Variable valve actuation controls for engines

A method of operating an engine system including a valvetrain comprising one or more intake valves and one or more exhaust valves, a variable valve actuation (VVA) system electronically controllable to vary operation of the valvetrain to selectably operate the engine in either a Miller cycle or a non-Miller cycle, and an electronic control system configured to control the VVA system, the method comprising:

• evaluating using the electronic control system whether an engine speed condition is satisfied, a peak cylinder pressure (PCP) condition is satisfied, whether an air-fuel ratio (AFR) condition is satisfied, and whether an oxygen-fuel-control (OFC) condition is satisfied, and a minimum off time condition for the VVA system is satisfied;
• and
• operating the electronic control system to change operation of the engine from the Miller-cycle to the non-Miller cycle in response to the evaluating indicating that the engine speed condition is satisfied, the peak cylinder pressure (PCP) condition is satisfied, at least one of the air-fuel ratio (AFR) condition and the oxygen-fuel-control (OFC) condition is satisfied, and the minimum off time condition for the VVA system is satisfied;
• wherein the evaluating using the electronic control system includes operating a virtual sensor to provide a peak cylinder pressure value in response to a set virtual sensor parameters including:
• an intake charge air-fuel ratio, an intake charge pressure, an intake charge temperature, an injector rail pressure, and an amount and timing of one or more fuel injection events;
• and determining the PCP condition by comparing the peak cylinder pressure value provided by a virtual sensor to a PCP threshold.

An apparatus for operating an engine system including a valvetrain comprising one or more intake valves and one or more exhaust valves, a variable valve actuation (VVA) system electronically controllable to vary operation of the valvetrain to selectably operate the engine in either a Miller cycle or a non-Miller cycle, and an electronic control system configured to control the VVA system, the apparatus comprising:

• a non-transitory memory medium configured to store instructions executable by the electronic control system to perform the acts of:
• evaluating using the electronic control system whether an engine speed condition is satisfied, a peak cylinder pressure (PCP) condition is satisfied, at least one of an air-fuel ratio (AFR) condition and an oxygen-fuel-control (OFC) condition is satisfied, and a minimum off time condition for the VVA system is satisfied;
• and
• operating the electronic control system to change operation of the engine from the Miller-cycle to the non-Miller cycle in response to the evaluating indicating that the engine speed condition is satisfied, the peak cylinder pressure (PCP) condition is satisfied, at least one of the air-fuel ratio (AFR) condition and the oxygen-fuel-control (OFC) condition is satisfied, and the minimum off time condition for the VVA system is satisfied;
• wherein the instructions are executable by the electronic control system to perform the acts of:
• operating a virtual sensor to provide a peak cylinder pressure value in response to a set virtual sensor parameters including:
• an intake charge air-fuel ratio, an intake charge pressure, an intake charge temperature, an injector rail pressure, and an amount and timing of one or more fuel injection events;
• and determining the PCP condition by comparing the peak cylinder pressure value provided by a virtual sensor to a PCP threshold.