An inferential exhaust gas recirculation flow detection device comprising: an exhaust gas recirculation valve having a gas input, a gas output and a signal input; an exhaust manifold of an engine having an output connected to the gas input of the EGR valve and to an input of a turbine, and having an input connected to exhaust ports of cylinders of the engine; an intake manifold of the engine having an input connected to an output of the EGR valve and to an output of a compressor, and an output connected to intake ports of the cylinders; a first pressure sensor situated in the intake manifold; a lambda sensor (19, 21, 23, 25) situated in an exhaust gas flow conveyance between the output of the exhaust manifold and the input of a turbine that is connected to the compressor, or between an output of the turbine and an exhaust output in an ambient environment, the lambda sensor sensing an oxygen content of an exhaust gas in an exhaust gas flow conveyance, and having an output of a laggy signal with an indication of the oxygen content; and a processor having an input connected to the first pressure sensor and to the output of the lambda sensor, and having an output connected to the signal input of the EGR valve; and wherein the processor is configured to calculate: an estimated oxygen content in the exhaust gas flow conveyance based on models of the EGR valve and the turbine; one or more rates selected from a group comprising an estimated EGR mass flow rate and an estimated fresh air mass flow rate based on the estimated oxygen content in the exhaust gas flow conveyance during transient operation of the engine and the estimated oxygen content and the indication of the oxygen content in the laggy signal during steady operation of the engine; and wherein the processor is configured to control the EGR valve. an exhaust gas recirculation valve having a gas input, a gas output and a signal input; an exhaust manifold of an engine having an output connected to the gas input of the EGR valve and to an input of a turbine, and having an input connected to exhaust ports of cylinders of the engine; an intake manifold of the engine having an input connected to an output of the EGR valve and to an output of a compressor, and an output connected to intake ports of the cylinders; a first pressure sensor situated in the intake manifold; a lambda sensor (19, 21, 23, 25) situated in an exhaust gas flow conveyance between the output of the exhaust manifold and the input of a turbine that is connected to the compressor, or between an output of the turbine and an exhaust output in an ambient environment, the lambda sensor sensing an oxygen content of an exhaust gas in an exhaust gas flow conveyance, and having an output of a laggy signal with an indication of the oxygen content; and a processor having an input connected to the first pressure sensor and to the output of the lambda sensor, and having an output connected to the signal input of the EGR valve; and wherein the processor is configured to calculate: an estimated oxygen content in the exhaust gas flow conveyance based on models of the EGR valve and the turbine; one or more rates selected from a group comprising an estimated EGR mass flow rate and an estimated fresh air mass flow rate based on the estimated oxygen content in the exhaust gas flow conveyance during transient operation of the engine and the estimated oxygen content and the indication of the oxygen content in the laggy signal during steady operation of the engine; and wherein the processor is configured to control the EGR valve. an estimated oxygen content in the exhaust gas flow conveyance based on models of the EGR valve and the turbine; one or more rates selected from a group comprising an estimated EGR mass flow rate and an estimated fresh air mass flow rate based on the estimated oxygen content in the exhaust gas flow conveyance during transient operation of the engine and the estimated oxygen content and the indication of the oxygen content in the laggy signal during steady operation of the engine; and wherein the processor is configured to control the EGR valve.