I just upgraded my BOV yesterday, I used to have a tiny one from siliconeintakes.com. It was a small 1.25 tube T'd off of my intercooler pipe between throttle body and intercooler. I was getting a lot of flutter and it didn't seem like it was venting enough. If I let off the throttle gradually, then I would get a smooth woosh sound, but all the way off it was fluttering.

I swapped it out for a 50mm one from EMUSA yesterday (2"). EMUSA 50mm BOV V-Band Black I didn't buy it from there though. It's still not a smooth woosh, but at least now I'm confident that it is plenty big enough. I do notice that I have way more vacuum on decell, 20" vs 16", most likely that my old valve was leaking vacuum past the piston.

What's a normal sound? I realise that they all sound different but is any flutter normal? Maybe I need to get a softer spring in this thing or something. I have 4mm vaccum line from the intake manifold to a vacuum block, where my bov, fuel pressure regulator, hobbs, and boost gauge are all also plumbed in.

 

If you are still getting turbo bark then its either not opening enough or not opening quick enough, which has to do with the spring. Since its a knock off chinese one finding a spring could be tricky. I had this issue with my ebay bov, it wouldnt open at all. All you have to do it trim back the coils on the spring until it works like it should. It sounds like yours is close to working so only trim like 1\4 or 1/2 a loop at a time and just fine tune it. Its a bitch taking it in and out but its better to have it right.

 

Here is a quick vid of my BOV when I first got my set up running. Its a 50mm race port.

 

Ufff^

 

Yup, I'm pretty sure mine is not opening yet. I need to cut the spring.

That's what I hope mine will sound like.

 

Update: Spring has been cut down little by little and now it is working perfectly.