A real-time system for modeling a turbo-charged engine includes a model configured to estimate various exhaust states such as turbine inlet pressure, turbine outlet pressure, turbine outlet temperature, turbine mass flow rate and waste-gate valve mass flow rate. The model is dependent only on the availability of normal operating values available in a conventionally-configured automotive controller and one or more measured intake side parameters such as ambient pressure, boost pressure, ambient temperature and compressor mass flow rate. The model is constructed to reflect a high-level application of energy conservation between the turbine (generated power) and compressor (absorbed power). A method for the indirect measurement of turbine and waste-gate flow uses turbine inlet and outlet pressure, inlet temperature and engine mass air flow rate measurements. A method for the indirect measurement of turbine efficiency avoids the need for manufacturer's turbine data.