High boost flutter/surge
 

Hey everyone, this is my first post because I can usually find all the info I need by looking through previous threads and all. So last night I went for a 3rd gear pull and right at about 5000 rpm at 17 psi I started hearing surging or flutter. Not sure which one. I looked through as many forums as I could find but it seemed like they were all just people having a flutter at low boost or when they let off the throttle. I couldn't find anyone who had fluttering/surging at high boost at high rpm. Could it be my BPV/BOV going out or something worse? (I have a TurboXS hybrid) If there is a thread out there that talks about high boost surge that I missed please let me know but I looked for a few hours and couldn't find any. Thanks! (Also in those threads people said high boost flutter/surge is bad and should be addressed ASAP but didnt say what could be causing it or how it may be fixed)

Can you post a data log replicating the condition?

Okay, i took these last night when it was happening. Thanks

I don't see anything out of the ordinary...
What is your setup? Did you ask Stratified about it?

I haven't yet but they will probably take a week or so to reply and if something is wrong I want to fix it as soon as i can. The weather also recently got colder, could that have anything to do with it?

I also have a hybrid BPV and one time I got flutter when i forgot to reconnect the recirculation hose to the top of the BOV. Could be something as simple as that, did you check your connections?

I just checked it and it seems fine

When is the last time your BPV was serviced? I'm wondering if the valve is opening and bleeding off boost. Maybe weak or broken spring? Damaged seal?

I'll check it tomorrow, I'll also put on the stock one and see if it makes a difference

Definitely check that, 90% sure its a bpv related problem

can your noise be the one of a leak instead ? if it doesn't work by fixing the bpv, i would do a piping pressure test...

Surging happen at spool if the intake restriction is too high or if discharge to the engine offer too much restriction or both added together. It can also happen if the BPV don't open when you let off gaz.
In any case, the wheel shaft is moving side to side trying to let the pressure escape and this make a lot of load on the thrust bearing and everything untill the wheel touch the case at high speed and something break.

I'm not sure if fluter can be part of the surge or if it is just when the BOV is pulsating open/close between too much pressure and not enough against the spring....The last case would be almost just a sound.

All that to say none of them should happen at wot at 5000rpm so i think it is something else like a leak.

Okay, thanks everyone. Also something I hadn't mentioned, my tune has a crackle tune on it and around the same time it stopped crackling by a noticeable amount, about 80% . Could it be that something in my exhaust malfunctioned like the wastegate or maybe I destroyed one of my cats and doesnt flow as well and the back pressure is making the hot side of the turbo flutter?

Too much pops and bangs will kill cats. You still haven't listed any of your mods...all we know is that you have a TurboXS hybrid valve.

Sorry. I'm new to this forum, I'll make it when I can but for now it's just short ram intake with turbo inlet hose, muffler delete, and bov and tune on 93

If my cats did get killed would it cause this?

UPDATE: Switched to stock BPV, no change

Got this video, not as loud on camera but still audible

really looks like a leak

Just did Boost leak test and put on stock inlet pipe on. No difference.

My other question, if my cats blew out could it cause something like this?

Thanks All

UPDATE: Got 2 CEL codes, p0421 and c1938, fuel trims now also jump up to 16.4%

C1938 is a steering wheel position or angle position code. Not related to your problem

P0421 is the low cat temp code we see when running catless without a raised bung on a catless downpipe. It means your primary cat has probably failed.

Okay thanks, so this is a dumb question but that's the second cat right?

No, that's the first cat built into your OEM downpipe. You can delete the second cat by replacing it with a race pipe and not throw any code.

Something is wrong with the first cat or sensor. You could just have a dirty or bad sensor.

Okay, I'll check the sensor first, thanks!

Could be the sensor for the code but it won't help for the noise you heard while a leaking cat would be heard at all time...

How did you process for the boost leak test ? Did you replace the intake by a tube connected to an air pressure source and check for leaks under 15-20psi ?

Yes, didn't hear any leaks. The pressure did drop after a couple minutes but I hear that's normal

Hey guys so i was at a stoplight and decided to give it a little WOT because its been a while and it started going then started fluttering THEN lost power. i noticed AFR's went really low. I've been really busy in school so i haven't been able to check the O2 sensor or downpipe yet. i got it captured on a log. Please let me know what you guys think. Do i need to bite the bullet and take off the downpipe or could it be something else? maybe a EGR valve stuck open? Intercooler with a leak? the boost leak tests ive been doing have been inconclusive. i pressure it up at the turbo at 20 psi and hear no leaks and the pressure slowly lets out. quickly at first then much slower, maybe from 20 to 10 psi in 30 sec then a minute to about 2-3 psi where it stays. is this normal? if not how can i find the leak if it makes no noise (couldn't feel it either) thank you to everyone who has helped this far.

Could it be my wastegate actuator?

Add smoke to the inlet before pressurizing.

Would a vape work? I personally dont smoke but I could get one of my Subaru Wrx buddies to vape in it lol

That might work. The problem with Vape is that it's water vapor, not smoke. By the time it reaches the leak...it will have precipitated or dissolved into the air.

Okay, I'll try to get a friend over that smokes. I did find out just now that the wastegate actuator IS faulty so I'll change that in a few days when it comes in then do the smoke test.

Keep us updated so everyone can know what the fix turns out to be. Maybe the rubber/synthetic diaphragm in the actuator has a leak. That would explain the symptoms. I hope it is that simple.

The basic part is cheap, usually under $50, although you can spend more for OEM and up to $200 on fancy billet ones or ones with special adjustment capabilities. Just be sure to match the arm adjustment length to be the same as your old one and then it is pretty much plug and play.

Will do, right now I'm in the process of tearing out the whole turbo, downpipe etc, I'm going to inspect each part because if it's not the wastegate then I dont want to have to go back there again

Not a bad idea to make sure that the wastegate, itself, opens and closes freely, and that the hoses are not leaking. A good time to test the actuator, arm and wastegate motion it is with the turbo off a on the workbench and applying air pressure to the diaphragm.

Be sure not to apply more that 18-20 psi, or you may actually blow a good diaphragm.

I don't recall the pressure at which the arm starts to move, maybe 10-12 psi (depending on spring pre-set) and then the arm travel increases with increase in pressure until it reaches maximum extension.

when i tested a k04 it was around 12 but i didn'T use 100% certified testing instruments....lol

the gate itself is suppose to remain very hard to move by hand so it help to put some pressure in it to install the rod on the flapper arm...

check for housing crack, wheel damages and bearing play but there should be minimal play. You can probably find online by a search what is an acceptable play...It will be slightly different if you still have oil in the journal or if it get dry.

Okay thanks! I know I have some play when I would wiggle the compressor wheel around but its doesnt seem like alot

btw if you see baked oil on the downpipe side, it may be because it smoke...

Was it ever asked what your wastegate preload is?
Or perhaps it's not adjustable. IDK.

No, it's the stock wastegate. Also it ran fine for a few months after getting it tuned then one day it started happening

Check the hot side coupler if you have tmic. Hot side piping couplers if fmic. Would double check intake couplers and piping. Pinhole leaks in bov hoses. Check for shaft play in the turbo and boost solenoid, map/boost sensor hoses on on the intake mani(dont think that would cause noise).

I took my 2nd dat off and found my first cat inside of it in peices. I think I found my problem