nsn240

Just looking for other opinions... i have 'custom' IC piping and mounted my bov on the cold pipe, if i recirculate it back into the cold pipe... simply so i dont have to run a hose alll the way across back to the intake pipe... It should do the same thing, if you recirculate back to the intake pipe, its still after the maf, just like a cold pipe recirc would be, as long as its still in the system, and not released into the atmosphere

Slidin240Wayz

Yea you can do that. Should of moved the Maf after the BOV to not have to worry about this. se la vi

trsilvias13

sounds like you just have a bov mounted onto the cold pipe and you want it vented back into the cold pipe? Why run a bov ?

93 240sxfastback

You should recirc to before the turbo.

S13Eye

How would that work? There needs to be a difference of pressure for the blow off to do anything. Obviously there is no difference in pressure between the cold pipe, and the cold pipe. You should be dumping out the recirculated air out before the compressor.

S13 S I L V I A

Well first off which do you have? A true BOV = Blow off Vavle or a stock CBV = Compressor Bypass Valve

Thats retarded, the purpose of the CBV is to recirculate boosted air pressure when the throttle body valve is slamed shut back into the intake track (non-boosted air) to elimenate compressor surge thats when the boosted air pressure has no where to go but backwards and thats not good when the turbo is running @ +500,000rpm then all of a sudden its being forced to turn in reverse NOT GOOD!.

A BOV on the other hand is designed different and can also be recirculated but the purpuse of buying one of these in the first place is mainly do in part to the cool sounds they make there is no performance gain unless you are boosting way more air than th stock CBV can handle in fact aftermarket BOV take away from performance the air that is used to help spool the turbo during a gear shift is lost to atmosphere (wasted energy) with a BOV.

If you try and run a stock CBV to atmosphere thats just retarded its not made for that, CBV remain partially open at idle and you will run like shit and risk sucken in dirt.

As you know Nissan's run on MAF senors which must have accountablity for all air entering the engine and any of this air being blow out to atmosphere will result in over fueling and shitty perfromance.

S13 S I L V I A

Exactly............why run one the air is just gonna equalize but thats just plan retarded and your gonna kill your turbo in no time.

S13 S I L V I A

If you ask me this is the only way...the correct way...the way Nissan designed it to be.

isdeways

Um... a CBV and a BOV are the same thing. They both serve the same purpose. People often get them confused when one is vented to the atmosphere and one is recirculated. Often times people like to call the atmospherically vented valve a BOV and a recirculated one a CBV. This is not true. They both function in the same manner and can both be vented to the atomosphere or recirculated.

EDIT: Even if you left the CBV open, it wouldn't cause you to suck in dirt. Both sides of the CBV (the side directly attached to the piping and the side attached to the recirculating hose) are in a close intake tract. As long as you have a filter on your turbo, you're fine.

S13 S I L V I A

Obviously your misinformed they are not the same thing, this is how things get outta wack by calling something what it isn;t, lets be technical here.

Compressor Bypass Valve well remain partially open at idle and cruise (non-boost) situations, in part from the factory this is probably done to help you stay outta bosst when cruisng at low speeds (non boost conditions) or a partial vacuum situation.

Blow Off Valve will remain shut at all times during idle and cruise (non-boost) situations and only blow off to atmosphere when the throttle is closed.

And yes you can suck up dirt with a CBV that isn;t recirculated, becasue at idle and cruise (non-boost/vacuum) situations the CBV is partial open and your engine is working as a large vacumm pump and since the CBV is on the cold side right next to the throttle body that is sucking in air....HELLO!

S13 S I L V I A

Now there are some aftermarket BOV that allow you to recirculate or blow off to atmosphere and thats fine but there is no performance gain just for looks and maybe a sound change.

isdeways

Actually there is a performance gain depending on what else you've got done to the car. Most CBV/BOVs are tested to hold a certain PSI. I'm sure the stock CBV can't handle 20lbs of boost can it?

It's not different than upgrading a wastegate. If you increase the boost, the corresponding parts must be able to handle the increase.

nsn240

damn... you got it there, putting it back in pre-turbo would keep the pressure you are trying to release in the piping... I didnt really think about it, but thats the reason why it would have to go back in the intake, not the ic piping. Yes, for the record, i know how a bov works, and thats not what i was asking, I have a Greddy RS mounted on the coldside. Thanks for the help, sorry bout the dumb question

S13 S I L V I A

I already said that brother....

yokotas13

but in all honesty, the recirculating back to the intake side of the turbo (im not hip on this hotside cold side shit so im not gonna act liek i am)
you are doing this to put the air back that is already compensated for by the MAFS and ECU. If you tak it out you will be in an overly rich condition between shifts and the begining of the entry into the gear. Slowing you down essentially.

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S13 S I L V I A

Yes that is why it must be done...........and it also helps in recycling the energy of the boosted air putting it back to work to help spool the turbo up that mush quicker and to prevent compressor surge which is very hard on the thrust bearing and will wear a turbo out in no time flat.

