Deusmortis

IIRC the Shimas 20km torps were 2.1km spotting? go check that and see if its different. 

They did a pretty large rebalance on torps and detection ranges back in the pre-6.0 series of WoWs.  They made the detection of the 20km torps 2.5 km and dropped the speed to 62 knots.  At the opposite end of the spectrum are the Khab torps - they have only 6km range and a speed of 53 knots, but they have a 0.5km detection range  So yes, you need to look carefully at the torps to see what the current detection range is.

Meant more recently than that.  Was playing for the first time in a few weeks yesterday.  Didn't see torps until it was too late.  Used to see them from much further out.