compressor surge, waste gate flutter, or what???
 

Hey guys, so I recently started noticing a flutter sound from my engine bay. It only happens during throttle lift at low boost levels, like around 1-8 psi. I've researched a ton and everyone is giving mixed info on what it could be. I didn't think it could be the waste gate since it doesn't occur under load and building up on boost. It only happens when I lift off the throttle. I tried a couple steady 3rd gear pulls all the way to 11psi and I get the the o'so good "pssshh" sound when I lift off, but at lower boost levels I get the flutter.

What I've done prior to hearing it: defi boost gauge install, and the solo instruction event. I also have to confess that I had a k&n typhoon sri without a tune during that event :~: (dumb move I know, but it's been on the car ever since I bought it) but I'm getting a stage 2 flash next week from kspeed I promise. But anyways, any ideas on what the sound could be? Stock BPV maybe?

My guess is it's just the BPV making a totally normal noise. Not quite enough boost for it to open all the way to vent, but enough that it bounces a few times.

There's probably nothing wrong, or perhaps there's just a leak in the by-pass hose or something that's making it louder (and would cause the car to run rich during shifts).

Have KSpeed check it out when you're there for the tune?

Thanks for the feedback Scott. I'm hoping it's nothing serious as well, just normal sounds. I read stuff about compressor surge and how it kills turbines and such and started getting paranoid about it. I looked over the t-section where I spliced the boost gauge hose and replaced my zip ties with actual house clamps that I can tighten, still has the flutter. I guess I'll just live with it for now until I come in at kspeed.

I think people used to say the K&N Typhoon is one of the few intakes that isn't very dangerous without a tune, if I remember correctly. Also, consider checking the preload on your WG in case it is WG flutter.

See the "Edit" info and image, here:

http://forums.nasioc.com/forums/showthread.php?t=425018

people on forums told me otherwise.. but i never blew up my car on the K&N intake ...

i have proof the Gorilla RS Intake actually does the opposite ... it makes the car run a touch richer than before for a short rpm band.

and now i'm getting OT, even for seccs standards

Thanks for the link Cody. I ruled out the wastegate when the flutter usually happens at throttle-lift. And from what I understand from reading online and hearing videos of wastegate flutter, it only happens during load and building up boost. Hopefully Kspeed will be able to tell me exactly what it is, and if it is the WG, then I'll be able to use that link as a guide.

As for the intake, I bought the car from CA with it on already. A day after I brought it over the hill to Reno, I threw a code for A/F too lean. The car ran fine still so I deleted the code to see if it'll come up again and babied the car keeping out of boost for a few days, and it never did (after the solo event, and many many power pulls). I'm guessing it was just the change in elevation, but I assume that the ecu adjusted itself the best it can since then.

Hmmm, it seems like WG flutter usually occurs at partial throttle with jived with your low boost comment, but not sure if it should be ocurring on throttle lift...that seems to point to the bypass valve, vacuum lines, or turbo, if I had to guess.