So I recently got my setup completely installed without any real issues (other than a pre-turbo exhaust leak currently) and have an extremely rough tune with Megasquirt. My question is, as of right now, everytime I let off the throttle I hear a fluttering noise from the turbo. Now, unfortunately, I'm assuming this is compressor surge, which is a bad thing. But, I can't figure out why as I have a BOV on the cold side of my intercooler piping.

Here is the BOV I am using, seems like a quality piece and I currently have the spring tensioned so it doesn't leak at idle, but is very close (IE, spring is not pre-tensioned at all)

http://cgi.ebay.com/ebaymotors/AUDI-...3357QQtcZphoto


The turbo itself is from a WRX and AFAIK it is good, doesn't smoke or burn oil, and little to zero shaft play.

Is this sound normal, or is there something I am doing wrong?

 

The BOV isn't opening. The sound is annoying, but you won't hurt your turbo.

 

Take a picture for us.
Are you using a large enough vacuum line?
Is the vacuum line kinked or crushed somewhere?
Where are you tapping for the vacuum line?

 

Also make sure the piston is not stuck. I used to have this problem with an old FM BOV when it was not lubed regularly.

 

what did you use to lube the piston? best thing I've used so far is a little Mobil1. I've also tried motorcycle chain lube (which I thought would have been perfect but sucked), spray lithium, and wd-40. Still, if it's over 1 month since I've cleaned and lubed it, the piston won't budge until I give it a good run to 12+ psi first, and then it works fine.

 

I've tried Mobile1,grease and graphite. Mobile1 one worked the best. I just lubed it up everything I changed my oil and it worked like a charm.

 

We use Mobile Mobilith SHC 220 in our valves. Its a fully synthetic bearing grease.

Fluttering can be caused by insufficient sealing in the top (vacuum) side of the valve. Basically if the top portion of the valve leaks to much vacuum will not keep the piston lifted during shifts, so the piston will drop - boost will lift it briefly until the pressure drops enough for the piston to lower - boost builds again and lifts the piston... so on and so on. This happens very rapidly and makes a fluttering sound.

OR the valve isn't opening and you are getting surge.

 

I use hydaulic fluid to lube my BOV.

I was told to use hydaulic fluid,sewing machine oil or any 0 viscosity oil.

 

My Forge BOV on my Saab Aero was the same way. I think it has something to do with the weather. After a good run into 10-17lb department and it was fine.....