Is it safe to vent your Blow Off Valve to atmosphere? [GO FAST BRETT]

[@blowngasket299]

all I needed to hear was one person saying its okay to vent to atmosphere, now I'm gonna buy one

[@Cheezel909]

Running this BOV would you need a tune?

[@2drpeppersplz]

@@Cheezel909 no

[@whitebread8068]

Lol

[@stew8fpv]

Atta boy, just got one put on my ST with a true vacuum source and it sounds amazing! Do it.

[@Mambomel]

I dun need validation I just need my car to go Pshhhh psshhhhh!

[@Sman16]

so when venting to atmosphere the mixture becomes rich meaning not all of the fuel will be burnt dumping un-burnt fuel to the exhaust where if sufficiently heated may cause it to reignite.... AKA shooting dank ass flames

[@NaN.404]

S-man 16 I like the way you think 😏

[@Basomga]

S-man 16 EXACTLY WHAT I THOUGHT

[@joeymilani4418]

Carmicha3l it vents when throttle plate is closed and there is fuel cut off when throttle closes therefore not dumping much fuel with an atmosphere blow off, as explained in the video

[@Basomga]

Carmicha3l I often hear people complaining about the reliability of modded Subarus

[@STEEVSUPREME]

If it is so unhealthy to run the engine rich then why do a lot of modified cars (including mine) run on decel ignition cut and not decel fuel cut? It didn't blow the turbo on the Subaru and it doesn't wreck your engine. Please provide me with facts towards your argument.

[@DUK33Y]

I'm liking this new series and how technical it is. As mentioned in the video, it's good to get a professional opinion that isn't some bloke on a forum site.

[@masterdinosawr]

Very true!

[@Truzo]

Just a Bloke that works for GFB and is trying to sell you stuff......

[@acousticpsychosis]

+Truzo doesnt mean the info isnt pertinent.

[@fairlifemilk3533]

The answer is yes. I recommend getting a GFB TMS respons hybrid BOV so that way you can vent whatever percentage you want and won't trigger a check engine light

[@levigrafton6854]

The absolute best thing you can do is, get an adjustable one, when you’re racing keep it closed and when you go to a meet, open it up.

[@valRockz1234]

That 2 port blow off value was the best item I purchased for my rexy. Made the best sounds, and when I got pulled over, I just quickly turned it to 100% recirculation and got away defect free :)

[@moto324]

do you backfire a lot more with it?

[@aidenater]

@@moto324 i have a proceed GT and haven't noticed my car to backfire any more than it already does. I have it half open, and i keep myscrew driver handy, in case I need to adjust mine, as it has a manual adjustment lever, not fancy remote control haha. The GFB DVX is what I have.

[@shaeerhassan8588]

Venting to atmosphere sounds so much better though

[@Gräsklipparmarodören]

fun fact, Brett means Wide in Swedish, so go fast Brett in Swenglish translates to Go fast Wide, as in when you drift. or "åka på tvären" as we say here. great series btw

[@Benana167]

Awesome video guys, love that you are helping to clarify issues you've found on the internet with people that actually know what they are talking about!! I was just wondering if you could clarify how you would go about determining the correct spring tension for your b.o.v in order to not cause stalling or backfiring. I.e how do you go about setting it up correctly ?? Cheers And love the videos !!

[@Korokukanas]

Thank you Go Fast Brett!! Always a delight to devour your knowledge!!

[@games_gains]

I've been trying to figure this out for 5 hours today and finally stumbled on this video. I have a 2014 Jetta GLI Autobahn (GEN3) and the forums are just like you said. Looking for a dual port valve now. Thanks

[@76cruiserAustralia]

This was the most informative video I’ve ever watched on KZbin re - BOV. Top job mate 👍👍👍

[@WasDrogan]

i'd like to see a follow up of this covering the differences between EFI systems using MAP sensors instead of MAF sensors and also Blow through Carby setups.

[@prerunnerwannabe]

Intestine video! On the turbo system that's on my Focus, the blow off valve is before the MAF so it makes no difference to idle or AFR when I vent to atmosphere. I'm also using an OEM diverter valve off of an Audi, and seems to work just fine as well. But of course, I specifically designed the system to have all of the venting stuff before the MAF so I could avoid all of these problems. But I don't know if most OEM turbo systems work that way, so probably trust Brett ;)

[@stew8fpv]

This guy is amazing, very good information and explained well, thanks for the wisdom mate, appreciate it!

