issue with twin turbo gtb bg5

[moneymaker9210]

IM only getting 5 psi on primary its getting very frustrating! it use to be 10 and i know it should be bewteen 12-14 so something is up! if anyone can help id be soooo grateful

[Thomistopheles]

Could be a bad wastegate actuator or the WG flapper may be stuck open/not closing all the way. Check for leaks between the turbo outlet and intercooler as well.

[moneymaker9210]

any way to check the Watergate actuator? theres no leaks in any of the piping i had leak test done and all piping is new

[hansvonaxion]

Check for codes.
Check all your vacuum lines are plumbed correctly and make sure the pills are in there.
Clean your vacuum lines.

Also check out UKlegacy because the UK guys mostly deal with the twin turbos and are more likely to be able to help, the twin turbo is a rare breed in the US.

[moneymaker9210]

theres no codes and all lines are correct and i have both pill plus i have posted on uk just trying to get insight

[hansvonaxion]

Just saw you have about 5 threads going there!

Sorry, can't help you anymore than those guys.

[moneymaker9210]

well its been a case of sorting out different issues each time

[hansvonaxion]

Well you could try asking Rueben, I think he's pretty knowledgeable (mind you he'll probably just tell you to go single turbo lol)

Also might pay to give a brief timeline of what happened and what you've tried (though I'm sure you're sick of writing about it), easier to diagnose with all the details.

[moneymaker9210]

Car has never gotten close to where the primary should be aka 12-14 psi its only ever been to 10, and just recently it went down to 5psi and wont go higher even with dissconecting line 23 which when u do that your suppose to get really high boost but i do not. I have new maf, oxy sensor, air filter, cat back, oil just changed and new spark plugs gapped correctly and have both pills correct. havent replaced knock sensor or map sensor yet as i havent got any codes! its a 96 gtb bg5 auto

[Thomistopheles]

Pull your downpipe off and see if the wastegate flapper is open or damaged. If it is closed and looks good, use an air compressor to send pressurized air into the vacuum port of the wastegate. There's a spring in the wastegate actuator that is supposed to hold it closed, and when it sees positive pressure it should open up the flapper to allow exhaust gasses to bypass the turbine wheel, thus preventing it from overboosting. If part of the assembly is seized, or the flapper is damaged, or it's stuck open... the turbo won't spin up enough to make 12psi.

There's always the possibility that the turbo is toast, but if the compressor and turbine wheels look good, then I doubt it.

[mike-tracy]

My BPV was leaking quite badly and wasn't letting me boost past 5psi for a while either. I found a primary BPV off of an ej20r and the working one fixed my problem.

[moneymaker9210]

mike what do u mean bpv sorry dont know that one? and i did pull off down pipe to test to see if turbo would boost more having the cat off thinking it could be clogged and nothing changed same psi! and i did put a compressor to the acuator it worked fine. so either turbo is going and have to get new one or missed something. everything has been replaced pretty much and all new silicone lines and pills are there as mentioned before so im at a loss. one thing to add though im also on uklegacy anyways i have a pressurized fuel tank which apparently that might be where some of my boost is going to if thats possible? theres a one way valve on the line of the carbon canister and you shouldnt be able to blow both ways through it which i can which means that valve is gone i just dont know what that valve is called or if i can even get it at dealership. plus i took off the one hose near throttle body which i was told to take off to stop system from pressurizing which worked. any thoughts

[mike-tracy]

^^ the bpv is the factory "blow off valve." your car should have two of them, but I would try borrowing a known good primary turbo one first. I don't have a TT so I can't be much help as to where it's located on your vehicle, unfortunately.

[moneymaker9210]

oh gotcha yea i swapped mine over to other side cause to see if one was bad or not and there both good cause i got same boost level. well a turbo for my car is about 70 bucks through the forum by people breaking there cars for parts.