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Methods and systems for controlling an engine are provided. In some examples, the method includes transitioning from operating a cylinder with a first number of strokes per combustion cycle to a second, lesser, number of strokes per combustion cycle in response to boost pressure rising above a thres

Methods and systems for controlling an engine are provided. In some examples, the method includes transitioning from operating a cylinder with a first number of strokes per combustion cycle to a second, lesser, number of strokes per combustion cycle in response to boost pressure rising above a threshold boost value. For example, the cylinder may transition from four-stroke combustion cycles to two-stroke combustion cycles, and the method may further include generating the increased boost via operation of an electric machine coupled to a turbocharger of the engine. In this way, transitions to the second, lesser, number of strokes may be enhances as sufficient boost can already be present.

대표청구항 ▼

1. A method, comprising: selecting, based on battery state-of-charge, from among a first mode including commencing two-stroke combustion in a cylinder for only a first combustion event of engine starting; and a second mode including commencing four-stroke combustion in the cylinder, transitioning fr

1. A method, comprising: selecting, based on battery state-of-charge, from among a first mode including commencing two-stroke combustion in a cylinder for only a first combustion event of engine starting; and a second mode including commencing four-stroke combustion in the cylinder, transitioning from four-stroke to two-stroke combustion responsive to boost pressure rising above a threshold boost value, and increasing electrically powered turbocharger boosting before the transition; andstarting the engine with the selected mode. 2. The method of claim 1 wherein the cylinder is transitioned in response to the boost pressure rising above the threshold boost value and peak cylinder pressure rising above a threshold peak cylinder pressure. 3. The method of claim 1 wherein the cylinder is transitioned in response to the boost pressure rising above the threshold boost value and ignition timing being retarded beyond a threshold timing. 4. The method of claim 1 further comprising adjusting boost pressure during the transition. 5. The method of claim 1 wherein the threshold boost value increases with increasing airflow. 6. 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;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;transitioning from the operation with two strokes per combustion cycle to four strokes per combustion cycle based on engine speed and torque requested; andadjusting the threshold boost amount with operating conditions, wherein the threshold boost amount is increased with increasing airflow, the boosting is adjusted via a motor coupled to a compressor of the engine, and the transition from the operation with four strokes per combustion cycle to two strokes per combustion cycle is further carried out only when a battery state of charge is above a threshold state of charge, where the motor drives the compressor to increase compressor speed before said transitioning. 7. The method of claim 6 wherein the transition from the operation with four strokes per combustion cycle to two strokes per combustion cycle is carried out in response to boost pressure rising above the threshold boost value and peak cylinder pressure rising above a threshold peak cylinder pressure. 8. The method of claim 6 wherein the transition from the operation with four strokes per combustion cycle to two strokes per combustion cycle is carried out in response to the boost pressure rising above the threshold boost amount and ignition timing being retarded beyond a threshold timing. 9. The method of claim 6 further comprising adjusting an amount of recirculated exhaust gas in response to at least one of the transition from the operation with two strokes per combustion cycle to four strokes per combustion cycle, and the transition from the operation with four strokes per combustion cycle to two strokes per combustion cycle. 10. 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; andtransitioning from the operation with two strokes per combustion cycle to four strokes per combustion cycle based on engine speed and torque requested, wherein during a starting of the engine, the method further comprises commencing combustion in the cylinder from a non-combusting condition, the commencing including operating the cylinder in a two-stroke combustion cycle for only a first combustion event of engine starting, where each cylinder of the engine has its first combustion event occur sequentially in a combustion firing order. 11. The method of claim 10 wherein the non-combusting condition includes the engine stopped at rest, wherein the first combustion event of engine starting is the first combustion event for the cylinder from a stopped engine condition.