performance variable converges toward the target value when operating in the engine optimization mode; and

ending the engine optimization mode when the engine performance variable converges toward the target value.

4. The method of claim 3 , further comprising:

identifying an optimal adjusted value of the first engine control parameter that causes the engine performance variable to converge toward the target value at the end of the engine optimization mode when the first operating condition and the second operating condition are within the first operating sub-region of the first engine map look-up table;

calculating an average optimal adjusted value of the first engine control parameter for the first operating sub-region of the first engine map look-up table based on the optimal adjusted value of the first engine control parameter from a plurality of executions of the engine optimization mode; and

updating the first engine map look-up table by replacing the first engine control parameter value corresponding to each operating sub-region with the average optimal adjusted value for the first engine control parameter for the first operating sub-region of the first engine map look-up table.

5. The method of claim 4 , wherein the act of adjusting the first engine map look-up table when the first sensitivity is greater than the threshold further includes

defining the first engine control parameter value corresponding to each of the new operating sub-regions as the average optimal adjusted value for the first engine control parameter for the first operating sub-region.

6. The method of claim 2 , further comprising

initiating the engine optimization mode when the first operating condition and the second operating condition are both within a defined region of optimization,

wherein the defined region of optimization including a range of values for the first operating condition and a range of values for the second operating condition, and

wherein the defined region of optimization includes one or more operating sub-regions.

7. The method of claim 6 , further comprising:

identifying a range of the most commonly detected operating conditions of the vehicle engine; and

defining the region of optimization based on the identified range of the most commonly detected operating conditions.

8. The method of claim 7 , wherein the range of the most commonly detected operating conditions includes the operating conditions of the vehicle engine at a cruising speed.

9. The method of claim 1 , wherein the engine performance variable includes a value indicative of fuel efficiency of the vehicle engine.

10. The method of claim 9 , wherein the target value of the engine performance variable includes a maximum fuel efficiency value.

11. The method of claim 1 , wherein the act of detecting the plurality of operating conditions of the vehicle engine includes detecting an engine speed and an engine load.

12. The method of claim 1 , wherein the act of determining the first sensitivity of the engine performance variable includes determining how quickly adjusting the first engine control parameter in the first operating sub-region of the first engine map look-up table affects the engine performance variable.

13. The method of claim 1 , wherein the act of determining the first sensitivity of the engine performance variable includes determining a change in amplitude of the engine performance variable corresponding to a change in the value of the engine control parameter when the vehicle engine is operating in the first operating sub-region of the first engine map look-up table.

14. The method of claim 1 , wherein the first engine control parameter includes a variable valve timing and the second engine control parameter includes a spark timing.

15. An engine controller comprising a processor and a memory storing instructions that, when executed by the processor, cause the engine controller to:

detect a plurality of operating conditions of a vehicle engine, the plurality of operating conditions including an engine speed and an engine load;

identifying an initial value for a first engine control parameter that corresponds to a combination of the detected engine speed and the detected engine load in a first engine map look-up table, the first engine map look-up table defining a plurality of operating sub-regions each corresponding to a range of values for the engine speed and a range of values for the engine load and defining a first engine control parameter value corresponding to each operating sub-region;

adjusting the initial value for the first engine control parameter based on a detected value indicative of fuel efficiency of the vehicle engine to cause the value indicative of fuel efficiency of the vehicle engine to approach a target value;

identifying an initial value for a second engine control parameter that corresponds to the combination of the detected engine speed and the detected engine load in a second engine map look-up table, the second engine map look-up table defining a plurality of operating sub-regions each corresponding to a range of values for the engine speed and a range of values for the engine load and defining a second engine control parameter value corresponding to each operating sub-region;

adjusting the initial value for the second engine control parameter based on the detected value indicative of fuel efficiency of the vehicle engine to cause the value indicative of fuel efficiency of the vehicle engine to approach the target value;

determining a first sensitivity of the fuel efficiency of the vehicle engine in response to changes in the first engine control parameter when the detected engine speed and the detected engine load are within a first operating sub-region of the first engine map look-up table;

adjusting the first engine map look-up table by dividing the first operating sub-region of the first engine map look-up table into a plurality of new operating sub-regions within the first operating sub-region of the first engine map look-up table when the first sensitivity is greater than a threshold;

determining a second sensitivity of the fuel efficiency of the engine in response to changes in the second engine control parameter when the detected engine speed and the detected engine load are within a first operating sub-region of the second engine map look-up table; and

adjusting the second engine map look-up table by dividing the first operating sub-region of the second engine map look-up table into a plurality of new operating sub-regions within the first operating sub-region of the second engine map look-up table when the second sensitivity is greater than a threshold.