Abstract: An exhaust gas turbocharger for an internal combustion engine has a volute or spiral turbine housing and a compressor housing where a turbine rotor and a compressor impeller are connected with one another by a common shaft. The exhaust gas inlet to the turbine housing has a fixed flow splitter. A pivotal flow control gate is attached to the downstream end of the fixed flow splitter. Control means is provided to timely pivot the pivotal flow control gate toward the turbine rotor and thus provide an initial high velocity spin to the rotor when turbo charged boost pressure is demanded. An adjustable directional flow control valve uses boost pressure from the compressor to timely actuate a piston and lever connected to the pivotal flow control gate or a signal from an engine control module (ECM) can be directed to an hydraulic, pneumatic or electrical actuator having a reciprocatable control rod connected to the flow control gate.

Abstract: Methods and Systems for using a measure of fueling rate in the air side control of an engine. By using a measure of the fueling rate, the air side control may, for example, anticipate the future air side needs of the engine, and adjust one or more air side parameters to meet the anticipated future air side needs of the engine. This may improve the responsiveness, performance and emissions of the engine.

Abstract: A combustion method for a supercharged four-stroke engine having at least four cylinders includes a combustion cycle during which a cylinder of the engine is in the exhaust phase while another cylinder is in the supercharged air intake phase with a burnt gas scavenging stage. The start of the exhaust phase of the cylinder in the exhaust phase is shifted in relation to the start of the burnt gas scavenging stage of the cylinder in the intake phase.

Abstract: A method of determining diagnostic limits for a vane position sensing system installed in a variable nozzle turbocharger (VNT). The method includes defining mechanical input probability distribution functions (PDFs) of the VNT, describing the vane position sensing system in terms of component models and defining component parameter PDFs for parameters associated with the component models. Vane position signal PDFs based are generated on the mechanical input PDFs, the component models and the component parameter PDFs, and diagnostic limits are set for the vane position sensing system based on the vane position signal PDFs.

Abstract: One embodiment of the present invention includes an internal combustion engine with a turbocharger. The turbocharger includes a compressor with an outlet coupled to an intake of the engine and a turbine coupled to an exhaust manifold of the engine. A a turbocharger speed estimate is determined from engine speed and a ratio between inlet and boost pressure for the compressor. The turbocharger speed estimate is further adjusted as a function of compressor boost pressure variation with time.

Abstract: A pop-off valve that, in one embodiment, provides overboost protection for an aircraft engine, is described. The pop-off valve includes a housing adapted for connection to a portion of a drive device containing a pressure medium. It also includes a pressure body movably disposed in the housing such that, in operation, a first side of the pressure body is exposed to the pressure medium while a second side is exposed to a reference force. In addition, the pop-off valve incorporates a control device adapted to receive at least one signal concerning at least one operating parameter of the drive device and, in response to the operating parameter signal, to control the reference force. As a result of movement of the pressure body within the housing, at least one first opening in the housing is exposed, permitting venting of the pressure medium.

Abstract: The present invention relates to a supercharged internal-combustion, notably indirect-injection engine comprising at least one cylinder (10) with two types of supercharged air intake means (12, 14), one type for non-carbureted supercharged air intake (12) and another type for carbureted supercharged air intake (14), said intake means being supplied with supercharged air by supply means (38). According to the invention, supply means (38) comprise a specific supercharged air supply device (46, 50) for each type of intake means (12, 14).

Abstract: To provide a jet propulsion boat that enables preventing the occurrence of cavitation. In a jet propulsion boat that jets water pressurized and accelerated by a water jet pump from a rear jet nozzle and is propelled by its reaction, a turbocharger is provided to an engine for driving the water jet pump and in case the rate of the rise of engine speed is a predetermined value or more, delay control is applied to the rise of the boost pressure of the turbocharger.

Abstract: An opening is provided for an exhaust bypass pipe that bypasses an exhaust turbine of an exhaust turbine supercharger. According to the opening, an exhaust gas amount bypassing the exhaust turbine is calculated. An exhaust gas amount supplied to the exhaust turbine is found by subtracting the waste-gate-valve-passing gas amount from an intake air amount (exhaust gas amount) detected by the air flow meter. A rotational speed of the exhaust turbine is calculated from this turbine-supplied gas amount. An estimated boost pressure is calculated from this rotational speed of the exhaust turbine. Consequently, a boost pressure can be accurately estimated without using a boost pressure sensor even under such conditions as to disable detection of boost pressures or degrade the detection accuracy in a system using a conventional boost pressure sensor.

