There are lot of legends on Inca Empirem but the truth is that they never entered too far down south of Chile:
"Once the Inca armies had secured the Titicaca basin, they pressed south through the altiplano into northwest Argentina and Chile. Beginning with the conquest of the Guasco and Coquimbo, the Inca then engaged the Chiriguanos and Zuries, east of the Andes, along the southeastern frontier. Finding the rough eastern terrain difficult, the army doubled back to the high country and crossed over to Chile in pursuit of gold and mineral wealth at Porco, Tarapaca and Carabaya. Pressing further south, the Inca army reached as far as the Santiago region. However at this point the advance was halted, with the records telling of either Thupa Inka Yupanki's desire to return to Cuzco or resistance from the allied Mapuche and Araucanian forces being the reason."
See at
http://trailingincas.info/empire.php the complete story