Pachacuti built a strong central government and also took his sons for training to Cuzco which ensured the loyalty.
Step-by-step explanation:
Moreover, he also kept the local people as rulers which increased their loyalty towards him.
Local administrators were made to collaborate with regional level administrators who looked after justice, land, labour, etc. The regional rulers were told to report to the supreme Inca ruler.
Also, the heirs of the local rulers were kept as prisoners to ensure loyalty of their people.