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Car fluttering on shifts?

1K views 11 replies 8 participants last post by  ChaseGT 
#1 ·
Well I took my friend for a ride tonight, hes been into turbo imports for a long time and hes saying my BOV shouldnt sound like that, the sound I am hearign is surge.
My BOV sounds just like a miniature version of the 7 sec drag radial cars. He tells me it should be just one loud swoosh not a fluttering of air.
I could probably get a sound clip but I hope you guys understand what I mean.
The BOv is a TIAL 50mm
 
#3 ·
compressor surge does kind of have a "sh sh sh" flutter sound. Might want to check which spring is in the Tial BOV, may be too stiff. How much vac does your car make?
 
#5 ·
You have to be hearing the compressor surge. I run the same BOV and you can not mistake the sound it is a very loud unit. I had a slight problem when I first installed it. I pinched the o-ring that goes in the mounting flange and it was making it hard for the BOV to open as soon as it should. once I got that fixed everything is great.

Start the car open the hood give the car a little gas and if the BOV doesnt open alittle when vacumm hits than something is wrong. could also be the spring as mentioned above.

Also my fox runs around -18 vac, maybe you have a little leak unless you are running a different cam.
 
#8 ·
The BOV spring rating has nothing to do with the boost levels you are running, but rather are a measurement of vaccum requirements.

With 10-15in/hg at idle you should be running a -7 or -9 psi spring. It's either that, or chop the existing one down until you get the proper actuation at idle. By design, the BOV should have as little resistance as possible at idle while remaining fully closed.

That fluttering sounds is most likely compressor surge caused from the BOV failing to open properly. The same thing was happening to me until I hacked my BOV spring down. Again, get the correct spring or hack the current one down and report back.

- 22 and -23 in/Hg Pink -12 Psi (-24 in/Hg )
-18 and -21 in/Hg Un-painted -11 Psi (-22 in/Hg )
- 14 and -17 in/Hg White -9 Psi (-18 in/Hg )
-10 and -13 in/Hg Black -7 Psi (-14 in/Hg )
 
#10 · (Edited)
that IS compressor surge !!! something is not right with the bov !!! thats EXACTLY what my car sounded like with NO bov at all..


that didnt sound like a easy shift and it still did it??

IF it only does it on easy shifts the spring to too much. hard shifts pull more vac. mine did that at first until I got it "adjusted" correctly..
 
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