Perkins introduced ?de-tiering? strategy for Stage IIIB/Tier 4i engines. Perkins said its Stage IIIB/Tier 4 Interim engines above 130 kW will not require any de-tiering for use in countries where fuel quality and sulphur content can vary. For engines under 130 kW, Perkins will provide ?authorised modification processes? through distributors from 2014.