Blow Off Valve vs No Blow Off Valve | Sound and Science

Today I ran my turbocharged car back to back, with and without a blow off valve (BOV). This included a sound comparison, an explanation of what a blow off valve is and what it does, and finally, my thoughts on if you need a blow off valve on a turbo car.
The car in this video is 2Broke2Boosted, my budget turbo Mazda Miata. This car is running an eBay, HKS knock off blow off valve that's been installed for the life of the turbo setup (since 2020). You can see more of this car on my channel!
Full build parts list available here: tinyurl.com/5a3ksb8k
End Screen Music: 3mbrace - Issues spoti.fi/3hpG1b0
*All links are affiliate links, purchasing through them means a small portion of the total cost goes towards supporting the channel, and there's NO additional cost to you! CashedOutCars is NOT liable for any damage done as a result of videos posted on this channel. Work on and modify your car at your own risk!

[@BigBenlolz]

Flutter all the way!!! Great comparison, so many people demonize no BOV like "you're gonna blow the turbo instantly", but you weren't biased, thanks for that.

[@CashedOutCars]

Thanks! Yeah, tons of people run without them with little to no issues long term. Since I like the sound and the bit of protection it provides, I'm happy to run mine but did love to hear it fluttering!

[@cristianseminario7899]

i honestly would always put a blow off just for the sound i can't care less if the turbo blows

[@skyslatts1280]

U can have it but turbosurge just isn’t good it’ll cause unnecessary stress and lower the turbos life time.

[@Pippy1]

That just made me cringe the second i heard it. Its just abuse for no fucking reason

[@skyslatts1280]

@@Pippy1 ong

[@shredder8910]

I did oil analysis after running BOV vs no BOV on a journal bearing turbo and saw copper wear levels after the no BOV and return to normal after running the BOV again. I'd be concerned about the axial wear on bearings if you're on a journal bearing turbo, if you're running a ball bearing turbo, I believe the bearings are more tolerant to axial forces. Otherwise have fun with the cool flutter! Now, I will mention this is on a 480whp STI running about 28 psi on speed density. On lower boost applications it's not going to affect it as much.

[@CashedOutCars]

Awesome to see some more real data on this. My car runs 14 psi and I’m happy to keep my BOV regardless :) thanks for watching!

[@ilyas5708]

So if its a ebay turbo then fuck it?

[@shredder8910]

@@ilyas5708 especially if it’s a ball bearing turbo I’d say go nuts. I haven’t really heard of ball bearing premature wear due to something like this. Otherwise I think it could affect the long term life of the turbo. Note that is not important to race teams, etc. for a daily driver that you want reliable long term I’d recommend a bov. But otherwise who cares

[@SI0AX]

@@ilyas5708 Ebay turbo's usually don't have ball bearings because those are expensive and they go for cheapest quality. The real problem with cheap Ebay chineesium copy turbos is that the quality control is really bad and that means you could buy 2 turbos from the same vendor at the same time and 1 is really bad and unbalanced and will fail prematurely while the other is perfect and will last a long time. I heard that what people do is buy the cheap turbo and take it to a turbo shop for balancing. You still end up saving money from what I hear.

[@4cyl]

@@shredder8910 i got a gt2560r which is a ball bearing, so bov would not damage too much? Or should i run no bov, is there any other thing other than a bov i just dont want damage on the turbo

[@michaelbarefoot6334]

Good explanation! I weld, fab and tune right out of my home garage, I cannot stress this stuff enough to "car guys" with big egos. They always think what Joe Schmoe said on a forum 20 years ago is total truth. I'll start using this video for them. I ran without one for quite some time, loved the flutter and it was tuned for it. Added a TurboXS RFL for a change up. Beyond noises, I did have issues with high boost and couplers coming off without the BOV, but that was only a couple van-gen clamps of a problem. Great video!

[@CashedOutCars]

Thanks for the kind words! I built this whole thing including the tune in my garage too, sounds like we’ve got quite a few similarities!

[@xboxonex7481]

I rarely ever like videos, but this was exactly what I was looking for, appreciate the video👍 I swapped from 1 50mm BOV to 2 forge diverters & haven’t done the vacuum lines for them yet, I like this because you showed what it does without vacuum to the BOV & justified my decrease in boost pressure for now👍

[@mitchio83]

I have an atmospheric diverter valve and i get the BOV sound at certain rpms and a flutter at other rpms, best of both worlds sound wise.