Abstract: Compressor surge on turbocharged Diesel engines when operating in temporary throttled airflow, such as are required for the periodic regeneration of lean NOx traps is prevented by controlled operation of a boost air blow-off valve positioned downstream of the compressor outlet of the turbocharger.

Abstract: The method for the control of an internal combustion engine combined with a gas-dynamic pressure wave machine comprising a rotatable housing in order to control the process tuning over the entire performance field of the internal combustion engine as well as a variable width adjustment of the high pressure exhaust gas channel includes a certain control sequence of steps in a positive load variation and a certain control sequence of steps in a negative load variation.

Abstract: A method for controlling an engine having both an electronically controlled inlet device, such as an electronic throttle unite, and an electronically controlled outlet device, such as a variable cam timing system is disclosed. The method of the present invention achieves cylinder air charge control that is faster than possible by using an inlet device alone. In other words, the method of the present invention controls cylinder air charge faster than manifold dynamics by coordination of the inlet and outlet device. This improved control is used to improve various engine control functions.

Abstract: A control apparatus for an internal combustion engine which is mounted in a vehicle and has a supercharger that is located along an intake passage of the internal combustion engine and driven by a motor, includes a controller which drives the motor to perform supercharging during warm-up of the internal combustion engine, and supercharges a plurality of times intake air to be supplied to the internal combustion engine. Accordingly, the intake air is supercharged a plurality of times during warm-up of the internal combustion engine, so the temperature of the intake air is raised sufficiently to warm up the engine, thus enabling the engine to be warmed up effectively.

Abstract: A control system for a variable-geometry turbocharger includes a supervisor logic (12) selecting a pulse control output (24) for large variation of desired and previous control signal inputs exceeding a threshold differential and a normal control signal (26) for small control signal input changes. The control system calculates an amplitude and duration for the pulse control output based on input control signal variation or the actual versus desired position of the variable-geometry system in the turbocharger.

Abstract: A vehicle system controls a compression ignition internal combustion engine equipped with a supercharger system including a plurality of superchargers. The compression ignition internal combustion engine has an exhaust gas recirculation (EGR) system. The vehicle system determines a desired intake manifold supercharging state (tQac) and a desired EGR rate (Megr). The vehicle system includes control logics, each having a first input parameter and a second input parameter, for determining desired set points (Rvnt1 & Rvnt2) for the plurality of superchargers, respectively. The desired set points are used to control the plurality of superchargers, respectively. The vehicle system also includes control logic for determining the first input parameters in response to the desired intake manifold supercharging state. The vehicle system further includes control logic for determining the second input parameters in response to the desired EGR rate.

Abstract: A control method of an EGR system of an engine capable of effectively performing an EGR control at a time of rapid acceleration. For this purpose, an intake air flow rate of the engine is obtained, and from a target EGR valve opening degree and a difference in pressure in front of and behind the EGR valve, a virtual EGR gas flow rate is arithmetically operated. A virtual EGR rate is obtained from the intake air flow rate, the fuel flow rate and the virtual EGR gas flow rate, and a difference from or a ratio to a target EGR rate obtained from the engine speed and the fuel flow rate is obtained. A command EGR valve opening degree is obtained from an EGR valve opening degree correction coefficient obtained from the difference or the ratio, and the target EGR valve opening degree, whereby the EGR vale is driven.

Abstract: The present invention relates to a combustion method for a supercharged four-stroke engine having at least four cylinders (10) with a combustion cycle during which a cylinder of the engine is in the exhaust phase while another cylinder is in the supercharged air intake phase with a burnt gas scavenging stage.

Abstract: In the control system for a turbo-charged diesel aircraft engine, a target value for a fuel injection amount is determined by the stroke of a throttle lever. A boost compensator determines the maximum limit for the fuel injection amount in accordance with the boost pressure of the engine in order to suppress the formation of exhaust smoke. The actual fuel injection amount is set at the target value or the maximum limit whichever is smaller. An electronic control unit (ECU) calculates an increase rate of the stroke of the throttle lever based on an output of the stroke sensor disposed near the throttle lever. The ECU determines that the current operating condition of the aircraft requires a rapid increase in the engine output power when the increase rate of the stroke is larger than a predetermined value and increases the maximum limit determined by the boost compensator.

