InjentC23

Hey everyone maybe someone can share their knowledge with me about their recommendations for a good recirculating bov. The Tial wastegate that comes with the zpi stage 0 turbo kit is as far as I know an atmoshperic bov. And once I get my kit I plan on switching to a recirculated bov.

I came to this decision based on the fact that I have heard many people talk about turbo tC's with atmoshperic bov's havin problems with poor idling/stalling. So if switching to a recirculated bov would help with those problems I would rather have the better performance than the "cool"sound.

The bov's that I am interested in getting are the hks ssqv and the greddy type rs bov. I know I have to get the actual recirculating kits for these two, so I have that base covered. Now as far as just replacing it I need to know which size flanges to get and
which material to get.
The three choices I see for the hks bov are 50 and 65mm in steel and 60mm in aluminum. Which one of these three would I need to get in order for it to fit the charge pipe on the turbo kit?

For the greddy bov they only offer either a steel flange or an aluminum one. So any info or help anyone can give me would be much appreciated. Thanks

tikbhoy

you still need to use a recirculiting fittin on the end of it, ssqv is atmospheric.



I hope you dont buy the knockoffs

InjentC23

Yeah, I'm definitely gonna be staying away from the knockoffs.

zer0

Just buy a greddy type S and a flange for whatever type of material your charge pipe is... the sound is amazing.

InjentC23

I'm assuming the charge pipe is steel, so I got that covered. But if I decide to go with the hks I still don't know whether to get the 50 or 65mm. Not sure if you meant type rs or just the old type s. I like the sound of the type s, but can they be recirculated?

ISmokeGuys

Just a little FYI...ScionDad has a stage 0 ZPI kit, and he corrected the idle/stalling issue, by upgrading the spark plugs to a colder plug (Denso IK22 iridiums to be exact). This allowed him to keep the atmospheric bov, and not have issues with idle/stalling. You should pm him for more details.

tikbhoy

https://www.scionlife.com/forums/vie...highlight=plug

MA_70

I fell bad to argue but you cant just fix an idle and stall problem by switching to a colder plug, the reason i say this is because of the way that turbocharger kit is setup, the mass air meter is before the turbo. So when the car takes in air the meter reads it, translates it and puts fuel in the motor, but the bov is venting to the atmosphere so that air that was just meter has been altered, either more air is present or less, which makes it super hard for the ecu to make correct a/f ratio changes. If the bov was recurlated back into the intake behind the mas air meter or if you were able to place the meter behind the bov and infront of the throttle body you wouldnt have these problems, because the metered air would never be changed. As far as scion dads problem, i can only assume that he ran a stock heat range plug and with teh boost the car is getting it fould that plug early and his replacing the plug helped the motor run but didnt correct the problem.

rhythmnsmoke

^^hmm...Maybe he was just making it up.

Dezod_Boosted_STi

...it took me a while to figure out what was going on here, it looks like they are tag teaming this thread

bbsciontc

It may have helped with the idleing issues, but plugs would really have no effect with stalling when the bov expells air. It is just a fact of MAF metered cars. ScionDad's car may be a bit less likely to stall since the auto trans will keep the engine engaged in a gear at nearly all times to keep the engine spinning. But i'm sure in the right situation even that car would stall when releasing air from the bov. For the best in drivability and reliability, you would still want a bpv to keep the entire intake system into one closed loop. Only real way to remedy this is to use either a speed density system as in the AEM EMS, or converting to a MAP sensor system which I don't think would be possible with the factory ecu.

Dezod_Boosted_STi

Pressure release valve or more commonly known as a "Blow Off Valve", releases turbo pressure when the throttle plate is closed. The turbo is still spinning and still creating pressure. The forced air will hit the throttle plate and return where it came from. When a BOV reads vacuum from the manifold, it either opens a valve, or softens the valve. Which lets the pressure escape from it's opening. In order to work correctly the air must go back into the intake before your turbo because the Air Flow Meter has accounted for it. If not you will have a temporary rich condition which will upset your idle slightly. Proper tuning can get around this hassle. Most choose to vent to the air, as they love the sweet sound the air makes when it runs to the atmosphere. If the pressure release valve (as some call it) contains a horn or small holes/vents it will cause the air to make a louder/higher pitched sound depending on what is used.



