Odd "flutter" sound from turbo on boost

[Spoolin92GSX]

I'll try to explain this the best I can, if anyone wants a video I'll see if I can capture the sound.. I've noticed off and on lately, that _sometimes_ when I boost I get what I can only describe as a fluttering sound coming from (I think) my turbo. The sound starts as soon as boost starts to build past 0, and continues until I shift/blow off. The flutter also speeds up (and gets a little louder) as the pressure climbs. It's not linked to engine RPM or turbo RPM though, as I've tested that by feathering the throttle to hold boost around 10psi instead of my full 15psi. As I keep accelerating, while maintaining the lower 10psi, the fluttering sound stays the same speed/volume until I let off or stand on it. I don't think it's the BOV leaking, since it starts AS SOON as boost starts to build, and boost holds perfectly steady. Also, this doesn't happen all the time, just once in a while - usually if it does it once, it will do it every time I boost until I park somewhere and come back later, and then may or may not keep making the sound. Any ideas? Thanks in advance!

 

[kenamond]

My stock T25 started to fail by making very bizarre sounds as I built boost. My guess is that it was the compressor wheel hitting the housing. Have you checked shaft play? If the turbo is going, you can rebuild it. If it goes, it might cost a bit more to fix. Depends whether you want to upgrade your turbo or not, I guess .

I know that a faulty BOV can cause flutter. If your BOV doesn't open, the stagnation of airflow within the compressor when you shut the throttle and back up the airflow causes stall of the compressor blades and applies abnormally-high pressure on the center section (high pressure loading on the compressor wheel, up the shaft, and into the bearings in the center section). This can wear out your bearings prematurely. But if you hear this sound while building boost, not when you lift off the throttle, then the BOV wouldn't be expected to open.

Not sure what the symptom would be if the BOV opened when it wasn't supposed to. You could do a BLT and see if the BOV pops open at too low of pressure.

 

[Spoolin92GSX]

That's kinda what I was afraid of, even though the previous owner 'said' the turbo was rebuilt recently.. I'm planning on poking around my car tomorrow anyway, so I'll check for shaft play and *try* to do a BLT (no air compressor) Thanks for the reply, cross your fingers for me haha.

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[Funfettie]

My 68hta made a fluttering sound too. Accept mine happened when i let off the throttle. It would build boost, and I could back the throttle off, and it would flutter. Id bet its the BOV, sounds like its not holding the boost pressure. Make sure your boost lines are connected to the top of the BOV. Also check shaft play. check up and down, side to side, and end to end! best of luck!
~Funfettie~

 

[forcefed86]

Probably compressor surge.

Sound like this...?

S14 SR20DET Compressor Surge - YouTube

Do you have your BOV hooked up properly? Many topics on this just do a search.

 

[Spoolin92GSX]

No, it's the exact opposite of compressor surge.. Flutter is a bad word to describe it, but the only way I can think of to explain the sound. I have a Greddy type S BOV and yes it's hooked up right. The sound only happens while _on_ throttle _building_ boost, everything works fine when I let off. I'll check for shaft play and leaks, and update.

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[romeen]

I've had a situation that sounded exactly like what you're describing. It ended up being a good size crack in my UICP at one of the welds. If it's only doing it under boost then a leak would be my first guess. Even if it ends up being something else, a boost leak tester will be your friend as far as keeping your car running strong. Ask Santa for a new air compressor. If no go, I've heard of guys using the air at service stations to do a BLT.

 

[Spoolin92GSX]

Yeah I have the tester made already, but all I have to hook to it is a bike pump.. Tried that already HAH! I'm sure I have at least one friend with a compressor, just haven't figured out who that is yet.. Hmm..

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[kenamond]

Buy a small compressed air tank from Walmart for $20. You need to BLT every so often anyway. Fill the tank at a gas station. That's what I use.

 

[DSMnOOb00]

Probably compressor surge.

Sound like this...?

S14 SR20DET Compressor Surge - YouTube

Do you have your BOV hooked up properly? Many topics on this just do a search.

My car sounds exacly like this car in the video, the BOV will flutter when I let go of the gas. I have a greddy bov, I bought it used. I'm planning on buying a NRG BOV at the moment

 

[turboglenn]

your profile says your on a stock turbo is that true/ (should fill it out up to date makes it easy to help ya) but it does sound like compressor surge, does it go away if you floor it?

 

[Spoolin92GSX]

your profile says your on a stock turbo is that true/ (should fill it out up to date makes it easy to help ya) but it does sound like compressor surge, does it go away if you floor it?

Yes I'm on stock 14b turbo, no it doesn't go away at WOT it actually gets worse. The sound only happens when I'm on the throttle, as soon as I let off my BOV does its job with zero compressor surge.