Abstract: A control system controls a turbo-charged trottled engine. The control system includes a throttle between the compressor and the engine, a wastegate communicated with exhaust upstream and downstream from the turbine, and a control unit for controlling the throttle and the wastegate. The control unit generates a desired air mass value per engine stroke as a function of a desired fuel flow amount and a stored compressor surge characteristic, generates a desired manifold air pressure value as a function of the desired air mass value and sensed engine parameters, and controls the throttle so that actual manifold air pressure matches the desired manifold air pressure. The control unit also generates a desired pressure boost value as a function of the desired manifold pressure value and a stored compressor surge characteristic, and controls the wastegate so that an actual boost pressure matches the desired boost pressure.

Abstract: A blow-off valve apparatus is used in an internal combustion engine having a supercharger. The apparatus has an inlet for receiving compressed air from the compressor of the supercharger, and two outlets, one of which exhausts the air to atmosphere and the other, of which is connected to the compressor inlet, to direct some of the air back to the compressor. The apparatus includes a sleeve configured for variably closing the outlets so as to vary the proportion of the air exhausted, relative to that directed back to the compressor. The sleeve can be moved manually by an actuator. A further sleeve is configured for shutting off the outlets when the engine conditions do not require air to be diverted by the apparatus, and to open them when the engine conditions are suitable.

Abstract: The invention is directed to a method and an arrangement for controlling an internal combustion engine (1) having a compressor (5) for compressing the air drawn in by suction by the engine (1). The compressor is especially an exhaust-gas turbocharger. With the method and arrangement, a requirement-proper and timely opening of a valve (10) of an air path (15) is ensured for avoiding compressor pumping. The air path (15) bypasses the compressor (5). The valve (10) of the air path (15), which bypasses the compressor (5), is controlled in dependence upon at least one pregiven characteristic line (20, 25) of a compressor characteristic field.

Abstract: A control system for a variable-geometry turbocharger includes a supervisor logic (12) selecting a pulse control output (24) for large variation of desired and previous control signal inputs exceeding a threshold differential and a normal control signal (26) for small control signal input changes. The control system calculates an amplitude and duration for the pulse control output based on input control signal variation or the actual versus desired position of the variable-geometry system in the turbocharger.

Abstract: Control method for variable geometry turbocharger and related system are disclosed, wherein a boost target for a turbocharger is determined. Next, an error value between target boost and actual boost pressure is calculated and utilized to determine a new vane position. For example, the new vane position can be determined by calculating a needed change in vane position from the equation, &Dgr;&thgr;=kp(err)+kd·d(err)/dt, where &Dgr;&thgr; is the change in vane position, kp is a proportional gain value, kd is a differential gain value, and err is the error value between the boost target and the actual boost. A new vane position for the turbocharger is then determined by summing &Dgr;&thgr; with the previous vane position, and the turbocharger's set of vanes is positioned according to the new vane position. An open loop diagnostic mechanism and a feed-forward mechanism can also be employed to enhance vane positioning.

Abstract: An engine is provided with a turbocharger which varies a supercharging pressure by an actuator. A controller calculates a first compensation value of a response delay from operation of the actuator to variation of an intake air amount of the engine, and a second compensation value of an operating delay of the actuator with respect to an input of a command signal to the actuator. The command signal to the actuator is calculated by performing a processing based on the first compensation and the second compensation value on an operational target value that was determined based on the running state of the engine, and the response of intake air amount control is thereby enhanced.

Abstract: The present invention provides a variable nozzle opening control unit insuring a low fuel consumption rate and excellent response speed in the low load mode for an exhaust turbine supercharger. To achieve the purpose described above, an opening of the variable nozzle of the exhaust turbine supercharger 10 is set to and maintained at the maximum value in the constant operating state when the load is not more than a prespecified load level, and also the opening is gradually made smaller, when the load is not less than the specified load level, as the load becomes higher. When the load shifts from the high load region to the low load region, the variable nozzle is more closed or maintained at the original opening. Further when the operating state may get close to the surging limit, the variable nozzle is more opened.

Abstract: A method for controlling an engine having both an electronically controlled inlet device, such as an electronic throttle unite, and an electronically controlled outlet device, such as a variable cam timing system is disclosed. The method of the present invention achieves cylinder air charge control that is faster than possible by using an inlet device alone. In other words, the method of the present invention controls cylinder air charge faster than manifold dynamics by coordination of the inlet and outlet device. This improved control is used to improve various engine control functions.

