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Discussion Starter · #1 ·
I got my Forge twin piston bov from GS about a month ago and it came with the yellow spring. The problem was that it fluttered every time I let off boost. So i ordered the spring tuning kit from forge and it now releases as a very brief flutter then a whoosh sound. I put the green spring in with out the shims. Does this sound normal?
 

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I find that the lightest spring will do the job in almost every case. There should be equal pressures on each side, all the spring does is help push against the initial pressure inequalities when building boost.
 

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That is the nature of the twin piston valve. The Yellow spring is best for that valve on T5 cars. Running the green spring will lead to premature failure of the helper spring since it is free to flutter more with the main valve being partially open at idle. (Thats I do not sell the spring kits.)
 

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Discussion Starter · #4 ·
So is the fluttering im hearing is the valve and not compressor surge because when I had the yellow spring in the valve I never got a whoosh sound it was all fluttering.
 

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Any flutter is bad flutter.

Are you sure your vaccum source is good?
 

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Discussion Starter · #6 ·
They should be. Not to long ago a replaced the vac lines with silicone lines and I sprayed throttle cleaner on them all to check for leaks and I found none.
 

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I've had the same issue with my forge twin piston BOV.
 

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Discussion Starter · #8 ·
I just rechecked the line to the bov from the throttle body and their are no leaks. I also took the valve apart and rechecked the internals and grease and everything is ok their. So right now everything is right the way it should. be. I still am running just the green spring with no spacers and their is a quick flutter then whoosh sound. Nick I took out the yellow spring because I never got the whoosh sound it always was really nasty fluttering everytime.
 

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the flutter sound is most likely compressor surge. i got alot with my turbo XS bov. but now that im running the HKS black ed. bov i get no compressor surge. with the push style bov (uses vac on one side to pull the plunger and boost on the other to push) you will get that surge until you find the right spring combination for your boost level. if u have a few spare springs find the softest one and cut a coil off, run it see if there is change, if not cut another off. and so on.;-)
 

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AZR do you get a bit of flutter with the HKS? I have the same one and it flutters under lighter boost...
 
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