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Thread: Diverter valve vs Blow-off valve on a 1.8T

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    Jetta Junkie Moderator TurboJettaBoy02 has disabled reputation TurboJettaBoy02's Avatar
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    Default Diverter valve vs Blow-off valve on a 1.8T

    ok, so this is for the many questions regarding the use of a dv vs bov on your turbo vw motors.

    First off, what does the DV do?

    When you hit the gas your throttle plate opens allowing air into the engine. The turbo is in the intake stream and compresses the air and forces it in to the engine at a certain pressure. When you need to shift and let off the throttle, throttle plate closes, and the turbo is still spinning. The turbo still spinning is a good thing because it will have less work to catch back up when you reapply the throttle, but... a spinning turbo means it is still compressing air and the throttle plate is closed so there is only one way for the compressed air to get out, back the way it came in. Well this is where the Diverter Valve comes into play. The diverter valve diverts the air that would have gone back through the turbo causing it to stop spinning in one direction and spin backwards, to go back into the intake stream pre-turbo so you recycle that air. Now since your Volkswagen is tuned to run the air back into the system after the MAF sensor the MAF is calculating based on a certain charge still being in circulation when the throttle plate re-opens. This is why using a DV is most efficent on vw's motors, rather then a BOV which vents to the atmosphere. If you were to put an aftermarket Blow-Off Valve on the system that air that is being calculated for just blew out into the atmosphere. This causes the computer to still inject fuel metered for the air that was in the system already as well as the new air coming through the intake. With an aftermarket blow off valve you will get a fun turbo sound but your engine will run a little richer. So basically you need to pick performance or sound?

    Benefits of an aftermarket DV:

    Your stock valve in your car regulates your turbo power. At idle, your valve is open from vacuum pressure. When you hit the throttle, the diverter valve begins to close. When fully closed, turbo boost is allowed to be delivered to your engine. When you lift the throttle, the boost pressure is released from the valve into your air cleaner box. Inadequate/defective valves have extended lag, loss of boost, sluggish throttle response. A aftermarket diverter valve can clear up the previously mentioned problems. Also, if you have a chip, you need an aftermarket valve now. Chips simply kill stock diverter valves.

    Stock oem DV:



    Here's a common upgrade for an aftermarket DV, Forge DV:



    here's a solution if you want both performance and sound with your 1.8T motor. It's called the splitter by forge, it does both recirculate to keep the performance, but it also vents some air to the atmosphere, thus actin like a normal BOV.



    Here's some common BOV's *i dont recommend, but its your car*

    HKS:



    Forge:



    Also here's another performance upgrade you can do with your DV. It's a relocation kit. By relocating the valve in this way there are two benefits. Firstly, due to operating in lower temperatures the longevity of the valve is increased. Secondly, after relocation, the air that is recirculated back into the intake tract to the turbo will be cooler. Cooler air has a greater density. The greater the density of the charge mix in the cylinder the more power generated on combustion. Here's a kit from forge.

    Forge Relocation Kit:



    Now, all of these products can be found at normal vw's parts stores online. Hopefully this helps some questions about DV's vs BOV's.

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    Default Re: Diverter valve vs Blow-off valve on a 1.8T

    very good write-up!

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    Jetta Junkie Moderator TurboJettaBoy02 has disabled reputation TurboJettaBoy02's Avatar
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    Default Re: Diverter valve vs Blow-off valve on a 1.8T

    Quote Originally Posted by joenewton07 View Post
    very good write-up!
    thank you. just tryin to share info to noobs with questions on DV's and BOV's .

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    Master Necromancer SKAREKROW is on a distinguished road SKAREKROW's Avatar
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    Default Re: Diverter valve vs Blow-off valve on a 1.8T

    would it be benificial to sub a DV in place of a BOV?

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    Jetta Junkie Moderator TurboJettaBoy02 has disabled reputation TurboJettaBoy02's Avatar
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    Default Re: Diverter valve vs Blow-off valve on a 1.8T

    Quote Originally Posted by SKAREKROW View Post
    would it be benificial to sub a DV in place of a BOV?
    if u have a stock dv, id say to upgrade to another dv, like forge or apr. if u have a bov, yes, switch it to a dv for better performance. vw's need the recirculation to run properly, if u want the splitter is the best way to go for bov sound and dv performance still. u can adjust how much recirculates and how much vents to the atomsphere.

