An internal combustion engine having intake and exhaust manifolds, a turbocharger with a compressor, and at least one of: an exhaust gas recirculation (EGR) valve and a variable geometry turbine (VGT). The system further includes a control computer configured to determine at least one of torque demand, pressure across the compressor, and pressure gradient ratio between the exhaust manifold and the intake manifold relative to one of exhaust manifold pressure, intake manifold pressure, and 1. The control computer performs at least one of: closing the EGR valve in response to the determined at least one of torque demand, pressure across the compressor, and pressure gradient ratio, and lessening restriction provided by the variable geometry turbine responsive to the determined at least one of torque demand, pressure across the compressor, and pressure gradient between the exhaust manifold and the intake manifold.

An internal combustion engine having intake and exhaust manifolds, a turbocharger with a compressor, and at least one of: an exhaust gas recirculation (EGR) valve and a variable geometry turbine (VGT). The system further includes a control computer configured to determine at least one of torque demand, pressure across the compressor, and pressure gradient ratio between the exhaust manifold and the intake manifold relative to one of exhaust manifold pressure, intake manifold pressure, and 1. The control computer performs at least one of: closing the EGR valve in response to the determined at least one of torque demand, pressure across the compressor, and pressure gradient ratio, and lessening restriction provided by the variable geometry turbine responsive to the determined at least one of torque demand, pressure across the compressor, and pressure gradient between the exhaust manifold and the intake manifold.

An upper-limit threshold value and a lower-limit threshold value of a fore-and-aft differential pressure of an EGR control valve is calculated based on an intake-air quantity detected by an airflow meter. An actual fore-and-aft differential pressure of the EGR control valve is calculated from detected values of an upstream-side pressure sensor and a downstream-side pressure sensor. Then, these threshold values are compared with the actual fore-and-aft differential pressure, and when the actual fore-and-aft differential pressure exceeds the upper-limit threshold value or when the actual fore-and-aft differential pressure is less than the lower-limit threshold value, it is determined that the pressure loss of an intake and exhaust system has changed. If it is determined that the pressure loss of an intake and exhaust system has changed, EGR is inhibited, and if not so, EGR is permitted to be performed. These threshold values are varied depending on a target EGR rate.

An upper-limit threshold value and a lower-limit threshold value of a fore-and-aft differential pressure of an EGR control valve is calculated based on an intake-air quantity detected by an airflow meter. An actual fore-and-aft differential pressure of the EGR control valve is calculated from detected values of an upstream-side pressure sensor and a downstream-side pressure sensor. Then, these threshold values are compared with the actual fore-and-aft differential pressure, and when the actual fore-and-aft differential pressure exceeds the upper-limit threshold value or when the actual fore-and-aft differential pressure is less than the lower-limit threshold value, it is determined that the pressure loss of an intake and exhaust system has changed. If it is determined that the pressure loss of an intake and exhaust system has changed, EGR is inhibited, and if not so, EGR is permitted to be performed. These threshold values are varied depending on a target EGR rate.

Provided is an engine which is provided with an EGR device, wherein: an actual intake/exhaust gas pressure ratio π1 of an intake-gas pressure P1 to an exhaust-gas pressure P2 is calculated from the detected exhaust-gas pressure P2 and the detected intake-gas pressure P1; an estimated intake/exhaust gas pressure ratio π2 of the intake-gas pressure P1 to the exhaust-gas pressure P2 is calculated from an engine rotational frequency N, and a fuel injection amount F; and, in cases when the actual intake/exhaust gas pressure ratio π1 is less than a prescribed value π0, an EGR gas weight Megr is calculated based on the actual intake/exhaust gas pressure ratio π1, and in cases when the actual intake/exhaust gas pressure ratio π1 is equal to or more than the prescribed value π0, the EGR gas weight Megr is calculated based on the estimated intake/exhaust gas pressure ratio π2.

Provided is an engine which is provided with an EGR device, wherein: an actual intake/exhaust gas pressure ratio π1 of an intake-gas pressure P1 to an exhaust-gas pressure P2 is calculated from the detected exhaust-gas pressure P2 and the detected intake-gas pressure P1; an estimated intake/exhaust gas pressure ratio π2 of the intake-gas pressure P1 to the exhaust-gas pressure P2 is calculated from an engine rotational frequency N, and a fuel injection amount F; and, in cases when the actual intake/exhaust gas pressure ratio π1 is less than a prescribed value π0, an EGR gas weight Megr is calculated based on the actual intake/exhaust gas pressure ratio π1, and in cases when the actual intake/exhaust gas pressure ratio π1 is equal to or more than the prescribed value π0, the EGR gas weight Megr is calculated based on the estimated intake/exhaust gas pressure ratio π2.

This engine includes an EGR device. The engine is provided with: an EGR gas temperature sensor; an EGR valve; an EGR control unit; an EGR valve position detection unit; a diagnosis unit; a first timer; a second timer; and a diagnosis control unit. The diagnosis unit diagnoses whether the EGR gas temperature sensor has failed, on the basis of a detected value from the EGR gas temperature sensor. The first timer, when the EGR valve is open, performs counting in accordance with the passage of time. The second timer, if a count value of the first timer is greater than or equal to a first threshold value set in advance, and if a predetermined condition is satisfied, performs counting in accordance with the passage of time. The diagnosis control unit prohibits diagnosis by the diagnosis unit if a count value of the second timer is less than a second threshold value set in advance, and permits the diagnosis if the count value is greater than or equal to the second threshold value.

This engine includes an EGR device. The engine is provided with: an EGR gas temperature sensor; an EGR valve; an EGR control unit; an EGR valve position detection unit; a diagnosis unit; a first timer; a second timer; and a diagnosis control unit. The diagnosis unit diagnoses whether the EGR gas temperature sensor has failed, on the basis of a detected value from the EGR gas temperature sensor. The first timer, when the EGR valve is open, performs counting in accordance with the passage of time. The second timer, if a count value of the first timer is greater than or equal to a first threshold value set in advance, and if a predetermined condition is satisfied, performs counting in accordance with the passage of time. The diagnosis control unit prohibits diagnosis by the diagnosis unit if a count value of the second timer is less than a second threshold value set in advance, and permits the diagnosis if the count value is greater than or equal to the second threshold value.

A computer control network is connected to a multiple-cylinder engine and implements aftertreatment temperature management. Processors are configured to determine an aftertreatment temperature-efficient air to fuel ratio that satisfies the sensed power output request, determine an air to fuel ratio adjustment, select an in-cylinder exhaust gas recirculation technique, select at least one EGR cylinder of the multiple-cylinder engine to implement the in-cylinder exhaust gas recirculation technique, and control the intake valves to open and the exhaust valves to close for the selected at least one EGR cylinder to adjust the oxygen and particulate content of the exhaust gas by applying at least a second compression stroke of the respective reciprocating piston of the at least one EGR cylinder to the exhaust gas to push the exhaust gas through to the intake manifold.

A computer control network is connected to a multiple-cylinder engine and implements aftertreatment temperature management. Processors are configured to determine an aftertreatment temperature-efficient air to fuel ratio that satisfies the sensed power output request, determine an air to fuel ratio adjustment, select an in-cylinder exhaust gas recirculation technique, select at least one EGR cylinder of the multiple-cylinder engine to implement the in-cylinder exhaust gas recirculation technique, and control the intake valves to open and the exhaust valves to close for the selected at least one EGR cylinder to adjust the oxygen and particulate content of the exhaust gas by applying at least a second compression stroke of the respective reciprocating piston of the at least one EGR cylinder to the exhaust gas to push the exhaust gas through to the intake manifold.