[@thomasjohnson1142]

Good video I found it was just easy to move the maff after the blow off valve that way the air that is being discharged never passes threw the mass air but yes most GM that I tune have DFCO deceleration fuel cut off as soon as your foot leaves the pedal your AFR is flat lined shutting off fuel. When tuning even in open loop with DFCO disabled still don’t see rich conditions even if so a little extra fuel will keep them cylinders cool lol thanks for the info brother God Bless

[@alexnelson09]

If you run a MAP sensor rather then MAF you won't experience lean conditions ! Surprised this wasn't mentioned.

[@Elxmo]

alexnelson09 rich*

[@numinous4789]

You mean speed density off of your MAP. I have a Speed 3 and we have MAFs and MAPs. But our air is metered at the MAF, so we end up venting metered air, getting idle bounce, afterfires, etc., esp if you're venting too much. If you vent just a little, you're usually okay.

[@jckf]

It was sort of mentioned. Brett explicitly said "if your car has an air-flow meter"

[@MrPanda834]

Numinous For a stock 2004 Subaru Forester xt turbo, which BOV would you recommend and would you also recommend a 50/50 ratio? Thanks

[@rileyrr2925]

Some people's MAF and IAT are sort of spilt up, you can move your IAT right before your manifold after the BOV. Then delete the MAF with a MAP based tuned. Obviously only can do this if you have a MAP sensor on the intake somewhere. Boom problem solved.

[@revengefullobster4524]

I had an 09 STI with one of these GFB BOVs on it and a Cobb intake. I had tuned it with the Cobb accessport and wasn't running a really aggressive map (just stage 1, low wastegate), but had ringland failure after about 15k miles. The Subaru dealer was cool and did a warranty repair on it, but really thought it was do to a rich mixture that the engine failed. As he said in the video, make sure you get a GOOD tune if you put one on.

[@trainsbangsandautomobiles824]

Wouldn't the ecu cut fuel on lift off anyway or was that not how that car was tuned (I.e. tuned wrong).

[@revengefullobster4524]

I think it did, but just not quick enough, so it would get just a bit rich on lift. Like a lot of people said, Subaru's are really sensitive to MAF. I recently got a 2015 STI, and did basically the same tune, but minus the BOV. I'm 6k into it and a couple track days as well, so we'll see what happens.

[@deiviy]

bwaaaaaaaa sutututu

[@littletickedoff2640]

Deivi Y how do you know the sound i make when i shit?!?!?!?

[@matt34323]

Deivi Y from your dump pipe?

[@breakingdecks1899]

More from the wastegate

[@billiamlivingston8531]

Woooooottt pshhhhhh***

[@bobkin611]

Sututututu is the Turbo.. due to an Anti-Lag system.. lol not the BOV.

[@lucrus25]

Thank you for clearing this up with actual knowledge

[@TheSpikyTurtle]

So an adjustable blow off valve apparantly allows to tune how many flames you shoot out? I love it

[@xharpoon]

my car have 2 MAP sensor, and I use bov spacer (means 100% vent to atmosphere) and I didn't notice anything change except for bov noise

[@coolbrz80]

This guys explains it nicely. Thanks Brett.

[@grimreefer5159]

It really depends if the turbo vents upstream or downstream of the MAF sensor. I had a 21 bronco that vented upstream and swapped to vent to atmosphere and never had an issue. However, I could see how venting to atmosphere with a turbo after the MAF could potentially be a problem...

[@thatoneguy454c]

If you plan on setting up for flat foot shifting than I would say a recirculating BOV is better. If you are not doing that it doesn't really matter. Having a vent to atmosphere BOV can also cause backfiring when you shift or let off the gas. Backfiring and shooting flames out of your tailpipe is nifty.

[@garyoaksify]

so happy this show is still going I love the GFB series so informative!

[@hrtbrk1]

So bov can cause backfire, and loud whoosh sound? He talked me into it.

[@turmat01]

What I've always been told is that it might gunk up your first catalyser. That's it. The unburnt fuel will just gunk it up over a (very) lengthy period of time, after which you either change it or just cancel it lol. I prefer keeping them as I'm not a fan of smelly cars, and they are a few hundred bucks I beleive, but yeah if you go with a 50-50 valve... You should be fine. I had one on my '04 WRX, and even tho subarus are reputed to not liking BOVs too much, with th 50-50 one, I had it on the car for 3 years and everything was still perfectly good.

