valve flutter or compressor surge

[Lurker]

I have a MAFT setup in blow-through fashion.
I got tired of the whistling noise on my 1G BOV ( at part throttle), so I bought a used TurboXS TypeH BOV.

I now have some sort of pigeon-like sound when I let off lightly.
I talked to TurboXS customer service, and they say this is valve flutter and not compressor surge.

In my case, after I heard the "pigeon" sound from letting off slightly, I can continue with letting off completely, and it will blow-off properly.

Is it true that the sound can't be compressor surge, because if it is compressor surge then my turbo is already stop spinning from surging backpressure. Therefore, I won't be able to blow-off when I let-off completely.

Please help me out how to differentiate between the two.
So, valve flutter is harmless then ?

Thanks in advance.

 

[doug]

I have a similar sound with my TurboXS H34 whenever I use more than 4 washers. I have been thinking it was compressor surge, but now I'm not so sure. A buddy of mine gets a slightly different sound on his car, but he has a HKS SSQ. He's also been told that his is BOV flutter. Mine sounds a little more metallic and echoey (that's the technical term) than his, but could be because they're different BOVs. So, to sum up, I don't know if yours is surge or not. But BOV flutter is supposed to be relatively benign.

 

[Satori]

My Greddy Type-S does that too. As long as it blows off properly when going from WOT to closed under boost you shouldn't worry too much.