FAQ: All your Blow Off Valve & Diverter Valve / By-Pass Valve Questions!

[1997gtx]

another quick question if you ran dual ssq's and recirced them would there be a problem

Most say there will, but so few have tried it, I can't say for certain. I only know of 1 person that sucessfully ran them. They are tech. never a fully circulated valve, as they still "blow-off air".
--Adam

[1997gtx]

reading through this thread, I see a little talk about it but nobody actually running splitters. I've got one on my TT that works flawlessly and I'm getting my S4 next week so I will be putting splitters on it.

Sweet! Good luck. Please be sure to do a write-up on what you think of them. So few people have them because the 710N's (from the TT, lol) are what most of us run. Those that do go the Forge route, usually stick to the proven 007's. It's hard to get us stubborn S4 guys to try new products that may or may not work just for a sound ;)
--Adam

[MavSBM]

Too much BOV talk.
"...I would greatly appreciate links to the cheapest / most reliable places to purchase aftermarket DV's."

I've found 710N's for $45 @ http://www.mjmautohaus.com/catalog/p...roducts_id=985 and http://www.ecstuning.com/stage/edpd/...l=&engine=2.7T

Anyone find them cheaper?

[Fabelhaft]

ok...should be my understanding pb...
so B5 S4 with BOV = fxked up, unless re-route?
and the other question is, is possible to have this bov sound on the B5S4 http://www.youtube.com/watch?v=NEZUk...eature=related
instead of this http://www.youtube.com/watch?v=nElyz...eature=related

[shadwarr1]

710N's for just under $39. Spend over $50 and get free shipping:
http://www.autohausaz.com/search/pro...ber=06A145710N

[Charlie]

Is it possible to Run the MAF after the turbos? example... before the TB

[Jung]

i've thought about that, and I think it's been done, like on this:http://www.youtube.com/watch?v=3rq9Q0qR9yA
but that ^ has massive $ put into it. You'd probably need a custom tune also.
I thought that maybe putting it before the TB would work like Charlie said. Get a custommade bipipe, but have it extend a little more towards the front of the car, so there'd be room for the MAF.
has anyone actually done this?

[Fabelhaft]

...anyone who can answer my question? post#85!!! PLZ!

[Auburnsky1287]

Update: There is a recirc kit for the HKS SSQ's.

Will it make the pshhh noise? Yes, but slightly muffled.

[Fabelhaft]

^un...which kind of pshhhhh sound? I posted 2 kinds in post#85
I am lookin for the pshshshshshsh sound instead of pshhhhhh...thx!

[supasuprase]

youre a ricer

[Jung]

^un...which kind of pshhhhh sound? I posted 2 kinds in post#85
I am lookin for the pshshshshshsh sound instead of pshhhhhh...thx!

what are you talking about? like turbo flutter? http://youtube.com/watch?v=MS1Q8AHqecE

you dont want that
and blow off valves dont make you a ricer dude ^... unless a 1200 hp supra is ricer (they have BOV's). stop being such an ignorant elitist.. "mmmyyes blow off valves hahaha.. my diverter valves are SOOO superior to your silly things mmmyesss."

[1997gtx]

It seems like an awful lot of work for a sound.

But if that's what you're into, pay the money, make the adjustments and report back :)
--Adam

[Fabelhaft]

well, my main point is, why are there 2 kinds of bov sound?
and 1, i am not a ricer and dont even like one, 2, if the mod will hurt my car, then nah.
so what I am askin is WHY some of the DV/bov has loud pshhh, some don't, and WHY some are pshhh and some are pshshshshsh?does it matter?
thx for the answer guys, and - comments are not needed.

[Jung]

what you're talking about with "psshshsh" is turbo flutter( i believe ). The Blow off Valve is not big enough for the boost level on the car, so there is some air going back into the turbo instead of being vented, so it creates a chatter sound. I'm not an expert and probably wrong, so would someone else like to elaborate?
It's really not a design in BOV's to make this type of sound, you will want a straight pshh when letting off the gas, nto flutter. Flutter decreases the life of your turbo

[1997gtx]

what you're talking about with "psshshsh" is turbo flutter( i believe ). The Blow off Valve is not big enough for the boost level on the car, so there is some air going back into the turbo instead of being vented, so it creates a chatter sound. I'm not an expert and probably wrong, so would someone else like to elaborate?

