NZ951

If you plugged the venting port on the DV, you would hear a vastly different gurgling sound. I video recorded the stock bosch DV when I was tracking this issue down about 10 years ago, and recorded the valve bouncing (fluttering). And it sounded like what people want to call compressor surge. You can argue it happens concurrently, when the valve is not releasing the pressure it causes the compressor to stall, but the sound for me, was fromt he valve fluttering, not back pressure in the IC pipes stalling the compressor wheel. Regardless, the fix is the same, revisit your valve and make sure the vac line is pulling vac.

Thom

I use a Forge recirculating valve with a 15psi spring and I get the same "fluttering" noise under medium boost. Quiet under full boost/WOT (15psi).
Is it compressor surge?

Adonay

I am curious The replacement billet diverter valve i have worked with out vacume to it as well so how easy is it to get compressor surge. The cable had was broken off after closing the hood to many times on the cable "tight fit with the wrong angle" I noticed i had a vac leak but did not check the DV as it was dumping like it should. After a quick fix the swooooosh sound was a little louder .

Black51

When did you first notice this happening? Did you change something, add a mod, or did it just start coming on gradually?

Zeff

Noticed it with my stock DV about 2 months ago. Looked for one on ebay and it never shipped (had to dispute ect) got another one from a different seller and installed it a couple days before it snowed here. The weather just cleared up enough to drive the car.

I'll have to go through the vacuum hoses when I've got time. I had a 26/8 swap right before summer, I had new vacuum lines installed at the same time.

Black51

When you switched to the other DV, was there any difference at all?

hot-J

Your bov spring pressure should match your vaccum in hg.

Zeff

I didn't notice a difference.

Zeff

Can you elaborate? So I need a spring to match idle vacuum or off throttle vacuum?

Black51

I can't see just the DV being the culprit then. Unless, in the rare case you got a bad one. That aside, are you sure the clamps on the hose that feeds the DV are tight? I could see this being an issue on opening the DV's valve.

Zeff

Yeah, when I get a chance I'll go over the vacuum hoses. I pull 12-14hg when warm and 22-24hg on deceleration. I thought those were in the normal operational range.

running_cold924

this is interesting....ever since i swapped out my k26-8 for the new garrett i have now it has made the same sound as yours...looks lik I may need a better DV as well...

AScholtes

Mine idles at 16-17"

Zeff

I'll dig around and see if I can find anything. My car came from Greenville, we should meet up sometime.

AScholtes

Definitely, I actually work in Asheville. I havent taken mine out much as I need to do the belts and waterpump...I just need the time to do so.