[@motochris26ify]

Newer into the car scene & just grabbed a GFB TMS for my WRX. 50/50 was my plan anyways based off of still having air recirculating and still getting the atmospheric venting “pssssh,” but after seeing your comment I feel a lot better about it, thanks for taking the time to leave your opinion 5 years ago LOL

[@ggalindezb]

I love the nerdery of this series. It's so good.

[@danstaszko6930]

So if you dont adjust it correctly worse case you stall it and then just keep readjusting till is stops stalling? And or back fires

[@vtr0104]

Good information and friendly as always. Thank you, Mr. Brett :)

[@luda00769]

Best explanation video around!

[@mugshotmarley]

Depends on what monitor u have. MAP or MAF. MAP can be vented to atmosphere for not, MAF only can be recirc

[@TheSidneySmith]

The recirculating bov will actually push air backwards across the MAF depending on the boost pressure....thereby still creating a rich condition as the air is metered twice. This air pressure wave will also blow backwards through your air filter.

[@MrAnteze]

You can move the MAF to the pressure side of the turbo after the BOV.

[@stifflers69mom1]

Anton Larsson 🤦‍♂️

[@stifflers69mom1]

Don’t do that please

[@Jack-wu3ie]

We've tried many BOV on a Mitsubishi Evo, the best performing one is actually the factory one. It leaks just enough air so you don't get compressor surge, and you can tune it so the recirculated air with some negative ignition timing will give you mega pops and bangs from the exhaust, as in blows the exhaust gaskets to pieces lol. sounds better than a BOV any day

[@kevinmcgeehan4374]

My exhaust gaskets have to be changed literally every 6 months on my evo 😂

[@racer5674]

It's only metered air if the BOV is behind the MAF. On a SC compressor setup the MAF is usually behind the BOV which means you can vent to atmosphere and not impact fuel.

[@Sandalssss]

I have a GFB Respons installed on my Impreza... really nice valve!

[@carlosxramirez]

SiriousSandals Did you need a tune?

[@Tony-tk4ht]

Does yours backfire?

[@Sandalssss]

@@Tony-tk4ht Every now and again, sometimes get a big pop after a dump

[@saintblamo]

FYI This entire topic/video pertains only to EFI and excludes carbureted vehicles. In fact when you run a BOV on a blow through carburetor this allows you to jet the primaries down which helps with fuel consumption. Even at 6 PSI still run a BOV.

[@Mitutumuch]

"I'm not here to debate that right now" well said Brett.

[@bwcordes]

Speed density carries the day yet again!

[@glenn9k]

Perhaps you could walk us through how this would affect an engine running without an air flow meter? Like with aftermarket ECUs and some OEM's, like Saab Trionic 5. Since these systems doesn't calculate fuel based on air flow, surely they respond differently to the use of atmospheric BOV's?

[@SMCca]

You can still get a nice Whoosh sound from a bypass valve if you have a pod filter attached to the intake of the car, especially if you've replaced the factory rubber inlet pipe with a metal one. My 1.8t a4 makes a nice audible bov sound and it's fully recirculated.

[@noxious89123]

+1 this. I have a K&N panel filter in a CDTi airbox on my Z20LET in my Astra, with a TurboSmart reciculating valve, and it is clearly audible. Not as loud as if I were to use a pod filter though, and definitely not as loud as a vent to atmoshpere bov.

[@Bupalooga1]

Can confirm Turbo falcons can go full atmospheric Bov without issues

[@hybiepoo]

Nice quick video and spot on. I'm told it's flat out illegal in NSW to vent to atmosphere, which is ridiculous. Do you know whether that is true Sir GFB? My car is supercharged, blows through a throttle body and uses MAP (amongst other things obviously) to determine fueling. Why should my bypass valve be illegal because it vents to air? Is it also illegal if I disconnect the intake pipe? Because it's the same thing essentially. So by the same logic, it must be illegal to have an air pump attached to nothing. They should be thanking me because I'm running that air through my air filter and huffing it back out. I'm HELPING the environment!

