The four major common-rail injector manufacturers solve the same problem in very different ways. Bosch's CRI/CRIN solenoid and piezo ranges, Delphi's servo-valve designs, Denso's G2/G3/G4 platforms and Siemens VDO (Continental) piezo units each have distinct coding schemes, failure characteristics and remanufacturing requirements. This category collects brand-specific engineering detail and cross-reference knowledge.