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Discussion Starter #1
So I have a invidia cattless downpipe and a friend of mine has a turbo XS catless and when boost starts i hear a sound that sounds like an exhaust leak... My buddy told me it is a pre boost flutter and i was jus wondering if anyone else has noticed or heard this... I was told it only happens on cattless
 

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you can hear the turbo spool.. not a flutter flutter is bad.. but with the DP you should be hearing the turbo spool up no though.. I have the same sound, a spool not a flutter..
 

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It could be normal or not. The wastegate makes sounds also when opening and closing but without much more description we can't really tell. However, you should have gotten a protune with the DP or an AP with an OTS tune so you/we or your tuner can at least monitor to see if its running properly then make a proper diagnosis.

Let us know and good luck
 

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We will need to know if you are spiking (boost) knocking (DAM) at the very least to see if you are at least "ok"
 

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Yes sorry I forgot to ask if you have at least an AP... A DP without one could cause major problems..
 

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Discussion Starter #6
Yeah guys i have an ap and i am running rallitek stage 2 94..... No boost spike and no knock that i kno of.... the noise like i said saounds like an exhaust leak and its only for the first few seconds of spool then it stops... its really weird
 

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I've talked with people at COBB and Jeff Perrin about this numerous times. The consensus is that it is compressor surge
 

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Yeah guys i have an ap and i am running rallitek stage 2 94..... No boost spike and no knock that i kno of.... the noise like i said saounds like an exhaust leak and its only for the first few seconds of spool then it stops... its really weird
Like a very soft traffic officer whistle, then might be compressor surge, someone said it might sound different though. Also see if it happens under WOT, if not, then I would be more inclined to assume it was preliminary compressor surge also.
Another thing to try would be to put on a CAI or the afta-maf hose and see if this alleviates the noise. These noises come predominantly from the intake tract though. Confirm this is the case then you should be ok.
The surge could be caused by the freer flowing DP so its certainly viable.
 

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Discussion Starter #9
Yeah its a soft traffic officer whistle like u said touge i guess it could be surge but i have the GFB Hybrid and this is also weird but my car runs better vta then 50 50 and i keep the screw level with the top of the bov which is recommended and i have a blitz induction cover instead of an intake... so do u think i should loosen the bov more? when i do it seems like the bov is staying open to long between shifts
 

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Discussion Starter #10
I've talked with people at COBB and Jeff Perrin about this numerous times. The consensus is that it is compressor surge
Did you ever get the problem to fix? Was it Surge?
 

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Yeah its a soft traffic officer whistle like u said touge i guess it could be surge but i have the GFB Hybrid and this is also weird but my car runs better vta then 50 50 and i keep the screw level with the top of the bov which is recommended and i have a blitz induction cover instead of an intake... so do u think i should loosen the bov more? when i do it seems like the bov is staying open to long between shifts
If it runs fine I wouldn't touch anything. If it is what you said (traffic officer whistle), the noise might also go away if you replace the intake tube going into the air box (afta-maf tube). The ribbed rubber design of the stock one is known to make that whistling noise.

Good luck.
BTW my car whistled like that until I got a CAI. (When I was running Perrin tune stage 1)
 

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Discussion Starter #12
Well i have the afta maf hose and the induction cover pretty much is an itake i think it may e somethin to do with my uppipe
 

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Here's the email I got from Jeff on this. I'm not a mechanic and this is my first turbo so I'm pretty much going on what he's saying here. The sound and the conditions he describes are exactly what I'm experiencing, I'm not sure if it's the same for you. Sorry I wish I had more to add but FWIW:

To make sure its not knock, watch the dynamic advance during the runs. It should be 3-5 degrees. If its 1 or lower, then its knock. But what you are hearing most likely is SURGE. EVERYONE (drives me nuts actually) thinks its wastegate flutter. What this actually is, is compressor surge, but not like a BOV compressor surge. This type of surge is when the turbo pushed more air than the engine can consume. This sound occures around 3000RPM and under heavy load, then goes away around 3400 or so. If this is what you are experiencing, don't worry, its normal. If you got a custom tune where they run 20+PSI it really does it at low RPM. But swap out the turbo and it will never do it because they are either laggier, or have a freer flowing exhaust housing. For sure do not tighten up the wastegate actuator!


JEFF PERRIN
RESEARCH AND DEVELOPMENT
OFFICE 503-693-1702-ext 105
FAX 503-693-1782
AIM ALTAPERRIN
[email protected]
WWW.PERRINPERFORMANCE.COM
 
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