Method and system for operating an engine having a turbocharger with at least two discrete positions and exhaust gas recirculation (EGR)

A method for controlling an engine having a variable geometry turbocharger with at least two discrete positions and exhaust gas recirculation (EGR), such method comprising:

• producing a control signal to the turbocharger, such signal having at least two discrete levels, corresponding in steady state to the two discrete positions of the turbocharger, one of such levels selected to provide a proper flow of air through the turbocharger to an intake of the engine and such selected level being modulated between such two levels over time to provide, over time, a proper average pressure at an input of the EGR to enable a proper flow of exhaust gases from the exhaust of the engine through the EGR back to the intake of the engine.

A control system for controlling an engine having a turbocharger with at least two discrete positions and exhaust gas recirculation (EGR), such system comprising:

• an engine control unit for producing a control signal to the turbocharger, such signal having at least two discrete levels, such signal having one of such levels selected to provide a proper flow of air through the turbocharger to an intake of the engine and for modulating such two-level signal between such two levels over time to provide, over time, a proper pressure at an input of the EGR to enable a proper flow of exhaust gases from the exhaust of the engine through the EGR back to the intake of the engine.

A control system for controlling an engine having a turbocharger having at least two discrete positions and exhaust gas recirculation (EGR), comprising:

• an engine control unit for producing a control signal for the turbocharger having two signal components, a first signal component having a level to drive the turbocharger to the either a desirable open or closed position selectively in accordance with engine operating condition, and a second signal component modulating the first signal, with such modulation being selected to control pressure across the EGR, such modulation having a bandwidth higher than the bandwidth of the turbocharger so that while the pressure at the EGR is changed substantially instantaneously wherein boost provided by the turbocharger is substantially invariant.

An engine control unit having a program stored therein for controlling an engine having a turbocharger, such turbocharger having a compressor portion and a turbine portion, such turbine portion having an inlet flow control device with at least two discrete portions, one of such positions being a relatively open position and another one of the positions being a relatively closed position, such engine having exhaust gas recirculation (EGR), such program causing the control unit to send a control signal to the inlet flow control device, such signal having at least two discrete levels, such signal having one of such levels selected to provide a proper flow of air through the turbocharger to an intake of the engine and for modulating such two-level signal between such two levels over time to provide, over time, a proper pressure at an input of the EGR to enable a proper flow of exhaust gases from the exhaust of the engine through the EGR back to the intake of the engine.

An engine control unit having a program stored therein for controlling an engine having a turbocharger with at least two discrete positions and exhaust gas recirculation (EGR), such program causing the control unit to produce a composite, bi-level control signal for the turbocharger, such composite signal comprising:

• a first signal component having either a first level or a second level, such first or second level being selected to provide either a relatively high or relatively low flow of air, respectively, through the turbocharger to an intake of the engine;
• and
• a second signal component for modulating such first signal component between the first and second levels to provide, over time, an average pressure at an input of the EGR to provide a proper flow of exhaust gases from the exhaust of the engine through the EGR back to the intake of the engine while the first signal component provides a proper flow of air through the turbocharger to the intake of the engine.