SERIES PARALEL COMPRESSORS OPERATION (SPCO) COMPRESSORS’ MAP The idea is to operate with the compressors in series connection operation (SO) (like a two stage compressor) at low and medium speed and PO at high engine’s speed. In all the operation cases, the turbines’ connection rest a parallel one and more, electronic control guarantees much the same speed for both compressors. In Figure 9 is presented the compressors’ map for the case of 2 x Garrett To4-60 turbocharger with equal speed electronic controlled operation. It is very clear shown in Figure 9 that the compressors’ map allow an important gain comparison with STO, especially in the low speed engine’s range operations.