[@usiiotv5264]

a friend of mine who has an STI has the same system ! i was wondering how it was called so thank you ;)

[@MattyManRC300]

same here! I got the Go Fast Bits DV - higher rpms throttle release - BOV sound - low rpms throttle release - turbo flutter

[@clapped1.629]

How are you not at a million subscribers. I havnt been here since the beginning but I’ve been here since 10k and I’m amazed at how much your video quality has increased. Your awesome please keep at it

[@CashedOutCars]

I appreciate you my man! I do plan to release some videos that will appeal to even wider audiences to try and boost the channel. Stay tuned for that :)

[@ueltrades9479]

it sounds so cool without the vacuum line disconnected

[@tonyjennings8199]

Thanks for explaining what a BOV does and how it works

[@Limit19970]

I really like both sounds, but I think I'd pick w/BOV hissing/breath sounds over flutter personally.

[@jh7548]

sweet video. “blow off valve” was said 358 times

[@CashedOutCars]

I was trying to break the record for most times said in a 10 minute video ;) thanks for watching!

[@gregchristofi1318]

Great explanations.

[@3Dsoundblast]

The information provided about everything with a bov on is correct, however some of the information with the BOV disconnected is just a bit off and car specific. Id recommend revisiting or relooking into this with a different style bov or possibly a more modern vehicle.

[@doublemiata]

Have no bov on my car and it loves it sounds so good, been playing with some different length intake tubes to tune the flutter sound 🙃

[@CashedOutCars]

Enjoy it! I've been messing around with intakes too.. stay tuned for the next video :)

[@82raptor]

I ran a BOV on my 93 XR-2 (a front wheel drive MX-5) and I had no problems. That car had the old school barn door MAF and I had no problems.

[@CashedOutCars]

It is common for cars to still run with atmospheric bovs. Did you have an AFR sensor? You’d very likely see it go quite rich when you let off

[@brycebecker3956]

I’ve been running mine with blow off valve disconnected for around 6 months. Haven’t noticed any leakage out of the flyin Miata/turbo smart bov with just line disconnected

[@ckryses3962]

New to your channel mate! You have explained so well with perfect examples! I was mad in love with hissing sound of turbos, during my childhood I watched Hotwheels aes driving with that swet decent hissing sound..since then I am a praiser of hissings!! No offense my stutu sounds like rats under the hood! Ugly sound... I enjoyed your video...subsed too! Keep up the work mate!

[@CashedOutCars]

Thanks for the sub and the comment my man!

[@kspades2530]

BOV sounds sick

[@CashedOutCars]

Thanks man! I enjoy it

[@thefearonshop]

Building a boosted RHD Accord wagon!! Thinking flutter for me 😊

[@2024s_truth-speaker]

Love the video. Building a twin turbo 347 in my mustang and still learning alot as this is my first turbo build. Thanks man.

[@backwoodsredneck1776]

I like the mx5 bro nice one, now make it a drift build

[@CashedOutCars]

Which sound do you prefer? Want to visualize air exiting out of the turbo? See this video! kzbin.info/www/bejne/hJPZdKN-bMl9hNU

[@grantt8760]

BOV 100%

[@shirtz69r]

Stu Stu Stu all day

[@guspac88]

SsssssssssssssSSSSSSSSSSSSTUTUTUTUTU

[@BFE08STI]

Anything other that HKS SSQV

[@CashedOutCars]

@@BFE08STI hahah it’s not even an HKS valve it’s an eBay special knock off.. but it’s been doing the trick great for more than 2 years

[@Vinny_Capatony]

My friends wanted me to get one for my Audi A3 but I found out the recirculatory valve it has factory is actually better and will make my turbo last longer so no blow off valve for me 😅

[@eternalrage1085]

Question: do diesel engines have blow off valve? I mean they dont have throttle plates. But i do here trucks make the blow off valve release sound between gear changes. But i dont here it in SUVs or small diesel engines.

[@danielponce2010]

I've always ran compressor surge on my drift car.