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    Default Re: Diverter valve vs Blow-off valve on a 1.8T

    nice write up, very helpful
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    Junior Member kevin is on a distinguished road kevin's Avatar
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    Default Re: Diverter valve vs Blow-off valve on a 1.8T

    soo the BOV is bad in a sense that you will loose power?

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    Default Re: Diverter valve vs Blow-off valve on a 1.8T

    Quote Originally Posted by kevin View Post
    soo the BOV is bad in a sense that you will loose power?
    Lose power and run rich...

    In short, the MAF sensor calculates the amount of air entering your system, which is placed before the turbocharger. The turbo compresses that air, and when you let off the throttle, the pressurized air in the system has to go somewhere, right? Well if you shoot it off into the atmosphere, that's a bunch of air lost that the car thinks is going into the intake. If the car thinks that air is there, its gonna send fuel to go with it... And thats how you end up running rich, thus losing performance too.
    Quote Originally Posted by darksidedub View Post
    come on dude really? most states in this country dont require a front plate. some states dont require an inspection sticker. new york just wants our money. i may as well leave the house with my pants down so i can make it a lil easier for this state to f**k me in the a$$.
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    Member 08GLI is on a distinguished road 08GLI's Avatar
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    Default Re: Diverter valve vs Blow-off valve on a 1.8T

    i have a 2008 VW GLI with the turbo 2.0L is there a good DV to add some power but also give me that BOV sound? And how will it affect my gas mileage

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    Default Re: Diverter valve vs Blow-off valve on a 1.8T

    Not exactly sure what a good DV is for you since you have the MKV with an electronically actuated diverter valve. I'm sure APR makes one, as well as Forge. Both are great companies, so check into them. However, diverter valves/blow off valves will never have an impact on horsepower/torque, as well as fuel mileage. The BOV noise your looking for has more to do with your intake system than with the valve. A short ram intake, dual intake, or even a modified airbox with a higher flow pannel filter will result in a decent amount of sound.
    Quote Originally Posted by darksidedub View Post
    come on dude really? most states in this country dont require a front plate. some states dont require an inspection sticker. new york just wants our money. i may as well leave the house with my pants down so i can make it a lil easier for this state to f**k me in the a$$.
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    I will fight you.

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    Euro Snob Vixen is on a distinguished road Vixen's Avatar
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    Default Re: Diverter valve vs Blow-off valve on a 1.8T

    So apparently hks makes a BOV that closes at idle, making it okay to run on a 1.8t? Saw it on YouTube. Anybody heard of this? Looking into some stuff for the bf since he's gonna buy a GLI.
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  13. #12

    Default Re: Diverter valve vs Blow-off valve on a 1.8T

    lol wtf? BOV's will just never work. Air exiting to the atmosphere instead of into the intake = rich conditions. There's no way to get around that unless you get one of those ''hybrid valves'' which does a little of both (Vent and recirculate).. And aparently the 1.8Ts don't mind it.
    Quote Originally Posted by darksidedub View Post
    come on dude really? most states in this country dont require a front plate. some states dont require an inspection sticker. new york just wants our money. i may as well leave the house with my pants down so i can make it a lil easier for this state to f**k me in the a$$.
    Quote Originally Posted by Vixen View Post
    I will fight you.

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    Euro Snob Vixen is on a distinguished road Vixen's Avatar
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    Default Re: Diverter valve vs Blow-off valve on a 1.8T

    Quote Originally Posted by Boost Addicted View Post
    lol wtf? BOV's will just never work. Air exiting to the atmosphere instead of into the intake = rich conditions. There's no way to get around that unless you get one of those ''hybrid valves'' which does a little of both (Vent and recirculate).. And aparently the 1.8Ts don't mind it.
    http://www.youtube.com/watch?v=Z_fG_...e_gdata_player
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    steelies.mandatory. JuicedJetta is on a distinguished road JuicedJetta's Avatar
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    Default Re: Diverter valve vs Blow-off valve on a 1.8T

    any thing from mighty car mods is sheer idiocy, keep your IQ intact by not watching them lol
    i have the hks bov and im losing valuable hp
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    Default Re: Diverter valve vs Blow-off valve on a 1.8T

    I watched a couple minutes of that and they guys argument doesn't make any sense. I mean wtf they put a bov on a NA car... and a bike...

