ok i know we are all sick of hearing about boost problems and there's plenty of info out there. but i am really stuck on this 1.

this problem occured during a few laps on the track
boost ranges from 2-10psi. when i get 2 psi, a weird noise can be heard. IMO it doesn't sound like a boost leak. though it only starts when pressure is made by the turbos. it feels as though the 2nd turbo kicks in when it should. it comes and goes and happens whether the engine is cold or warm

i checked for intake leaks and found nothing. that includes the 2 rubber pipes from the intercooler, the y-pipe coupler, UIM, TB, TB elbow. the plastic pipe which leads to the intercooler is zip tied down. the main cat has been gutted. the 2 actuator rods seemed to be closed fully. no error codes from ecu. checked all relevent solinoids and vacuum hoses. replaced suspected TCA solinoid. vacuum and pressure tanks hold there pressures. no restrictions in the air box, has 3 extra intakes.

i can only put it down to 3 things
1. intake leak (what's left to check? Stock Intercooler?)
2. wastegate gets stuck open (checked actuator rods)
3. huge chunk of pre-cat material loose (replacing with HKS item)

is there something i'm missing. any sugestions?

 

did you remove your Y pipe coupler and very carefully inspect it? just checking the clamps w it in place doesn't rule it out. i found a Y pipe coupler w a 4 inch circumfrential crack around it that was impossible to detect until i removed it. boost and noise similar to yours...

after you have ruled it out... tap into the rear turbo w a pressure gauge and go for a drive. you should see 12 psi. then do it for the front. you should be able to zero in on which half of the system is leaking. or rule in the wastegate.

good luck,

howard coleman

 

thanks howard! yep i removed the coupler and inspected it.

i currently have a boost gauge hooked upto the y-pipe and it will ussually be 2psi higher then the manifold pressure (i guess that is to be expected with losses through the intake)