Air escaping OUT of inlets

Boosted_135

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Nov 21, 2017
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Afternoon,

I think i have a small issue and need some advice on what to look for.

N54, vrsf relocated inlets. external PVC (ports plugged), new oe RB turbos, AMS intercooler, Tial BOV (10psi spring) with 1/4" line.

Whats happening now, when over 1 psi i hear a weird weird whoosh noise from the turbo side of the motor. The bov also goes off slightly. 18psi, 11.5-11.7 afr, MHD stage 2+ 91oct. Its not BOV noise, or turbo spooling up.

so i had my friend rev it at idle. I can clearly tell air is being sucked into the inlets, but once released, you can feel/hear air coming back out. Mainly the rear turbo inlet.

This noise wasn't there prior to doing the external PVC, plugging head ports and installing new turbos.
 

doublespaces

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Oct 18, 2016
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The sound of air is probably just just the sucking sound from the intake? Also, when your bov is making that choooo noise, particularly at low boost levels, that usually is an indicator that your bov spring is too stiff or your vacuum nipple isn't 1/4". This means you're probably surging from time to time. Use the lightest spring you can find, there really is no reason to put a stiff one in there.
 

Boosted_135

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Nov 21, 2017
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The sound of air is probably just just the sucking sound from the intake? Also, when your bov is making that choooo noise, particularly at low boost levels, that usually is an indicator that your bov spring is too stiff or your vacuum nipple isn't 1/4". This means you're probably surging from time to time. Use the lightest spring you can find, there really is no reason to put a stiff one in there.

when the motor gets reved up, i can clearly feel the air being sucked in (can hear the turbos spool up), BUT once the throttle pedal is released, you can feel the air coming back to the filter. (which is making the noise you hear)

I do have the upgraded 1/4" line to the manifold.

too stiff or not stiff enough? i figured a less stiff spring, it would open more when the throttle body closes? its got the basic 10 psi spring (none colored). You think an 8psi spring would help? Would that let the BOV open slightly at idle?

thanks for the reply by the way. I appreciate the help or feedback.
 

doublespaces

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when the motor gets reved up, i can clearly feel the air being sucked in (can hear the turbos spool up), BUT once the throttle pedal is released, you can feel the air coming back to the filter. (which is making the noise you hear)

I do have the upgraded 1/4" line to the manifold.

too stiff or not stiff enough? i figured a less stiff spring, it would open more when the throttle body closes? its got the basic 10 psi spring (none colored). You think an 8psi spring would help? Would that let the BOV open slightly at idle?

thanks for the reply by the way. I appreciate the help or feedback.

I run a 6 psi spring and I'm 650whp. I could even run a 1 psi spring. You just need enough force to physically push down on the plunger, boost pressure has nothing to do with it as you may know because boost is applied to the top and bottom equally, so the spring pressure is largely meaningless. Yes, the plunger stays open during idle because the vacuum of the engine is stronger than the spring, but who cares. People claim something will fly into their intake tract, uh, no it won't unless you're spraying water right at the hole with a hose or something. Put your hand over the bov, at idle you can feel air coming out. Remember, you WANT the bov to be twitchy and rapidly open when you let off the accelerator, especially with this platform because it uses drive by wire and not a normal throttle cable. A heavy spring will just make that more lethargic and for what exactly? To keeping your bov closed while you're parked? You want that bad boy flying open, not barely cracking so the air coming out barely slips by like a closed cheek fart.

There are times when you let off the throttle and the throttle blade only opens partially for a moment before fully opening. With a spring on the heavy side, the vacuum generated by a throttle valve only half closed may not be enough to actuate your bov, causing your turbo to surge or experience forces it otherwise shouldn't. The throttle blade is used for various things and you want the quickest response here possible. But I do know that I've seen people running more boost than me, and its still a normal PSHHH sound. Perhaps when you get to really large boost levels that CHOOO comes back, but you were not really getting on it that hard so I can't think of a good reason for that to happen. I am doing 24-25psi on a 6266, only air sounds no honking or train choo choos out of my Tial. My bov line is a short, less than 1 foot length hose coming from a 4AN utility port on my cast intake manifold. Its 4AN stainless braided hose, so no collapsing either.
 

