Air escaping OUT of inlets

[Boosted_135]

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.

 

[matreyia]

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.

Closing distance is an obvious difference. Though closing speed is not a concern at small opening width, at some point the distance will be a factor. Everything has a threshold of diminishing returns. I prefer to be cautious than just take a principle and go to the extreme...ie: let it be very wide open vs. a little open at idle.

I am sure the gap changes at different contexts... the context that I chose to address is when I open the hood with the AC on.

 

[Beemin]

For sake of discussion, I’ve read conflicting info about intake tract pressure for the n54. Some say intake is under pressure and others say it’s under vaccum.

I tested it on my car and unfiltered air is clearly getting sucked into the diverter valves. I held a piece of paper over it to be sure. Others have said the opposite, that they can feel air coming out of the bov or dv like @doublespaces

I wonder if it’s situational. Possibly dependent on turbo setup, idle rpm, default wastegate position (because of its effect on vacuum), etc. Thoughts?

 

[doublespaces]

For sake of discussion, I’ve read conflicting info about intake tract pressure for the n54. Some say intake is under pressure and others say it’s under vaccum.

I tested it on my car and unfiltered air is clearly getting sucked into the diverter valves. I held a piece of paper over it to be sure. Others have said the opposite, that they can feel air coming out of the bov or dv like @doublespaces

I wonder if it’s situational. Possibly dependent on turbo setup, idle rpm, default wastegate position (because of its effect on vacuum), etc. Thoughts?

If you have vacuum while the throttle blade is closed, then I think something is going on with your engine? Perhaps your turbos aren't spinning very well? I have tested this on stock turbos and also my 6266 ball bearing turbo.

But if for some reason you have air being sucked in, even Tials recommended setting is bad for you and I think that is an indicator of something being wrong with your car perhaps?

 

[matreyia]

For sake of discussion, I’ve read conflicting info about intake tract pressure for the n54. Some say intake is under pressure and others say it’s under vaccum.

I tested it on my car and unfiltered air is clearly getting sucked into the diverter valves. I held a piece of paper over it to be sure. Others have said the opposite, that they can feel air coming out of the bov or dv like @doublespaces

I wonder if it’s situational. Possibly dependent on turbo setup, idle rpm, default wastegate position (because of its effect on vacuum), etc. Thoughts?

If you have a BOV installed...and it would not different with DV - what I read and also see in reality is that at idle, the CP is positive pressure so it should push air out of the BOV - thus the BOV is slightly open due to the pressure of air leaving the CP. When you press the pedal the throttle opens and the engine sucks in the positive air from the CP flying past the open throttle body blade, that air was previous escaping out of the slightly open BOV - this causes the BOV to instantly close and so the air inside the CP can only flow into the throttle body and intake manifold into the valves to combust.

 

[doublespaces]

When you press the pedal the throttle opens and the engine sucks in the positive air from the CP flying past the open throttle body blade, that air was previous escaping out of the slightly open BOV - this causes the BOV to instantly close

This is incorrect and is part of the reason you don't understand my previous conversation with you possibly.

When the accelerator is pressed, the vacuum inside the intake manifold is gone. This relieves the pressure on the top port of the bov which previously pulled upward on the spring inside, and is instantly equalized with the pressure inside the chargepipe. Since the pressure on top of the plunger is now the same as on the bottom of the plunger, no matter what boost level, the only other force is the spring you choose which is pressing the plunger downward into the closed position. That is why it can be a twenty psi spring or a 1 psi spring. When the throttle opens, pressure is equalized above and below the plunger and it cancels out. The only other force impacting the bov plungers position is the spring inside. So as long as the spring is at least 1 psi spring, it will now close because the boost in the plenum is now pressing down on the plunger just as hard as the boost in the charge pipe is pushing up on the plunger.

In short the bov doesn't close because it is being sucked downward. It closes because the vacuum inside the plenum is gone from the top port of the bov, and the spring is no longer being held open.

 

[matreyia]

This is incorrect and is part of the reason you don't understand my previous conversation with you possibly.

When the accelerator is pressed, the vacuum inside the intake manifold is gone. This relieves the pressure on the top port of the bov which pulls upward on the spring inside, and is instantly equalized with the pressure inside the chargepipe. Since the pressure on top of the plunger is now the same as on the bottom of the plunger, no matter what boost level, the only other force is the spring you choose which is pressing the plunger downward into the closed position. That is why it can be a twenty psi spring or a 1 psi spring. When the throttle opens, pressure or vacuum, it is equalized above and below the plunger and it onkyodoes what the spring inside says which is close.

In short the bov doesn't close because it is being sucked downward. It closes because the vacuum inside the plenum is gone from the top port of the bov, and the spring is no longer being held open.

