Abstract: The described embodiments relate generally to skip fire control of internal combustion engines and particularly to mechanisms for determining a desired operational firing fraction. In some embodiments, a firing fraction determining unit is arranged to determine a firing fraction suitable for delivering a requested engine output. The firing fraction determining unit may utilize data structures such as lookup tables in the determination of the desired firing fraction. In one aspect the desired engine output and one or more operational power train parameters such as current engine speed, are used as indices to a lookup table used to select a desired firing fraction. In other embodiments, additional indices to the data structure may include any one of: transmission gear; manifold absolute pressure (MAP); manifold air temperature; a parameter indicative of mass air charge (MAC); cam position; cylinder torque output; maximum permissible manifold pressure; vehicle speed; and barometric pressure.

Abstract: In one aspect, a method for mitigating detonation in a skip fire engine control system is described. The working chambers of the engine are operated in a skip fire manner to deliver a desired torque. One or more detonations are detected in the engine. In response to the detection of the one or more detonations, the spark timing for one or more of the working chambers is retarded. Additionally, the firing fraction used to operate the engine is increased. The increase in the firing fraction helps to compensate for torque lost due to the retarding of the spark timing.

Abstract: A variety of methods and arrangements for determining conditions when an engine-decoupling friction interface may be locked-up during skip-fire operation of an internal combustion engine are described. In some embodiments, the engine-decoupling friction interface is the lockup clutch of a torque converter situated in a powertrain that transmits motive power from the engine to a wheel. Rotation of the wheel causes vehicle motion.

Abstract: A variety of methods and devices for mitigating power train vibration during skip fire operation of an engine are described. In one aspect, the slip of a drive train component (such as a torque converter clutch) is based at least in part upon a skip fire characteristic (such as firing fraction, selected firing sequence/pattern, etc.) during skip fire operation of an engine. The modulation of the drive train component slip can also be varied as a function of one or more engine operating parameters such as engine speed and/or a parameter indicative of the output of fired cylinders (such as mass air charge).

Abstract: Methods and arrangements for transitioning an engine between a deceleration cylinder cutoff (DCCO) state and an operational state are described. In one aspect, transitions from DCCO begin with reactivating cylinders to pump air to reduce the pressure in the intake manifold prior to firing any cylinders. In another aspect, transitions from DCCO, involve the use of an air pumping skip fire operational mode. After the manifold pressure has been reduced, the engine may transition to either a cylinder deactivation skip fire operational mode or other appropriate operational mode. In yet another aspect a method of transitioning into DCCO using a skip fire approach is described. In this aspect, the fraction of the working cycles that are fired is gradually reduced to a threshold firing fraction. All of the working chambers are then deactivated after reaching the threshold firing fraction.

Abstract: In one aspect of the invention, an engine is operated in a skip cylinder engine braking mode. In the skip cylinder engine braking mode, selected working cycles of selected working chambers are deactivated. Other selected working cycles of the selected working chambers are operated in a braking mode. Accordingly, individual working chambers are sometimes deactivated and sometimes operated in the braking mode while the engine is operating in the skip cylinder engine braking mode. Various methods for cylinder control are described, which improve fuel economy, catalytic converter performance, and vehicle NVH characteristics.

Abstract: Methods and devices are described for performing engine diagnostics during skip fire operation of an engine while a vehicle is being driven. Knowledge of the firing sequence is used to determine appropriate times to conduct selected diagnostics and/or to help better interpret sensor inputs or diagnostic results. In one aspect, selected diagnostics are executed when a single cylinder is fired a plurality of times in isolation relative to a sensor used in the diagnosis. In another aspect, selected diagnostics are conducted while the engine is operated using a firing sequence that insures that no cylinders in a first cylinder bank are fired for a plurality of engine cycles while cylinders in a second bank are at least sometimes fired. The described tests can be conducted opportunistically, when conditions are appropriate, or specific firing sequences can be commanded to achieve the desired isolation or skipping of one or more selected cylinders.

Abstract: A variety of methods and arrangements are described for selectively reducing intake manifold pressure in a skip fire engine control system. In some embodiments, a throttle is adjusted to generate a manifold vacuum, which is used for various applications, including but not limited to purging a fuel vapor canister, reducing pressure within a brake vacuum booster reservoir and/or venting gas from a crankcase interior. An engine firing fraction is increased to help maintain a desired torque level. Other techniques for reducing the intake manifold pressure are also described, such as applications involving a return to idle.

Abstract: Methods and arrangements are described for controlling transitions between firing fractions during skip fire operation of an engine in order to help smooth the transitions. Generally, firing fractions transitions are implemented gradually, preferably in a manner that relatively closely tracks manifold filling dynamics. In some embodiments, the commanded firing fraction is altered each firing opportunity. Another approach contemplates altering the commanded firing fraction by substantially the same amount each firing opportunity for at least a portion of the transition. These approaches work particularly well when the commanded firing fraction is provided to a skip fire controller that includes an accumulator functionality that tracks the portion of a firing that has been requested, but not delivered, or vice versa.

