Not to freak you out or anything but that's what my stock turbo sounded like before the shaft snapped in half. I thought it was like a belt slipping or something.
low boost
i have a 2012 sti. so i recently installed forged pistons added a downpipe and went stage 2 ots with some lc table adjustments for parrallel fuel rail mod. overall the car runs fine but i have been underboosting quite a bit especially in 1-3 gears. when i was stage 1 i never had a problem hitting peak boost, not that this would mean anything. i have heard the 3.30 tunes commonly experience this so stayed 3.10. the issue is near peak boost i start to hear a sound that almost sounds like a belt squeal. i have pressure checked the intake with soapy water, removed and reinstalled the intercooler, and inspected the bpv. none of which seem to show any signs of leaks. if i run in s mode i dont hear anything out of the ordinary. it only comes up in s# and when full throttle. i am thinking it possibly is the bpv leaking but i am unsure. target boost is 19psi and i typically only see 15-16psi. the most i ever saw was 6th gear at 18psi. no knock and doesnt seem like anything is running bad. this may just be due to the downpipe and the stage 2 tune but the sound tells me something is awry. so in closing is there anything else to check? the stock bpv doesnt look very servicable/adjustable
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i would assume the noise would have been from the shaft allowing the wheels to contact the housings? as the turbo and engine rpm changed did the frequency vary? mine doesnt sound rpm/frequency dependant its kind of the same tone any time it does it. i did a hard pull 6th on the highway on my way to work this morning and got 18.8psi and no noise. later i did one in 3rd and then it did it. if the rate of accel is causing enough of a pressure drop through the throttle body im thinking the bpv may be opening slightly? has anyone experienced this happening before?
i would assume the noise would have been from the shaft allowing the wheels to contact the housings? as the turbo and engine rpm changed did the frequency vary? mine doesnt sound rpm/frequency dependant its kind of the same tone any time it does it. i did a hard pull 6th on the highway on my way to work this morning and got 18.8psi and no noise. later i did one in 3rd and then it did it. if the rate of accel is causing enough of a pressure drop through the throttle body im thinking the bpv may be opening slightly? has anyone experienced this happening before?
It's funny you mention that because the turbo I put in after the stock one let go had the problem with the bearing getting so worn that the compressor wheel would come in contact with the housing. It almost sounded like it would slightly scrape every couple seconds. When you shut the engine off and the wheel was still rotating you could hear it the best. This happened until one day it got so bad that a large chunk of compressor wheel embedded itself into the housing and put a hairline fracture in it. Needless to say it wasn't rebuildable.
Also if you datalog you can look at wastegate duty cycle and target boost for each gear because there is a perameter that changes target boost by gear and maybe see if it's different.
still looking for some info on past experience with stock bpv leaks. i am at wgdc high limit most of the time in boost for the default tune. leaking air back to the intake through the bpv would do that. i am not near target boost (due to wgdc at upper limit). also i dont want to run more wgdc unless i know for certain there is no other problem so i dont risk overspooling the turbo. if i dont need to drop 300 bucks on a aftermarket bpv id rather not but if the stock one just isnt doing its job then its necessary.
an update for topic completeness. tested the bpv today. when pressured at the entry and the diaphram, it held over 20psi(didnt go past this). when only the entry was pressurized it held 7psi. this would infer i would need to drop 7psi off nominal boost through the throttle body and manifold, which i doubt is happening. case in point bpv seems good. added 5% wgdc and pressures are closer to target in 1-3 gears. thoughts are that downpipe with factory cat back may be enough restriction to cause the need for more wgdc.
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