Of course it's not being sucked down. I assumed that people know there is a spring pressing the bov piston closed that does it instantly when the pressure in the
CP gets relieved from the throttle opening which let's the CP pressure equalize.

The engine sucking air in simply means the vacuum in the intake is sucking the CP pressurized air.

All this from vargas' BOV info flyer.

 

[matreyia]

I

This is incorrect and is part of the reason you don't understand my previous conversation with you possibly.

When the accelerator is pressed, the vacuum inside the intake manifold is gone. This relieves the pressure on the top port of the bov which previously pulled upward on the spring inside, and is instantly equalized with the pressure inside the chargepipe. Since the pressure on top of the plunger is now the same as on the bottom of the plunger, no matter what boost level, the only other force is the spring you choose which is pressing the plunger downward into the closed position. That is why it can be a twenty psi spring or a 1 psi spring. When the throttle opens, pressure is equalized above and below the plunger and it cancels out. The only other force impacting the bov plungers position is the spring inside. So as long as the spring is at least 1 psi spring, it will now close because the boost in the plenum is now pressing down on the plunger just as hard as the boost in the charge pipe is pushing up on the plunger.

In short the bov doesn't close because it is being sucked downward. It closes because the vacuum inside the plenum is gone from the top port of the bov, and the spring is no longer being held open.

In our conversation I told you I did not want the BOV open too much (a almost one inch). But you kept arguing that it was ok. Well if you don't mind it open that much, then it's your prerogative. I simply wanted it to be at TIAL's recommended opening width..."normal to be open a little".

Now I think that you believe I do not understand the mechanics of BOV. What I am telling you is, there is a threshold to everything. Just because it is normal to be open a little l, doesn't mean it is normal to be open a lot. That's all.

 

[Beemin]

If you have vacuum while the throttle blade is closed, then I think something is going on with your engine? Perhaps your turbos aren't spinning very well? I have tested this on stock turbos and also my 6266 ball bearing turbo.

But if for some reason you have air being sucked in, even Tials recommended setting is bad for you and I think that is an indicator of something being wrong with your car perhaps?

Could be I guesss, but the engine is running great. Logs are perfect. Vacuum measurements are normal. Newer turbos, No smoke, etc.

There are quite a few reputable vendors that have the same experience as me. Tiago has said multiple times that air is being sucked in at idle and you need little filters to run open DV (unless he has since changed his mind). Turbosmart uses two different springs for their plumback system vs their kompact DV system that can recirc or vta. Same valves, different springs, because they say they need the non-recirc option to stay closed at idle so unfiltered air doesn’t enter the engine.

I’d bet a default wastegate position of 0 would have an effect because a lot more air is bypassing the turbos. You could try holding your wastegate open on the 6266 and see if the air is still being pressurized. Altitude may have an effect on it as well.

I’ll have to do some experiments on a few different cars just to see if I can find a common denominator.

 

[MoRaeee]

Hi guys

I'm not sure if I'm posting this in the right place but I need some urgent help. I'm getting a whooshing air noise. Like an air rushing noise. I recently fitted a vrsf 5 inch intercooler so I though that one of the couplers might of been loose. I double checked everything and the noise was still there. I then checked the v band clamps on the downpipes cause I thought that might of been loose but the noise is still there. Its definitely not a boost leak because the car is boosting fine and feels strong. I don't know what to check next but I did notice that the afr are now sitting around 15 compared to the normal 12. I'm sure there is an air leak somewhere. Let me know what you guys think.

Thanks

 

[doublespaces]

Have you done a pressure test? Checked for tears or burn holes in your charge piping? Put the pipes under 10-15 psi of pressure and see what happens. A simple smoke test doesn't stress the hoses enough sometimes.

Having boost is not meaniful. Your turbos could simply be working overtime. Have you checked waste gate duty cycle?

When does the sound occur?

Please upload a log to this site's datalog section then post the bb code for it here.

 

[MoRaeee]

Have you done a pressure test? Put the pipes under 10-15 psi of pressure and see what happens. A simple smoke test doesn't stress the hoses enough sometimes

I haven't done a smoke test or a pressure test yet. I'll start with that I guess. Thanks for the quick reply

 

[doublespaces]

I haven't done a smoke test or a pressure test yet. I'll start with that I guess. Thanks for the quick reply

I updated my post.

Also getting the charge piping under pressure will require creativity.

 

[MoRaeee]

I updated my post

I have a small log that was done in 3rd gear. I don't have the guys to hammer it fully. The sound happens all the time under normal driving. It's sounds as if the air is rushing in or out of somewhere. Here's the link to the log

datazap.me | MoRaees | Log 11

datazap.me

 

[doublespaces]

I uploaded the datalog here for you:
View graph 60275

 

[MoRaeee]

I uploaded the datalog here for you:
View graph 60275

Thanks so much for the help. What do you think it could be ?