[@mohamedsakka2338]

sound is science

[@GilbrianLopez125]

I have a Kia Forte gt 2020. Still OEM with the BOV and turbo but I will like to hear the turbo also but also the BOV. Right know I just hear the BOV

[@darkomtc]

Hey. I have almost identical surge sound as you when you have no vacuum line connected. Only problem is, I don't have a BOV. I'm on diesel, so only wastegate. It doesn't happen every time, but there are periods when almost full ride is stututuing or long scraping. Could it be that my wastegate has vacuum leak, since is not constant?

[@v8_sami]

Well guess I am going no BOV This summer for the Miata. Thanks lol

[@CashedOutCars]

Hahaha enjoy the noises!

[@MasterSumai]

Anyone know that this dude talks ALOT with his hands? Lol! Very good video & very well explained in detail.

[@michaelbrown9031]

Cool video. I have a BOV on my FD, but don't have it plumbed in as I love the flutter. The car isn't used a great deal, so turbo life expectancy isn't a high worry for me.

[@CashedOutCars]

Thanks! Enjoy that car, it’s a special one!

[@foxdinestie3899]

I run a tial on my rx8, every now and then I will plug the line and I love the sound of it.

[@craftingnl]

I would recommend removing the blowoff entirely. With it "unplugged" you might run into it boostleaking at higher boost levels. Had that same problem on my rb25.

[@icebreaka1969]

mini cooper S F series make turbo flutter sound all the time, it does not have diverter valve or BOV from the factory.

[@user-tj6ws1my6y]

So I have a Honda accord with a k24z3 I plan on throwing a turbo on it and I want the no bov option for the louder turbo noises what would I need to not blow the turbo and keep it reliable or is there no diffrence just don’t run a bov ?

[@ludwigagawin]

Why your BOV leaking boost when vacuum line is disconnected? The pressure should be holding that BOV closed. Did you not plug the disconnected vaccum line? I'm also using an hks SQV4, I'm not losing boost when my vacuum line to the BOV is disconnected.

[@valentinvasilev8590]

Im driving a lexus is200 turbo on 0.7 bars of boost and running NO BOV, no issues whatsoever (with the turbo :D)

[@CashedOutCars]

No blow off valve doesn’t guarantee issues, but I generally accelerates them. Enjoy that car!

[@Reaper1008]

What if my car has a Stock Diverter Valve, but I just disconnect the hose so it releases to the atmosphere ? My car is a 2016 Veloster Turbo

[@00powersmoke]

Diesels run no bov, do to no throttle plate to close. And also run 20-30 psi factory depending on the make and model. The issue that comes from compressor purge is it wears out the thrust bearing. Thats the bearing keep the rotating assembly in the center of the turbo. Just like the crankshaft thrust bearing. The reason it wears it out is the imbalance between boost and drive pressure. It'll live just not as long.

[@minusthemachineagain9342]

Some industrial Volvo diesels have a throttle plate and still no blow off valve

[@00powersmoke]

@@minusthemachineagain9342 that throttle plate is a failed attempt too increase gas velocity and prevent the EGR goo build up in the intake system

[@minusthemachineagain9342]

@@00powersmoke you are correct, it should only be active during a regen, still weird to see on a diesel.

[@00powersmoke]

Most diesels since 2008 have a throttle plate thanks to the epas crippling ridiculous emissions standards. Yet China and Indiana are unregulated and economically and environmentally killing the rest of the world..

[@sircefiro]

most efi diesels run a tb, in smaller things anyway

[@callofdutycoop1548]

Honest question! A urgent matter is at task in a few days I’m going stage 3 on Audi s3 with ots tune is it cool if I use a blow off valve ? Or it is dangerous

[@ohheccwaddup3225]

Nice video, man! Wow, the blow-off valve you have is just as meaty sounding as the one on my old '05 Legacy GT! Sounds awesome! How much boost pressure are you running?

[@CashedOutCars]

Thanks my friend! 14 psi

[@ohheccwaddup3225]

@@CashedOutCars Very nice. I hope your Miata keeps bringing you joy. Cheers!

[@claudioreverb]

Nice video, I would like to understand if a valve with recirculation or one that discharges into the atmosphere is preferable to have the maximum performance from the engine, clearly tuning the ecu correctly and if there would be a way to have the valve discharging externally with a map for track use and bypass to another recirculation for use on the road. Thank you

[@QuincyStick]

for racing a recirculation valve would be better, as you're able to maintain boost pressures whereas an atmospheric blow off valve makes you lose all your boost.

