BOV, PCV, And Intakes Stating The Facts
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BOV, PCV, And Intakes Stating The Facts

This is a discussion on BOV, PCV, And Intakes Stating The Facts within the Tork Motorsports forums, part of the Vendors category; OK my car loving enthusiasts... I am here to help you understand one of the most miss-understood items in vehicle modding. Air intake in relation ...

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Thread: BOV, PCV, And Intakes Stating The Facts

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    BOV, PCV, And Intakes Stating The Facts

    OK my car loving enthusiasts... I am here to help you understand one of the most miss-understood items in vehicle modding.

    Air intake in relation to BOV recirculation and crank case breather hoses.

    Tonight I made a comment, that "all intakes are not created equal". And, here is why.

    I have attached a picture. First, we have to understand what we are looking at, so I am going to point out the arrows and explain a few things about the colors. The, when I am walking you through the details, I will refer to those arrows and reference the names of the areas I am talking about.

    Why is this so important?

    1. Understanding is key, to making power.
    2. You want to make more power? (that one should be easy)
    3. I don't have to point out any of my competitors intakes, because the descriptions I give, will allow you to go and look for yourself.

    So, here we go.

    1. Breather hose. This hose is highlighted in yellow text. It has red arrows and red circles showing its travel points. The red arrows indicate flow. Red indicates that its hot, and the paint spray line indicates that it has oil inside of the air flow. What this line does is sucks in cool fresh air when the car is under vacuum, which is good for the engine (I didn't note that in the drawing because its not important to whats happening). When you go into boost, this hose pushes hot oily air into the air intake. Indicated by the red spray pain lines. The blue arrows represent cool air flow.

    2. PCV Valve. This is highlighted by yellow text and it has both green and red arrows. Also, it has termination points indicated by the green and red circles. I could not show you the underside of the manifold because that is where the hose connects, so I had to show on the top of the manifold where that hose goes. This hose will have flow both directions. Green for vacuum, and red for boost. Red is stopped at the PCV valve (well stopped enough for factory boost cars). Green is the important part of this hose, so pay attention close when I start to explain myself.

    3. BOV Hose Recirc. This has white text and has a series of red arrows, this will be your bonus information if you can follow with all the other info I am about to give you.

    How does the PCV system work, why do you need oil catch cans, and what are all intakes not created equal?

    The PCV system works when you are not in boost. The green line sucks at the intake manifold creating a vacuum to draw in vapors from under the valve cover (big silver thing with the number 224102B6*0 on it). These vapors are filled with oil, carbon deposits, and other such things. You would normally put an oil catch can on this line because it generates more oil collection (on most cars) than the breather side. When you go into boost, you can see the PCV valve has a red line indicating flow (red arrows) back to the PCV valve. The PCV valve is suppose to stop boost from going into the engine and it does for the most part a good job. The PCV system will put oil deposits inside the intake manifold and the intake manifold only. There, you now know how the PCV system works on a car.

    The breather hose now this one is important and the most miss-understood component on the car. The breather hose has two ways it can flow. When under vacuum, it draws in fresh air from the air intake. This is normal, and no oil or deposits are formed when you are in vacuum. The tricky part with this hose is this, when you go into boost... the breather hose turns into a pressure hose, pushing crank case pressure into the intake hose (blue arrows). Do you see all the red spray paint I have drawn on the intake hose? That is oil vapors, carbon deposits, and other debris getting into your intake hose, running through your turbo, intercooler pipes, intercooler and eventually making its way into the intake manifold. Let me repeat that... When you go into boost, the breather hose becomes a pressure hose, pushing hot (crank case hot) oil vapors, carbon deposits, and other debris into your intake hose, turbo, intercooler pipes, intercooler and finally into your intake manifold (intake manifold is the big black W on the bottom part of the picture).

    Ok, so a raise of e-hands. How many think that hot (like 200 + degrees air) oily air getting pushed into the cold intake tract is beneficial for performance? Anyone?

    Next. Oil works against the cooling benefits of the intercooler, it coats the intercooler pipes and fills the inlet of the turbo. Wait.. you are asking yourself, "how did oil get into there". Well, the oil vapors coming out of the breather hose when you are in boost are coming out at 200 + degree's. When it hits the cool air from the intake, it drops the temps, this drop in temps causes the oil vapors to form into oil drops (microscopic drops). The drops start to settle on the inlet, turbo, intercooler, intercooler pipes, and finally the intake manifold.

    Oil, does not like to burn. Oil vapors, do not like to burn. Oil and fuel getting mixed inside your engine during the combustion event... is no good for power production.

