i have the greddy type s bov and i been boosted about a month, my question is what would cause a bov to kinda cough instead of sound off, b4 i use to get a good pssssssssssT now i kinda get a cough if that makes sence? i also use to be able to build boost in neutral now i cant? not sure if thats involved or not but if it helps any i still hit 8 Psi so im guessing no boost leak??? but you guys are the pros let me know
joe

maybe a vac leak or if you build low boost it will flutter because it doesnt have enough boost to fully open .

After reading up more i believe what i am experiancing now is compressor surge, just before the bov sounds off i get the flutter (gobble) i tried loostening the bolt on top of the bov but all that did was make me loose boost pressure, with the bolt almost all the way out i couldnt boost past 4psi with it all the way in it went to 10psi, somewhere in the middle seems to be where it needs to be, if i look inside and rev the engine i can see the little actuator go up and not seal back down till the screw is half way in??? but either way all the way up or all the way down i still get the flutter, anybody have anyidea and whay did it start now, wasent there b4??
and how bad is compresson surge and what causes it? i will be searching more as im sure this will be responded to, i just dont wanna screw anything up
joe

two things to check. Might want to lube up the actual actuator arm that controlls the flapper going up and down. Had one that get stuck a little and just needed some lithium grease or wd-40 to get it back working ok.

Second thing you might want to check on the inside as far as the coughing noise is concerned is that the diaphram inside the BOV isnt ripped or torn.

compressor surge is pretty unmistakable, if you've heard it once and had it pointed out to you. might want to check with someone thats had a little more experience in person to check on that or search for a sound byte or something (google maybe?)




just some sugestions to try out

the more i looked into these great forums the more i figured i seriously doubt its compressor surge, i believe the issue im having is im running a greddy bov and im only running 5-8 psi so i dont think there is enough pressure for the bov to sound off right, i did the type-s mod and tookl the center spring out we will see what that does, but while i was driving home today after messing with it i noticed 2 things that concerned me, 1 is my fuel gauge seemed to stop working and is stuck in the 3/4 of a tank position??? factory gauge maybe i nocked something loose??? dont know (DSM) and the second thing which really concerned me it happened twice today, at a stop light i gunned it and everything was going good than all of a sudden loss of boost and bam kinda like an instant stop?? im sure this is not a good thing, also noticed when this happened the a/f gauge went to red but not sure if it was because i let off the gas? i hear no sound or indication of detonation, the main thing that concerns me is i have the fmu, turbo actuator, bov, boost gauge all tapped off the same source with 3 different t's, everything seems to be operating ok and things have been fine for a month now it all just kinda started today??? WTF??? any idea what the heck is wrong with my dsm?

The sudden loss of power and A/F guage going lean after boost sounds like fuel cut. Make sure your map sensor is reading the correct voltage and isnt seeing positive pressure. Make sure the voltage clamp, missing link whatever your using isnt defective.

If your using Voltage clamp, run a wire from the wire to the inside of your car using an electrical meter and make sure it dosent go into positive pressure (anything above 4.7v I believe?)

if your using missing link make sure filter is clean and all that good stuff.

As for the fuel gauge, hmm... sounds like a totally different wire unless you tapped the wrong wire for your voltage clamp maybe...?

well after performing the bov mod for the type s it fixed the gobble problem so it wasent compressor surge now i got my loud psssst back with now flutter. as for the fuel gauge i dont know whats up with that cause i wasent messing around near it??? its just stuck at 3/4 of a tank? cant remember if our gauge goes down when you shut the car off or not, might be ok just loosing my mind, and as for the fuel cut ill have to watch it next time, but i believe the lean reading was because when it happened i let off the gas? it almost felt like a misfire but i logged it and got no code? thanx for the help,

That is compressor surge that you're hearing..

You have too many vacuum robbing devices on a tee... No matter what you adjust your BOV to, you will still have this because there isn't enough vacuum to pull the valve open and leave enough pressure to keep it closed under boost... I'd strongly advise putting your FMU on it's own VAC source, or T off of the brake booster.. The only thing I'd share with the BOV is the boost gauge...

For a good clip of what compressor surge sounds like, watch "The Fast And The Furious", when the Supra rounds the corner to catch up with the Charger just before they drag race... That little flutter sounds kinda cool, but can do serious damage to fins at high boost... Considering that Supra was probably running some heavy boost, that only happens at low pressure, he'd need a SSQV to solve this problem..

He's right, you have too many vac dependant devices on one line. Your FMU needs its own line. Take the egr line off and use that if you need to. Remove cruise (if you have it). Do what you gotta do but make sure the FMU has a dedicated vac line. That's much more important than how a BOV sounds.

i did re run my own independant line for the fmu and now have the bov and boost gauge off the same line. however it was all due to the bov being to powerful for the amount of boost, when i modified the bov and took the spring out it now sounds off as it should, this was all b4 running new lines so thank god but the sound i was hearing was not compressor surge, but thanx to everyone who responded
joe