[@tbas8741]

depends if you worried about turbo lifespan

[@jaysullivan8350]

So question. I have a 2016 Audi A3 2.0 that originally came with a diverter valve. I switched it out for a TurboSmart 50/50 Bov. Will that make the car run rich, or is it perfectly fine?

[@sircefiro]

Should be fine, that's the idea behind the dual port

[@enhancedphysique6452]

Hey man is that thing one of those 40psi 79whp inline 2 cylinder that rev 15k rpms? Things are mean buggers, you know like those Hondas.

[@craftingnl]

Not running a blowoff valve won't damage your turbo in any way shape or form. Building boost with a closed throttle body will ruin your turbo however, this is the same with or without a bov.

[@pprb123]

What other way is there to avoid building boost without a BOV?

[@scubascuba]

@@pprb123 external/internal wastegates! They stop your turbo from building boost past the specified boost pressure

[@user-ce5qz6ps2r]

I got a 2015 sonata 2.0t automatic that I have a blowoff valve but not getting the flutter

[@CashedOutCars]

Newer cars usually mask the sound, likely an aftermarket intake would wake it up noise wise, though I haven’t specifically tried it on a Huyundai

[@scattkiwiman]

good explanation. I'm running a diverter valve iso a Bov. Works good and makes less noise

[@AustinCProductions]

good video, I just want to sneak in quick a couple small things. the new VW MK7s don't have diverter valve on the Jetta S models, but they do have small boost pipes that run from the charge pipe, and manifold and pump them back into the turbo inlet for boost pressure relief ( to an extent ) I built my own charge pipe with a Turbo smart duel port valve and its been great, far faster spool up, but a small lag between shifts. setting up an adjustable BOV is key to a good running engine, and turbo response time. also one last thing, not running BOV isn't totally bad for the turbo, yes it can cause damage to the compressor but the sound you're actually hearing is the hair breaking surface tension from the compressor blades themselves. but yes, any turbo vehicle should run a BOV, and or a plumb back valve for longer service life of the turbo, and engine. but a again, good video, and its nice to watch a video with good audio.

[@FIHBANKORT]

how can in intake be more air near the maf when having a blow off, this doesnt make sense to me

[@shimmytube777]

I like the BOV sound more than the fluttering.

[@CashedOutCars]

As do I :)

[@prestonranger3082]

Great information, just which I had a car like that

[@CashedOutCars]

Thanks! This car is a blast, I’ve built it over 7 years :)

[@prestonranger3082]

@@CashedOutCars I’m looking into getting a 4 cylinder car. Automatic/ manual so I can get better gas mileage. Got any recommendation on what to look for? I’m currently driving a 4.0L V6 Ford Ranger so looking to get better fuel mileage.

[@ErikSeastead]

@@prestonranger3082 manual Honda insight are super cool. 60mpg and pretty cheap.

[@Kabal1247]

A BOV can be "tuned" to open half way so there's both a little tss and flutter right?

[@CashedOutCars]

In many cases you can tune them with different springs, though this isn’t something I’ve experimented with with mine

[@rajgj7041]

I have a touran 1.4 Tsi 140 hp and my turbo was broken, should i use a bow off valve or not , and which one you suggest

[@CashedOutCars]

Typically I'd go with what is OEM on non-project cars. That car may have a diverter valve from the factory, which does a very similar job, but I'm not sure

[@timothystrunk7323]

That little pod on your valve cover might be messing with things. When I put one on my car ran rough

[@CashedOutCars]

I haven’t had issues with mine, but it’s tuned on a standalone ECU with no MAF sensor. What is yours running?

[@haroldencarnacion6862]

I drive a 10th gen Civic 1.5 turbo with recirculating bov from the factory. Do you think running a vent to air bov will run rich and do harm the engine in the future? I was reading forums and some says yes some says they’re running those kind of bov with no issues. Appreciate for the answers. More power to your channel dude.

[@bladercomedy]

You have a gaurdian design wheel too??

[@CashedOutCars]

This is a wrap I did from East Detailing!

[@cumminscummins5684]

Question, what about yes to the BOV & no to a waste gate?