Abstract: The present invention includes a method and apparatus for controlling the exhaust temperature of an engine is disclosed. The method includes the steps of sensing the exhaust temperature of the engine, determining a desired air pressure in response to the exhaust temperature, and controlling the air flow into the engine in response to the desired air pressure. The apparatus includes an air temperature sensor for sensing an actual exhaust temperature within the exhaust manifold and responsively generating an exhaust temperature signal. The apparatus also includes a controller for receiving the exhaust temperature signal and comparing the exhaust temperature signal to a desired exhaust port temperature, determining a desired air pressure in response to the comparison.

Abstract: The controller (41) selects premixed combustion or diffusive combustion of the diesel engine (1) based on the running state detected by a sensor (33, 34) (S4, S5). The controller (41) calculates the target oxygen concentration and the target oxygen amount of the intake gas for the selected combustion type. When premixed combustion is selected, the controller (41) preferentially controls the oxygen concentration of the intake gas to the target value. When diffusive combustion is selected, the controller (41) preferentially controls the oxygen amount of the intake gas to the target value. By immediately shifting the target values according to the combustion type without setting transitional target values, increase of noxious substances in the exhaust gas due to the shift of combustion type can be prevented.

Abstract: A method for controlling a supercharging device for an internal combustion engine includes controlling a variable (x) using different control characteristics in each of at least four sub-ranges defined by a gradient (dx/dt) of the variable to be controlled (x) and a difference (x) between the variable to be controlled (x) and a control variable (xs). An apparatus for controlling a supercharging device for an internal combustion engine includes a controller having a range of control that includes at least four sub-ranges devided in accordance with a gradient (dx/dt) of the variable to be controlled (x) and a difference (x) between the variable to be controlled (x) and a control variable (xs).

Abstract: A method of engine compression release braking with avoidance of turbine overspeed is disclosed. Initially, an electronic control module determines whether a turbine overspeed condition is present. If an overspeed condition is present, then the blow down timing of an engine compression release braking event is advanced. The present invention is particularly applicable to preventing turbine overspeed for vehicles operating at higher altitudes while compression braking.

Abstract: A control for a turbocharger system in an internal combustion engine particularly useful for multiple parallel turbochargers having turbines with discrete step variable nozzles. In response to a need for adjustment the variable nozzles are adjusted sequentially, not simultaneously. Sequential adjustment of the turbines minimizes the impact of the adjustment.

Abstract: A method for controlling an engine having both an electronically controlled inlet device, such as an electronic throttle unite, and an electronically controlled outlet device, such as a variable cam timing system is disclosed. The method of the present invention achieves cylinder air charge control that is faster than possible by using an inlet device alone. In other words, the method of the present invention controls cylinder air charge faster than manifold dynamics by coordination of the inlet and outlet device. This improved control is used to improve various engine control functions.

Abstract: A device for switching an exhaust gas turbocharger and an exhaust gas turbocharger having such a device are described. The device is used for exhaust gas turbochargers (1) having a variable turbine geometry as well as for other turbochargers (e.g., waste-gate turbochargers) having an (electronically) regulated final controlling element. The exhaust gas turbocharger is switched by a switching signal P from a regulated operation A with a boost pressure regulator (2) to an unregulated operation B with a boost pressure control (3), wherein a delay device (4) is provided for generating the switching signal P with a time delay.

Abstract: The intake air amount of an engine (1) is controlled by a variable nozzle (53) of a turbocharger (50). A controller (41) calculates an open loop control value of a drive signal of the variable nozzle (53) based on a running state of the engine (1), and calculates a feedback correction amount comprising an integral correction value of the drive signal such that the intake air amount coincides with a target intake fresh air amount (S367). It also calculates a learning value based on the integral correction value when the intake air amount coincides with the target intake air amount (S395, S400), and modifies the feedback correction amount such that the sum of the learning value and feedback correction amount is constant (S366). In this way, the response of intake air amount control or supercharging pressure control is enhanced.

