At higher RPMs under boost I hear a rush of air under the hood briefly, followed by a *really* loud whooshing sound. Doesn't seem right - am I venting boost? Is there a way to check without tearing apart the Y-pipe and crossover tube?

 

Get a boost gauge.

It's really not that much effort to check the IC and y-pipe couplers. You have to pull them off to check for leaks.

 

If it only happens when you shift, it's your blow off valve releasing the boost. That's supposed to happen. (based on the noise, you probably have an atmospheric BOV). The BOV will also engage when you rev and engage boost and then go back to idle... basically any time the turbos have shoved more air in than the engine needs or can handle.

A boost gauge would tell you if you are venting boost unnecessarily.
john

 

I've got a boost gauge - boost doesn't decrease when this happens, but it never climbs past a certain threshold.

If there is a leak somewhere, the piping is only able to handle up to a certain psi before the crack is forced open and the extra pressure is vented, right? If there was really a leak would boost spike and then *decrease* as the crack is opened? That's not what I'm seeing.

It doesn't happen when shifting, it's happening under acceleration. The pedal is down, the boost is at a constant level but the "whoosing" sound grows increasingly louder.

 

Is your Fd an Auto or Manual Tranny? As the "venting sound" is occuring, does it diminish or completely stop when you accelerate?

 

OK its not your BOV releasing when it's supposed to. Though, you might have a BOV releasing prematurely if it's not a particularly well made model
-john

 

You also wanna let us know how much boost your getting?

 

It's a manual. The sound only continues as long as I'm accelerating. Once I let off the gas the whooshing stops.


I hadn't considered this - another possibility, but I've heard the BOV when I let off the gas - this whooshing is really loud.


Oh sorry. At best I'm getting 7 psi

 

You have a boost leak. Just check your couplers, it doesn't take that long. Loosen clamps and pull couplers and piping off. Carefully inspect the couplers by stretching them to make sure there are no leaks. Make sure you clamp them back on properly.

If you check all your couplers and remount them and you still have boost problems, come back and we'll go from there.

 

Sounds like a cracked IC coupling/pipe or Y-pipe coupling....or cracked cross-over tube. Or bad BOV. Check these parts very carefully.

 

It sounds like you just have a plain boost leak somewhere if your only getting 7 psi. Check all the couplers, and pipes.

 

check the silicon hose couplers. I had one that would expand and vent boost becase the hose clamp wasnt tight enough. Then check the big rubber pipes to the intercooler. One of mine just split this past summer. Didnt leak until about 4-5 PSI then it got really loud.

 

Thanks for all the help guys - I'm going to check out all the couplers and the crossover pipe.

 

Let us know what you find. Good Luck