[@CashedOutCars]

In that case with no wastegate you’d have no control over boost levels, and would just be running at whatever the turbo puts out. In most cases this will be far too much

[@slickstrings]

uncontrolled boost spike and its a race for which blows up first, turbo or engine

[@sircefiro]

lol nice 1

[@eunositsme2769]

the issue with my car is it idles at 2k rpm’s. do you think this could be the issue? i have a BOV and it flutters like there isn’t a bov.

[@Pippy1]

sounds like a vac leak because the bov is working backwards

[@estebanod]

Quick question Dump valve = blow off valve ? And I thought BOV made a stutututu sound?

[@anthonylodi8980]

I’m trying to make my Jaguar e-pace faster but also make the bov sound we love. Any comments

[@AL-ru3nk]

Is it normal for a blow off valve to make that whoosh sound when just taking off slowly or driving normally? It doesnt work every time i boost i can just hear the turbo flutter. Does that mean the blow off valve is broken?

[@Doughy3205]

Could be overboost

[@AL-ru3nk]

@@Doughy3205 how do i fix that

[@Doughy3205]

@@AL-ru3nk take it to shop mate, could be a load of shit, faulty pressure sensor, broken hoses etc

[@mrcash34]

How you finding the eBay special BOV? Any issues with it? Keep up the good work! Cheers

[@MJohonez299]

Wow! If I had to choose between that BOV or no blow off valve, I'd definitely chance my reliability and never purchase whatever you did. If you "pssh" for more than 2 seconds than you're just playing with it. Flutter all day.

[@DirtyGarageTx]

Link to the bov?

[@justinemorales4833]

With BOV Sounds cooler and we can’t argue

[@CashedOutCars]

That's my preference, but I like both :)

[@CarloLeonKolega]

1:28 its only for gasoline engines, not diesel :)

[@CashedOutCars]

Yes I should have clarified that in this video. Diesels are very different animals!

[@Scott-ez9ns]

If u thought about it you could have capped the bov with a rubber line and a screw ;)

[@SkYxLeGaCY]

The disc's are rubbing not only because they're under pressure.

[@chevy383jt]

I just don't have a TIG welder to weld my BOV flange to my intake pipe. Single 98/88 cheap turbo on a gen 4 5.3 with forged pistons. The flutter it makes sounds awesome, but I don't want to damage my turbo. I made a new friend a few days ago, who has a working TIG setup and offered to weld it. I will be doing that. I have a TIG welder, but the welding gas shops won't fill my gas bottle with 100% argon since it's already had 75/25 argon/CO2. Bottles are expensive. $300+ for a new, empty bottle. Bleh

[@bomanndk4805]

What about VW and their Diverter Valve? How Does that Work

[@CashedOutCars]

If I remember correctly that’s essentially a recirculating valve. It still relieves boost pressure, but directs it back into the intake track rather than to atmosphere

[@richolishis94]

Just so everyone knows, they make turbo for this application. It’s the ones with all the fancy holes around the turbo inlet side. Those control flutter for non BOV applications. However most modern day cars have internal wastegate s now and there is no need for a bov as the exhaust pressure is regulated to in tern regulate boost pressure.

[@CashedOutCars]

Unfortunately that’s not what an internal wastegate does. It does regulate boost pressure (this isn’t particularly new tech) but it doesn’t replace the need for a blow off valve.

[@Persocondes]

holes around the inlet side is NOT for compressor stall (sudden off throttle), it's for protection against self destruct from compressor overspeed if the wastegate fails to open to regulate boost pressure. Internal wastegate is on the hot side of the turbo and has nothing to do with the cold side of the turbo, BOV relieves the pressure on the cold side of the turbo.

[@DriftNick]

@@Persocondes The holes are literally called "anti surge", they are designed to prevent compressor surge on throttle, they are not designed to stop overspeed if a wastegate fails, if you wastegate fails they will do nothing to stop that.

[@Persocondes]

@@DriftNick ah ok, i learned something new today Thanks! i never knew there's On throttle surge, usually when the engine is too small paired with too big of a turbo

[@adriandangelo3029]

I don't even have a car but cool video though xD

[@CashedOutCars]

It’s fun to watch and learn, thanks for watching!

[@timscott7136]

The best option is a recirc valve.

[@spcpatterson6586]

Sometimes not always.

