Misfire detection system

A misfire detection system for determining whether a particular working chamber has misfired, the misfire detection system being used in an engine operated in a skip fire manner, the misfire detection system comprising:

• an engine parameter measurement module that is arranged to:
• assign a window to a target firing opportunity for a target working chamber;
• and
• measure change in an engine parameter during the window;
• and
• a misfire detection module that is arranged to:
• determine whether a firing opportunity before the target firing opportunity involves a skip or a fire and whether a firing opportunity after the target firing opportunity involves a skip or a fire;
• and
• determine whether the target working chamber misfired based at least in part on the skip or fire determination from before and after the target firing opportunity and the measured change in the engine parameter.

A method for detecting misfire in a skip fire engine control system, the method comprising:

• assigning a window to a target firing opportunity for a target working chamber;
• attempting to fire the target working chamber during the target firing opportunity;
• measuring a change in an engine parameter during the window;
• determining whether a firing opportunity before the target firing opportunity is a skip or a fire and whether a firing opportunity after the target firing opportunity is a skip or a fire;
• and
• determining whether the target working chamber misfired based at least in part on the skip or fire determination,
• wherein the misfire determination involves determining whether the engine parameter change exceeds a predetermined misfire threshold, and
• wherein the misfire determination further comprises selecting a misfire threshold from a set of at least four different predetermined misfire thresholds, each of the four predetermined misfire thresholds corresponding to a different combination of skips and fires for the firing opportunities before and after the target firing opportunity.

A method for detecting misfire in a skip fire engine control system, the method comprising:

• assigning a window to a target firing opportunity for a target working chamber;
• attempting to fire the target working chamber during the target firing opportunity;
• measuring a change in an engine parameter during the window;
• determining whether a firing opportunity before the target firing opportunity is a skip or a fire and whether a firing opportunity after the target firing opportunity is a skip or a fire;
• determining whether the target working chamber is misfiring based at least in part on the skip or fire determination;
• and
• determining a firing sequence that takes into account the misfiring working chamber wherein the determination of the skip fire firing sequence involves selecting one of a plurality of predetermined firing sequences and wherein the selection is based on an identity of the misfiring working chamber and at least one selected from the group consisting of gear, engine speed and firing fraction.

A misfire detection system for determining whether a particular working chamber has misfired, the misfire detection system being used in an engine operated in a skip fire manner, the misfire detection system comprising:

• an engine parameter measurement module that is arranged to:
• assign a window to a target firing opportunity for a target working chamber;
• and
• measure change in an engine parameter during the window;
• and
• a misfire detection module that is arranged to:
• determine whether a firing opportunity before the target firing opportunity involves a skip or a fire and whether a firing opportunity after the target firing opportunity involves a skip or a fire;
• and
• determine whether the target working chamber misfired based at least in part on the skip or fire determination.
• wherein the misfire determination involves determining whether the engine parameter change exceeds a predetermined misfire threshold, and
• wherein the misfire determination further comprises selecting a misfire threshold from a set of at least four different predetermined misfire thresholds, each of the at least four predetermined misfire thresholds corresponding to a different combination of skips and fires for the firing opportunities before and after the target firing opportunity.

A misfire detection system for determining whether a particular working chamber has misfired, the misfire detection system being used in an engine operated in a skip fire manner, the misfire detection system comprising:

• an engine parameter measurement module that is arranged to:
• assign a window to a target firing opportunity for a target working chamber;
• and
• measure change in an engine parameter during the window;
• and
• a misfire detection module that is arranged to:
• determine whether a firing opportunity before the target firing opportunity involves a skip or a fire and whether a firing opportunity after the target firing opportunity involves a skip or a fire;
• determine whether the target working chamber misfired based at least in part on the skip or fire determination;
• a firing control unit arranged to operating an engine in a skip fire manner, the engine including a plurality of working chambers, which includes the target working chamber wherein, if the misfire detection module determines that the target working chamber is misfiring, the firing control unit is arranged to deactivate the misfiring working chamber while operating the other working chambers in a skip fire manner;
• a firing timing determination module that is arranged to generate a firing sequence that is used by the firing control unit to operate the working chambers of the engine in a skip fire manner wherein:
• the firing timing determination module is arranged to select one of a plurality of predetermined firing sequences when the misfire detection module determines that the target working chamber is misfiring;
• and
• the selection of the predetermined firing sequence is based at least in part on an identity of the misfiring working chamber and at least one selected from the group consisting of gear, engine speed and firing fraction.

A method for determining engine error in a skip fire engine control system, the skip fire engine control system including an engine having a plurality of working chambers, the method comprising:

• assigning a window to a target firing opportunity;
• determining whether each of a plurality of firing opportunities including opportunities before and after the target firing opportunity are skips or fires wherein each firing opportunity is associated with a different one of the working chambers;
• providing a torque model that helps indicate expected engine torque generated by the working chambers during the window wherein the torque model is based at least in part on the skip or fire determinations;
• measuring an engine parameter during the window;
• and
• determining whether an engine error has occurred based on the measured engine parameter and the torque model which is based at least in part on the skip or fire determinations before and after the target firing opportunity.