Boost falling off (checked everything)

[KAOTIC95gst]

ok, so i finally got to put on the buschur fmic kit and crank the new vtrim up to 20 psi. the problem is that it spools to 20 sits there till about 5800 then boost starts to die off slowly to about 13-14 psi by 7400. I did a boost leak test when I put on the fmic and it held 20 psi for a good amount of time. The turbo is new, but while everything was out for the boost leak test I felt for shaft play and there was none. It has a mbc from dejon tool so I dont think thats the problem either. I was maybe thinkin it was because the wastegate is routed back into the o2 housing??? any advice or suggestions would be awsome. thanks -Jordan

 

[Zmann42087]

the problem is that it spools to 20 sits there till about 5800 then boost starts to die off slowly to about 13-14 psi by 7400.

Wait.... Are saying you rev to 7400RPM?!?

 

[KAOTIC95gst]

why you cant? no i dont go to 7400 all the time because it doesnt do too much whith out cams. i am trying to say why is my boost dropping off as the rpms climb.

 

[CanadianTSi]

Internal wastegate is blowing open, try to shorten the arm on the actuator to make it hold the flapper closed tigther.

 

[94Jettameowpsst]

I think you awnsered your question when you said theres no point to rev that high w/ out cams.....when i had my boost set to 17 it would fall off to 13-14 by 6k (auto cams). But it is a possibility that your flapper is blowin open

 

[KAOTIC95gst]

i dont have an internal flapper to blow open. tial 38mm external

 

[94Jettameowpsst]

Oh, CanadianTSi Internal wastegate is blowing open, try to shorten the arm on the actuator to make it hold the flapper closed tigther. thought you did. Yea, its prolly just your cams

 

[CanadianTSi]

It can't be the cams...

If the boost is falling off this means that the motor is flowing more air than the turbo can...unless you have some other problem(boost leak,exhaust leak, etc.)

 

[JoeWagon]

Yea, its prolly just your cams

Are you suggesting that his cams are a boost leak? Cams can contribute to boost dropping off, but only because the engine can consume more air with them. What we are determining is if a 2.0/cams can take a v trim to 13psi at 7400rpm. Doesn't sound right to me.

 

[KAOTIC95gst]

i dont have a boost leak i have checked it twice. the only other thing is that there is a small exhaust leak from the wastgate gasket but i dont see how that would make my boost drop off

 

[CanadianTSi]

i dont have a boost leak i have checked it twice. the only other thing is that there is a small exhaust leak from the wastgate gasket but i dont see how that would make my boost drop off

Because exhaust gasses are going out the leak and not through the turbo therefore it can't spin fast enough to maintain the desired boost level.

 

[KAOTIC95gst]

ok so this is the manifold/wastegate setup i have
http://www.dnperformance.com/images/extkit_05.jpg
http://www.dnperformance.com/images/dnp32_2.JPG

the exhaust leak is at the base of the wastegate against the manifold, so when the Wastegate opens I didn't think that it mattered because the exhaust would be forced through the wastegate and not the leaking gasket. I just thought that it would hurt performance before full boost (slow spool up) and not after full boost (dieing off).
BTW thanks for all the help, greatly appreciated