[@CashedOutCars]

For many cases yes, which is why OEMs tend to do that

[@spcpatterson6586]

Both serve to vent residual charge pressure at throttle lift to prevent reversion back into the compressor wheel preventing lag upon reapplication of the throttle. Whether the air is vented to atmosphere or recirculated makes no difference as to preventing reversion and subsequent lag. The only reason to reciculate is if the engine management system (MAF-based usually) requires it or for quiet operation.

[@srhabb]

And now for the no blow off valve comparison = $$$$$$$

[@stephenstarling2578]

I run turbo engine it had recirculation to the air intake but I have seen remove that so it vents to atmosphere is safe for long term use

[@CashedOutCars]

It often won’t cause damage on maf cars, you’ll just be run richer after letting off than you typically would

[@stephenstarling2578]

@@CashedOutCars thank you im trying to figure out a straight answer for awhile thank you

[@CashedOutCars]

You’re welcome, typically the worst that would happen is you’d fowl put plugs or have idle issues because of the excess fuel. If it’s extremely rich you could damage your catalytic converters. There likely wouldn’t be anything more catastrophic than that though!

[@stephenstarling2578]

@@CashedOutCars true the car only 12,000 miles on it .it's a kia forte gt 1.6 t

[@ConalFlood]

My inner child is screaming BWAPPPP BWAAAAAAPPPP BWAAAAAAAAAPPPPPPPP

[@grantt8760]

ftssss vs stutututu

[@VoltzyBoi]

IKRRRR, I want the stustustustustu😂

[@samb3188]

This really makes me curious how the turbo can “blow off” during free revving. I also have a turbo 1.6, and it never does it. I wonder if the turbo is too big (t3) and it just doesn’t spool enough for there to be an audible noise.

[@CashedOutCars]

Yeah it all depends on if you’re making any boost or not! This isn’t making much under revs, but it’s a bit. Also, different BOVs can have different springs in there, making them open at different levels of vacuum

[@vzr314]

This is an old car with obsolete turbocharger technology. Modern forced induction engines are based on variable-geometry turbocharger where BOV is completely redundant.

[@foxjoakill7288]

What is your turbo name ?

[@CashedOutCars]

It's a generic eBay T3 turbo!

[@ianzalewsky3051]

Bov for reliability

[@MJmusikstix]

Zuuuuuuuu Stututututu~

[@dropp5708]

i do not have a car

[@makantahi3731]

install turbo behind throttle body and then you do not need bov

[@Drunken_Hamster]

I don't want flutter. It sounds basic and annoying and I'd just prefer a BOV at that point (especially a loud one like a turbosmart RFL. No, what I really want is that CHOOOOOOO-CHOOCHOOCHOOCHOOCHOO when I let off the throttle like in those stereotypical Skyline and Supra clips.

[@DriftNick]

The choochoo sound is turbo flutter.

[@BUZDRIFT]

I only run a friggin BOV over 50 psi of boost and tight AF! Every other car has no BOV with Zero damage to anything!

[@_.oddy.oddy._]

4:59 angry horse

[@dmlarry]

my 22 civic si has a BOV and it’s kind of a shitty OEM one but it sounds great. I want to run a waste gate when warranty is up

[@shaoyang5650]

If your car is turbo from factory it has a bpv (bypass valve). It is NEEDED not wanted. If your car is boosted you NEED a bpv or bov. The difference is the bov vents directly to the atmosphere and the bov recirculates the air back into the system. If you run a turbo or supercharged car without bpv/bov you will get surge and it will result in premature failure.

[@DriftNick]

My car had a bypass valve from factory, been running it for many years without it.

[@his18v2000]

Volvo S80, no blow off valve

[@axisbreeze429]

I'm sorry but that fucking bov sounds so good ugh shhhhhhhhhh

[@cobii5174]

small turbos shouldn’t be exposed to this surge

[@DriftNick]

How small? 30+ year old factory Nissan turbos have no issues with it.

[@i3lack4u95]

With sound like some nfs car Without Ahh that flutter

[@roelandzw1846]

It's time for alignement to set the steering wheel straight. So annoying and it's not even my own car😉😇

[@CashedOutCars]

Absolutely, I put the wheel on quick after rewrapping it and definitely need to fix that. It was even more annoying on track this past weekend. I’ll fix that soon :)

[@Das-eq2wk]

Air doesn't go back through the turbo without a BOV. Its a common misconception. The turbo is operating at hundreds of thousands of RPMs and the air can't force the turbo to start having negative RPMs and allow it to flow backwards. Compressor surge occurs because the air pressure in the intake tract becomes so high that the compressor physically can't compress the air anymore. Instead of compressing, the air at the turbo detaches from the blades of the compressor causes the stutter sound.

