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JDM '94 gen3 turbo
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Discussion Starter #1 (Edited)
My car sounds good while boosting, but after I let off the throttle, I hear a kind of a vibrate-ey noise that sounds.. wrong? I don't know if I'm crazy, but I thought that previously my car made a blowoff valve kind of "pssh" noise when letting off the throttle, but I know the stock car has a BPV not a BOV. I was under the impression that a stock BPV doesn't make BOV noises. (I've looked for a BOV in my engine bay, but haven't found anything, and I can see that my BPV is still in the engine bay and attached to everything.)

I don't think it made this noise before I tried my couple of fixes (ECU caps, frankenstein vaccum tube removal, and faulty wiring fix.)
In fact, I feel like I remember hearing this exact noise when my car previously went on the fritz (Full explanation of what was happening here.) I feel like its made this noise ever since.

Was curious if anyone could describe the expected sound of these cars when letting off the throttle during boost. If there even is a distinct sound. I've read that if your BPV or BOV doesn't work properly it can be very bad for the car as then extra pressure will force air the wrong way back through the turbo. I'm kind of afraid of this being the problem, but I don't know what that would sound like though.

These cars won't build boost in neutral right? Mine doesn't at least. I want to find the source of the noise, but don't know a good way to figuring out what it is if I can only recreate it while car is moving. Anyone have any ideas for how I can find the source of this noise?

Car is a jdm '94 (gen3) turbo
 

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91t gen5
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No you can't build boost in neutral that's normal. A lot of people around here don't have a BOV or BPV myself included, no problems.

If you could make a video of the sound we might be able to help.
 

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Driving MR2s since '89
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The stock ABV can make some pretty weird noises if you're getting on and off the throttle right around the boost threshold. The stock intake and its resonator muffles this but you can still hear it. With an aftermarket intake all sorts of sounds make their way out.
 

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JDM '94 gen3 turbo
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Discussion Starter #5
I've struggled to capture decent audio of the noise. My window seals aren't sealing very well and are letting alot of wind noise into the cabin that makes it very hard to hear anything else. @JimKing I would believe that you might be correct then. The sound definitely has some relation to the amount of boost built.

Something else I noticed is my stock boost gauge kinda acts crazy. It'll sit low, then suddenly jump to "halfway" then slowly climb. I've heard the stock guages are basically worthless though and that it acting weird is kind of normal.
 

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Yeah, I'm pretty certain I have a boost leak to contend with, and the stock boost gauge just complicates things. The "seat of my pants" gauge (more accurate IMO) will tell me one thing, and that stupid stock gauge another. I picked up an Omori gauge a few months back, but have yet to get it installed. As much as I prefer a factory look, it'll be nice to have that stock gauge gone.
 

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In theory you can change out the board that drives the gauge to make it much more accurate/fast-reacting, AFAIK someone posted about how they did it on this forum. The only issue then is just figuring out what a gauge without numbers would represent.
 

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The stock BPV on my Caldina rattles when letting off throttle. I'd say it's damaged but I'm not using it. a BPV or BOV are pretty much the same thing. On a GEN2 3SGTE it keeps the metered air in the engine after the AFM but on a GEN3, 4 and 5 it just vents to the airbox which muffles the sound. It's not really bypassing anything here, more a sounds emissions things for selling an OEM car. I don't think everyone buying a new car wants the BOV noises.
 

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I had
My car sounds good while boosting, but after I let off the throttle, I hear a kind of a vibrate-ey noise that sounds.. wrong? I don't know if I'm crazy, but I thought that previously my car made a blowoff valve kind of "pssh" noise when letting off the throttle, but I know the stock car has a BPV not a BOV. I was under the impression that a stock BPV doesn't make BOV noises. (I've looked for a BOV in my engine bay, but haven't found anything, and I can see that my BPV is still in the engine bay and attached to everything.)

I don't think it made this noise before I tried my couple of fixes (ECU caps, frankenstein vaccum tube removal, and faulty wiring fix.)
In fact, I feel like I remember hearing this exact noise when my car previously went on the fritz (Full explanation of what was happening here.) I feel like its made this noise ever since.

Was curious if anyone could describe the expected sound of these cars when letting off the throttle during boost. If there even is a distinct sound. I've read that if your BPV or BOV doesn't work properly it can be very bad for the car as then extra pressure will force air the wrong way back through the turbo. I'm kind of afraid of this being the problem, but I don't know what that would sound like though.

These cars won't build boost in neutral right? Mine doesn't at least. I want to find the source of the noise, but don't know a good way to figuring out what it is if I can only recreate it while car is moving. Anyone have any ideas for how I can find the source of this noise?

Car is a jdm '94 (gen3) turbo
a gmc syclone and no bov and ur correct the extra air does go back and make a noise. My 91 mr2 i bought had a jdm motor with a good bov and it made no bad noise it functioned fine. I just sold it. The car was a rocket guy who did motor swap did it right.Im srry its gone i just sold my87 aw11 also needed car for moms wheelchair shes real sick so had no choice. Buy a good bov itll help.Be safe
 
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