Abstract: A regulating device is proposed for the mixture composition of an internal combustion engine having a signal sensor and having regulating ranges which can be switched over between lambda equals one and the lean range. The lambda-equal-to-one regulation is effected by means of a two-point regulator and the lean regulation is effected either via an altered set-point value of the two-point regulator or with the aid of a steady regulator. The transitions between the two types of regulation take a course dependent on a selectable function, in order to avoid abrupt changes in rpm. A switchover is also made to controlled operation for a brief period at the beginning of each type of regulation.

Abstract: An apparatus for controlling fuel injection in a multicylinder internal combustion engine, wherein fuel injectors for each cylinder are simultaneously operated synchronous with crank angles. The amount of injection is controlled by signals from an air flow meter. The apparatus includes a system operating, nonsynchronous with crank angles, the injectors when the engine is accelerated. The amount of nonsynchronous fuel injection is controlled in accordance with the position of the nonsynchronous injection (i.e., occurrence of acceleration) between adjacent synchronous injections.

Abstract: An i.c. engine fuel control includes a main fuel control which controls fuel flow to the engine in accordance with one or more engine operating parameters. A roughness sensor provides an electrical signal varying with the magnitude of fluctuations in the engine speed and an integrator integrates the error between this signal and a reference signal. Two active clamp circuits operate to limit the excursion of the integrator output which provides a limited authority trim input to the fuel control.

Abstract: To improve the operating efficiency of a diesel engine, a plurality of engine operating parameters are detected and the engine cylinders to which the fuel supply is to be cut off are computed in accordance with the operating parameters, thereby stopping the generation of fuel control pulses in response to crank angle sensor output pulses indicative of the computed cylinders. A fuel injection pump is so constructed that the fuel is metered in response to the fuel control pulses and the metered fuel is pressurized, compressed and distributed to the cylinders, and the distribution of the pressurized and compressed fuel to the cylinders is stopped by stopping the application of the fuel control pulses.

Abstract: Disclosed is a multi-cylinder internal combustion engine in which a group of cylinders is disconnectable in dependence on one or more operational parameters of the engine. The connection or disconnection of the groups of cylinders occurs in response to an engine load variation, to an acceleration signal or to a deceleration signal and to the engine temperature. The switchover takes place within a predetermined time interval. During the switchover of the cylinder groups, the ignition angle and if desired the volumetric efficiency are controlled. When only a part of the cylinders of the engine is in operation after a predetermined number of engine rotations the active cylinders are disconnected and simultaneously the inactive cylinders are connected into operation. During the switchover process any unintentional switchover is prevented by a signal blocking device.

Abstract: A system for controlling fuel injection for a multiple-displacement engine in which the number of operating cylinder changes according to the load on the engine by cutting off fuel to some of cylinders. The engine has solenoid-operated fuel injection valves and a switch is provided for rendering each solenoid-operated fuel injection valve inoperative. A sensor is provided for detecting load on the engine and for producing an output dependent on the load. A fuel injection control circuit is responsive to the output of the sensor for operating the switches to cut off the fuel to the corresponding cylinder. The fuel injection control circuit is so arranged to cut off the fuel to cylinders in accordance with idle cylinder patterns which are such that particular cylinders are not repeatedly idled and such that the number of idling cylinders by the fuel cut-off decreases with an increase of the load on the engine.

Abstract: A fuel cut-supply control system for a multiple-cylinder internal combustion engine which can effectively prevent engine vibration or shock generated when fuel is cut off or resupplied. The cylinders of the engine are divided into two cylinder groups and fuel is cut off or resupplied to one cylinder group a predetermined delay time after fuel has been cut off from or resupplied to the other cylinder group. The delay time is so determined that vibration caused by the first cylinder group is 180 degrees out of phase with that caused by the second cylinder group. The control system according to the present invention comprises a delay circuit and a first and second fuel cut-supply control sections, in addition to the conventional fuel cut-supply control system.

Abstract: A sensor for detecting an air/fuel ratio is fitted to an exhaust pipe of an internal combustion engine so as to effect feedback control and to keep the air/fuel ratio of the engine at a predetermined value. To improve the feedback control accuracy, the sensor response must be increased. If the response is increased too much, however, the sensor output is found deviated from the true air/fuel ratio, and the deviation quantity is also found proportional to the change of the air-fuel ratio with respect to time. The invention makes it possible to make appropriate air/fuel ratio control by compensating for the output signal of the sensor using the signal component based upon the change of the air/fuel ratio with time, among the sensor output signals.