Boosted_135

Specialist
Nov 21, 2017
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BMW 135i
I run a 6 psi spring and I'm 650whp. I could even run a 1 psi spring. You just need enough force to physically push down on the plunger, boost pressure has nothing to do with it as you may know because boost is applied to the top and bottom equally, so the spring pressure is largely meaningless. Yes, the plunger stays open during idle because the vacuum of the engine is stronger than the spring, but who cares. People claim something will fly into their intake tract, uh, no it won't unless you're spraying water right at the hole with a hose or something. Put your hand over the bov, at idle you can feel air coming out. Remember, you WANT the bov to be twitchy and rapidly open when you let off the accelerator, especially with this platform because it uses drive by wire and not a normal throttle cable. A heavy spring will just make that more lethargic and for what exactly? To keeping your bov closed while you're parked? You want that bad boy flying open, not barely cracking so the air coming out barely slips by like a closed cheek fart.

There are times when you let off the throttle and the throttle blade only opens partially for a moment before fully opening. With a spring on the heavy side, the vacuum generated by a throttle valve only half closed may not be enough to actuate your bov, causing your turbo to surge or experience forces it otherwise shouldn't. The throttle blade is used for various things and you want the quickest response here possible. But I do know that I've seen people running more boost than me, and its still a normal PSHHH sound. Perhaps when you get to really large boost levels that CHOOO comes back, but you were not really getting on it that hard so I can't think of a good reason for that to happen. I am doing 24-25psi on a 6266, only air sounds no honking or train choo choos out of my Tial. My bov line is a short, less than 1 foot length hose coming from a 4AN utility port on my cast intake manifold. Its 4AN stainless braided hose, so no collapsing either.


Thanks a bunch for the information!
 

Boosted_135

Specialist
Nov 21, 2017
90
27
0
Canada
Ride
BMW 135i
I run a 6 psi spring and I'm 650whp. I could even run a 1 psi spring. You just need enough force to physically push down on the plunger, boost pressure has nothing to do with it as you may know because boost is applied to the top and bottom equally, so the spring pressure is largely meaningless. Yes, the plunger stays open during idle because the vacuum of the engine is stronger than the spring, but who cares. People claim something will fly into their intake tract, uh, no it won't unless you're spraying water right at the hole with a hose or something. Put your hand over the bov, at idle you can feel air coming out. Remember, you WANT the bov to be twitchy and rapidly open when you let off the accelerator, especially with this platform because it uses drive by wire and not a normal throttle cable. A heavy spring will just make that more lethargic and for what exactly? To keeping your bov closed while you're parked? You want that bad boy flying open, not barely cracking so the air coming out barely slips by like a closed cheek fart.

There are times when you let off the throttle and the throttle blade only opens partially for a moment before fully opening. With a spring on the heavy side, the vacuum generated by a throttle valve only half closed may not be enough to actuate your bov, causing your turbo to surge or experience forces it otherwise shouldn't. The throttle blade is used for various things and you want the quickest response here possible. But I do know that I've seen people running more boost than me, and its still a normal PSHHH sound. Perhaps when you get to really large boost levels that CHOOO comes back, but you were not really getting on it that hard so I can't think of a good reason for that to happen. I am doing 24-25psi on a 6266, only air sounds no honking or train choo choos out of my Tial. My bov line is a short, less than 1 foot length hose coming from a 4AN utility port on my cast intake manifold. Its 4AN stainless braided hose, so no collapsing either.


So i put in another spring. BOV opens up at 15 in/hg instead of the orignal 19/20in/hg. I THINK the sound has gone away on lower part throttle boost pulls, but any heavy acceleration its still there. Maybe i need an even smaller spring in it?

where can you get the tial fitting to screw on a 4an or 6an line?
 

doublespaces

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Oct 18, 2016
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I think I have one of those laying around I could sell you. The spring is only going to help with the choo choo bov sound. The air suction noise is going to be something else, but they say its louder when you have inlets or intakes.

You can pressure test your intake tract, thats the best way to figure out what is going on. And also looking at your wgdc in your logs.
 

matreyia

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Apr 19, 2017
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I put in a black spring but the bov was open almost an inch at idle so I put the unpainted one back in.
 

doublespaces

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There is nothing wrong with it being open. Think about it, that just means when you're not boosting the turbos can actually vent. This is not a leak of any sort in fact tial says this is normal.
 

matreyia

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There is nothing wrong with it being open. Think about it, that just means when you're not boosting the turbos can actually vent. This is not a leak of any sort in fact tial says this is normal.