Abstract: A variety of methods and devices for mitigating power train vibration during skip fire operation of an engine are described. In one aspect, the slip of a drive train component (such as a torque converter clutch) is based at least in part upon a skip fire characteristic (such as firing fraction, selected firing sequence/pattern, etc.) during skip fire operation of an engine. The modulation of the drive train component slip can also be varied as a function of one or more engine operating parameters such as engine speed and/or a parameter indicative of the output of fired cylinders (such as mass air charge).

Abstract: Various methods and arrangements for operating a skip fire engine control system are described. In one aspect of the invention, a distinct firing sequence is determined for each bank of working chambers that is used to operate the bank in a skip fire manner. Each firing sequence uses a different firing fraction. In another aspect of the invention, a determination is made as to whether a firing sequence should be dynamically generated or selected from a set of predefined firing sequences.

Abstract: Methods and devices are described for performing engine diagnostics during skip fire operation of an engine while a vehicle is being driven. Knowledge of the firing sequence is used to determine appropriate times to conduct selected diagnostics and/or to help better interpret sensor inputs or diagnostic results. In one aspect, selected diagnostics are executed when a single cylinder is fired a plurality of times in isolation relative to a sensor used in the diagnosis. In another aspect, selected diagnostics are conducted while the engine is operated using a firing sequence that insures that no cylinders in a first cylinder bank are fired for a plurality of engine cycles while cylinders in a second bank are at least sometimes fired. The described tests can be conducted opportunistically, when conditions are appropriate, or specific firing sequences can be commanded to achieve the desired isolation or skipping of one or more selected cylinders.

Abstract: In one aspect, a skip fire engine controller is described. The skip fire engine controller includes a skip fire module arranged to determine an operational firing fraction and associated cylinder load for delivering a desired engine output. The skip fire engine controller also includes a firing controller arranged to direct firings in a skip fire manner that delivers the selected operational firing fraction. Various methods, modules, lookup tables and arrangements related to the selection of a suitable operational firing fraction are also described.

Abstract: Methods and devices are described that utilize skip fire techniques to rapidly meet requests for transitory changes in the output of an engine. Specifically, the fraction or percentage of the working cycles that are fired can be changed during a transitory event so that the engine delivers the desired transitory engine output. Once the transitory event is over, normal engine operation may be restored. The described techniques are useful in a variety of applications that require a relatively quick, but transitory, reduction in engine output to meet vehicle control requirements. One particularly useful application is during transmission shift events. Other representative applications include: loss of traction events, stability control events, wheel hop prevention events, etc.

Abstract: A variety of methods and arrangements for determining conditions when an engine-decoupling friction interface may be locked-up during skip-fire operation of an internal combustion engine are described. In some embodiments, the engine-decoupling friction interface is the lockup clutch of a torque converter situated in a powertrain that transmits motive power from the engine to a wheel. Rotation of the wheel causes vehicle motion.

Abstract: In one aspect, a method for mitigating detonation in a skip fire engine control system is described. The working chambers of the engine are operated in a skip fire manner to deliver a desired torque. One or more detonations are detected in the engine. In response to the detection of the one or more detonations, the spark timing for one or more of the working chambers is retarded. Additionally, the firing fraction used to operate the engine is increased. The increase in the firing fraction helps to compensate for torque lost due to the retarding of the spark timing.

Abstract: Methods and devices are described for performing engine diagnostics during skip fire operation of an engine while a vehicle is being driven. Knowledge of the firing sequence is used to determine appropriate times to conduct selected diagnostics and/or to help better interpret sensor inputs or diagnostic results. In one aspect, selected diagnostics are executed when a single cylinder is fired a plurality of times in isolation relative to a sensor used in the diagnosis. In another aspect, selected diagnostics are conducted while the engine is operated using a firing sequence that insures that no cylinders in a first cylinder bank are fired for a plurality of engine cycles while cylinders in a second bank are at least sometimes fired. The described tests can be conducted opportunistically, when conditions are appropriate, or specific firing sequences can be commanded to achieve the desired isolation or skipping of one or more selected cylinders.

Abstract: Various methods and arrangements for determining a combustion control parameter for a working chamber in an engine are described. In one aspect, an engine controller includes a firing counter that stores a firing history for the working chamber. A combustion control module is used to determine a combustion control parameter, which is used to help manage combustion in the working chamber. The combustion control parameter is determined based at least in part on the firing history.

Abstract: A variety of methods and devices for mitigating power train vibration during skip fire operation of an engine are described. In one aspect, the slip of a drive train component (such as a torque converter clutch) is based at least in part upon a skip fire characteristic (such as firing fraction, selected firing sequence/pattern, etc.) during skip fire operation of an engine. The modulation of the drive train component slip can also be varied as a function of one or more engine operating parameters such as engine speed and/or a parameter indicative of the output of fired cylinders (such as mass air charge).

Abstract: A variety of methods and arrangements are described for selectively reducing intake manifold pressure in a skip fire engine control system. In some embodiments, a throttle is adjusted to generate a manifold vacuum, which is used for various applications, including but not limited to purging a fuel vapor canister, reducing pressure within a brake vacuum booster reservoir and/or venting gas from a crankcase interior. An engine firing fraction is increased to help maintain a desired torque level. Other techniques for reducing the intake manifold pressure are also described, such as applications involving a return to idle.