[@NaN.404]

hybiepoo probably you have told wrong, the only thing I know it's illegal is blow the oil breather hose straight into the atmosfer, that way you are blowing oil vapor that goes to the intake manifold in a stock car

[@hybiepoo]

Even that is not true for everything. Older cars never had PCV.

[@ThaVoodoo1]

In Queensland vent to atmosphere Blow Of Valve is illegal for street use.

[@ThaVoodoo1]

I want to fit a blow-off valve to my turbo vehicle, do I need a modification plate? Fitting a blow-off valve is considered a minor modification and does not require approval. When fitting a blow-off valve, it must be vented back into the vehicle's induction system. Blow-off valves that vent directly to the atmosphere must not be fitted. www.tmr.qld.gov.au/Safety/Vehicle-standards-and-modifications/Vehicle-modifications/Frequently-asked-questions-vehicle-standards-and-modifications.aspx#blow

[@hybiepoo]

john reece so nsw is probably the same. Understandable for airflow meter applications, but ridiculous on MAP based vehicles.

[@erebus38]

I ran a vent to atmosphere BOV on a nearly stock Nissan SR20DET engine with a stock ECU and MAF for a long time,and absolutely never had any problems because of the BOV,whatsoever.

[@lynnmckenney1987]

Go fast brett, shutting down forum know it alls. Love it.

[@BulliKid]

Question. How would this affect a automatic transmission where you are WOT all the time between trans shifting??

[@barsaf9989]

I think since there is still pressure in the intake manifold while the cars shifts, the bov stays closed. So I don't think the bov is a factor until you let off the gas.

[@IGoProEVERYTHING]

I think he is talking about a specific car manufacturer. Fords along with every other car company that I have seen under the hood have a mass air flow meter after the airbox, NOT before it. I took the recirculation hose off of my 2022 Ford Bronco 5 months ago without issue.

[@anmolbehl1883]

If car has MAF sensor yes, its should lead to momentary rich condition and rpm spike and cat clogging. But if you have a MAP sensor, it doesnt matter. Also if you drive your car hard often enough you can usually get the CAt hot enough to burn off deposits

[@Void_Astrea]

I think my blow off might be saving my clutch right now since im not constantly running boost on my Si with this +6 tune

[@patonbike]

What about blow-through MAF? In a blow through MAF should the BOV be closed at idle? And only open on shifts? I've got this setup on a centrifugal supercharger, so slightly different scenario than normal.... Since it wants to "make boost" at just about all rpm. Trying to figure out how to set this up.... It idles like garbage if I open the valve up at idle.

[@jessekelly6150]

mean while venting to atmo is illegal here in Australia

[@insanityprod]

Austrailia has the most sissy traffic laws I've ever seen, it can even piss me off while not living in Australia.

[@john123mike]

So even farting in public is illegal?

[@drugoodman1136]

Jesse Kelly damn tht sucks

[@Iron_lab]

Mean while its neighboring country nz has literally no law against modification

[@MadazMazdas]

meanwhile our metro buses use their noisy af airbrakes

[@inkno701]

How about a video on how to make the different blow off valve sounds, like chirp vs flutter vs whoosh vs whistle.

[@bstevenson1002]

Vegaspsycho .... I know right.... the #1 questions keep getting ask is that . And everyone seems to talk.about everything but that

[@GenesisGenius]

Different bovs different sounds. Hks ssqv has a nice chirp.

[@кяуртіс]

The tututu is not the bov nor is it good for the turbo, its the air going back through the compressor wheel and that shit fucks with it.

[@Bbeavis]

This totally missed out on factoring in cars that do not run a MAF/AFM.

[@HenkkaWRC]

True, but I reckon that people who watch technical videos like this can figure that out by themselves.

[@GT86GT400]

This is only the case if the MAF sensor is bevore the BOV or not? My MAF sensor is behinde the BOV,.

[@g-track5065]

Thanks you solved my problem Brett Happy Easter My Doggy!!!!

[@dinojudge]

Surely to solve all issues and problems it would be best to use a map sensor over a maf as this would read the pressure in the manifold and the ecu would adjust the fuel accordingly??? if your modifying a car make it safe and do it right

[@Donn29]

Brett! You forgot about part throttle lifting on AFM cars under boost!

[@82toyotalandcruiser]

How would this effect a Mitsubishi SST transmission?

[@stephen9944]

I'll let you know as soon as mine gets installed, just ordered.