Abstract: A fuel control system for actuating injection means for controlling small fuel flows is described in a microprocessor based engine control system. The short time duration fuel pulses are sensed and the control system processes the skipping of the injection pulses in the opposite direction of cylinder ignition or precesses skipping around the engine. In one example, in every three fuel pulses, one is omitted and the remaining two are increased in time duration. This processing of the fuel pulses allows each cylinder to omit receiving fuel only once in four engine cycles for a four cylinder engine. Other counts may be used providing that the count is not a multiple of a factor of the total number of cylinders. The increased time duration of the fuel pulses allows actuation of the injector in its linear region of operation.

Abstract: A multiple-displacement engine is provided with a cylinder number control means and a cylinder-reduction determination means in order to switch the operating state of the engine from the full-displacement operation to the part displacement operation or from the latter to the former according to the operating condition of the engine. A period calculating means receives signals generated from a crank angle detecting means every predetermined crank angle and calculates the time interval corresponding to the predetermined crank angle. An engine speed calculating means calculates the engine rpm on the basis of the calculated time interval or period. A crank angle determination means which receives the output from the cylinder-reduction determination means and sets the predetermined crank angle to be submitted to the period calculating means to include a crank angle corresponding to the power stroke of a working cylinder in the part-displacement state of the engine.

Abstract: A process for intermittent control of a cyclically operating internal combustion engine wherein, in the succession of working cycles, working strokes are skipped--in approximately uniform distribution--and the number of skips is varied in dependence on the load. Fuel is fed in a controlled fashion only to the nonskipping working chambers of the internal combustion engine independently of the load in a constant quantity optimal for consumption. For a sensitive power distribution, especially in the low load range, the number of skips is varied chronologically at least approximately randomly and independently of the speed, i.e., the temporal density of the working strokes is varied. This can be accomplished by setting differently finely staggered firing patterns or by a stochastic ignition setting.

Abstract: An electronic controlled fuel injection system having electromagnetic fuel injection valves each of which injects fuel twice during 4-cycle operation strokes, wherein a reference cylinder is provided to inject fuel at intervals of 360.degree. in crankshaft angle, and the next operating cylinder is made to inject fuel 180.degree. after the fuel injection timing for the reference cylinder.

Abstract: A method and apparatus for controlling the injection of fuel into an internal combustion engine having a plurality of unit injectors which are each controllable separately for each cylinder of the engine. The occurrence of a malfunction in the fuel injection of each of the injectors is discriminated in accordance with the engine operating condition detected by sensors whereby when the presence of a malfunction in the injector of any one of the cylinders is discriminated, the operation of the engine is not stopped but the operation is continued in a fault mode of operation so that the injection of fuel from the malfunctioning injector is stopped and the injection of fuel from the injector of at least one of the other cylinders is stopped or its number of events of injection is decreased from the standpoint of balance in the generation of engine power output.

Abstract: Three way valves forming a fuel cut-off valve are arranged across respective injection pipes connected to injection nozzles associated with preselected cylinders of the engine. In a first valve position, the three way valves connect the injection pump body or bodies of the fuel injection pump to the respective injection pipes, and in a second valve position, they connect the injection pump body or bodies to a lower pressure zone in the pump. Preferably, the fuel cut-off valve is pneumatically operated for high speed valve position changing action.

Abstract: The number of working cylinders of the internal combustion engine is controlled so that the load of the internal combustion engine is relatively increased thereby to keep the combustion effect within an expected range. By controlling the number of working cylinders of the internal combustion engine also to other than integral numbers, the torque control of large freedom is continuously effected. Thus the torque characteristic is smoothed, thus improving the fuel efficiency and driveability at the same time.

Abstract: In a multi-cylinder internal combustion engine having a plurality of cylinders which are supplied with air via one common throttle valve and a control unit for regulating the number of operating cylinders which suspends the operation of an arbitrary number of cylinders by intercepting the air supply to said cylinders, it is noted at a point the output of the engine under Z.sub.1 -cylinder operation coincides with the output under Z.sub.2 -cylinder operation at the same degree of opening of the throttle valve at a given constant rate of engine rotation. Based on such a fact, the multi-cylinder internal combustion engine is made capable of shifting to and from Z.sub.1 -cylinder operation and Z.sub.2 -cylinder operation in the proximity of said point where these outputs coincide. This way, there will be no fluctuation in the output nor shock at the time of switching, and the control unit for this purpose can be made simple in construction.

