I agree with you on the consistency thing. I'm just still surprised by how my efficiency has dropped from 80% for fly sparging to mid-60's for no sparge. If this is what it's going to be, then fine, I'll adjust my recipes. I'm just wondering why such a drop. Is it a solubility thing? Don't know.
It's not about solubility, it's about dilution. Solubility limit of sugar solutions are around 1.300, so it's definitely not that.
When you mash, the starches are converted into sugars and that sugar dissolves into the wort. The resultant wort volume is higher than the original strike water volume by approximately
WortVolume=Strike + (0.0016 * GrainPotential*GrainWeight)
Then the run off volume is Strike Volume - absorption rate, leaving behind a known volume in the grain, and grain bed. When you sparge (batch), you're diluting this reminding wort volume with the new sparged wort volume (retained wort volume + sparge volume). It's all 100% dilution based.
Fly sparging is unique since it relies more on even water dispersion and should exceed the lauter efficiency of a batch sparge process when done properly, in equipment suited to fly sparging
Again, if you check out my calculator above you can see how a batch sparge and no sparge should go. Something I'm learning recently is that, for whatever reason, recirculation seems to improve lauter efficiency in some way similar to fly sparging. Haven't quite figured out how yet.