Hey guys I have an 04 z with a power lab 35r turbo kit . The reasons why I'm starting this tread is because the car is having a hard time holding boost I have it set at 9psi it would hit that boost level then fall off only through higher RPM's and it's better when the weather is warmer for some reason, all the clamps and vacuum hoses are secure my only guess would be the wastage spring is disfunctional or the manifold has a leak. Thanks for the suggestions!

 

Do you have a bypass valve ( AKA re-circulation valve)..or just blow off? That can leak. You can do a boost leak test as far determining if a leak is present anywhere in the system. If you have an intercooler....could leak there too.
If it was wastegate, I don't think you would be able to attain max boost to begin with..but I guess anything's possible. Injector gaskets/seal can also be a source.

here's the bible:
http://www.thumper300zx.com/z32/boos...leak_guide.htm

 

what kind of boost controller?

normally as rpms go up there is more backpressure so boost will taper. If you are using an open loop boost controller that has a set duty cycle the duty cycle will need to be increased as the rpms increase otherwise the boost will be lower at higher rpms.

as an example: my open loop duty cycle for 16psi is roughly 20% at 4k rpms and it ramps up to 28% at 7k rpms. if i set 20% all the way across the board my boost pressure will drop off at higher rpms.

If you had a manifold leak then the wastegate will see a lower boost and just spin the crap out of your turbo so if your intake temps aren't skyrocketing then it's probably not a leak. Wastegate spring being the problem is very low on the list. Not often is something simple like a spring going to be the problem.

my guess is on the boost controller being setup incorrectly and needing some adjustments.

 

The boost controller is a Grimm Speed manual , I wish it was a spring ! Process of elimination.

 

you have it hooked up to the bottom port?

 

well then check to see if it's set up correctly. The duty cycle should be higher as the rpms go up. If it's on a set duty cycle for the entire rpm range then that would be the issue. If it does change see if you can record or see what duty cycle it is near the end of the rpms verse the begining. If the duty cycle is shooting up a bunch (if it's a closed loop system) then you do probably have an exhaust or boost leak. If that's the case i would first check the vac lines going to the wastegate for leaks.

 

there is no duty cycle on a manual boost controller

 

lol, nice. I saw grim speed but i didn't see "manual" after it.

so, i'm no expert on manual boost controllers but wouldn't it be plagued with boost dropping off just like in a normal spring setup as well?