Control system and method for preventing stochastic pre-ignition in an engine

1. A control system for an engine, comprising:

an initiation module that selectively initiates a stochastic pre-ignition (SPI) process to induce SPI and that generates a request signal indicating initiation of the SPI process to induce SPI;

a spark module that, in response to receiving the request signal indicating the initiation of the SPI process to induce SPI, advances spark timing of a cylinder R degrees past a spark limit for N consecutive cylinder firing events, and retards spark timing of said cylinder past said spark limit for M consecutive cylinder firing events after said N consecutive cylinder firing events; and

a fuel module that supplies, in response to receiving the request signal indicating the initiation of the SPI process to induce SRI, a rich fuel-air charge to said cylinder for said M consecutive cylinder firing events,

wherein R is a real number greater than zero, N and M are integers greater than zero, and said spark limit is a control value used to limit an amount of spark advance to prevent spark-knock.

2. The control system of claim 1 , wherein the initiation module determines when an engine speed is within a predetermined range, and wherein said spark module advances spark timing for a first one of said N consecutive cylinder firing events when said engine speed is within said predetermined range.

3. The control system of claim 1 , wherein:

the initiation module determines when at least one of the following criteria is met:

(i) an engine torque is within a predetermined first range; and

(ii) a boost pressure is within a predetermined second range,

wherein said spark module advances spark timing for a first one of said N consecutive cylinder firing events when said at least one of said criteria is met.

4. The control system of claim 1 , further comprising a detection module that detects when an SPI event occurs in said cylinder, and wherein said fuel module supplies a rich fuel-air charge to said cylinder for P consecutive cylinder firing events when said SPI event is detected, P being an integer greater than zero.

5. The control system of claim 1 , wherein said M consecutive cylinder firing events begin on a next cylinder firing event of said cylinder after said N consecutive cylinder firing events.

6. The control system of claim 1 , wherein, for each of a plurality of remaining cylinders, one cylinder at a time:

said spark module advances spark timing R degrees past said spark limit for another N consecutive cylinder firing events; and

said fuel module supplies another rich fuel-air charge for another M consecutive cylinder firing events after said N consecutive cylinder firing events.

7. The control system of claim 1 , wherein a fuel-air equivalence ratio of said fuel-air charge is greater than 1.0 and less than 1.5.

8. The control system of claim 1 , wherein N is an integer greater than zero and less than three.

9. The control system of claim 1 , wherein M is an integer greater than zero and less than twenty.

10. The control system of claim 1 , wherein said engine is one of a turbocharged engine and a supercharged engine.

11. A method for controlling an engine, comprising:

selectively initiating a stochastic pre-ignition (SPI) process to induce SPI;

generating a request signal indicating initiation of the SPI process to induce SPI;

in response to the request signal indicating the initiation of the SPI process to induce SPI, advancing spark timing of a cylinder R degrees past a spark limit for N consecutive cylinder firing events and retarding spark timing of said cylinder past said spark limit for M consecutive cylinder firing events after said N consecutive cylinder firing events; and

in response to the request signal indicating the initiation of the SPI process to induce SPI, supplying a rich fuel-air charge to said cylinder for said M consecutive cylinder firing events,

wherein R is a real number greater than zero, N and M are integers greater than zero, and said spark limit is a control value used to limit an amount of spark advance to prevent spark-knock.

12. The method of claim 11 , further comprising:

determining when an engine speed is within a predetermined range; and

advancing spark timing of said cylinder for a first one of said N consecutive cylinder firing events when said engine speed is within said predetermined range.

13. The method of claim 11 , further comprising:

determining when at least one of the following criteria is met:

(i) an engine torque is within a predetermined first range, and

(ii) a boost pressure is within a predetermined second range; and

advancing spark timing of said cylinder for a first one of said N consecutive cylinder firing events when said at least one of said criteria is met.

14. The method of claim 11 , further comprising:

detecting when an SPI event occurs in said cylinder; and

supplying a rich fuel-air charge to said cylinder for P consecutive cylinder firing events when said SPI event is detected, P being an integer greater than zero.

15. The method of claim 11 , wherein said M consecutive cylinder firing events begin on a next cylinder firing event of said cylinder after said N consecutive cylinder firing events.

16. The method of claim 11 , further comprising:

advancing spark timing R degrees past said spark limit for another N consecutive cylinder firing events for each of a plurality of remaining cylinders, one cylinder at a time; and

supplying another rich fuel-air charge for another M consecutive cylinder firing events after said N consecutive cylinder firing events for each of said plurality of remaining cylinders, one cylinder at a time.

17. The method of claim 11 , wherein a fuel-air equivalence ratio of said fuel-air charge is greater than 1.0 and less than 1.5.

18. The method of claim 11 , wherein N is an integer greater than zero and less than three.

19. The method of claim 11 , wherein M is an integer greater than zero and less than twenty.

20. The method of claim 11 , wherein said engine is one of a turbocharged engine and a supercharged engine.