[@CashedOutCars]

I didn’t say it spins backwards! It doesn't need to for air to find it's way through. I have a slow motion with fog videos i took that shows air escaping back out the turbo, to be featured in an upcoming video Also, here’s an article that I sourced some of this info from, with experts saying the air does go back to and through the compressor wheel. themotorhood.com/themotorhood/2015/9/14/does-your-car-need-a-blow-off-valve-we-talk-to-the-experts How would high pressure air escape the system, once the throttle is closed, if not through the turbo itself?

[@Hunteratloppshop]

@@CashedOutCars even with the throttle plate closed, it doesn't stop the engine from pumping air out of the system.... Flutter is the buffeting of air that is now at a significant velocity delta in terms of compressor RPM's

[@CashedOutCars]

For those saying air doesn't go back through the turbo, please see this video starting at 5:13 kzbin.info/www/bejne/hJPZdKN-bMl9hNU

[@DriftNick]

The air goes back out the intake of the turbo, it's not a common misconception, it's a fact, it's one of the things that can cause issues with air flow meters.

[@DriftNick]

@@Hunteratloppshop The amount of air the engine lets in when the throttle plate closes is a fraction of the air that is in the piping between the turbo and the throttle plate, most of the air goes out the intake of the turbo.

[@user-vp1xm7oj3b]

I’m conflicted

[@junitomaster6689]

and its cheaper to not run a blowoff since you dont have to buy one, specially if you are like me and you are running 20 bucks diesel turbos

[@Useless_101]

This is something i see alot of snd its so misunderstood. Turbo's do pull more air into the engine BUT they do not push it, semantics i know but for a better learing experience it makes sense to explain it the correct way. Exhaust gases cause the rear turbine to spin which in turn causes the attached front turbine to spin pulling in more air, the amount of air a turbo can pull into a turbo is dictated by the amount of exhause it is pushing out. So the TLDR version turbo chargers pull air not push it, again semantics but in my mind it helps to understand things from an accurate perspective.

[@Pippy1]

U might already know if u bought it that way but thats a fake SQV

[@CashedOutCars]

Yeah this whole turbo setup is eBay parts, it was $40 and has worked great for a bit over 2 years at this point

[@agustingerosa]

This is not science. The soud part was great

[@inevitabilityx366]

So you're telling me all the formula drift drivers that have the Sssstutututu are all wrong you do not need a blow off valve this backwards pressure does not exist and holds pressure in the tubing if your turbo start spinning backwards stop buying eBay turbos bro my EcoBoost and my v6 turbo Camry have no blow off and 75k miles on both engines and turbos the Camry is super getto and I still have had no issues please experience a turbo braking or wearing you'll find something else broke it like for you your enjoy fucking turbo and 1980s blow off👍 like I understand it's a nice sound but there is no actual need for it but if it make you happy do it

[@inevitabilityx366]

Also please go put a turbo in a vacuum put pressure in remove pressure you'll never see that thing f****** spin please stop saying stuff you don't clearly know

[@CashedOutCars]

No one said your turbo will spin backwards except you. Air escapes through the turbo as it surges, but that doesn’t require it to spin backwards. As mentioned in the video, there’s no guarantee of issues. Lots of people run without them. Turbos have come a long way. Top level Motorsport is often very different than street cars as well, this video is aimed at street cars. But regardless, there absolutely is significantly force on a turbo as air escapes back through it. That’s why major turbo OEMs like Garret recommend blow off valves in their paperwork. Also, car manufacturers wouldn’t use recirculating valves if they did nothing!

[@creedns]

A bov might not be necessary, but you know what is? Some fucking punctuation so people can remotely understand a god damned thing you're trying to say on here.

[@Keep_Crying_Son]

Any good mechanic will tell you they're a waste of money....

[@CashedOutCars]

Several turbo manufacturers recommend them in their paperwork, and OEM car makes wouldn’t use recirc valves if they were a waste of money, there’s a ton of merit to them. But cars do make great noises without them