Boost trouble over 10 psi
 

Background: TB changed about 2 weeks ago... While I had the car apart I changed my intake mani gasket. While doing that I broke the coolant flange on the back of the head. I tried to jerry rig it, and took it for a test drive and noticed I lost a bit of power and the car made a wierd noise, but only over 10 psi. My first guess was a boost leak. However my jerry rigging didn't work, and I had a nasty coolant leak. So she sat waiting for more parts.

I just replaced the coolant flange and let the car warm up to operating temp, and no more leak. I torqued the intake mani down a little tighter thinking that maybe the gasket is leaking a little boost at higher psi. I went for a test drive down the street, but it's still having the problem. I can't get a video of it, because it only happens under load when I'm making boost, so I have to be driving. I tried to make it do it a few times to get a good idea of what is happening, but it really kills the power and the noise it pretty awful. It almost sounds like it's coming from the right side, like it's being forced back out of the filter.

I've double checked all my lines, and everything it still connected and no obvious damage. The only thing I can think of is possibly my DV has gone bad (it's either a Forge or APR DV, not stock). Does anyone else have any suggestions, or know of a way to check the DV? I really don't want to replace it and find out it's not the issue. If all else fails, I'll try to see if one of my neighbors has a compressor and I'll give the tennis ball trick a try. The thing that gets me is the car still runs great up to 10 psi. If I had an obivous leak, I don't think I would make any boost at all.

Any ideas are welcome and greatly appreciated... TIA

well remove your dv and suck on the small vacuum line. you should hear it pop when you stop, and feel the diaphram moving on the underside. under a load though, your dv is closed, so that wouldnt affect your boosting. maybe your coolant squirted on something important? while the engine is on, the cooling system is pressurized. this is a weird one, im trying to think about everything that would cause this. maybe your n75 valve took a shi*? one way to know for sure if its something in your vacuum system is to pull the vac line going to your waste gate and drive it. you should peak at like 25 psi like that, but dont drive it like that more than a few seconds haha or youll go into limp mode

Do the free stuff first :) See if you can find a boost leak. Try and describe the noise...does it sound like a hair drier blowing, a whining, whistling etc...

I'll drive it again tomorrow and try to get a better idea of the sound. It's hard to tell, between having the window down, and my test pipe/ cat back. There is just all around all sorts of noise, then this happens. Maybe I'll zip tie my camera under the hood and take it for a spin... haha. You never know, I might get lucky.

Colony, I'll try to disconnect the wastegate line and see if the boost changes any, as well as mess around with the DV.

Update: I can hear the DV "accuating" when I apply vacuum to the line (i.e. I suck really hard), so I think it's ok. I disconnected the vac line from the wastegate and went for a spin. It still won't boost past 10 psi, making a funny noise, kinda like a hair dryer, but not really. The only thing different about the vac line disconnected was after about a second of making the noise, there would be a loud pop, a drastic loss in power, and psi would drop really low. Needless to say, it scared the crap out of me, and the vac line is back on again.

Guess the next step is to get a tennis ball...