[eltharyon]

Recently brewed a Black IPA.  Did my mash as normal, after I reached my boil volume, I stopped pulling out of the mash.

Instead of dumping the mash right away I added a small amount of water and rinsed another bit out of the mash, I was going to use to feed my bugs so I wasn't too concerned about it being too dextrinous.  It actually came out as pretty good wort, had a little sample taste.

So after the boil, it was a little cold and dry out, I think I boiled off a bit too much as well as lost some volume to hop material.  Instead of being happy with being short on volume, I just added the liter+ of wort that I had pulled off after the mash.
As I dumped it, I realized I hadn't boiled.

The beer came out great, finish is clean and dry with a good malt and hop character.  Not watery, not sour, nothing seemingly wrong.  But I did end up with about 80% Apparent Attenuation, the yeast is listed as I think up to 75%.  My numbers were on up until I added the liter of extra wort, didnt measure after that, and the FG was a bit lower than expected.  I didnt think much about this until I was talking to a buddy at the LHBS, he suggested that the enzymes might still have been active in the extra wort and done some work on the already boiled stuff.  Again I'm not complaining, its actually pretty nice.  Sneaky beer for 8%, almost too easy to put it down.

Anyone have an idea what might be going on here?

[morticaixavier]

I would guess that the guy at the lhbs was correct. Until you exceed 170 or so for a significant amount of time the enzymes are still active. until the extra wort cooled below the activity threshold that would have stopped most of the conversion but there would still be a significant amount of conversion going on.

[tschmidlin]

There is probably some effect from that, but don't forget that you diluted the beer with those extra runnings.  You said you didn't measure after that right?  If you measured 1.080 with 18 liters, and added a liter of water, you'd have 19 liters at ~1.076.  You didn't really add water, but you added more than a liter of unknown gravity.  Anyway, keeping with the example, if you expected 75% attenuation that 1.080 would finish at 1.080, but if you started at 1.076 that would be 1.019.  That doesn't get you all of the way there, but it's a start.

The other thing that could be affecting this is contamination with bacteria or wild yeast from the unboiled wort.  The flavor may not be evident (yet), but they could ferment things that the yeast you pitched could not, further lowering the gravity.

All of this is assuming that you didn't mash lower than expected (it was cold out) and cause the wort to be more fermentable.

Since the beer is tasting good right now I would recommend drinking it.  If you sit on it any contamination may take over and make it less than pleasant to drink.

[eltharyon]

I actually had it sitting a week or so extra, no noticeable drop in FG, assuming no infection, combined with no taste or smell. 

The beer seems clean, just finished lower.  I'm assuming what I added wasn't as low as water, it tasted pretty sweet an a bit viscous.  I honestly probably could have run that into the kettle. 

Hey who the hell knows right, its beer, and its tasty.

I'll let you know if it goes south.