Abstract: In a multi-cylinder internal combustion engine having a plurality of cylinders which are supplied with air via one common throttle valve and a control unit for regulating the number of operating cylinders to rest an arbitrary number of cylinders by blocking the air supply to said cylinders, the output of the engine under Z.sub.1 -cylinder operation is known to come to coincide with the output under Z.sub.2 -cylinder operation at one point with the same degree of opening of the throttle valve under a given constant rate of the engine rotation. At such a point, the pressure of the intake manifold under both the Z.sub.1 -cylinder operation and the Z.sub.2 -cylinder operation remain at or close to a certain value respectively over a wider range of rotation of the engine. This multi-cylinder internal combustion engine enables smooth switching between the Z.sub.1 -cylinder operation and the Z.sub.

Abstract: A multicylinder engine whose working cylinders are variably controlled in number to suit operating requirements, with an air fuel mixture fed from a single throttle valve to the working cylinder or cylinders through an intake manifold, includes at least one normally closed control valve installed in at least one intake pipe of the intake manifold. When the throttle valve has opened to a prescribed degree, the control valve instantly opens fully or almost fully or to a prescribed degree, independently of the throttle valve.

Abstract: An internal combustion engine is disclosed which comprises first and second cylinder units each including at least one cylinder, a control circuit responsive to engine load for supplying a mixture of an optimum air/fuel ratio to the first and second cylinder units and for terminating the supply of the mixture to the second cylinder unit when the engine load is below a given value, and an exhaust system having therein a catalytic converter. An emergency circuit is provided for forcing the control circuit to lean out the air/fuel ratio in response to an increase in the temperature of the catalytic converter.

Abstract: A split engine comprising a plurality of cylinders divided into a first cylinder group and a second cylinder group. The second cylinder group is connected to the outside air via a second surge tank. The first cylinder group is connected to the second surge tank via a first surge tank. A shut-off valve is arranged in the connecting portion of the first surge tank and the second surge tank. When the level of the load of the engine becomes higher than a predetermined level, the shut-off valve is slowly opened by a DC motor.

Abstract: A fuel control system for an internal combustion engine senses a failure in the coolant system and supplies fuel alternately to each of the two cylinder banks for predetermined periods of time so that one of the cylinder banks is supplied with an air and fuel mixture to power the engine and the other one of the cylinder banks is supplied with air only to be cooled thereby to extend the safe operating time of the engine. The air/fuel ratio of the mixture supplied to the bank provided with a combustible mixture is adjusted to limit the speed of the vehicle to further extend the safe operating time of the engine.

Abstract: Supercharging pressure produced by a supercharger driven by the exhaust gasses is detected so that frequency of combustion in an internal combustion engine is reduced to lower the engine output power. In order to reduce the frequency of combustion, the number of times of fuel injection may be thinned out or fuel injection into one or some of the cylinders of the engine may be stopped for a given period of time. Alternatively, the frequency of ignition may be reduced or ignition in one or some of the cylinders may be stopped for a given period of time. The control of fuel injection and the control of ignition may be combined. A microcomputer may be used to perform the method according to the present invention where the microprocessor thereof is arranged to execute a main routine and an interrupt service routine. In the main routine, data related to the supercharging pressure is stored in a memory, and the interrupt service routine, fuel injection and/or ignition is performed.

Abstract: A control device for the fuel feed actuators of an internal combustion engine comprises a detector for detecting a first engine parameter (e.g. engine RPM), another detector for detecting another engine parameter (e.g. throttle angle), a further detector for detecting the operative condition of the engine (e.g. the temperature of the coolant), a pulse generator connected to the engine shaft, another pulse generator connected to an auxiliary shaft, a processor (CPU), a read only memory unit (ROM), a random access memory unit (RAM), two timers, the processor unit (CPU) performing a sequence of programmed steps in order to select which of the electric fuel injectors must be actuated, at what instant of time, for what time period and with what quantity of fuel each time.

Abstract: A split engine comprising a plurality of cylinders divided into a first cylinder group and a second cylinder group. The second cylinder group is connected to the outside air via a second surge tank. A throttle valve is arranged in the inlet of the second surge tank. The first cylinder group is connected to the second surge tank. A shut-off valve is arranged in the connecting portion of the first surge tank and the second surge tank. The first surge tank is connected to the exhaust manifold of the engine via an exhaust-gas recirculation passage. The recirculation control valve is arranged in the exhaust-gas recirculation passage. When the level of the load of the engine becomes higher than a predetermined level, the shut-off valve opens, and the recirculation control valve closes. At this time, if the opening speed of the throttle valve is lower than a predetermined speed, the opening operation of the shut-off valve is started when the closing operation of the recirculation control valve is completed.

