BOV Setup for your N54

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Captain
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Hey all, continuing our article series, this one is about blow off valves and proper setup with respect to reducing surge. Additionally, since it's pertinent, here are a couple of videos Tony made showing what surge does and why it's something you want to avoid.

VTT Turbo Thrust 101:

VTT BOV 101:

Finally, for those that don't want to click on documents, I did screen shots of my article:

BOV 1.jpg


BOV 2.jpg


Hope you guys enjoy.

-Chris
 
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doublespaces

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Good article as always. I wonder how many people actually know what spring their bov has and if it's the right one for their car. For whatever reason my car only pulls 17" at idle with the AC off, which is about 8.3psi, exactly what MHD reads. When my AC is on, it sits just over 6psi, 12.5" or so.
I have the unpainted, 10psi spring in my bov but it feels like there is a delay so I bought the white spring which it claims is an 8psi spring for the Tial Q. Your video says the black spring, which is actually the 6 psi spring based on what I read.

received_1533036140048879.jpeg
 
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Xm-n54

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So is this article basically saying we need to tap into the intake manifold for larger vacuum lines going to the BOV to avoid surge?? I know a lot of people that have ran tial bov with the stock vacuum lines with no issues. Or is the larger vacuum line only needed for upgraded turbos?
 
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This is an interesting article. While BOV surge can cause damage over time, it's a lot less severe than surge under acceleration. You should also hear a very distinct noise when surge occurs and have evidence of surge on the compressor wheel as well. How does Tony diagnose this damage as being surge VS too high of axial load?
 

DennisKing

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So is this article basically saying we need to tap into the intake manifold for larger vacuum lines going to the BOV to avoid surge?? I know a lot of people that have ran tial bov with the stock vacuum lines with no issues. Or is the larger vacuum line only needed for upgraded turbos?
Yes, when you have an upgraded BOV, you will need a more sufficient line from the intake than the stock vacuum line. A good time to install the connector for your vacuum line is when you clean your intake valves.
 
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doublespaces

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So is this article basically saying we need to tap into the intake manifold for larger vacuum lines going to the BOV to avoid surge?? I know a lot of people that have ran tial bov with the stock vacuum lines with no issues. Or is the larger vacuum line only needed for upgraded turbos?

Due to the varying levels of vacuum that each engine pulls, the length of the vacuum hose and how rigid it is, how much boost they run and their ability to detect all forms of compressor surge caused by any of these items all play a factor in this.

I've got a 1/8 NPT (1/4" ID) Vibrant hose, a run only a few inches long, going directly to a 1/8 NPT barb on my EOS intake manifold. I'll be installing the white, 8 psi spring today since my car only pulls just over 8 psi of vacuum. With the AC on it pulls less as I explained, but if it doesn't work out, I'll switch to the black, 6 psi spring.
 

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Captain
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This is an interesting article. While BOV surge can cause damage over time, it's a lot less severe than surge under acceleration. You should also hear a very distinct noise when surge occurs and have evidence of surge on the compressor wheel as well. How does Tony diagnose this damage as being surge VS too high of axial load?

Yes, surge under load is worse, but that's normally the land of have a compressor that's way too big -not really a common occurrence with the N54's. The thing is... low load surge is still bad and quickly wears things out. Not sure why you'd think the compressor wheel would have evidence of surge on it, unless it backed the nut off and lunched the compressor.
 

roywillems

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Hi guys, so i changed my tial spring to the white version, and when i start the car the bov is not completly closed, is it bad or normal? And if its bad what could be the cause?

Thanks
 

doublespaces

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Hi guys, so i changed my tial spring to the white version, and when i start the car the bov is not completly closed, is it bad or normal? And if its bad what could be the cause?

Thanks
It means your car generates more than 8psi of vacuum, which is normal. The moment you press the gas, that vacuum will disappear and there will only be the 8psi spring forcing it closed so it will shut immediately. Hold a paper by the outlet you should see even at idle it's pushing a small amount of air out so nothing should get in. If you're worried about it springs can be shimmed, but I wouldn't worry about it as long as it's not open very much.

Try turning your air conditioning on and see if it's still open or not.
 

doublespaces

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roywillems

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I cant monitor with mhd, dont got the license, im using jb4+bef, and in the license store i see that the monitor module is not compatible with jb4
 

doublespaces

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Here is the 10, 8 and 6 psi springs. (unpainted, white black). I decided to use the black spring after I had already ordered the white one. So now if I get my vacuum issue fixed I can switch back.
xRzvJjr.png
 
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doublespaces

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Well ofcourse there is a boost gauge, on idle its 0.2psi, dont see it really change when i put my a/c on.
Sounds like it only displays the charge pipe pressure sensor which is never going to show vacuum. You need the intake manifold signal which is after the throttle blade.

If it's open a little bit, i really wouldn't worry about it. I prefer my bov that way.
 
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Yes, surge under load is worse, but that's normally the land of have a compressor that's way too big -not really a common occurrence with the N54's. The thing is... low load surge is still bad and quickly wears things out. Not sure why you'd think the compressor wheel would have evidence of surge on it, unless it backed the nut off and lunched the compressor.

Surging usually causes damage to the compressor wheel
IMG_3938.JPG
 
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