According to TIAL, "a little open" is normal. Now I don't know about you, but "a little" would not be almost one full inch in my book. So I went back to the unpainted. How large a gap do you have on yours at idle?
 

doublespaces

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Depends, when my ac is on and various conditions sometimes not even open. Other times halfway or all the way open. Vacuum at idle can vary just like vacuum when you release the pedal. You can't have a spring that is too weak as long as it has some pressure. You can have a spring that is too stiff. Think about it, your car is in vacuum at idle and its not open. That means you're going to be in boost situations where it won't be open also. Relying on an excess buildup of pressure in the chargepipe the engine cannot ingest in order to forced the bov open is how you get surge and excess fluttering. People continue to want it closed because they don't understand how it works. You want it open all the time unless you're not in vacuum...why wouldn't you?

If you cant give me a good reason for that last question then you should research the topic a bit more as it pertains to drive by wire throttle bodies
 

doublespaces

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Remember if there is ANY time your engine is in a vacuum state and the bov isn't open, you're building an unwanted pressure in the chargepipe and hoping it will force the bov open before the turbo hits the surge limit. That is not how bovs were designed, in fact they are designed so that very situation does not happen but you're actually causing it with a stiff spring. This puts pressure against the compressor wheel in the wrong direction even without surging and is excess stress on the bearings.

Downside of being on the stiff side means you're going to put unwanted pressure on the compressor and surge sometimes. Downside of being on the soft side means your bov is open at idle/vacuum. So what? It is a good thing if it is in my book!

Also when they say a "little open" they assume you've sized your spring appropriately for your vacuum levels(which you have not). And since its okay for it to be open, they err on the soft side just like me. You are doing the opposite.
 

matreyia

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Remember if there is ANY time your engine is in a vacuum state and the bov isn't open, you're building an unwanted pressure in the chargepipe and hoping it will force the bov open before the turbo hits the surge limit. That is not how bovs were designed, in fact they are designed so that very situation does not happen but you're actually causing it with a stiff spring. This puts pressure against the compressor wheel in the wrong direction even without surging and is excess stress on the bearings.

Downside of being on the stiff side means you're going to put unwanted pressure on the compressor and surge sometimes. Downside of being on the soft side means your bov is open at idle/vacuum. So what? It is a good thing if it is in my book!

Also when they say a "little open" they assume you've sized your spring appropriately for your vacuum levels(which you have not). And since its okay for it to be open, they err on the soft side just like me. You are doing the opposite.

There is no other inbetween size from the unpainted to the black springs. Either it is closed or open between those two.
As I said, open a little is fine, open almost one full inch... nope. Unless Tial has the definition of "a little" as almost an inch, then I will keep it closed for now until I can test cutting off some of the unpainted.
 

doublespaces

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There is no other inbetween size from the unpainted to the black springs. Either it is closed or open between those two.
As I said, open a little is fine, open almost one full inch... nope. Unless Tial has the definition of "a little" as almost an inch, then I will keep it closed for now until I can test cutting off some of the unpainted.
You've provided zero evidence for what you're doing but that is fine with me. The bov system is actually not very complicated but a lot of people don't understand it.
 

matreyia

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You've provided zero evidence for what you're doing but that is fine with me. The bov system is actually not very complicated but a lot of people don't understand it.

Actually, there is one more inbetween spring rate - white. I will give that one a try as cutting the unpainted spring will cause imbalance at contact point.

zero evidence? I am only obeying TIAL's definition of "open a little" which I interpret as not almost one full inch. Simply put, I am only attempting to adjust the opening to be "open a little". What does evidence have to to with this?
 

doublespaces

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You realize that your vacuum fluctuates at idle right? To keep your bov open the exact same amount at idle you'd have to change your bov spring multiple times every time you start your car. When your car warms up it produces vacuum better. As you engage and disengauge the air conditioning your vacuum levels will go up and down by a couple psi. The vacuum being pulled while you decelerate is not the same as when you are parked. You're trying to find a spring for a situation that doesn't even matter. All you should be doing is making sure it's not too stiff. As I said you are doing the opposite.

Please tell me one bad thing that will happen if you put the black spring back in.

Then tell me the functional difference between the bov being open a little at idle and all the way.