    They are saying that BOV and DV will make the same power. Which is true, but that doesn't mean they will both work properly. The reason BOV's are bad is because when you left of the gas they vent all the air to the atmosphere. That's bad because the car is expecting it to be there and its not which cause your car to run lean and takes longer to build boost after shifting. HKS's don't cause as much of a problem's because they are closed at idle, but they still vent to the atmosphere like other BOV's.
    If you get the HKS and get the recirculation adapter.
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    Quote Originally Posted by Vixen View Post
    Why do that when you could S my D?

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    Default Re: Diverter valve vs Blow-off valve on a 1.8T

    Quote Originally Posted by canucme3 View Post
    I watched a couple minutes of that and they guys argument doesn't make any sense. I mean wtf they put a bov on a NA car... and a bike...

    They are saying that BOV and DV will make the same power. Which is true, but that doesn't mean they will both work properly. The reason BOV's are bad is because when you left of the gas they vent all the air to the atmosphere. That's bad because the car is expecting it to be there and its not which cause your car to run lean and takes longer to build boost after shifting. HKS's don't cause as much of a problem's because they are closed at idle, but they still vent to the atmosphere like other BOV's.
    If you get the HKS and get the recirculation adapter.
    Thanks for the info!
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    Default Re: Diverter valve vs Blow-off valve on a 1.8T

    Quote Originally Posted by Vixen View Post
    Thanks for the info!
    You're welcome
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    Quote Originally Posted by Vixen View Post
    Why do that when you could S my D?

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    Default Re: Diverter valve vs Blow-off valve on a 1.8T

    Quote Originally Posted by canucme3 View Post
    I watched a couple minutes of that and they guys argument doesn't make any sense. I mean wtf they put a bov on a NA car... and a bike...

    They are saying that BOV and DV will make the same power. Which is true, but that doesn't mean they will both work properly. The reason BOV's are bad is because when you left of the gas they vent all the air to the atmosphere. That's bad because the car is expecting it to be there and its not which cause your car to run lean and takes longer to build boost after shifting. HKS's don't cause as much of a problem's because they are closed at idle, but they still vent to the atmosphere like other BOV's.
    If you get the HKS and get the recirculation adapter.
    Agreed except BOV's make you run more rich, not lean. The MAF expects ALL of the air to be there after its passed through it (as you mentioned), so if there's x grams of air, the ECU sends y gpm of fuel. If you take away some of that air, y gmps of fuel is still being sent to the cylinders.

    But heres more reasons why these guys are idiots...

    1. They have a cone filter on the GTI with the MAF sensor not more than half an inch after it. That makes for inaccurate intake air readings to begin with

    2. @ 3:13, check out the hood on that car. Epic rice

    3. They drive the car onto the dyno and immediately start driving like its cool? ... One flick of the steering wheel and that thing is flying off the dyno

    4. They don't strap the car down when dynoing..... I think my mother could pick that out as being extrordinarily unsafe.

    5. They don't have a fan rushing air over the radiator/intercooler/engine while dynoing

    6. They've designed a valve that will keep boost in the intake system between shifts. 6a. That's terrible for the turbocharger 6b. That doesn't help you pick up boost more quickly in the next gear. How quickly you pick up boost depends on engine speed but more importantly, turbocharger impellor speed. When you remove your foot from the throttle so it's closed, and there's still pressure in the system, it's going to provide backpressure on the impellor, causing it to slow down, making it MORE difficult to build boost because it has to slow, then speed back up. F*cking idiots.

    7. And like Canucme3 said, they've invested time and dollars into making a ''BOV'' for NA cars. That's blasphemy.

    These guys are total morons and nothing they say should be recorded in your mind as fact. They belong far, far away from cars. Ofcourse BOV's and DV's make the same power, they both provide a closed force inducted system. It's when you vent that system, and inbetween shifts when you need to worry about what kind of valve you have.
    Quote Originally Posted by darksidedub View Post
    come on dude really? most states in this country dont require a front plate. some states dont require an inspection sticker. new york just wants our money. i may as well leave the house with my pants down so i can make it a lil easier for this state to f**k me in the a$$.
    Quote Originally Posted by Vixen View Post
    I will fight you.

