Big thanks to SAM at GT MOTORSPORTS.
Sam tried everything imaginable to try to figure out what the problem was. Then, checked everything again. I was getting impatient and was ready to just buy a totally different turbo. Sam suspected that it was a turbo issue however he wanted to be sure. Sam took off my turbo to see if it was in fact a turbo issue. When he took the turbo off he found the problem. The problem was that the silicone coupling that connects to the intake side of the turbo was in terrible shape. It was basically collapsing at high rpms. Turns out it was a simple fix.
I am now holding steady boost to redline. My numbers are 374.7whp and 370.5tq i beleive it was at 8.5psi (please correct me if i am wrong)
Stay tuned. more to come.

 

I use semi truck radiator hose on my junkyard turbo cars. They didnt blow out at 25psi from a t3 heh. The piston melted before a hose poped....

 

Great to see that there are other shops properly installing and diagnosing the APS single turbo problems, besides us!!Big props to Sam!!

 

sweet. Sams the man.

 

nice, i hope i get those numbers with my new exhaust. Congrats man!

 

When you picking that thing up?

 

hmm, very interesting. did he say how he fixed it? did he reinforce it somehow? i wonder it thats whats causing most of this boost drop? oh yeah, btw, sugarspun, i get my new downpipe tomorrow, im gonna look into that silicone coupler too. is it the one that looks like an accordian.

 

oh my oh my. simple fix - nice numbers. All I want to see you post now are positives.

Glad you got it fixed

 

Is the inside of the coupler rough like an "accordian" as well? Possible he replaced it with something with a smooth inner surface? I remember IPcheck put a flex pipe on his wastegate dump that had a ridged inner surface and it made huge backpressure issues.

Anyway, its good to hear you got it working right. Now go enjoy it.

 

taurran, it looks like this, its pretty flexible once its stretched out. but when its stretched out, the inside isnt very rough.

 

I would also think he swapped that pipe out with something else that wasn't going to collapse.

I have been weary about pipes/tubes that may give under suction.

 

after seeing his post on another forum i think its a different pipe, he said its the pipe on the intake side, which is the one i posted a pic of, but he says its part #93 which is a silicone coupler on the turbo outlet side, which shouldnt collapse, i just need him to clarify.

 

Yes, maybe he can post a picture of what the part and what they did exactly.

 

Glad to hear.... Interesting.. Afterall Sugar bought a used APS ST kit... Sugar, please clarify which part it was.. I'm also confused as well...

 

pwheew!! that was easy, huh? only been about what, 2 months since that kit was installed? glad you're finally getting the benefit of it, now crank up the boost!

 

Wow that would be crazy if that was the APS ST problem.

 

Nice numbers! Glad it was a something easily fixed
Welcome to the APS ST Club!!

 

comon sugar, let me know which part is was.

 

as far as i know it is #93
it is the turbo inlet hose.