Guys, there is no difference in performance between delta and wye winds. The difference between the two are kv related. A Neu 1515 1D motor has a kv of 4100. A 1515 1y has a kv of 2200. The main reason for using one wind over the other is to target a certain kv. Wye winds are usually favored over deltas becuase they are more tollerant to timming advances. Deltas work best at low timming, advancing the timming on a delta only generates more heat and not performance. Hope this helps.
Mark