I have just bought 2 new GTX 650 Ti for two different computers.
When playing the same game(Borderlands 2) using the same settings card A's temperature is 48-51 C and card B's temperature is 80~ C.
-both computer are ventilated in a similar way.
-I did not removed heat-sink/fan
-I increased B's fan temperature to 100% and the max temperature went down from 80C to 72C
-B's fan is working
-B's computer is dust-free
B's computer specifications that are different from A's:
1-Asus motherboard P5P43TD (PCI Express 2.0)
2-Intel Q9550 with ISGC 400 Tt fan