[@stephen9944]

Have had it on for a few months now, no issues at all running in any position. I prefer it at 50/50 because it is loud. I spoke to my tuner, told him it goes to 10 AFR and immediately into fuel cut (20 AFR) when I lift and told me that's great, no issues. I told him when I lift and get back on the throttle, I get some nice pops and bangs. He told me that's great. Mind you the tuner has over 850 Evo tunes under his belt, it's hitting 29lbs at 4400k, tapers down to 22 but in traffic it runs like stock. I run an AEM intake, manifold back exhaust, ETS 3.5 fmic, all piping, Cobb 3 port EBS. Because the SST is stock and in great shape, my tuner keeps torque at 330lbs peak and I run Teach In every time I change the fluid, which is every 20,000km. It's at 124,000 km...shifts like it did leaving the dealership.

[@evteach]

This was great and very informative, thanks Brett and GFB!

[@MasterSumai]

How should my GFB blowoff valve be set to achieve a medium to loud whoosh sound? I have the T9014 model of blowoff valve.

[@MrXr8260]

Fgx xr6 turbo..if I got my car tuned bigger turbo injectors intercooler etc with the bov blocked completely off then few weeks later hooked it up for re circulating it will that cause a lean condition when coasting or light acceleration..I'm getting no where on the forums

[@goldenvtr]

no mention of part throttle i.e on track cars mid corner, as i had overfuling issue on my mx5/miata turbo before i went with a stand alone MAP based ecu.

[@jensensphotography4570]

How do you know if you got the spring preload right on a Kia Cerato gt?

[@TJDash]

How come in Australia BOV are an issue where you are only venting air into the atmosphere? I'm not able to find a legit reason.

[@gregclayton8831]

Great video. Very intelligent, and excellent message delivery. Subed, hope to see more.

[@marcus123841]

Is it possible to increase the boost if you have the latest tech diesel car with a electronic stepper motor that moves the waste gate

[@wilfreddiazvellon7896]

Do you need tune to your 2012 Subaru wrx premium when installing this type blow off valve?

[@TheMrSelby]

at the end of each go fast brett video he should tell us what he uses on his car or at least what he recommends we use on ours

[@pigeonsil240sx]

after installing 300zx maf on sr20det and dumping to atmosphere my engine actually stalls anytime it dumps to atmosphere,the fix was recirculating but now i have no bov sound. do you think the dual port will give me best of both worlds where i can keep maf happy enough to not stall and also retain bov sound?

[@marcusliboriussen7473]

I have a question How do i know, that the blow off valve it's set up correct ? if i take my diesel car and put a valve on it, when do i know the setup it's wrong. You say it can makes a back fire, if it's setup wrong, so do i need to set the valve on it, og adjusting after what it sounds right ? It's maybe a dump question, but just to learn more. But a great video, just what i wanted.

[@albi2k88]

Some VW 1.8 turbo and 2.7 biturbo has vacuum reservoir and N249 solenoid for DV to pert it at part throttle. If somebody want to swap to aftermarket blow-off without recirculation then must disconnect this vacuum system and connect it directly to intake manifold.

[@HenkkaWRC]

So "sutututu" from the engine bay and "bang bang" and flames from the exhaust? Sounds pretty freaking good to me! :D

[@theboostpig]

if it goes to atmosphere its more of a "psssh". My 180SX has a bolt in the end of a bit of vacuum pipe on the intake and that goes "sututututu" really fucking mint-ly. no bov at all

[@Fergesslich]

The "sututututu" comes from the air decelerating the turbo which is not that great for its lifespan, at leats that is how I understood it.

[@Solar_Daddy]

I have a turbo kia forte and I disconected the reserc tube amd pluged the intake, no problems at all. Most CAI come with BPV deletes for it anyways. All depends on the car and i love my kia

[@abdulhaqq1980]

Awesomely explained.

[@duo02]

So in a nutshell the only reason you vent to atmosphere is for the sound and best case scenario it doesn't really do damage. Worst case it makes your car shitty (bad idle, backfires,stalls)

[@Username_8886]

It makes your car run like dookie if you don't have the right balance point. With my RDX I have to do a 70/30. 70% back to the intake 30% to atmosphere

[@Username_8886]

If the valve is closed when idling and throttling you should be okay to vta. But I could wrong. Please let me know if I am . I'm inclined to learn.

