I just installed my TurboXS RFL BOV, I'm boosting about 6psi and when the BOV goes off, it flutters for a moment, then blows off nice and crisp.

The fluttering sounds cool in my opinion and I don't mind it, however some people say that that itself is compressor surge, and others disagree.

Is fluttering bad?

many people say it is...but i have seen MANY very high HP large turbo grand nationals running around with no BOV at all...fluttering thier ass off and notghing ever going bad on the turbo...so who knows?? maybe just a turbo urban legend...

bov fluttering is diff than compressor surge.. ^^ your talking about compressor surge. i think bov fluttering is normal, as long as you'r not getting compressor surge

Not having a BOV on ANY turbocharged car is bad...at least street-wise. with the throttle butterfly closed, the boosted air has nowhere to go when it hits it, except backwards, back to the turbo compressor. this violently causes the compressor to spin the opposite way. that isnt good. your BOV is fluttering at first because you arent boosting enough to open it all the way sufficiently. open it up, take a washer or two out, or cut the spring inside it a tad. it will help.

1999 Black C5
1997 Silver RS
Wiseco 8.8:1 Pistons(back to low compression!)
Eagle Rods
T3/T4 Turbo
Custom FMIC
Greddy Exhaust
390's
Most current 1/8th mile time: 8.3@90mph 2.015 60'(Nitto Drag radials, i suck)

why is it bad? i don't see why the wheel spinning backwards is bad....not like its a gear drive being reversed fast...just a liquid bearing...:shrug

well it causes the turbine to rattle side to side

Originally posted by 97eclipseRS
well it causes the turbine to rattle side to side

and it takes a little longer to spool up, but the rattling is more important of a problem.

Worse case scenario: it's bad because it could cause the wheel shaft to move or "float," which will allow the compressor wheel to scrape against the housing, building up metal debris and wheel floating. The turbo will spool very very slow when that happens.:-)

Flutter is not bad.

Compressor surge is bad.

Fluttering doesn't hurt a damn thing though. All it is, is your BOV slightly opening and closing quickly since you didn't let off with enough boost and your BOV wasn't forced open enough to make that normal louder forceful sound. To me, it makes sense that your BOV will only make enough noise to flutter relative to a small amount of boost being evacuated, rather than the alternative, not open at all (if your spring is set too tightly). If that would happen, then you might get a little <5psi compressor surge. Probably not a big deal, but at the same time, it's not for me.

sorry to steal the thread, but you mentioned how tight the spring is compressed? how tight should you bolt down the bov. i have the HKS generic (STAR kit).

i think you start the car and loosen it all the way, then tighten it until it doesnt leak anymore at idle. i may be completely wrong though, i am still learning.

Ryan, when you said the bov futters, does this occur when you are shifting when not in full boost, or does this occur when you are shifting in normal driving (low boost)? If the fluttering is present in the first situation, then it's an indication that the bov is set too hard (resulting in compressor surge); if it's the latter, then it's normal to hear the flutter.

Originally posted by Diceman19
i think you start the car and loosen it all the way, then tighten it until it doesnt leak anymore at idle. i may be completely wrong though, i am still learning.

heh..i duno, i just tightened it as much as i could.

Hey how did you get that turbo xs bov to fit? Did you have to buy a new flange or does it come with a adapter that you can order. Because what this shop was telling me was, I had to weld it on there but that would hit my cf hood.

I have custom piping, so my BOV aims downward, no hood clearance issues. And it fits on sotck HRC piping perfectly....no welding.

BOV flutter is exactly whats been said. The turbo isn't spinning very fast (relatively) at our low boost levels like stage 1 and 2. It simply isn't forcing enough air to "blow off" right after you let off the gas. That's why it flutters first, and immediately after, completely opens after the turbo has built up a little more pressure in the intake. Also, compressor surge isn't as bad as everyone makes it out to be. Race cars dont even use blow off valves (real race cars). Compressor surge should be avoided, but your going to get a little no matter what, while your boost levels are low and the BOV can't instantly open.


1996 Eclipse RS / 5-Speed / Aerogear Body / Coated in Magnetic Red Metallic rev.2 / T3 Turbo Intercooled @ 8 psi / More at http://home.insightbb.com/~mgalyan/
Mark Galyan - Indianapolis, Indiana

Fluttering can potentially cause compressor surge, but on a properly made bov it will not. The reason your bov is fluttering Ryan is because it's not mabe for that low boost level. Thier isn't enough air to open the bov all the way.

My bov sounds like someone stepping on a cat when it goes off, I got used to it. Your not going to surge at 6 psi with a decent bov, don't sweat it.