Abstract: A charge limit manager arbitrates between desired EGR system and/or turbocharger behavior and the actual capabilities of EGR system and/or turbocharger control mechanisms under current operating conditions. In one embodiment, the charge limit manager includes three limiter blocks producing offset signals as separate functions of turbocharger compressor outlet temperature, turbocharger speed and pressure differential (&Dgr;P) across an EGR valve. A charge limit selector block is responsive to the offset values produced thereby, and also to commanded values of charge flow and EGR fraction as well as operating values of EGR valve position and &Dgr;P, to limit the charge flow and EGR fraction commands to controllable values. These values are preferably subtracted from actual or estimated values of charge flow and EGR fraction to produce charge flow and EGR fraction error values for use in controlling one or more EGR system and/or turbocharger swallowing capacity/efficiency control mechanisms.

Abstract: A control system for a variable-geometry turbocharger connected to an internal combustion engine, whereby the geometry of the turbocharger is controlled alternatively according to a first operating mode, a second operating mode or a third operating mode; the system providing for switching from one operating mode to another fully automatically.

Abstract: An internal combustion engine, in particular a stationary gas engine, comprising a compressor arranged in the induction tract, in particular an exhaust gas turbocharger, an electrically operable blow-off valve connected downstream of the compressor, and a pressure sensor for detecting the pressure actual value of the mixture in the region of the blow-off valve. In according with the invention there is provided a device (9) for detecting the engine power output (N), a device (10) for calculating a pressure reference value in dependence on the detected engine power output and a relationship previously stored in a memory between engine power output (N) and pressure reference value (Psoll), and a regulating device (11) for regulating the blow-off valve (7) until the pressure actual value (Pist) reaches the calculated pressure reference value (Psoll).

Abstract: The invention relates to a method for controlling the boost pressure on an unsteady-running piston internal combustion engine with a turbocharger. According to the inventive method, a blow-off valve, which is connected upstream from the supercharger turbine in the exhaust gas tract, is controlled by an engine control, the position of the pedal and a boost-proportional gradient are detected by the engine control when initiating an acceleration operation and, when a predeterminable value for the boost-proportional gradient is surpassed, the blow-off valve is actuated in an opening direction in order to effect a predeterminable controlled increase of pressure.

Abstract: A variable nozzle turbocharger (12) creates engine boost. Boost is controlled by controlling the position of vanes within turbocharger. A processor develops a control signal (29) for controlling vane position. The processor develops a value for desired boost and processes that value with a value. corresponding to the amount of boost being created by the turbocharger to generate error data (48A) defining error between the amount of boost being created by the turbocharger and the desired boost, and the processor develops a component of the control signal by P-LI-D processing (62) of the error data. Other components of the control signal are a feed-forward value from a look-up table (34) and a value from an overspeed protection function (60).

Abstract: The present invention relates to an engine diagnostic system for detecting malfunctions in an engine system having a variable geometry turbine exhaust system. The engine diagnosis system includes a variable geometry turbine adapted to receive exhaust gasses exiting an engine, a variable geometry turbine position sensor operationally connected to the variable geometry turbine, a compressed air reserve, a pressure capsule pneumatically connected between the compressed air reserve and the variable geometry turbine, a pressure regulator pneumatically connected between the compressed air reserve and the capsule, a pressure sensor pneumatically connected between the pressure regulator and the capsule, and an electronic control module electrically connected to the variable geometry turbine position sensor, to the pressure regulator, and to the pressure sensor. The sensors may be integrally connected to the engine exhaust system, or may be part of a diagnostic station.

Abstract: A control method for a supercharged internal combustion engine wherein actual supercharging pressure values are adjusted to prescribed desired supercharging pressure values by setting a variable component and influencing the supercharging pressure of a supercharger in accordance with a prescribed control law. In order to monitor the control of supercharging pressure in a supercharged internal combustion engine with the aid of simple means and, if appropriate, to display a malfunction, use is made as control law of a PID controller, the integration component is compared in the integration element of the PID controller with a prescribed tolerance band, and a fault signal is generated if the integration component is outside the tolerance band.

Abstract: A method for a closed-loop or an open-loop control of a forced-induction internal combustion engine that includes an exhaust turbocharger having an exhaust turbine with a variable turbine geometry for a variable adjustment of an effective turbine cross section and with a boost-air compressor, different operating states of the engine are assigned different characteristic maps with engine-operating and/or engine-state variables and the turbine geometry is adjusted in accordance with the characteristic maps between an open position and a pressure build-up position. When there is a change in a significant engine parameter, the system switches between two characteristic maps.

