won't boost over 7 psi,no boost leaks,bad turbo?

rab · 03-19-2007, 07:17 PM

my turbo don't boost over 7 psi.
im running a .60/.63 t3 from a nissan 300ZX,before i ran a .42/.48 t3 with no problems.
i did a boost leak test and found a leaking comp housing gasket, fixed that redid a boost leak test and it
does not leak now.
im running a voodoo MBC and it working correctly, with the test i did, by pressurizing the system and watching the wastgate open, then adjusting the mbc and the gate open at a diffrent psi, so the mbc is good.

the turbo has none to little, in and out play and a little more up and down play but minamal.

how can i check if a turbo is bad???
also could i just keep the wastegate closed and go for a little run and see if it makes boost over 7psi,its not
really a good idea, but were should i go from here, any other ideas besides a bad turbo?
thanks

c4uldr0n · 03-19-2007, 07:22 PM

maybe the wastegate isn't making a good seal, and leaking there.

rab · 03-20-2007, 07:52 AM

im going to be doing some more testing today.
thanks

mitsured420 · 03-20-2007, 08:02 AM

Sounds like your waste gate is stuck or leaking,you can remove your control line but BE CAREFUL watch your boost and control your throttle.if it boosts up you got a problem with your mbc.if it stays the same theres a waste gate problem.

rab · 03-20-2007, 12:19 PM

so should i just pull the vac. line off the wastegate, so there is no line attached to the gate, or put a block off on there to do this test.

rab · 03-20-2007, 03:28 PM

well i pulled the wastegate line and just left it open to the atmosphere
, when thru a 1st and 2nd gear run and still got only 7psi,
then i went and pluged the line with a vacuum block(the wastegate actuator) and i
when for a nother run thru 1st and 2nd and in 2nd
i got about 9 or 10psi.
also this is on a internal wastegate.
thanks

rab · 03-20-2007, 09:52 PM

anyone else have some thoughts.
thanks

SleepingTsi94 · 03-20-2007, 09:55 PM

Check the pcv valve. Where I found my leak.

mitsured420 · 03-20-2007, 10:08 PM

how did it spool fast or slow?how old is the turbo?9psi full thottle?

rab · 03-21-2007, 08:51 AM

Quote:

Originally Posted by mitsured420

how did it spool fast or slow?how old is the turbo?9psi full thottle?

spooled fast , it's a older turbo but all the blades are in good condtion, and very minimal play in any direction, and my psi rates were full throttle.

deletrius · 03-21-2007, 08:59 AM

can you open it up and check the seals?

mitsured420 · 03-21-2007, 04:51 PM

Im thinking your turbine housings trashed, full throttle your boost should have gone through the roof!!if its an old turbo theres a good chance there are cracks in the turbine housing around the w/g to check pull the o2 housing and look in the top port in the turbo,there are no seal persay just a flapper held tight by the w/g actuator.pic is of a 16g but you get the idea,if the rest of the turbo is good you might find just the housing

SleepingTsi94 · 03-21-2007, 10:24 PM

Id check the pcv valve like I said. I couldnt get my car to go over 10psi and I have a ebc. Cranked it all way up and nothing. Changed pcv after doing a boost leak when seen it was going in the pcv and out the side. Back into the intake causing a big leak.

oldman · 03-21-2007, 11:10 PM

1. Boost leaks, how much pressure registered on the boost gauge during the test and how long did it hold?

2. Exhaust leaks before turbo, this includes cracked manifold and turbine housing.

3. An unsealed flapper or weak actuator being blown open by exhaust pressure.

4. Dying turbo.

rab · 03-22-2007, 10:34 AM

I do remember a slight crack by the wastegate hole on the exhuast housing.
I'm going to change the pvc also cause it pretty old and cheap,no matter what.
Also i can't remember my psi i held when preforming the boost leak test.
Thanks for all the help so far.

rab · 03-22-2007, 05:40 PM

Did not get a chance to work on it today.