ct 26 issues Options

[blckcelica95]

i have a 5sfte, its been on the road for roughly 2 years and in the time span i have blown 2 ct-26 50 trim turbos. i recently dissambled the turbo trying to figure out why i keep blowing these things. On both turbos the thurst bearings were damaged, but had no scoring . so i dont think the turbo's prematue deaths were caused by an oil issue . the thurst bearing looked almost brand new except for were it had worm . Which is in the center section were the bearing connects to another part which connects to the shaft. this picture may explain it better http://www.alltrac.net/images/turbo/rebuild9.jpg . Now i was pushing these turbo at 17 psi . until i was told that 17psi is to high for a stock ct26 exhuast side. im am wondering if it is possible that the increase in back pressure from running it so high, could have damaged the thurst bearings. any input would be appricated. for the record i am not putting on another ct26 based turbo i am upgrading to a t3/t4 but i want to figure out why i keep killing them before i blow another turbo.
Sean