[StevesSTI]

As I have said in past threads, I am completely new to the turbo scene, so please, if this is a dumb question, now you know why. Whener I let off the gas, whether it is to upshift, or goosing it and letting off, watching the turbo guage, whenever the needle backs off from wherever it was, be it in the positive or negative, I can here what sounds like air escaping from something. Is this the BOV? I thought it only worked when it passes a given amount pressure,....or does it work all the time, whenever the RPM's come back down to idle. I have had the car for about 3 weeks now and never noticed it before, but tonight I was driving with the windows up and a/c on low, talking to my wife when I noticed it.
Is this normal?

Thanks,
Steve

 

[xither0ckxi]

how many miles u have on it?

 

[StevesSTI]

just under 700

 

[Black_Rain]

Did you do any mods to it. I know w/ my friends REX he put a new turbo back exhaust system, and you can hear his wastegate. Also your BOV probably wouldnt be blowing off all the time, although once agian, w/ my friends REX he has the psi set so high that his BOV is always blowing off at random times throughout his acceleration. I'm not sure b/c i havnt driven in one, this might be your wastegate but thats more of a whining sound than anything. Right now w/ your info you gave me, i would assume its your BOV b/c BOV's work all the time to release the "excess" pressure also considering that your needle goes into vacuum. But i'm not 100% sure...see what other people say. This might be the reason though.

Or it could be your A/C...probably not b/c its a new car, but w/ my minivan whenever i accelerate w/ it on, the belt gives a loud loud loud squeek...but thats probably not it.

 

[StevesSTI]

No, it is completely stock, and after I started noticing it, I turned the a/c off, and it still made the same noise. It is definately a whoosh sound whenever the RPM's drop, and the turbo guage needle drops back to the negative. It is completely connected to what is going on with the turbo guage, whenever I let off the gas to shift, or leave it in gear and accelorate, the let off the gas,....whoosh,...as the needle goes to the negative again. And I done meen that I am hammering it to get it to do it, from 2500 rpm steady in 2nd, and let go of the gas and I can hear it.

 

[Terminator]

no, it's the BOV, same way in my car, if it's at 20 vacuum and I rev it up to not even any boost but about 1 or 2 vacuum, the blow off valve still....blows off, lol, I think it sounds bad ass personally, but don't worry about it, it's the BOV, can't wait til i get a LOUDER one, muahaha :twisted:

 

[Black_Rain]

ok...its definately the bov....i'm not sure why you hear the sound b/c it should be 100% recirculating....meaning you wouldnt hear it. i'm not sure though...anyone know?....But dont worry...its just doing its job...blowing off the excess pressure once you let off the gas...its a good thing.

 

[StevesSTI]

Thanks for replying,....it is definately faint, and now that I know what it is I like it a bunch more now.

Thanks everyone

Steve

 

[Black_Rain]

Yeah...it is really cool...i think its 100% recirculating...thats what they put on all new turbo cars...if you get like a 50% recirc and 50% atmospheric, you will hear it 10x's more....its sounds really bad ass

 

[StevesSTI]

So, if its 100% recirculating,...should I not be hearing anything, or will I still get that fairly faint whoosh?

 

[Black_Rain]

you should still be gettin a faint woosh...i'm surprised you could hear it at all...most stock cars it is very very hard to recognize it...but then again...mopar is unique. I'm almost positive that its 100% recirc.

 

[SilverBullet]

...and now that I know what it is I like it a bunch more now.

You're funny! :lol: :lol: :lol:

 

[kcoozzy]

I hear it also, have heard it since day one. I can hear it also when I am going around 50 or so in 5th gear. I press the gas at that point and then let off, that whooshing sound is there. Sounds cool. Make sure you have your window down and the radio off to hear it.

 

[srt4geezer]

Mine does it too. I can always hear it when I decelerate. Love the sound. Not dramatic. Very subtle, but it is there every time.

 

[Jeremy Smolik]

yes its the BOV. mine does the same thing even when pressure is not quite 0. Low speed, windows down...it sounds like a toilet flushing but you're in an adjacent room with the door shut. people on here have told me straight out that you CANNOT hear it...but you CAN. you can also hear a whooshing coming from the intake hole in the fender under full boost if you listen real hard. also, if parked with the parking brake pulled tight, you can hear a tone singing from the cable. let off the e-brake and the singing stops. maybe its years of pro sound that picks up this kinda stuff.

and our stock BOV is not quite recircuilating. its not atmospheric, but i think the recirc refers to cars with a mass-air flow system, which our cars do not rely on. wrx's are an example of this. our bov does dump into the intake pipe though.

someone may want to correct me, but the reason why you can hear it while not under positive manifold pressure is this:
the system is naturally under vaccuum. throttle opens, engine sucks in air. boost builds and overcomes the vaccuum, gradually building enough pressure to bring the piping up to 0 (equal to the atmosphere), then continues to build positive pressure in the pipes. if the pipes are at less than 0 and there is still some vaccuum, what happens when the throttle closes? the engine is not sucking as much air, thus there is less vaccuum. the gradual pressure that has been built up to overcome the vaccuum is still there, but the vaccuum is quickly taken away...thus that little bit of pressure becomes higher. you just raised the 0 point by removing the vaccuum so now the BOV has to get rid of that pressure differential. anyone disagree? seems like the physics makes sense.

 

[WarPainted]

yes its the BOV. mine does the same thing even when pressure is not quite 0. Low speed, windows down...it sounds like a toilet flushing but you're in an adjacent room with the door shut. people on here have told me straight out that you CANNOT hear it...but you CAN. you can also hear a whooshing coming from the intake hole in the fender under full boost if you listen real hard. also, if parked with the parking brake pulled tight, you can hear a tone singing from the cable. let off the e-brake and the singing stops. maybe its years of pro sound that picks up this kinda stuff.

and our stock BOV is not quite recircuilating. its not atmospheric, but i think the recirc refers to cars with a mass-air flow system, which our cars do not rely on. wrx's are an example of this. our bov does dump into the intake pipe though.

someone may want to correct me, but the reason why you can hear it while not under positive manifold pressure is this:
the system is naturally under vaccuum. throttle opens, engine sucks in air. boost builds and overcomes the vaccuum, gradually building enough pressure to bring the piping up to 0 (equal to the atmosphere), then continues to build positive pressure in the pipes. if the pipes are at less than 0 and there is still some vaccuum, what happens when the throttle closes? the engine is not sucking as much air, thus there is less vaccuum. the gradual pressure that has been built up to overcome the vaccuum is still there, but the vaccuum is quickly taken away...thus that little bit of pressure becomes higher. you just raised the 0 point by removing the vaccuum so now the BOV has to get rid of that pressure differential. anyone disagree? seems like the physics makes sense.

I AGREE, I THINK IT RELEASES WHEN THE THROTTLE CLOSES SO MUCH. NOT SURE HOW MUCH. WHICH IS WHY BOVS ARE USUALLY CLOSE TO THE THROTTLE BODY. STOPS SURGE BEFORE IT REACHES TURBO AND CAUSES DAMAGE.

 

[Jeremy Smolik]

which makes me wonder about the people with aftermarket BOV's that are set (washers or screws) to only blow off under positive manifold pressure. if the bov makes noise even when not under boost, dont ya think that means theres pressure being released? and if you set your bov to blow off only when the pressure is higher than that, what happens to it? my guess is there are some people hurting their turbo with compressor surge and dont know it.

 

[inzin]

yep

This Car is bit different. I have heard the swoosh noise too. That is why I am going to stick with the Mopar blow off plate when it comes out.