It's really not a design in BOV's to make this type of sound, you will want a straight pshh when letting off the gas, nto flutter. Flutter decreases the life of your turbo

You're kinda right. The HKS SSQ is a "sequential" BOV. It's supposed to make that sound. A normal BOV should not. If you have something like an HKS RFL, it should not make the shuddering sound. It should be one, nice, smooth sound. The HKS SSQ will, however, make a shuddering (psshshshsh) sound becuase that is the way it is designed to work.
--Adam

[Fabelhaft]

^thx for the answers, now I know more!!!
but after all these readings, I find out most of the people are sayin bov are bad for B5S4 (but they still have them...what?)
what kind of dmg will it do? and if normal bov is makin flutter sound, how to fix that?
oh...and...can u guys put it in a easy way why we aren't supposed to use bov?
I appreciate your help, guys!
(i am still lookin for the right S4...damn...)

[supasuprase]

what are you talking about? like turbo flutter? http://youtube.com/watch?v=MS1Q8AHqecE

you dont want that
and blow off valves dont make you a ricer dude ^... unless a 1200 hp supra is ricer (they have BOV's). stop being such an ignorant elitist.. "mmmyyes blow off valves hahaha.. my diverter valves are SOOO superior to your silly things mmmyesss."

Ironic, I came with my S4 from a supra (hence my screen name)
Also, your right, blow off valves don't. But posting on forums and making computer sounds like "pshshshshh"...makes you one.

[supasuprase]

But to answer your question on a more educated level, the reason that the BOV's often sound different is for a few different reasons, which I believe may or may not have been mentioned before. The first thing that can make an impact on sound, is that of the spring in the BOV. The sound, (in my experience HKS SSQv) will change with the tightening or loosening of the spring (you can use a basic tool to do this). Another thing that can affect sound is whether you get an open loop or closed loop system, as well as design. The same way cat-back exhausts sound different, BOV's are the same way,.

[1997gtx]

^thx for the answers, now I know more!!!
but after all these readings, I find out most of the people are sayin bov are bad for B5S4 (but they still have them...what?)
what kind of dmg will it do? and if normal bov is makin flutter sound, how to fix that?
oh...and...can u guys put it in a easy way why we aren't supposed to use bov?
I appreciate your help, guys!
(i am still lookin for the right S4...damn...)

There are very very few (I can count these people on a single hand) people that run BOVs on the B5 S4. Reason being is that our car's computer uses the MAF after the turbo's (ie - metered air). A Blow OFF Valve vents the air to the atmosphere (hence the sound) before it hits the MAF. Thus, when the air hits the MAF, it's off, and the car suffers for it.

Some people have also tried to use a recirculating BOV, which works better, but still not to the desired 'stock' metered effect.

If a BOV makes a flutter sound on a NORMAL car that CAN use BOV's, typically you're experience "boost surge" and the boost is turned up too high.

On a B5S4, there is no way to healthily run a BOV unless it 100% reciruclates. But then you no longer have a Blow OFF Valve. You have Diverter or By-Pass Valve, like we currently run. And even when that happens, it still isn't 100% kosher.
--Adam

[Fabelhaft]

On a B5S4, there is no way to healthily run a BOV unless it 100% reciruclates. But then you no longer have a Blow OFF Valve. You have Diverter or By-Pass Valve, like we currently run. And even when that happens, it still isn't 100% kosher.
--Adam

so basically they are the same thing just the different circulation?
and thx for the info, guys, gotcha!

[1997gtx]

so basically they are the same thing just the different circulation?
and thx for the info, guys, gotcha!

They are the same thing in 'air flow', but DV's are made differently than BOVs. Meaning, you simply can't take one hose off of the DV and expect it to act like a BOV ... and vice versa.
--Adam

[Fabelhaft]

︿thx, but if shxt happen with BOVs, what kind of dmg will it do?

[Jung]

please elaborate your question more. if what happens to a BOV? if it breaks?
and use the entire keyboard. from my measurements, from 'd' to 'a' is less than an inch. not too hard to spell a word.
i've tried taking my recirculating side of the DV out, and it does not work. we have wayyy to much vacuum for it to work, and it's not constructed as a BOV.

[1997gtx]

︿thx, but if shxt happen with BOVs, what kind of dmg will it do?

I'm assuming you mean what will happen to the engine if you run a BOV?

It will cause you to run rich. The MAF is expecting a certain amount of air; and, in turn, mixes fuel with that expected air. If you vent that air back out, the car will send the same amount of gas for less air -- thus, making the car run rich. All the extra gas will enter your exhaust -- this is when you see a car shoot flames or 'pop'. Your car would run like crap enough for you to stop before you did permanent damage...but, eventually, you could see clogged injectors, bad 02s, cats and EGT sensors.
--Adam

[Fabelhaft]

^understood, thx for the lesson!!!

[1997gtx]

=)

[saucys4]

someone just needs to do before and after logging. Then we will all know for sure how rich and how crappy they will make your car run.