[@joshsmith-uy5iw]

if your bov was before your air sensors wouldn't it eliminate the rich problem? since it would be regulating the mixture according to the "true" air input.

[@shane39767]

The bov only opens to release pressure that the turbo/turbos create by still spinning after the throttle body is closed. Manufacturers only use recirculating diverter valves to deaden the sound. It makes no difference if you recirculate the air, or vent it to atmosphere.

[@WheelsAndBusiness]

That is completely wrong lol

[@shane39767]

@@WheelsAndBusiness no, it's not

[@WheelsAndBusiness]

Shane Hubert Look, I’m not a genius expert on turbos but it doesn’t take a genius to have common sense. A blow off valve is getting the air from a turbo and throwing it to the atmosphere. Then when you are on the gas again the it’s throwing enough gas for the air that was supposed to be recirculated. It’s gonna give you a lag, then it’s gonna give you backfires because there’s too much gas. If you’ve driven any turbo car, put a BOV on it. It’ll run rich without a proper tune. Even with a tune I hear it won’t run 100% healthy. There’s a reason why the companies that make the BOVs put “Tune required”....

[@shane39767]

@@WheelsAndBusiness no, it's excess air that can either be recirculated, or vented out, your car doesnt just throw random amounts of air in no matter where it comes from. By that logic, when you get a bigger turbo and it takes much much longer to start making compressed air, the car would just run like shit and run rich, that's not how your engine works. It maintains an air to fuel ratio.

[@shane39767]

@@WheelsAndBusiness also, i drive a 335i and I assure you that it doesn't lag any more with a recirculated diverter valve vs my hks bov.

[@mitchio83]

“If you have it set up wrong you can cause backfiring” hmmm intrigued..😆

[@martinasis80]

How about a sound plate? Using the oem recirculation valve? Is that bad?

[@SamFBM]

Can you do a video on turbo surging as I hear many people do it but I also hear that it can damage the turbo

[@ashleyjohnson1454]

What about diverter valve spacers? Will they have idle problems sense they use the factory dv?

[@albertohart5334]

Do you know about venting to atmosphere in Qld and how strict the law is etc

[@SupramanTRD]

Here is an easy way to determine the bov you should have. -MAP sensor-Atmospheric BOV -MAF sensor-Recirculated BOV

[@whitebread8068]

So how do you know what to exactly set it at?

[@ahowardcg]

How old is that Dell laptop

[@AKay4tothe7]

I tried this on my 2016 expedition. She ran a little warm, the whistle sounded more like a rush and the boost maxed from 15 to 16 psi. Do with that what you will.

[@traieking]

Wish you told us how to know how much to recirculate and how much to atmosphere

[@cameroncurtis8271]

TRAIE K depends on your car like he said

[@traieking]

@@cameroncurtis8271 yeh? That don't answer my question does it. Of course it will depend on the car. it will most likely be unique to each car even if the same make. People have bigger turbos, better air flow ect so my question still stands... It's probably a case of having access to a Dyno and just tryna find what's best doing little adjustments. I don't know

[@strokeracer]

Does Go Fast Brett have a business name?Another excellent video from Brett.

[@a.p.2472]

But when you use a recirculating bov wouldn't all the air just go right back through the intake and out the air filter?

[@onlynexus]

If the air vents to intake it isn't immediately going to the engine to lean the mixture anyway. Right?

[@s.b9913]

missed this so much

[@yorrickwi]

so i was wondering a turbo stops spooling when the wastegate opens but what if there was no wastegate in the turbine but there would be one in the pump side when the car needs boost its always there because the turbine is always spooled

[@aliqadri4672]

What happen if we decel or let off the throttle on full speed going car for very long time and not accelerate again on recuculate bov valve i mean not at atmophear..????what happen than..???

[@shxkn]

Yaaaa I don’t get the obsession for the BOV sound. I be about that EWG life though

[@MrBooyahmofo]

What about a spacer on the diverter? Cause any problems?

[@samgab]

Thank you for talking sense!

[@ConfusedRaccoon]

I've a question about when the ecu cuts fuel when you close the throttle. Is it really cutting all fuel? How long have they been doing this? so on and so forth.

[@Kollida89]

So if you position your BOV so that it vents to atmosphere before the air passes through the MAF, then the MAF will be reading the amount of air entering the engine correctly.