What does Kensei Muguruma's bankai do? His shikai, Tachikaze, is a wind-based zanpakutou that can launch long-range, string-like, blades that slices enemies. But what special abilities does Tekken Tachikaze, Kensei Muguruma's bankai, possess?
It was confirmed in chapter 560, taken from  Bleach Wikia:


  It appears to greatly augment his strength, as he is able to create a
  large explosion upon attacking. This is due to the fact that in this
  form the power of his Bankai is transferred to the knuckle blades. The
  bursting power continues to hit his opponent endlessly as long as his
  fists are touching his opponent.