Abstract: A split engine comprising a plurality of cylinders which are divided into a first cylinder group and a second cylinder group. The second cylinder group is connected to the outside air via a second intake passage. The first cylinder group is connected to a first intake passage which is, in turn, connected to the second intake passage via a shut-off valve. The first intake passage is connected to the exhaust passage of the engine via an exhaust-gas recirculation passage. When the level of the load of the engine becomes high, the exhaust-gas recirculation passage is shut off, and the shut-off valve is initially opened at a high speed and then opened at a low speed.

Abstract: An internal combustion engine comprises an induction passage divided downstream of a throttle valve into two intake passages respectively communicating with first and second cylinder units, and an EGR passage connected from the engine exhaust to the induction passage downstream of the throttle valve. The EGR passage has therein an EGR valve whose position determines the flow area for exhaust gases through the EGR passage. A control unit disables the second cylinder unit to shift the engine from full engine operation into split engine operation when the engine load falls below a predetermined value. The control unit comprises a computer including at least two read only memories, the first storing EGR ratio values arranged in relation with engine speed and load for the engine being in full engine operation. The second read only memory stores EGR ratio values arranged in relation with engine speed and load for the engine being in split engine operation.

Abstract: A split engine comprising a plurality of cylinders divided into a first cylinder group and a second cylinder group. The second cylinder group is connected to the outside air via a second surge tank. The first cylinder group is connected to the second surge tank via a first surge tank. A shut-off valve is arranged in the connecting portion of the first surge tank and the second surge tank. The supply of fuel into both of the cylinder groups is stopped when a predetermined time period has elapsed after the decelerating operation is started. Then, the shut-off valve opens when a predetermined time period has elapsed after the supply of fuel is stopped.

Abstract: The invention relates to a multi-cylinder Otto cycle internal combustion engine for motor vehicles, arranged to operate with a number of working cylinders which varies with the power delivered by the engine. The working cylinders which deliver the complementary portion of the maximum power have a compression ratio which is less than that of the remaining group of cylinders.

Abstract: The invention relates to a multi-cylinder Otto cycle internal combustion engine for motor vehicles, of the type in which the number of working cylinders varies with the power delivered, and in which the working cylinders for any power condition have a compression ratio which is greater than the compression ratio of the complementary cylinders, these latter being supercharged.

Abstract: In the range where the fuel efficiency may be improved by relatively increasing the load of working cylinders at the time of partial loading of a multicylinder internal combustion engine, the intake pressure of the engine is maintained at a fixed optimum value. Also, the number of working cylinders is controlled, so that a torque actually required by the driver is obtained, and under any load, the maximum improvement of fuel efficiency may be attained at a saving of fuel consumption.

Abstract: The invention relates to a control system for preventing wheel spinning in the drive wheels of a motor vehicle with an engine with fuel injection. The control system has wheel speed sensing means and a processor unit which limits the quantity of fuel injected in steps in proportion to the wheel slippage. In a first step, the injected quantity is reduced to a cylinder by one half for example. In a second step, the fuel supply is completely shut off to this cylinder. The process then continues correspondingly by incremental shutting off of portions of cylinders until the wheel slippage drops, and the process is then reversed.

Abstract: An internal combustion engine and control system therefor are disclosed of either the gasoline or diesel type having an odd number of cylinders one of which is a master cylinder with a displacement larger than the remaining cylinders. The master cylinder's function is to operate the engine's auxiliary equipment during idle to conserve fuel and assist the other cylinders during heavy load conditions but be cut off from operation when the load is light.

Abstract: An internal combustion engine is disclosed which comprises first and second cylinder units each including at least one cylinder, an intake manifold divided into first and second intake passages leading to the first and second cylinder units, respectively, and an exhaust passage leading from the first and second cylinder units. The second intake passage has therein a normally open stop valve. The second intake passage is connected to the exhaust passage through an EGR passage having therein a normally closed EGR valve. Control means is provided for providing a control signal to disable the second cylinder unit when the engine load is below a predetermined value. The control signal is applied to valve drive means which thereby closes the stop valve and opens the EGR valve. The valve drive means is constructed to prevent the simultaneous opening of the stop and EGR valves.

