Method and apparatus for controlling a multi-mode powertrain system

1. A method for controlling a multi-mode powertrain system including a transmission configured to transfer torque among an internal combustion engine, torque machines and an output member, the method comprising:

executing a deceleration fuel cutoff state, the executing comprising:

stopping fuel flow to the engine; and

operating a deceleration fuel cutoff state pumping loss reduction mode comprising opening an air throttle to a fully open position to reduce engine pumping losses during the deceleration fuel cutoff state;

exiting the deceleration fuel cutoff state, the exiting comprising, prior to restoring the fuel flow to the engine, operating an engine intake manifold pump down mode comprising closing the air throttle to reduce an air intake manifold pressure and reduce an engine torque realized upon engagement of the engine once the fuel flow is restored.

2. The method of claim 1 , further comprising controlling one of the torque machines to spin the engine.

3. The method of claim 1 , wherein operating the engine intake manifold pump down mode is performed selectively based upon programmed pump down mode abort logic.

4. The method of claim 3 , wherein the programmed pump down mode abort logic disallows the pump down mode based upon a factor comprising one of exceeding an operator torque request, exceeding a battery power limit, exceeding a battery discharge limit, and exceeding a torque capacity of one of the torque machines.

5. The method of claim 1 , further comprising restoring the fuel flow to the engine after completion of the pump down mode.

6. A method for controlling a multi-mode powertrain system including a transmission configured to transfer torque among an internal combustion engine, torque machines and an output member, the method comprising:

executing a deceleration fuel cutoff state, the executing comprising:

stopping fuel flow to the engine; and

operating a deceleration fuel cutoff state pumping loss reduction mode comprising opening an air throttle to a fully open position to reduce engine pumping losses during the deceleration fuel cutoff state;

exiting the deceleration fuel cutoff state, the exiting comprising, prior to restoring the fuel flow to the engine, selectively operating an engine intake manifold pump down mode comprising closing the air throttle to reduce an air intake manifold pressure and reduce an engine torque realized upon engagement of the engine once the fuel flow is restored, the selective operation being provided by programmed pump down mode abort logic; and

restoring the fuel flow to the engine.

7. The method of claim 6 , wherein operating the intake manifold pump down comprises closing an engine throttle and controlling one of the torque machines to spin the engine.

8. The method of claim 6 , wherein restoring the fuel flow to the engine is initiated when an engine airflow torque achieves a torque value defined by an accelerator torque request.

9. The method of claim 8 , wherein the accelerator torque request is determined based upon an operator input to an accelerator pedal.

10. The method of claim 6 , wherein restoring the fuel flow to the engine is initiated when an engine airflow torque achieves a target engine torque.

11. The method of claim 6 , further comprising aborting the intake manifold pump down mode and initiating refueling when system constraints rendering the pump down mode acceptable are violated during the intake manifold pump down mode.

12. The method of claim 11 , wherein violating system constraints during the intake manifold pump down mode comprises exceeding an output torque request.

13. The method of claim 11 , wherein violating system constraints during the intake manifold pump down mode comprises exceeding a battery power limit.

14. The method of claim 11 , wherein violating system constraints during the intake manifold pump down mode comprises exceeding a battery discharge limit.

15. The method of claim 11 , wherein violating system constraints during the intake manifold pump down mode comprises exceeding a torque capacity of one of the torque machines.