Intake noise (grinding-woosh?)

I'm not really sure how to describe this noise but I think everyone with an intake will know what I'm talking about. It's the noise you get when you give it some gas and immediately let off. It almost sounds like a grinding/coughing noise. (I'm certain it's not anything grinding though.)

 

When I first installed an intake about 3 years ago I noticed it. I ended up switching intakes thinking it was something about the K&N. I still had the same issue with the Cobb, and the AEM and KSTech though less noticeable with the AEM/KSTech.

 

After about a year of it, I made a major tuning change and zero'd all wastegate duty at and under 300 requested torque so I could set I-Mode up to run wgdc pressure only. Immediately noticed that noise was essentially gone.

 

This weekend, I installed a 3port BCS, retuned the 310, 320 and 330 requested torque columns for WGDC and left everything from 300 and under set to a max of 0%. Well that noise is back and I assume it has something to do with the way the 3port works vs the stock BCS.

 

Unfortunately at the same time I also installed a GFB BOV, so it's possible it has something to do with this. While I'm fairly certain this noise isn't a problem, I'd really like to better understand what the cause is. I'm debating swapping the stock BPV back on to rule that out but think I would be wasting my time as I'm fairly certain this noise is more wastegate related.

 

So assuming it is the 3port BCS, is there anything I can do other than swapping it back out for the stock setup or putting the stock intake back on?

In case anyone cares, my assumption that it was the 3port BCS was pretty much totally wrong. It seems to be the GFB blow-off valve. If I loosen the spring tension considerably most of that noise goes away, unfortunately it then idles very poorly (if not recirculated). If I add some tension, the noise gets progressively worse as I do. I suspect it's due to the piston in the BOV not releasing the boost fast enough, so the air flows back into the turbo causing the coughing noise. I still get a bit of this with the stock BPV, but a barely audible amount.

the answers to your questions are here:

http://legacygt.com/forums/showthread.php/technical-info-bov-bpv-set-up-and-operation-170987.html

Thanks man.. I actually read that whole thread but didn't see any definitive answers to the specific noise I was hearing or the cause/solution.

 

The GFB spring tension appears to be both too loose (poor idle) and too tight (horrible noise). I guess the idea is to find a middle ground that you can accept or go back to the stock BPV, which is what I ended up doing.

In that link, there is mention of wastgate chatter. Is that something that you would hear at idle ?

^Should not.

 

The sound at shift is not bad. You actually want the BPV fighting the WG until the last possible moment. If running a FMIC and venting to atmosphere a lighter spring is available to help idle. But I do not recommend venting more than 50%.

I noticed this in my buddy's gt after he installed a K&N. I don't hear it in my car though.