  20. #19

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    I'm sorry to say this but the BOV on the bike was freaking epic hahaha

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    Default Re: Diverter valve vs Blow-off valve on a 1.8T

    So I have a question, if I go with the Forge Splitter Valve is it also possible install it with the relocation kit? Im wanting to put an aftermarket DV on, but i want the BOV sound. After reading this thread I'm convinced to go with a DV. So why not go with the best of both? I'm liking the benefits of the relocation kit too, thats why i ask.

  22. #21

    Default Re: Diverter valve vs Blow-off valve on a 1.8T

    is there any maintenance for the forge splitter?
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  23. #22

    Default Re: Diverter valve vs Blow-off valve on a 1.8T

    Quote Originally Posted by Knox147 View Post
    So I have a question, if I go with the Forge Splitter Valve is it also possible install it with the relocation kit? Im wanting to put an aftermarket DV on, but i want the BOV sound. After reading this thread I'm convinced to go with a DV. So why not go with the best of both? I'm liking the benefits of the relocation kit too, thats why i ask.
    I don't see why not, there's not going to be any hoses for the BOV port just the DV port so there's not reason you cant use it with the relocation kit. Just remember the forge splitter gets installed upside down compared to a regular DV so just make sure you hook it up right or else you'll have a vaccuum (spelling..) leak.

    Quote Originally Posted by theller View Post
    is there any maintenance for the forge splitter?
    The forge splitter is a piston type valve so yes it will require maintenence every 5k miles or so. Same as any piston type valve, DV or BOV. It's only the diaphram type valves that don't require maintenence and maybe a select few valves say that they don't require lubing.

  24. #23

    Default Re: Diverter valve vs Blow-off valve on a 1.8T

    so i just lube it?ha with what?
    king-kong's in my trunk =o

  25. #24

    Default

    Synthetic motor oil, I've hear mobile 1 5w-30 is fine.

    Btw I should add

    CLEAN synthetic motor oil lol you never no some people might just go out and use whatevers in their back yard

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    Senior Member I4N is on a distinguished road I4N's Avatar
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    Forge actually recommends synthetic grease, it's what they send you in the repair kits. I think oil will wear away to fast.


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    Senior Member ThatNewGuy is on a distinguished road ThatNewGuy's Avatar
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    Default Re: Diverter valve vs Blow-off valve on a 1.8T

    Ok, so BOV will make you run richer. And having a open intake will make you run leaner? Woulnt it even out?

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    Senior Member Mk4T is on a distinguished road Mk4T's Avatar
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    Default Re: Diverter valve vs Blow-off valve on a 1.8T

    i know it doesnt make a difference here. but BOV's are just bad in general on all turbo setups?? im gunna be going forge DV but im just wondering.

  29. #28

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    Quote Originally Posted by Mk4T View Post
    i know it doesnt make a difference here. but BOV's are just bad in general on all turbo setups?? im gunna be going forge DV but im just wondering.
    No. Custom turbo setups use mafless intakes. Meaning they use readings from an A/F gauge to custom tune the fueling to match the air flow (that's the proper way to do it, guys that just slap on MBCs are stupid). Our cars use a maf that comes before the DV. Our computer automatically calculates how much fuel to use based on the maf readings. The air going through the DV is precalculated so if you remove the DV you're taking air away that the car thinks is there and since its air that goes in after the maf the car has no way of knowing that its not being put in.

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    Senior Member Mk4T is on a distinguished road Mk4T's Avatar
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    Gotcha. :thumbup:

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  31. #30

    Default Re: Diverter valve vs Blow-off valve on a 1.8T

    sooooo, i have an HKS sqv bov on my car. I have the extra tip that would allow you to "recirc" the air back to where the DV would be. Is this a better or worse idea?

    and also, would it still make more noise than a DV or splitter even with the "recirc" tip and hose?
    Last edited by stesk; 08-24-2012 at 02:31 PM. Reason: forgot

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