UPDATE 03/13/09 - I have certainly found out that dialing the Carb Ratio and Active Insulin time up and down do not necessarily mean that you will get better control. It is more of a balancing act between these two settings and that is why it is important to work with your endo or educator to tune these settings.
When it comes to Auto Mode for the MiniMed 670G, tuning the settings to get as close to your sugar targets feels a little more complicated as compared to the manual mode. This is because the closed loop system has a feedback mechanism which will likely throw-off one setting when you change another.
In the course of your day, the system is performing a balancing act between bolus and basal to keep you as close to Auto Mode’s fixed and preset BG target of 120mg/dL by introducing a third input – the micro bolus.
When it is all said and done, the user has control of two settings only, namely Carb Ratio and Active Insulin time.