I've got an ls vtec on 14 psi, once it builds 14 psi it slowly falls off. it will build 14psi quickly, but as soon as it hits 14, it will kind of slowly lose boost. Any body else dealt with this? Is it just a boost leak?, or maybe a wastegate or boost controller issue?

 

Leaky wastegate?

 

That's what I think it might be. it's an emusa wastegate (cheap) with a 7psi spring, and a turbonetics boost controller.

 

What size turbo
what manifold
wastegate placement?
etc

 

emusa .55 trim turbo
xs power mini ram manifold
emusa wastegate mounted right on the front of the manifold.... all cheap stuff I know, which I'm sure is the issue. I'll post a pic in a couple hrs

 

.55 trim means nothing. unless you have wheel measurements we can't tell you anything. for all we know that turbo is so small it can't maintain full pressure across the operational rpm range. or the turbo has fallen apart or is on it's way to falling apart.

cheap *** parts definitely don't help.

 

What type of clamps are you using on your couplers? T-bolt clamps? Your best bet is to do a boost leak test - you can build a boost leak tester very inexpensively... This will pinpoint any points where you could be losing boost pressure. There are also a few companies that sell them.

 

Yea you can make one for under 10 dollars using PVC pieces and a quick disconnect air fitting. remember you have to make a block off out of PVC for the throttle body end of the piping, just slide it in and clamp it down just like the piping at the turbo outlet.

you could make one that goes on the compressor inlet, that way you can see if the compressor housing is leaking. it's not uncommon for Chinese turbos to have poor casting quality, they can develop cracks, even break in half. often the Chinese turbos don't come with an o-ring for the sealing surface between the compressor cover and backplate.

chinachargers aren't known for high precision, quality machine work either. I've seen knockoff turbos where the mating surfaces I talk about above are warped and won't seal, o-ring or not.

I've seen people do leak tests with the piping connected to the throt body and they don't know why the system doesn't hold pressure lol.

it won't take much pressure, maybe 20-25psi at most. in order to spot leaks you can put water in a spray bottle with a few drops of dish soap. a leak will show up as bubbles at a connection. the best tool is a smoke tester but few people and shops have them.

it could be something as simple as a worn/torn/pinched coupler either from misalignment or the clamp cutting the coupler.

or you could have a pinhole on the front of the intercooler, it's not uncommon for one well placed rock or piece of debris to puncture an air passage so spray it liberally as well.

what blow off valve are you using? the knockoffs are known for shitty diaphragms that pinch, tear, wear through or just leak in general. also the seal in the bov body where the shaft passes through is known to leak on certain Chinese bovs. also a few China bovs just leak out of the box no matter what.

it could also be the gasket or o-ring (if there is one) between the bov and the mating surface of the flange. sometimes it can also be poor valve seal between the valve and the bov body where the two meet at the flange. also if the valve is using the wrong springs or isn't adjusted properly that can also cause leaks.

check any vacuum lines as well, sometimes with heat they get brittle and crack or split. I would recommend replacing any rubber lines with quality silicone hose. it's much more supple and heat resistant. it wouldn't take too much effort considering you're going through the whole system during the leak test.

 

holy f*ck...... thanks for the input. I'm sure this cheapo Chinese turbo and wastegate are the issue. the bov is a turbo xs. lol it wasnt cheap, and its pretty new. I've got a Borg Warner turbo and a turbosmart wastegate collecting dust that needs a good manifold to be attached to. Anybody have a nice b series manifold?!?

 

Don't guess, DIAGNOSE. Do you a boost leak test ;-)

 

The turbo xs piston type bovs are notorious for leaking... a lot.

 

that's what bov I have^^