[Fabelhaft]

hehe, sounds good to me~lol
cuz at least it's someone else's car....jk

[1997gtx]

You don't need to log a car to know that if you are supplying less air than expected and the same amount of gas to the MAF, you're going to run rich.

That's the definition.
--Adam

[GramCracker]

this is all the input i have...
http://www.youtube.com/watch?v=VbNxu...elated&search=

even though i don't mind BOVs in general, this is hilarious! lol =]

ROFL. I can't stop watching this. Its too funny! How do you think they did it? I want to try it to a friends car as a prank.

[YMJ]

ROFL. I can't stop watching this. Its too funny! How do you think they did it? I want to try it to a friends car as a prank.

LMAO AHAHAHAHHA.. pleeeeeeeeeeease iwant to know too..

that's just TOOOOOOOOOOOO fuking funny!

[Unispeed]

Diverters stay open while in vacum.... they close while in boost and open up again when a vacuum condition is formed in the intake (closing of throttle body). BOV on the other hand have enough tension on them to stay closed also while in vacum (otherwise they would be sucking in air from the BOV, stay closed while in boost, and open up with the immense vacum created in the intake manifold by the closing of the throttlebody. SSQV valves are the only ones that I know of that use pressure to keep them closed. All the rest (like the Greddys) have to have a spring that can keep them closed at the max psi your turbo is putting out (thats why they are adjustable). Vacuum from the intake manifold though can overcome that spring when needed and makes it open.

[Jung]

Ok guys, I got my flame suit on, and I'm ready for some shit...
I took the liberty of buying for dirt cheap on ebay, some 1st gen SQV's from HKS with adapters. Installed them last weekend, very easy, blah blah blah. i plugged the y pipe recirc hose. started her up, and she ran fine. Gave it a few revs, got some nice chirp. but then i let off the gas, and my revs wobbled a couple times, from ~1800-300 then 1500-700 then stabalized. I drove it around for about 20 miles, getting some ince chirp when going into boost. sounded alrite. It definitely took longer to spool, and wasnt as quick, i get wheel chirp when going into 2nd gear at WOT, but with the BOV's on i couldnt get much. driving around town, if you get less than 10lbs of Vacuum or boost, then let off, the car doesnt feel like it's running well. After about 30 miles, I got a CEL. I could definitely tell i was running rich as well. Very sweet smelling gas whenever i was at a stoplight. i cleaned my exhaust tips as well, before i put them on. at the end of hte week of driving it like that, it was HEAVILY covered in black soot, more so than normal.
So I put my Forge's back on and will be selling the BOV's.
if anyone wants them just lemme know.
i definitely would NOT recommend them for our cars unless we had a MAF right before the TB

[1997gtx]

Thank you for at least trying, lol.

Just further confirms what physics tells us :)
--Adam

[Rated S]

So, because the MAF is before the DVs it pretty much reads all the airflow and tells the computer "X" amount of air becuase 'none' (air) is lost by the time it gets to the TB, correct? Because the DV solely recirculate and there is no air lost from the time the MAF read it after the airbox.

What if you fabbed the MAF away from the airbox and put it in the TBB, which is right after where the DV do all their "magic" and replaced them with BOVs? Wouldn't you theoretically just need to minorly tweak it with Lemmiwinks to get the A/F right as it would be different readings from the "stock" location, but it would be reading the 'right' amount of air actually going IN the TB (which I am assuming the whole 'problem' is)?

[Jung]

while in theory this would work, we would need an entirely new kind of MAF. we couldnt use just our stock ones. i think someone elaborated on this somewhere in previous posts. It would have to be a full tune using a dyno to get everything right. Lemmiwinks is too simple of a thing to do a full tune on. because a new MAF would be needed, and due to its placement, you'd need a custom bipipe/TBB and a different ECU tune.

but yeah, i thought I'd give them a whirl, just to prove to everyone here, via firsthand account, that they blow ass. dont get me wrong, i love BOV's. I think they're the shit, but they're actual SHIT on our cars

[saucys4]

You don't need to log a car to know that if you are supplying less air than expected and the same amount of gas to the MAF, you're going to run rich.

That's the definition.
--Adam

But "how rich" is the question and by how much would performance be harmed? Trust me, I'm not considering a BOV and I will never get one. It just seems that everyone says you will be running uber rich and no one ever posts TRUE evidence of this.

EDIT just read JUNGB5S4's post and this is what I am talking about. Finally someone has done this. I would still want to see analytical data to show how rich we are talking about.

[Jung]

look above. i didnt log it, you didnt have to to tell that i was. by smell alone.

also read above for performance hinders.

[Jung]

what is normal A/F ratio? like 12.7 or something? i was probably like 8-9. this is paired with my bad passenger EGT causing me to run rich as well.