flutter noise when shifting

[drethib]

when driving moderatly hard on the throttle i get this fluttering noise for 1-2 seconds when i either shift or let of the gas immediatley. wheres this noise coming from?

 

[ilco187]

check the vacuum hose at the bov that goes to the intake, also how crushed is the bov.

 

[craziloki]

also see if your plugs are fouled out...

 

[brian9397gsx]

sounds like your bov is not opening like said before check your hose if that is good may be time for a new bov

 

[zrb16]

when my car made that sound, it was because my intercooler piping got disconnected... do you have a boost gauge? if so, is it showing boost?

 

[STEVEn95tsi]

Sounds like compressor surge...Thats air being blown back into the turbo because it cant get out of the intercooler piping...Check the vacuum hose running to your blow off valve...Make sure your BOV is adjusted correctly if its an aftermarket one...

 

[goodhart]

Sounds like compressor surge...Thats air being blown back into the turbo because it cant get out of the intercooler piping...Check the vacuum hose running to your blow off valve...Make sure your BOV is adjusted correctly if its an aftermarket one...

I guarantee its not compressor surge with a 14b. You are confusing compressor surge and BOV flutter. I would check vacuum lines, adjust your BOV, or if you are still using the stock unit, look at "crushing" it to hold more boost. I'm sure there is more things you could do also, I just can't think of any off the top of my head.

This is the best explanation of compressor surge I have heard yet:

Real compressor surge happens during spoolup/high boost, not when you let off of the gas. The surge noise in that video is caused by the BOV not letting all the air out in 1 smooth blow. Too tight of a BOV opening and closing over and over might not be the best thing for the turbo, if the air is actually backing up that far, but it isn't real compressor surge and the kind that ported/anit-surge compressor covers are for. People call this noise BOV surge/flutter or "internet surge" because most people on the internet don't know what real compressor surge actually is.



Compressor surge happens when the turbo is flowing A LOT of air and the motor can't actually ingest all that air. A turbo makes boost inside the compressor housing, it isn't like a roots blower/positive displacement blower that works by stacking air in the intake manifold. When air starts stacking up on a turbo car and gets stacked all the way back to the compressor housing, then surge happens. The stacked air starts stopping the spinning compressor wheel or trys to turn it backwards. When you try to stop a compressor wheel going 80,000RPMs, bad things happen.



Compressor surge is common on 2.0l motors with the 61mm turbos. The 2.0l spools the turbo to high boost levels too fast and makes more air than the motor can take in. You can try to get rid of surge by going to a larger exhaust housing/wheel, to make the turbo spool up slower. You can get bigger cams, bigger intake manifold, port the head, to try to be able to take in more air. You can goto a bigger displacement motor that can take in more air each stroke.



A ported shroud/anti-surge cover has passage ways for the backing up air to come back out the front of compressor housing and into your intake pipe to try to avoid reverse flow pressure waves from causing surge.



Basically you can't have your cake and eat it too. If you spool a big turbo too fast you get surge.

Here is a good video of compressor surge: True Turbo Compressor Surge - Car Videos on StreetFire

And here is mistaken "compressor surge"
YouTube - SR20DET Compressor Surge


Hope I helped.

 

[Blak Pearl]

I agree with goodhart..check or adjust your bov

 

[drethib]

bypass valve has been crushed and the hose coming off of it is sealed tight.

 

[Dert]

I guarantee its not compressor surge with a 14b

Why wouldnt that be compressor surge just because its a 14B? The sound he described is the same as the video. Hell My T25 can make it sound sound like the video if I turn adjust my bov too tight, you can hear it right through the intake and out the filter, isn't that compressor surge? I think so my friend...and if a T25 can have compressor surge sure as sh*t a 14B can too

also the synapse video is actualy a video of turbo stall which is when boost pressures are elevated and imbalance of pressures occurs between the turbine side and compressor side, and when the forces arn't strong enough to drive the compressor side adequately, the turbo stalls out making a chirping sound, it happens alot with diesel trucks

 

[goodhart]

Hell My T25 can make it sound sound like the video if I turn adjust my bov too tight, you can hear it right through the intake and out the filter, isn't that compressor surge?[/B] I think so my friend...and if a T25 can have compressor surge sure as sh*t a 14B can too

No, compressor surge is experienced during spoolup, during acceleration of the turbo, not when you let off the gas. I'm not saying a 14b can't develop compressor surge, I'm saying there is a 99.9999999% chance that it won't I was gauranteeing him that with a 14b and his level of mods, what he was getting was not compressor surge. Read through ecoli's description of real compressor surge again.

also the synapse video is actualy a video of turbo stall which is when boost pressures are elevated and imbalance of pressures occurs between the turbine side and compressor side, and when the forces arn't strong enough to drive the compressor side adequately, the turbo stalls out making a chirping sound, it happens alot with diesel trucks

they are basically the same thing.

 

[drethib]

No, compressor surge is experienced during spoolup, during acceleration of the turbo, not when you let off the gas. I'm not saying a 14b can't develop compressor surge, I'm saying there is a 99.9999999% chance that it won't I was gauranteeing him that with a 14b and his level of mods, what he was getting was not compressor surge. Read through ecoli's description of real compressor surge again.





they are basically the same thing.

still experiencing the flutter. I replaced the bypass valve with another stock one uncrushed. Could the clutch or wastegate acuator be the culprit? I am have shifting trouble and I know the acuator needs to be replaced with a stiffer one since it's been opening to early