Control of spark ignited internal combustion engine

1. A method of controlling a spark ignited internal combustion engine having a fuel injector which injects fuel directly into its combustion chamber, comprising:

stopping the fuel injection if a desired torque for said engine is a predetermined torque or less and a speed of said engine is a predetermined speed or greater;

resuming the fuel injection by injecting a first amount of fuel directly into said combustion chamber during a negative pressure period which is a part of a negative valve overlap period that is after an exhaust valve of said combustion chamber is closed and before an intake valve of said combustion chamber is opened in a cylinder cycle and during which a pressure in said combustion chamber is lower than a pressure when said exhaust valve is closed and injecting a second amount of the fuel into said combustion chamber during an intake period in which said intake valve of said combustion chamber is opened when the engine speed has decreased to said predetermined speed, said second amount being less than said first amount and including zero; and

resuming the fuel injection by injecting a third amount of the fuel directly into said combustion chamber during the negative pressure period and injecting a fourth amount of the fuel into said combustion chamber during the intake period when the desired engine torque has increased to said predetermined torque, said third amount being less than said fourth amount and including zero.

2. The method as described in claim 1 , further comprising increasing said first amount as volatility of the fuel decreases.

3. The method as described in claim 2 , further comprising determining ethanol content in said fuel, and determining the fuel is less volatile when the determined ethanol content is greater.

4. The method as described in claim 3 , further comprising increasing said first amount as a temperature of said internal combustion engine decreases.

5. The method as described in claim 4 , further comprising decreasing said negative valve overlap period as the desired engine torque increases.

6. The method as described in claim 5 , further comprising opening said intake valve earlier during a cylinder cycle as the desired engine torque increases.

7. The method as described in claim 2 , further comprising increasing said first amount as a temperature of said internal combustion engine decreases.

8. The method as described in claim 7 , further comprising increasing said negative valve overlap period as the desired engine torque decreases.

9. The method as described in claim 8 , further comprising opening said intake valve later during a cylinder cycle as the desired engine torque decreases.

10. The method as described in claim 1 , further comprising increasing said first amount as a temperature of said internal combustion engine decreases.

11. The method as described in claim 10 , further comprising increasing the negative valve overlap period as the desired engine torque decreases.

12. The method as described in claim 11 , further comprising opening said intake valve later during a cylinder cycle as the desired engine torque decreases.

13. The method as described in claim 1 , further comprising increasing said first amount as a temperature of said internal combustion engine decreases.

14. The method as described in claim 13 , further comprising opening said intake valve later during a cylinder cycle as the desired engine torque decreases.

15. The method as described in claim 14 , further comprising closing said intake valve later during a cylinder cycle as the desired engine torque decreases.

16. The method as described in claim 1 , further comprising opening said intake valve earlier during a cylinder cycle as the desired engine torque decreases.

17. A system comprising:

a spark ignited internal combustion engine;

a fuel injector which injects fuel directly into its combustion chamber; and

a controller configured to control said fuel injector to:

stop the fuel injection if a desired torque for said engine is a predetermined torque or less and a speed of said engine is a predetermined speed or greater;

resume the fuel injection by injecting a first amount of fuel directly into said combustion chamber during a negative pressure period which is a part of a negative valve overlap period that is after an exhaust valve of said combustion chamber is closed and before an intake valve of said combustion chamber is opened in a cylinder cycle and during which a pressure in said combustion chamber is less than a pressure when said exhaust valve is closed and injecting a second amount of the fuel into said combustion chamber during an intake period in which said intake valve of said combustion chamber is opened when the engine speed has decreased to said predetermined speed, said second amount being less than said first amount and including zero; and

resume the fuel injection by injecting a third amount of the fuel directly into said combustion chamber during the negative pressure period and injecting a fourth amount of the fuel into said combustion chamber during the intake period when the desired engine torque has increased to said predetermined torque, said third amount being less than said fourth amount and including zero.

18. The system as described in claim 17 , wherein said controller is further configured to control said fuel injector so that said first amount increases as volatility of the fuel decreases.

19. The system as described in claim 17 , further comprising a valve lift adjusting mechanism which changes the negative valve overlap period, and wherein said controller is further configured to control said valve lift adjusting mechanism so that the negative valve overlap period increases.

20. The system as described in claim 19 , wherein said controller is further configured to control said valve lift adjusting mechanism so that said intake valve opens later during a cylinder cycle as the desired engine torque decreases.