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

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

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

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.

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.

Venting to atmosphere sounds so much better though

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

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 :)

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

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 !!

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

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

bwaaaaaaaa sutututu

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.

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

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

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

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 ;)

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

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

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.

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

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

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.

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.

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

Thank you for clearing this up with actual knowledge

Can confirm Turbo falcons can go full atmospheric Bov without issues

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

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

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

This guys explains it nicely. Thanks Brett.

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

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

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

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.

mean while venting to atmo is illegal here in Australia

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.

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.

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.

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

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!

How old is that Dell laptop

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

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

backfiring? sign me up 🚗💥

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

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...

Fantastic video, thank you :)

I blew off my valve when I saw Brett 😉

Best explanation video around!

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.

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

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

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

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.

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

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

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?

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)

I did ecu tune , down pipe , bmc filter and renntech bov for my amg gts , but it still runs like a stock amg gts just a bit faster. Is it because of bov

Great episode. Would have been nice to mention MAP cars and put that one to bed.

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.

Awesomely explained.

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

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

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.

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

My brother took his recirculating blowoff valve off his 97 forester 5 SPD manual and everytime he stopped at the lights it would stall 😂 I have a auto version I'm still going to try it out 😂

wow thank you for this video, super helpful

Thank you for talking sense!

Speed density carries the day yet again!

Irrelevant if your car uses a MAP not a MAF.

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

Prime example, on an ecoboost f150 the blow off valve tube connects after the mass air meter. With it like this there are no extreme rich or lean factors within the motor. And that is with the factory location capped off. Only difference is you don’t have useless vapors recirculated through the engine. Hense factory setups usually collect enough moisture within the inteecooler which cause the infimous hesitation on fords that people complain about. Let the crap vent and save future issues

missed this so much

time to run a bov venting to atmosphere on my draw through carby setup.

Awesome explanation!!thank you!!

Thanks for this info! Very Helpfull!

Thanks Brett. 👍

I don't disagree with any of this, but there's something that's overlooked every time this is talked about. Every mechanism, port, valve, etc on the inside of the intake is protected by Factory design, by a simple air filter. If you run your valve to atmosphere, the components of your valve are now open to dust, engine heat, grime Etc. And if you run a piston type blow off valve like I've installed, its really just tolerance on the cylinder wall and Lube to get the tightest seal out of the internal cylinder. Lube attracts dust. Your valve May wear out quicker. If you run a diaphragm type, you are subjecting that diaphragm to engine heat possible dust fumes Etc that will make it dry out and crack and leak sooner . Thank you so much for this video it's a hundred percent correct, this is Just a point that's always seems to be overlooked, but in my opinion worth mentioning as I try to build my projects to outlast my great-grandchildren with as little maintenance as possible.

no mention of Check engine light possibilities? Huh. I would have thought he would have mentioned that at least in passing.

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

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

Great video and topic.

I'm sure someone owns a mps/Mazdaspeed 3/6. XD

WRX/STI guys on here tryna see if they can run an hks ssqv lol....

What if the BOV is before the AFM ;)

Brett. You mentioned a MAF sensor set up but didn't mention a MAP sensor set up. Is there a difference?

Forgot to say that if your car doesn't have a MAF or a AFM you can vent without any real affects.

Short answer: if you're venting metered air, it CAN be okay, depending.... It also can be very bad. If you're speed density based, no worries...

Actually if you know good tunner, you can "turn off" DV in ECU. It will not count air vented into atmosphere by BOV. The. It will work awesome. 1 thing, with bov you have little bigger lag because of vented out air from the system, but on the other hand, turbo will live longer. BOV is ok when your car is far away from stock. Flyes away

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

i put on a pod filter and removed all the silencers in the intake and get a fantastic purge sound, and my car still has the factory diverter valve.

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

Rich conditions = VROOM PTSHH BANG POPOPOPOPOP BANG.

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

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.

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.

Just get a the duel port turbo smart bov it’s recirculating and vent to atmosphere so it’s best if both world and you can adjust the spring pressure