OK I am a little confused now. If someone could clarify. I have read that flutter is not good for the turbo because it causes the turbo to spin backwards and you should change to a VTO if this is happening. On the flip side, all of the Evo/RA forums say you need a recirculating BOV because it reduces hp and is not healthy for our cars. Any one know when to use a VTO on our car. I get flutter all the time especially when releasing the throttle at low RPM. Any insight?

 

I'm no specialist, but if you BOV flutters is probable because of one of the followings:
- Your tune achieve a pressure higher than the one you BPV is set for, so it keeps opening.
- Your BPV pressure setting is too low (which is actually similar to the first possibility).
- The mechanism in your BPV might be misfunctionnal or worn out.

As for your question about venting to atmosphere instead of recirculating, the principle is quite simple. The air the your turbo compresses into your intake is metered. The amount of air forced in is used to compute the amount of fuel that should be injected. When your BPV opens, the air is sent back to your turbo inlet and bypasses the MAF, thus the computer does not read any "new air" coming in. The problem with BOV (vent to atmosphere) combined with our setup is that, the computer is not aware the some air has been taken off. Some when your turbo starts spooling and air is metered by the MAF, the ECU reads it as air being suck by your engine and you'll run rich.

From my understanding, this should not bad in itself, it's just that you'll get poor performance and fuel economy. If you're hear, I assume you are craving for performance.

 

It should not flutter. Is it while you are on te throttle or when you lift the throttle?

Causes would be boost leak, cracked vac line, or a vac line popped off. You will not lose hp if you vent to atmosphere. Are you sure it's installed properl? Not on backwards?

 

Only when I lift off the throttle. It is more noticable at lower RPM with a heavy load, such as if I let off the throttle in 5th gear at 2000 RPMs. I have watched videos online and mine doesnt appear to be as loud as most. A very similar video I found is at http://www.*******.com/watch?v=TGMCWy7Czxs. Just put the youtube stuff in front. So are you saying you dont have not even a little bit of this sound when letting off the throttle?

Update:
I have not really driven my car since adding the exhaust on and I went to try and record the sound. I noticed the sound is not there anymore or at least I can no longer duplicate the sound like I used to. I am guess the restricted exhaust had something to do with it.

 

are you driving and you shift into 6th or 5th and you have low rpms and then you let go of the gas thats when?

 

OK so I drove the RA all day yesterday instead of the Fusion. I definately have flutter while driving in 5th gear at 1600-1900 RPM and releasing the throttle. Should I even worry about that?

 

Na, don't worry about it. If you do then just purchase an adjustable bov. OR, dont floor it in 5th gear while you are at 2k rpm. Simple as that.

 

the typical rule of thumb is that if the noise happens when you let off the pedal, especially at low rpms and light boost, it's bpv flutter and not much you can do other than changing out the bpv, its not considered very detrimental to the operation of the vehicle. on the other hand, if the noise happens on-throttle especially under heavy boost conditions, you are likely experiencing compressor surge and the issue should be addressed immediately

 

I had exactly this when i used to have my Type RS (now sold... cuz i find it a little annoying...)

but i really dun think its a problem.. that doesnt sound like compressor surge..
Correct me if im wrong

(im using Evo X BPV now, thinkinf of trying Synapse soon)

 

after talking to many bov company's trying to figure the flutter problem i had was that it's not normal and shouldn't be driven like that.

 

was just watching clips on Youtube and listen to all the flutter...
http://www.youtube.com/watch?v=rSPXmhBHZJk

BOV flutter seems to be caused by stiffs spring (which is required to hold high boost, like cars in that video)

 

Funny, I ran 30 psi on my 6262 and didn't have to run a tight spring. I actually cut a coil off of my spring in my tial (I'm going to order a softer one, i was just experimenting) It fixed any surge that was there before.

In actuality a properly designed BOV will just need minor spring pressure, as there is an equal amount pushing the on the top and the bottom of the valve under power. You really only need enough spring to keep it closed at idle. That's why TiAl rates their springs in vacuum.