System and method for controlling fuel injection when an engine is automatically started to decrease an engine startup period

1. A system comprising:

a stop-start module that stops an engine and thereby interrupts a compression stroke of a cylinder in the engine when a driver depresses a brake pedal while an ignition system is on and the engine is idling, and that restarts the engine when the driver releases the brake pedal;

a fuel control module that, when the engine is restarted, selectively injects fuel into the cylinder as the cylinder completes the interrupted compression stroke based on an amount of crankshaft rotation corresponding to a difference between a position of a piston in the cylinder when the piston is stopped and top dead center; and

a spark control module that, when the engine is restarted, selectively generates spark in the cylinder as the cylinder completes the interrupted compression stroke based on the amount of crankshaft rotation.

2. The system of claim 1 wherein the fuel control module injects fuel into the cylinder during the interrupted compression stroke when the amount of crankshaft rotation is greater than a first angle.

3. The system of claim 2 wherein the fuel control module determines an injection amount and injection timing based on the amount of crankshaft rotation.

4. The system of claim 3 wherein the fuel control module applies a multiplier to the injection amount that is based on a propensity of the engine to automatically ignite, wherein the multiplier is greater than one.

5. The system of claim 2 wherein the fuel control module determines an injection amount and injection timing based on a compression ratio of the cylinder and an amount of air trapped within the cylinder when the engine is shut down.

6. The system of claim 5 wherein the fuel control module estimates the trapped air amount based on the piston stopping position, engine geometry, an intake air temperature, and a manifold pressure, and the fuel control module estimates the compression ratio based on valve timing and a ratio of a first volume of the cylinder at the piston stopping position to a second volume of the cylinder at top dead center.

7. The system of claim 1 wherein the spark control module generates spark in the cylinder during the interrupted compression stroke when the amount of crankshaft rotation is greater than a first angle.

8. The system of claim 7 wherein the spark control module determines spark timing based on the piston stopping position.

9. The system of claim 8 wherein the spark control module determines the spark timing further based on at least one of an engine shutdown period, a manifold pressure, and an intake air temperature.

10. A method comprising:

stopping an engine and thereby interrupting a compression stroke of a cylinder in the engine when a driver depresses a brake pedal while an ignition system is on and the engine is idling;

restarting the engine when the driver releases the brake pedal;

when the engine is restarted, selectively injecting fuel into the cylinder as the cylinder completes the interrupted compression stroke based on an amount of crankshaft rotation corresponding to a difference between a position of a piston in the cylinder when the piston is stopped and top dead center; and

when the engine is restarted, selectively generating spark in the cylinder as the cylinder completes the interrupted compression stroke based on the amount of crankshaft rotation.

11. The method of claim 10 further comprising injecting fuel into the cylinder during the interrupted compression stroke when the amount of crankshaft rotation is greater than a first angle.

12. The method of claim 11 further comprising determining an injection amount and injection timing based on the amount of crankshaft rotation.

13. The method of claim 12 further comprising applying a multiplier to the injection amount that is based on a propensity of the engine to automatically ignite, wherein the multiplier is greater than one.

14. The method of claim 11 further comprising determining an injection amount and injection timing based on a compression ratio of the cylinder and an amount of air trapped within the cylinder when the engine is shut down.

15. The method of claim 14 further comprising:

estimating the trapped air amount based on the piston stopping position, engine geometry, an intake air temperature, and a manifold pressure; and

estimating the compression ratio based on valve timing and a ratio of a first volume of the cylinder at the piston stopping position to a second volume of the cylinder at top dead center.

16. The method of claim 10 further comprising generating spark in the cylinder during the interrupted compression stroke when the amount of crankshaft rotation is greater than a first angle.

17. The method of claim 16 further comprising determining spark timing based on the piston stopping position.

18. The method of claim 17 further comprising determining the spark timing further based on at least one of an engine shutdown period, a manifold pressure, and an intake air temperature.

19. The system of claim 2 wherein the fuel control module adjusts the first angle based on a target engine speed.

20. The method of claim 11 further comprising adjusting the first angle based on a target engine speed.