Go to page 22 in the EIS manual. There is a threshold setting for the flight timer. If you set it to zero, you get Hobbs time, e.g., the actual time the engine is running. If you set the threshold to something like 1600 rpm you get something closer to, but not the same, as tach time. e.g., you get actual time the engine is running above 1600 rpm. Basically Hobbs time excluding taxiing and other idling time.