My car sounds exacly like this car in the video, the BOV will flutter when I let go of the gas. I have a greddy bov, I bought it used. I'm planning on buying a NRG BOV at the moment

Well before you trash the Greddy, check the tension screw on top (3mm allen key) and loosen it up as far as you can so it's just snugged down on the spring plate. If you still get compressor surge you can remove the _small_ spring inside the BOV and keep the larger one in. I did that and it actually helped with drivability too

 

[slow4g6392tsi]

Like this right?
<iframe width="560" height="315" src="http://www.youtube.com/embed/g6XdOZiznos" frameborder="0" allowfullscreen></iframe>

 

[Spoolin92GSX]

WOAH. Haha well mine doesn't shake like that, and the sound is a lot... More frequent? Than that. Like if you say that's ft--ft--ft--ft mine is ftftftft.. Sorry that's the best way I can explain it typing and mine doesn't go away after a certain RPM/boost pressure - it'll go all the way from 2500rpm/1psi to 6000-7000rpm/15psi if I let it. I'll try to get a video of it tomorrow, IF it decides to act up.

 

[awd4u]

it's not fuel cut is it? it's possible.

 

[turboglenn]

slow4g what turbo is that and what in your setup is contributing to it, that's the worst surge i've ever heard and the most i've seen EVER under WOT loading WOW!!!!!!!!!!!

 

[DSMnOOb00]

Yes I'm on stock 14b turbo, no it doesn't go away at WOT it actually gets worse. The sound only happens when I'm on the throttle, as soon as I let off my BOV does its job with zero compressor surge.



Well before you trash the Greddy, check the tension screw on top (3mm allen key) and loosen it up as far as you can so it's just snugged down on the spring plate. If you still get compressor surge you can remove the _small_ spring inside the BOV and keep the larger one in. I did that and it actually helped with drivability too

Ill try that tomorrow morning thx

it's not fuel cut is it? it's possible.

if it was fuel cut you would know it, fuel cut feels like you just hit a brick wall or your engine just blow up! trust me!

 

[92nolatist]

I had almost the same exact thing happen to me but I have ALOT more mods than you, so its probably not what I was experiencing but it sounds like the same damn thing thought. As I built boost, it would start to....for lack of a better word...flutter. Really bad too, between 10 and 30lbs and even past that, YIKES!! Turns out that with my external wastegate and mbc hooked up together, the mbc was disrupting the boost control of the external gate; so I took off the mbc and viola! boosting was smooth as glass. A nice solid 20lbs of boost on a 14lb wastegate spring.

Heres a thread I started about it but no one knew what the hell I was talking about . Maybe it will help you understand a little more about whats going on so we can help you figure it out:

http://www.dsmtuners.com/forums/bolt-tech/414005-dodge-garage-bov-not-holding-high-boost.html

 

[Spoolin92GSX]

I had almost the same exact thing happen to me but I have ALOT more mods than you, so its probably not what I was experiencing but it sounds like the same damn thing thought. As I built boost, it would start to....for lack of a better word...flutter. Really bad too, between 10 and 30lbs and even past that, YIKES!! Turns out that with my external wastegate and mbc hooked up together, the mbc was disrupting the boost control of the external gate; so I took off the mbc and viola! boosting was smooth as glass. A nice solid 20lbs of boost on a 14lb wastegate spring.

Heres a thread I started about it but no one knew what the hell I was talking about . Maybe it will help you understand a little more about whats going on so we can help you figure it out:

http://www.dsmtuners.com/forums/bolt-tech/414005-dodge-garage-bov-not-holding-high-boost.html

This made the most sense of anything posted! "Cheap MBC" I'm using a $45 inline controller. Maybe it is/was our bleed valves making noise!

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[92nolatist]

It definitely could be, who knows? Give it a whirl and get back to us!

 

[DSMnOOb00]

opened up the BOV and the diaphragm had a rip in it, I'm going to order a NGR diaphragm replacement asap

 

[92nolatist]

Good find

 

[Spoolin92GSX]

Figured I should mark this resolved in case anyone was following/curious/interested - turned out it was an exhaust leak between the manifold and turbine housing! New OEM MLS gasket and no noise, go figure!

 

[Artago]

It was an exhauat leak? I thought you said it was bov flutter under part throttle. I have the same problem but running a 1g bov. Sorry to bring up an old thread...

 

[Spoolin92GSX]

Nope, because I was using the word "flutter" to describe the sound, everyone instantly said BOV. The sound would happen at (almost) any amount of throttle, as long as it was enough to build at least 1psi of boost. As far as I can tell, it was an exhaust leak small enough that it wouldn't leak on a non-turbo vehicle, but with the added backpressure of a turbo it would be pushed open.