Air charge estimation for use in engine control

A method of estimating cylinder air charge on a cylinder intake event by cylinder intake event basis for an engine during operation of an engine in a dynamic firing level modulation mode in which firing level decisions are made on a working cycle by working cycle basis, the method comprising:

• estimating the inflow of air into an intake manifold;
• estimating an outflow of air from the intake manifold, wherein the air outflow estimate includes, for each of a multiplicity of specific potential cylinder intake events, estimating an amount of air withdrawn from the intake manifold corresponding to that specific potential cylinder intake event, wherein each specific potential cylinder intake event corresponds to an associated working cycle having a corresponding firing level decision and wherein the air outflow estimation utilizes specific firing level decisions or specific cylinder intake decisions to help determine the amount of air withdrawn from the intake manifold during respective corresponding specific potential cylinder intake events;
• estimating a manifold pressure based at least in part on the estimated air inflow and estimated air outflow;
• and
• utilizing the estimated manifold pressure in individual estimation of an air charge for each cylinder intake event in a series of cylinder intake events, wherein the estimated manifold pressure is updated for each individual air charge estimation, whereby each of the individual air charge estimations factor the impact of at least one potential cylinder intake event that has not yet occurred but for which the associated firing level decision has been made at the time such individual air charge estimation is made.

An engine controller for an internal combustion engine having a plurality of working chambers, each working chamber being configured to operate in a series of working cycles, each working cycle having a potential induction event, the engine controller comprising:

• a dynamic firing level modulation controller arranged to determine a firing level for each working cycle;
• a manifold pressure estimator arranged to estimate a manifold pressure for a selected one of the working cycles, and arranged to make the manifold pressure estimation (i) before an induction event associated with the selected working cycle begins, and (ii) after the firing level determination is made for the selected working cycle, the manifold pressure estimation being arranged to account for impacts from one or more intervening potential induction events that will occur between the time that the manifold pressure estimate is made and the time that the induction event associated with the selected working cycle occurs, each potential induction event being associated with a different corresponding working cycle;
• and
• an air charge estimator configured to estimate an air charge for the selected working cycle based at least in part of the estimated manifold pressure for the selected working cycle.