Can't go past 15 lbs of boost, motor doesn't want to rev

[Mountain GN]

Not sure why, but a while back I noticed that I'm limited to about 15 PSI no matter how I adjust the wastegate. It also seems like the turbo starts to get "rough" around 12 lbs of boost. It almost sounds like it's making the horsey sneeze sound under boost with your foot still in the throttle. At the same time, I can tell the motor really doesn't want to rev.

As a result of these problems, I replaced the 160,000 mile valve springs with a new set of Comp Cam 980s. I also put a new cam position sensor in it. I replaced the coil pack, which was slightly weak with a new high-output unit from Highway Stars. The module was replaced about 3 years ago so I left it alone. Timing chain was replaced last fall.

I also replaced a slightly flakey LS1 MAF with the new plastic GM unit. All this did was make it idle better and brought my BLMs back down to the 128 range.

After all of these changes, the problem is still there...No better, no worse than before.

Any idea what else I should be looking at? Mods are in sig.

 

[WSLN 6]

I would take off the downpipe and inspect the exhaust wheel for damage. Mine sounded like a small fire engine while trying to make boost when I had a chewed up exhaust wheel. Worth a shot...

 

[droptopturbo6]

I agree. Just pull the intake tube off and see if the shaft moves up and down. Mine did that same thing when my turbo failed. If it wont rev and it wont boost, the other possibility is a major exhaust leak...

 

[Mountain GN]

I'll check that today, thank you!

I first began to notice this while tuning a couple of months ago. We had an overboost situation with a momentary spike to 28 PSI. Thankfully, there was no knock when it happened, but I wonder if that spike was part of the cause.

 

[Mountain GN]

Just pulled the hose off the cold side (I don't have time to get the downpipe off), and there's up-down play...It doesn't feel like a ton of play, but it's there and you can even hear it.

I guess it's turbo time.

Any suggestions, given my mods below, as to what to get? It's been a while since I bought a turbo!

 

[1quick6]

I'd just get the TE-44 rebuilt, myself. It's a good turbo.