Staged injection allows the use of primary and secondary injectors of different sizes. The primary injectors are always used, and may be stock or other injectors with a rapid opening time and good spray pattern., The secondary injectors activate based on driving conditions, and may be larger than the primary injectors. The injector sizes and dead times for each set of injectors do not need to be the same. eg stock 310cc injectors can be used until boost, at which point both 310cc and 1300cc injectors are used.
It also is possible to use two independent fuel systems for each set of injectors. eg the secondary injectors may use E85 or race gas.
Staged injection requires ECU outputs. Currently this is only supported by the s300 & KPro as almost all FlashPro ECUs do not have accessible outputs.