Abstract: An internal combustion engine is disclosed which comprises first and second cylinder units each including at least one cylinder, sensor means for providing a signal indicative of engine vibration, and control means for disabling the first cylinder unit when the engine load is below a predetermined value. The control means is adapted to hold the first cylinder unit active, regardless of engine load conditions, when the engine vibration indicative signal exceeds a predetermined value indicative unstable engine operation.

Abstract: The switching off of one or more cylinders of a multicylinder engine to save fuel when the engine is running lightly loaded has been found to reduce the effectiveness of computer control of ignition timing and fuel injection unless additional fields of stored control information are provided for responding to the various combinations of engine parameter values that arise in operation. Accordingly, with each step of reduction of the number of working cylinders, the control of ignition timing and fuel injection is shifted to a different bank of fixed value memory (ROM).

Abstract: A system is provided for controlling fuel flow within an internal combustion engine having a plurality of cylinders. The system includes a fuel source; a fuel pump responsive to the engine speed; and a multimode adjustable control valve connected to the fuel pump and a predetermined number of first cylinders. The control valve, when in a first mode, substantially shutting off fuel flow to the first cylinders, except for a minimal amount of fuel leakage from the valve to the first cylinders for lubricating purposes. When in a second mode, the control valve allows substantial fuel flow to the first cylinders. The control valve assumes its first mode when the operating temperature is below a predetermined amount and/or the engine is operating under a predetermined load.

Abstract: An internal combustion engine is disclosed which includes an active cylinder unit always active and an inactive cylinder unit being inactive when the engine load is below a predetermined value. The engine has an intake passage divided into first and second branches leading to the active and inactive cylinder units, respectively. The second intake passage branch is connected through an EGR passage to the exhaust passage of the engine. The second intake passage branch has therein a stop valve and the EGR passage having therein an EGR valve. Means are provided for closing the stop valve and opening the EGR valve at a predetermined time after a low engine load condition occurs.

Abstract: An electronic control circuit for a fuel injected internal combustion engine in which fuel flow is alternated among selected engine cylinders at low speed engine operation. Alternate fuel delivery results in improved idle, fuel economy and reduced emissions. Conventional engine operation is progressively restored as the engine approaches high speed operation.

Abstract: An internal combustion engine is disclosed which includes first and second cylinder units each having at least one cylinder, and a control unit responsive to engine load for rendering the first and second cylinder units active at high load conditions and rendering the second cylinder unit inactive when the engine load is below a predetermined value. A rapid acceleration detector is provided which is responsive to rapid engine acceleration for causing the control unit to render the first and second cylinder units active regardless of the engine load.

Abstract: Arrangement for fuel supply to the combustion chambers of a vehicle internal combustion engine with an engine-braking disconnection. A sensor determines the rotational speed of the engine. Function generators determine the limit value signals which are a function of the rotational speed of the engine. Comparators compare the signals determined by the function generators with a load signal received from a potentiometer acting as a position sensor indicating the position of the intake manifold throttle valve. The comparators are connected to switches which regulate or eliminate the fuel supply to the combustion chamber depending upon the output of the said comparators by supplying fuel to all combustion chambers, to groups of combustion chambers, or to no combustion chambers, so that the operation of the engine is fuel-consumption optimal.

Abstract: An internal combustion engine is disclosed which comprises first and second cylinder units each including at least one cylinder, a stop valve provided between the first and second cylinder units, an EGR passage for recirculating exhaust gases into the second cylinder unit, an EGR valve provided in the EGR passage, and control means for disabling the second cylinder unit when the engine load is below a given value. Means is provided to ensure that the EGR Valve opens after the stop valve closes when the engine load changes from its high condition to a low condition and to ensure that the stop valve opens just after the EGR valve closes when the engine load changes from its low condition to a high condition.

Abstract: An internal combustion engine is disclosed which includes first and second cylinder units, an intake manifold divided into first and second intake passages leading to the first and second cylinder units, respectively, an exhaust manifold divided into first and second exhaust passages leading from the first and second cylinder units, respectively, and control means for providing a control signal to disable the second cylinder unit when the engine load is below a predetermined value. The second intake passage has therein a first normally open valve adapted to close in response to the control signal. The second exhaust passage has therein a second normally open valve adapted to close in response to the control signal. Pressure control means is provided which is responsive to the control signal for supplying a predetermined pressure not less than atmospheric pressure to the second intake passage, thereby maintaining the second intake passage at the predetermined pressure.