The main function of a blow-off valve is to vent excess boost pressure when the throttle butterfly is closed. The lower chamber of the blow-off valve is plumbed into the intercooler front pipe while a small vacuum hose leads from the top of the valve to the inlet plenim on the engine. Inside the blow-off valve is a diaphragm (usually made of rubber) and a spring with a small insert to support the diaphragm where it seats against the valve body.

When the throttle butterfly is open, the boost pressure that enters the upper chamber above the diaphragm, via the small hose from the plenim chamber in the top of the blow-off valve, is equal to the manifold absolute pressure (MAP). Because the pressures are equal and positive, the spring holds the diaphragm on the valve seat and stops the pressurised air from being vented away. When the throttle butterfly is closed, the MAP is in vacuum and the diaphram lifts away from its seat, allowing the boost pressure to vent to atmosphere




When the throttle butterfly is reopened, the pressure in the blow-off valve becomes positive once more, the spring pushes the diaphragm onto its seat reventing boost pressure from being vented away. There are a number of reasons why a blow-off valve is a good idea. When the throttle butterfly is closed, the spooled-up boost pressure cannot escape and subsequently puts tremendous stress on the turbo by stalling the compressor wheel, compressor shaft, and turbine wheel.

The blow-off valve vents his boost pressure allowing the turbo components to spin freely in a vacuum. This prevents significant turbo lag and allows the turbo to spool-up more quickly. Over time, the blow-off valve can help to minimise stress on the turbo components and prolong the turbo's life.


A blow-off valve, helps to keep the turbo spinning when the driver lets off the throttle.

Without a CBV, the throttle plate would close, creating a wall to the pressurized air wooshing out of the turbo. The air would crash into the closed plate, then air behind it would pile up, and eventually a wave of pressure would travel back to the turbo. Besides being a shock to the turbo, it would basically cause the turbo to come to a stop.

Then when you wanted to get back on the gas, you'd have to wait for the turbo so spin up all over again. With a CBV, the turbo can free-wheel for a while (like when you're shifting), because the intake pressure is relieved.

raamaudio

Great write up, or cut and paste, either way excellent info. I prefer to recirc a BOV because of drivability issues but mainly for making it a bit quieter so I can have more fun sneaking around using boost as much as possible, not showing off and getting the wrong kind of attention;)

Rick

Simplyscion

Thats correct...instead of dipping off in between shifts, the boost spikes in between keeping it from stalling or poor idle. Same thing in my xB...I was able to run an atmospheric BOV simply due to the fact that the spiking was what kept me from stalling

Dezod_Boosted_STi

Thank you. I'm not as stupid as what people think lol. I will post my knowledge where it can be posted, I've stopped with the nonsense posts.

BigPinoyTC

Is there a considerable difference in how loud the BOV a recirculating BOV is compared to a atmospheric?

I have only heard atmospheric bkuz thats what everyone gets. In the kit thats being made for my car they are using a recirculating do to stalling problems and other issues. As long as you can heat it when in decent range of the car then im find. I dont need it to be so loud you can hear me around the block.

Anyone have sound clips or now where some are?

ctruss

Check out EIP Tuning's website. Yes they are into VW performance, but they sell Greddy Type S BOV's and recirculation kits for them.

tjbartjr

You could just get a performance bypass valve, I had the TurboXs Racing Bypass valve on my 89 Probe GT (also a MAF car) and it worked flawlessly.

Simplyscion

I hear constantly that the TurboXS bypass valve leaks really badly

tikbhoy

possibly but cant tell anymore between the knockoffs! too many on ebay and its hard to tell the difference.

theres two bypass valve they sell its the H25 25mm inlet to fit bosch oem's and H34 34mm inlet