SSpeed Posted September 11, 2015 Share Posted September 11, 2015 This problem has developed in the last couple days. Under boost, in any gear, at 5500 rpm I get what almost sounds like a rattlesnake, air whistling mix. I pulled the turbo to intercooler hose and pressure tested from the intercooler in to the motor up to 30 psi. The only place it was leaking was at the tester, but on the intercooler itself. I felt there and there is a flattish spot, maybe that's my noise? Other thoughts I had were the header or one of the uppipe gaskets, but it doesn't sound like that. The other weird thing is its at 5500rpm no matter what gear I'm in, if it were boost related I would think the rpm would move around according to gear? Ideas? Link to comment Share on other sites More sharing options...
SSpeed Posted September 11, 2015 Author Share Posted September 11, 2015 Video is shaky as hell as I was just holding the phone and flooring it, but here it is, right at 5500-redline. https://www.youtube.com/watch?v=lL7bGoyC2Hs Link to comment Share on other sites More sharing options...
SSpeed Posted September 12, 2015 Author Share Posted September 12, 2015 Another video with a better capture. https://youtu.be/lHYJWbmxG3g You hear it at the top of the powerband in this clip. It's always around 5500rpm, but varies slightly between gears and seems boost related. So far I've: 1) Tested everything in the post-turbo intake to 25+psi. 2) Run 5500rpm on the highway on no boost to rule out drivetrain/clutch/bearing issues 3) Cleaned and regreased BPV 4) Revved the car in neutral to 6000 to see if the same noise was there The noise is subtle and you probably wouldn't notice if I didn't point it out. It's like a vibrating rattlesnake. I guess next I: 1) Try to look at all exhaust connections 2) Log and see what airflow does right as the noise happens. For those conspiracy theorists I included the most recent dyno, look at the boost flutter right at 5500rpm in my dyno, The initial flutter is actually upwards. I wasn't hearing the noise at the time of the dyno. Thinking out loud and would like input, if it were an exhaust leak, isn't pre-turbo exhaust pressure highest right before the turbo spools? I would assume if it were an exhaust leak I'd hear it early on and it would decrease (or at least change in pitch) as boost built? Link to comment Share on other sites More sharing options...
SSpeed Posted September 26, 2015 Author Share Posted September 26, 2015 Hopefully this thread isn't annoying, I'm talking to myself. I have a new theory to the noise, please check my logic. On both 91 oct and e85 dynos, at 5500rpm I show boost abruptly rise, abruptly drop, then rise again and stabilize (the variation is less than half a psi, but it's pronounced). Power at the same time slowly drops and recovers once boost stabilizes. The fact that boost first goes up and power drops seems to indicate it's an obstruction in the airpath and not a boost leak. I pressure tested to 30psi with no leaks or noise, but what's different with a boost test? The throttle plate is closed, even though some air still gets by. The tumbler valves are closed and not seeing near the airflow as full power. http://www.wrxtuners.com/forums/attachment.php?attachmentid=1055&stc=1&d=1137623197 I let someone else drive the car the other day and I hardly heard the noise sitting in the passenger seat, in the driver's seat it's much louder. So what's on the driver's side? Throttle body, driver's side tumbler valves, BOV, fuel pressure regulator, brake booster. I took the BOV apart and regreased it,there's not much to that. FPR and brake booster wouldn't seem to make that noise. So I'm left with the throttle plate or tumbler valves wobbling in the airstream at full boost. The throttle seems right, so the tumbler valves seem like the obvious problem. A motor is supposed to keep them open once the car is warmed up, but I wonder what is really happening. Worst case scenario a plate screw is working its way out and that will be bad if it gets ingested. Question: is there any way I can lock the TGVs and throttle plate open with Romraider or any other software while I boost test? I still won't have the same volume of airflow, but maybe I can hear the noise if indeed a TGV is fluttering. Link to comment Share on other sites More sharing options...
SSpeed Posted May 20, 2016 Author Share Posted May 20, 2016 Well, I think I probably figured this noise out. I had some time to kill and decided to remove the entire exhaust, header to muffler. 1) A header nut was missing. What's worse is the rest were loose. With hindsight I should have re-torqued after a heat cycle, but it worries me. You can see leakage on both header gaskets. I don't know if I should just trust re-torqueing after a heat cycle, or look for some better locking nuts? http://i85.photobucket.com/albums/k62/dil222/missingnut.jpg http://i85.photobucket.com/albums/k62/dil222/leakage.jpg Would something like this be better? http://www.treadstoneperformance.com/product.phtml?p=67998&cat_key=305&prodname=Hex+Crimplock+Nuts 2) My wastegate flapper has shifted ever so slightly. I've been suspecting this because I have a late spool when it's hot. Surprisingly it's early when it's cold. I tapped it with hammer and it's covered again, but suffice it to say I don't trust it staying in place. Heck, at this point the turbo is a few bolts from coming off, maybe I should go EWG. http://i85.photobucket.com/albums/k62/dil222/wastegate.jpg 3) Turbine wheel is in decent shape, but does it look like the ends of some of the blades are bent? Hard to tell from the pic. http://i85.photobucket.com/albums/k62/dil222/wheel.jpg 4) Grimmspeed uppipe's flex section is questionable. Flex section is intact, but you can see that the cap can be pulled off the flex section at least 1/4 of an inch, I don't think that's right? http://i85.photobucket.com/albums/k62/dil222/flexsection_comparison.jpg Link to comment Share on other sites More sharing options...
quick4dr Posted May 20, 2016 Share Posted May 20, 2016 you answered your own question. Just go EWG one of my most favorite choices that I have done. Grimmspeed up with EWG, Tial 38mm Vent to air originally on BNR 16g, now a 1.5xtr (3inx10cm) You can route it back in, but depending on how you daily drive and what kind of boost you desire, the volume of vent to air is only brutal when you hammer it. just before I found my crack in my Perrin headers few years back, I had a ticking noise that I discovered not only was a flange nut missing, for no explained reason the stud was gone. threads on head were perfect nothing stripped. (never figured it out) new stud, new nut, torqued down headers on reinstall, about 50 miles later, re torqued. id say it was maybe 1500-2k later my Perrin split open at the merge. Link to comment Share on other sites More sharing options...
SSpeed Posted May 20, 2016 Author Share Posted May 20, 2016 I'm considering it. My 16g is constantly in boost though, I think the noise would be obscene. I guess I could do something like this: http://www.lindseyracing.com/LR/Porsche//LRA-951-WGM.html http://www.lindseyracing.com/mm5/graphics/00000001/LRA-951-WGM-1d.jpg Link to comment Share on other sites More sharing options...
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