Methods and Systems for Engine Control

A method of operating an engine having at least a cylinder, the method comprising:

• boosting intake air delivered to the cylinder;
• operating the cylinder with four strokes per combustion cycle;
• during at least the operation with four strokes per combustion cycle, adjusting boost of the intake air responsive to operating conditions;
• in response to a selected condition, transitioning from the operation with four strokes per combustion cycle to two strokes per combustion cycle only when a boost is greater than a threshold boost amount;
• and
• adjusting throttling, spark timing, and the boost during the transition from the operation with four strokes per combustion cycle to two strokes per combustion cycle.

A method of operating an engine having at least a cylinder, the method comprising:

• boosting intake air delivered to the cylinder;
• operating the cylinder with four strokes per combustion cycle;
• during at least the operation with four strokes per combustion cycle, adjusting boost of the intake air responsive to operating conditions;
• in response to a selected condition, transitioning from the operation with four strokes per combustion cycle to two strokes per combustion cycle only when a boost is greater than a threshold boost amount and when cylinder peak combustion pressure is greater than a threshold peak cylinder pressure;
• adjusting throttling, spark timing, and the boost during the transition from the operation with four strokes per combustion cycle to two strokes per combustion cycle;
• and
• transitioning from the operation with two strokes per combustion cycle to four strokes per combustion cycle based on engine speed and torque requested.