A fuel injection control strategy and system for engines for maintaining good performance under normal running conditions and also for providing cylinder engine speed slow-down under abnormal conditions by cylinder skipping. Transitional operation between these modes is improved by changing injection timing and/or injection duration of the operating cylinders during this time. Adjustment in spark timing may also be incorporated along with this routine.
A personal watercraft includes a hull and a jet propulsion unit that propels the hull. An engine powers the jet propulsion unit. The engine includes an air intake system to introduce air to a combustion chamber. The intake system includes a throttle valve to regulate an amount of the air. The throttle valve is moveable generally between a closed position and an open position. A fuel injection system is arranged to spray fuel for combustion in the combustion chamber. The engine also includes an intake pressure sensor, a throttle valve position sensor and an engine speed sensor. A control device is provided to control an amount of the fuel using either a D-j control mode or an .alpha.-N control mode. The D-j control mode is based upon a signal from the intake pressure sensor and a signal from the engine speed sensor. The .alpha.-N control mode is based upon a signal from a throttle valve position sensor and the signal from the engine speed sensor. The control device uses the D-j control mode either when the throttle valve is relatively in a low opening degree range or when an engine speed is relatively in a low speed range, and uses the .alpha.-N control mode either when the throttle valve is relatively in a high opening degree range or when the engine speed is relatively in a high speed range. Additionally, the control device is configured to detect the malfunction of the throttle valve position sensor and the pressure sensor. If the throttle valve position sensor malfunctions, the control device uses only the D-j control mode. If the pressure sensor malfunctions, the control device uses only the .alpha.-N control mode.
An engine speed calculating apparatus capable of calculating an engine speed without being affected by pulsating revolutions in a low engine speed range. A time required for a crankshaft of an engine to revolve through a predetermined angle is measured upon each completion of revolution through the predetermined angle, and an engine speed is calculated on the basis of measured result data of the time required for revolution through the predetermined angle. When the preceding calculated engine speed is determined to be lower than a predetermined engine speed, an engine speed is calculated on the basis of a time required for the crankshaft to revolve through an angle larger than the predetermined angle.
An engine speed calculating apparatus capable of calculating an engine speed without being affected by pulsating revolutions in a low engine speed range. A time required for a crankshaft of an engine to revolve through a predetermined angle is measured upon each completion of revolution through the predetermined angle, and an engine speed is calculated on the basis of measured result data of the time required for revolution through the predetermined angle. When the preceding calculated engine speed is determined to be lower than a predetermined engine speed, an engine speed is calculated on the basis of a time required for the crankshaft to revolve through an angle larger than the predetermined angle.
A propulsion system for a watercraft includes an engine. An air intake device delivers air to a combustion chamber. A throttle valve regulates an amount of the air. A control device sets the throttle valve to a desired position. A remote controller provides the control device with the desired position. The engine can include an auxiliary intake device that delivers supplemental air to the combustion chamber. A control valve normally shuts the supplemental air from the combustion chamber. The control device determines whether an abnormal condition occurs in setting the throttle valve to the desired position. The control device determines whether the amount of the air is insufficient. The control device controls the control valve to allow the supplemental air to move to the combustion chamber when the control device determines that the abnormal condition occurs and the amount of the air is insufficient.
A propulsion system for a watercraft includes an engine. An air intake device delivers air to a combustion chamber. A throttle valve regulates an amount of the air. A control device sets the throttle valve to a desired position. A remote controller provides the control device with the desired position. The engine can include an auxiliary intake device that delivers supplemental air to the combustion chamber. A control valve normally shuts the supplemental air from the combustion chamber. The control device determines whether an abnormal condition occurs in setting the throttle valve to the desired position. The control device determines whether the amount of the air is insufficient. The control device controls the control valve to allow the supplemental air to move to the combustion chamber when the control device determines that the abnormal condition occurs and the amount of the air is insufficient.