Abstract: There is provided a system and method for using an engine's exhaust back pressure to control a variable geometry turbocharger. The control system determines a desired exhaust back pressure based on engine speed and engine load. The desired exhaust back pressure is compared with a measured exhaust back pressure to determine the difference between the measured and desired exhaust back pressures. The difference value is used to determine the duty cycle. In an alternate embodiment, the exhaust gas pressure is used to adjust the duty cycle determined by other operating parameters. A base duty cycle is determined from the engine speed and the engine load. The difference between the measured and desired exhaust back pressures is used to determine an exhaust pressure control duty cycle. The base duty cycle is then adjusted by the exhaust pressure control duty cycle to give a turbocharger duty cycle.

Abstract: An aircraft control system includes a propeller governor in which a stepper motor is used to apply a compression force on a speeder spring, and a turbocharger in which a stepper motor is used to actuate a needle valve associated with a diaphragm cell. An electronic control unit may be used to control the stepper motor in the propeller governor and the stepper motor in the turbocharger. The integration of the propeller governor and the turbocharger into a single control system decreases the number of individual adjustments that must be performed manually by the pilot.

Abstract: In a method of limiting the charge pressure of an internal combustion engine charged using an exhaust gas turbocharger, a control unit performs an actual value/setpoint value comparison of a controlled variable with a predefined limit value and generates or limits actuating signals for an actuator drive of an actuator acting upon the controlled variable. The setpoint value is taken from a characteristic map memory as a function of the instantaneous operating state of the internal combustion engine. In order to allow the internal combustion engine to operate at the highest possible charge pressure and corresponding power output, measured values of the temperature and of the pressure upstream and downstream, respectively, from a compressor of the exhaust gas turbocharger are used for reading the limit value from the characteristic map memory.

Abstract: An internal combustion engine having an exhaust-gas turbocharger is provided. The exhaust-gas turbocharger includes a variable turbine geometry that allows for a greater range of use. The exhaust-gas turbocharger is used as a throttling device to dimension the combustion-air quantity delivered to the engine. The variable turbine geometry can be adjusted in such a way that the direction of rotation of the rotor of the exhaust-gas turbocharger is reversed. The intake pressure in the air inlet of the internal combustion engine is set as a function of the direction of rotation of the rotor.

Abstract: An exhaust-gas turbocharger for an internal combustion engine has a turbine having a variable turbine geometry for the variable setting of the effective flow inlet cross section to the turbine wheel. The exhaust-gas turbocharger has a compressor which is connected to the turbine via a shaft. The variable turbine geometry can be adjusted by means of a regulating device between a closed position and an open position. To compensate for wear, a stop limiting an end position of the variable turbine geometry is provided, and the position of this stop can be set in a variable manner.

Abstract: In the apparatus for controlling a coasting air recirculation valve of the turbocharger of an internal combustion engine, the coasting air recirculation valve is arranged in the coasting air recirculation line bypassing a compressor in the intake duct, and the coasting air recirculation valve is controllable by way of the intake duct pressure on the downstream side of the throttle valve. In order to ensure defined opening and closing of the coasting air recirculation valve, an additional control pressure, with which the coasting air recirculation valve can be opened independently of the intake duct pressure, can be delivered to the coasting air recirculation valve.

Abstract: An internal combustion engine having one or more parallel exhaust-driven turbochargers that each comprise an activatable delivery capacity adjusting unit for variable adjustment of the boost air delivery capacity with malfunction monitoring of each individual delivery capacity adjusting unit wherein, upon detection of a malfunction of a respective delivery capacity adjusting unit, a corresponding malfunction datum is emitted.

Abstract: A turbo charger system (32) for a diesel engine (1) with a simple structure, but improved in output, torque and fuel consumption rate. A high-stage turbine (3) and low-stage turbine (4) are provided in series on an exhaust gas line (2) of the engine (1). A high-stage compressor (6), which is connected to the high-stage turbine (3), and a low-stage compressor (7), which is connected to the low-stage turbine (4), are provided in series on an intake air line (5) of the engine (1). A bypass line (20) with a valve (21) is provided over the high-stage turbine (3). The bypass valve (21) is completely or substantially completely closed until the engine (1) reaches its maximum torque point (14) so as to raise a supercharging pressure. From the maximum torque point (14) to the maximum output point (15), the bypass valve (21) is gradually opened to adjust the supercharging pressure. The bypass valve is completely or substantially completely opened at the maximum output point (15) to suppress the supercharging pressure.