Abstract: A fuel injection control system is disclosed for an internal combustion engine having fuel injectors. The system comprises fuel cut-off means operable for rendering some of the fuel injectors inoperative only when the engine speed exceeds a first predetermined value during engine deceleration and for rendering the remaining fuel injectors inoperative only when the engine speed exceeds a second predetermined value higher than the first predetermined value during engine deceleration. Control means is provided for increasing the second predetermined value when rapid engine deceleration occurs.

Abstract: An internal combustion engine is disclosed which includes active and inactive cylinders, an intake passage divided into first and second branches leading to the active and inactive cylinders, respectively, valve means provided at the entrance of the second intake passage, and fuel supply means for supplying a controlled amount of fuel into the active and inactive cylinders. A load detector is provided for detecting engine load to provide a low load indication signal to the fuel supply means which thereby cuts off the supply of fuel to the inactive cylinders and also to the valve means which thereby cuts off the flow of air to the inactive cylinders. Delay means is provided for delaying the start and end of application of the low load indication signal to the fuel supply means.

Abstract: A fuel injection control system is disclosed for an internal combustion engine having fuel injectors. The system comprises fuel-cut means operable for rendering some of the fuel injectors inoperative only when the engine speed exceeds a first predetermined value during engine deceleration and for rendering the remaining fuel injectors inoperative when the engine speed exceeds a second predetermined value higher than the first predetermined value during engine deceleration. Control means is provided for rendering the fuel-cut means inoperative when rapid engine deceleration occurs, thereby permitting the operation of all of the fuel injectors regardless of the engine speed.

Abstract: An internal combustion engine is disclosed which includes first and second cylinder units each including at least one cylinder, means for cutting off the supply of air and fuel to the second cylinder unit so as to render it inactive when the engine load is below a given value, a three-way catalytic converter for purifying the exhaust from the cylinders, a sensor exposed to the exhaust from the cylinders to provide a signal indicative of the air/fuel ratio at which the engine is operating, and means responsive to the signal from the sensor for controlling the fuel supplied to the engine to maintain the stoichiometric air/fuel ratio. Means is provided for introducing a predetermined amount of air into the second cylinder unit.

Abstract: An internal combustion engine is disclosed which includes active and inactive cylinders, a load detector adapted to provide a low load indicative signal when the engine load is below a predetermined value, first means responsive to the low load indicative signal for cutting off the flow of air to the inactive cylinders, and second means for supplying a controlled amount of fuel into the active and inactive cylinders so as to achieve a somewhat lean air-fuel mixture therein. The second means is responsive to the low load indicative signal for cutting off the supply of fuel to the inactive cylinders and increasing the amount of fuel supplied to the active cylinders so as to achieve a somewhat rich air-fuel mixture therein. Third means is provided for monitoring the oxygen content of the exhaust from the engine to control the second means so that the fuel supplied to the engine is correct to maintain the stoichiometric air/fuel ratio.

Abstract: Apparatus for controlling the number of enabled cylinders of an internal combustion engine during deceleration comprises a plurality of comparators responsive to a signal indicative of the engine rotational speed upon deceleration of the engine. The threshold voltages of the comparators are arranged stepwise so that each comparator produces an output signal when the engine speed falls below each threshold voltage. The output signals of the comparators are supplied to logic circuits to control a plurality of switches via which the fuel injection control pulse signal is respectively applied to fuel injection valves to increase in a stepwise fashion the number of enabled cylinders from the fuel cut-off state thereby preventing occurrence of impacts or shocks in the transition period of reactivation of the cylinders upon deceleration.

Abstract: The engine crankshaft rotational speed is detected to be compared with stepwise arranged threshold speeds so as to stepwise enable fuel injection valves of respective cylinders during deceleration of the engine. Accordingly, the number of enabled cylinders is increased in a stepwise manner from a fuel cut-off state as the engine rotational speed decreases to prevent engine stall, while occurrence of shocks upon reactivation of cylinders is avoided. The threshold speeds are controlled in accordance with the variation of engine load which may be increased upon operation of auxiliary power consuming units, such as an air conditioner the compressor of which is driven by the engine, for preventing undesirable vibrations of the engine during the stepwise reactivation of the cylinders.

Abstract: A split engine control system includes a load level detector for generating a first signal in response to a relatively high engine load and a second signal in response to a relatively low engine load. A certain of the cylinders of an internal combustion engine is deactivated in response to the second signal to operate the engine on partial cylinders and activated in response to the first signal to permit the engine to operate on full cylinders. A discriminating circuit is connected to the load level detector to disable the second signal when the duration of the latter is smaller than a preset time interval which corresponds to the duration of a false indication of engine load reduction which might occur in response to gear changes during full cylinder operation.