These are voltage minimums:
It's very noticeable when it bottoms out. The dash lights dim a lot and a few times the headlights have turned off (Mach HID's).
I logged generator duty cycle last night but I've no clue if it shows anything useful. I had expected it to be a percentage much like injectors PW or fuel pump duty cycle, it wasn't. Most of the time it just read zeros. But near the times voltage was dropping it would register numbers; .3-.6 generally and only for a very short time. So I'm not sure if it even logs correctly.
Also the genDC and low voltage don't always correlate, actually the DC reads zeros more times than it registers working.
Here is the log (it's long, ~45 minutes) --> http://www.sendspace.com/file/2kvf2o
Here is the tune file --> http://www.sendspace.com/file/r4o7by