Various methods and systems are provided for estimating fresh intake air flow. In one example, a system comprises an engine having an intake manifold to receive fresh intake air and an exhaust gas recirculation (EGR) system to supply EGR to the intake manifold, where flow of EGR through the EGR system is controlled by one or more exhaust valves. The system further includes a controller configured to adjust a position of the one or more exhaust valves based on an estimated fresh intake air flow rate, where during a first set of operating conditions, the fresh intake air flow rate is estimated based on a total gas flow rate into the engine and further based on a current position of the one or more exhaust valves, intake manifold pressure, air-fuel ratio, and fuel flow to one or more cylinders of the engine.

Various methods and systems are provided for estimating fresh intake air flow. In one example, a system comprises an engine having an intake manifold to receive fresh intake air and an exhaust gas recirculation (EGR) system to supply EGR to the intake manifold, where flow of EGR through the EGR system is controlled by one or more exhaust valves. The system further includes a controller configured to adjust a position of the one or more exhaust valves based on an estimated fresh intake air flow rate, where during a first set of operating conditions, the fresh intake air flow rate is estimated based on a total gas flow rate into the engine and further based on a current position of the one or more exhaust valves, intake manifold pressure, air-fuel ratio, and fuel flow to one or more cylinders of the engine.

Various methods and systems are provided for estimating fresh intake air flow. In one example, a system comprises an engine having an intake manifold to receive fresh intake air and an exhaust gas recirculation (EGR) system to supply EGR to the intake manifold, where flow of EGR through the EGR system is controlled by one or more exhaust valves. The system further includes a controller configured to adjust a position of the one or more exhaust valves based on an estimated fresh intake air flow rate, where during a first set of operating conditions, the fresh intake air flow rate is estimated based on a total gas flow rate into the engine and further based on a current position of the one or more exhaust valves, intake manifold pressure, air-fuel ratio, and fuel flow to one or more cylinders of the engine.

Various methods and systems are provided for estimating fresh intake air flow. In one example, a system comprises an engine having an intake manifold to receive fresh intake air and an exhaust gas recirculation (EGR) system to supply EGR to the intake manifold, where flow of EGR through the EGR system is controlled by one or more exhaust valves. The system further includes a controller configured to adjust a position of the one or more exhaust valves based on an estimated fresh intake air flow rate, where during a first set of operating conditions, the fresh intake air flow rate is estimated based on a total gas flow rate into the engine and further based on a current position of the one or more exhaust valves, intake manifold pressure, air-fuel ratio, and fuel flow to one or more cylinders of the engine.

Methods and systems are provided for refurbishing an engine using ionized air. During a service mode, a service technician may stream ionized air from an external ionized air source to an engine cylinder via the engine intake system. Concurrently, the service technician may connect a service tool to a vehicle diagnostics port to relay operator input, the input allowing a vehicle control system to rotate the engine and adjust engine throttle and cams.