    Now, everytime I explain this to people they ask, "why do the manufactures do it this way". Emissions reason and its easy. Its work for the last 100 years, why change it if its working. It also gives the aftermarket community ways to improve on the horrible designs by the manufactures

    So, do we understand what is happening here? Oil vapors are bad! We don't want oil vapors inside our intake, intercooler, turbo, and blah, blah, blah (if you don't have this figured out by now, meh).

    Getting to my point... all intakes (blue arrow replacement performance parts) are not created equal. Why and how do you ask? Our BigGulp intake does not have the provisions for the breather hose to dump hot oily air back into the cool intake path, and eventually coat the system over time. Our intake utilizes an oil catch can, or we use a breather filter to keep the oily air from entering the system. What does the competition do with this hose???

    Last thing to point out... this oil collection doesn't happen overnight. It takes miles of use to have enough oil get dumped out of the breather hose to create an issue, or... if you drive in boost all the time or race the car professionally/semi professionally, you may have a tragic build up of oil very quick thus causing a loss in performance. Performance being the may goal when getting "performance parts". You don't want to have the oil getting pumped back into the intake and coating everything everytime you get into boost... thus, "not all intakes are created equal".

    Bonus round...

    The BOV Hose Recirc (white letters and red arrows at the bottom of the picture). What does this do? Well, this hose dumps hot air from inside the intercooler into the inlet of the intake. Some manufactures put this hose back on their aftermarket intake. We, do not. Why? Well, hot air getting pumped back in at 15 psi into the cool air that is in the intake, HORRIBLE IDEA!!! The whole purpose of getting an intake is because you want more performance... why would you want to dump the hot compressed air from the intercooler back into the intake.

    Now, some are going to arrgue with me about the hot air and say that the intercooler is going to cool it so it doesn't matter how hot it is, nope, nope and nope... wrong. Intercoolers only work on a % of cooling based on how cool it is outside and its efficiency. An intercooler cannot cool colder than the outside air, sorry, but not possible (it breaks the laws of physics). Now, if you have a really good location for a cold air intake, and you have a bad ass intercooler and you are traveling at 100 mph at 2 psi, you will get close... but you will never get colder than the outside air temp. What does that mean (remember this is the bonus round). This means, you don't want to put this hose on your new intake, and you should remove it right away from the stock intake (its a 1" cap for the intake (blue arrows) and remove the hose from underneath the grill, just takes a pair of pliers). I you can tolerate the sound from the BOV after you remove this hose, you just picked up 2-5 WHP from removing it. Its not a lot, but its worth every little bit you can get.

    So.. are all intakes created equal? No... and not all manufactures of said intakes will take the time to explain this, or use paint to draw little arrows and stuff on a picture for you

    I really hope this helps explain why we build the Big Gulp line of intakes the way that we do. I hope that you understand what is being said, and if you have any questions about this, want to call me an ass, or just don't understand what I am saying.. don't worry, you are not alone

    But seriously, if you have any questions about this or the operation... feel free to ask the questions and I will do my best to get you guys answers.
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    Thanks,
    Tyson
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    Senior Member SXTurbo's Avatar
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    Is it safe to just put a filter on the breather hose?
    2016 SX Silver
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    Quote Originally Posted by SXTurbo View Post
    Is it safe to just put a filter on the breather hose?
    Yes, though it is suggested to go with a catch can instead, a filter isn't an issue, just not as beneficial.
    Tyson
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    Good info thank you.
    2014 Koup "SX" A/T Silver. Mods; Tint, 6th EE Delete Pipe, Sylvania SilverStar Head, Nokya Fog, Interior LEDs, Debadge (Forte) Trunk-75A Red Dogbone (one side only) Done.

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    Thank you. You helped me so much, now can you explain all the other mods for are cars like this? That would be so helpful to me.

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    Is there a proper way to remove the BOV Hose Recirc?
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    PLP
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    Quote Originally Posted by charlesquik View Post
    Is there a proper way to remove the BOV Hose Recirc?
    Not really. It is just plain simple.
    Basically there are two ways.
    - disconnect the part that goes to the air intake
    - remove the hos completely (form BOV as well). But I just do not know if dirt could accumulate there...
    SXTurbo likes this.

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    I had to remove the whole air filter box to get to the second clamp on the bov hose where it is connected directly to the bov. I really like the bov sound this makes with the whole hose disconnected, good to know it has a positive affect. With the opening of the bov facing towards the engine I'm not concerned with anything getting in there.
    PLP likes this.
    2016 SX Silver
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    Quote Originally Posted by Jim Nelson View Post
    Thank you. You helped me so much, now can you explain all the other mods for are cars like this? That would be so helpful to me.
    In due time, these take quite a bit of research, as well as time to get set up. But we will be covering others!
    Tyson
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    Won't it affect vacuum from the intake if I leave the hole open?

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