420sx

theres really no significant difference in recirculating and not doing so. this has been beated to death, you are kicking a dead goat. yes u will run a little rich, ok, but thats about it. its really more a matter of preference. do you think most guys that drag their high boosting cars really give a flying shit about recircing? lol...

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g6civcx

Several comments:

1) A compressor bypass valve (CBV) is the same thing as a blow off valve (BOV). You can distinguish the two types by calling each a vent-to- atmosphere (VTA) or recirculate type.

2) The hotpipe is between the turbo and the intercooler. The coldpipe is between the intercooler and the throttle body. If you do not have an intercooler, you obviously do not have a coldpipe.

3) The ideal location for a CBV is on the cold pipe, but it is also acceptable to place it on the hotpipe for simplified installation.

4) For vehicles equipped with a Mass Air Flow Sensor (MAFS), the ideal location to recirculate the discharged air is to the pipe between the air filter and turbo. This allows the turbo to vent compressed air to the intake pipe which isn't compressed. It is not advisable to vent the air to atmosphere because the MAFS has already metered the amount of air in the intake plumbing.

5) For vehicles equipped with a Manifold Absolute Pressure Sensor (MAPS), it is acceptable to vent to the atmosphere because the MAPS measures the pressure variance between the intake manifold and barometric pressure. You may also recirculate if you like. This is because air metering isn't done at the air filter; it's done at the intake manifold. Discharging air from the intake plumbing will not affect the MAPS because you are discharging unmetered air.

6) It is absolutely useless to recirculate a CBV mounted on the coldpipe back to the coldpipe. This defeats the purpose of a CBV as pressurised air is not bypassing the turbocharger's compressor. You are better off venting it to the atmosphere or run no CBV at all (which I highly do not recommend!). See #4 above.

7) Race cars get more maintenance than street cars. Plus running a VTA valve will save some intake plumbing, which helps the reliability of the car for short sprints. Do as you wish.

S13 S I L V I A

Well im done here but know there is a correct way and a incorrect way of doing things.....there aren't very many anal tunners around these forums anyways so do what ever floats your boat.

Blowing off to atmosphere should be left to MAP sensor equiped cars or cars with similar air flow reading devices to a MAP other than MAF equiped cars.

MELLO*SOS

So 420sx... Running rich briefly after shifting and subsequently losing some speed isn't something that drag guys have to worry about? I would guess that many drag guys you speak of run either a MAP setup or a blow through MAF... Not picking an arguement with you, but your post contradicts many threads I've read regarding recirc vs non-recirc. cheers.



Speaking of BOVs... I have come across this style BOV design from "Go Fast Bits" on the aussie boards I frequent:

Manual adjustment


Electronic adjustment



Essentially they have an adjustable valve that vents a percentage of the air to atmosphere and the remainder back to the compressor inlet/intake pipe. They have a few variations, like in the 2nd picture with a solenoid & in-car adjustment pot. This design is supposed to help prevent the rich issue while retaining that beloved BOV noise...

Anyway I haven't seen many of these available here in the US. Maybe I'm not looking hard enough, but what other "readily available" brands make BOVs with this same type of design? Thanks...

S13 S I L V I A

Sadly this type of reply you would expect to come from the minority (10%) but in out case its the majority (90%) mostly due to a lack of knowledge and not taking the time to learn hows things actualy work.

nsn240

haha... this thread just turned into another atmospheric vs recirc argument it seems. I think its pretty obvious be reading the responses who is educated on the subject, and who isnt. ie: Whoever said something about not recirculating doesnt matter, this might be true if you run a MAP or blow-thru MAF setup, but for the most part, an atomospheric bov causes a rich condition between shifts that leads to a loss of power among other things. If you were to drive around with me for a while, no doubt my car needs tuned, but i shoot flames high end and backfire on almost every shift above ~3500rpm (in boost) and letting off to partial throttle high end is ridiculous becuase of all the bucking caused by the blow off, running rich. Like i said, my car really needs tuned, but if i could do it again, i would just run hotside and recirculated.

isdeways

That's the part I didn't agree with. It's only lost to the atmosphere if you have it vented that way... remember it's the same as a CBV... You're getting the ideas (CBV/BOV vs. Recirc/Atmos) mixed up again...

EDIT: I'm done.

S13 S I L V I A

Well read it again obvioulsy you could conclude from my other post I know the difference's between the two and what I meant there was if your blowing off to atmosphere there is a performance loss, obviosyly if your after market BOV came with the capability of being vented back to the intake that fine.....but you fail to recognize the very thing that makes aftermarket BOV sounds so cool is in fact a restriction ofcourse that can be over come by making them larger.

Im not mixed up theres just more way than one to skin a cat when it comes to Blow off valves.

S13 S I L V I A

I guess we could also it closed loop vs open loop but you should also know there is a difference between CBV and BOV and i'll explain it again:

Described below are two main types and the essential difference between them:

CBV Compressor bypass valve (CBV)
In the CBV case, pressurised air is returned to the turbo compressor inlet for reuse, instead of being dumped to atmosphere. The bypass valve is open under normal low-load engine running conditions, and closes firmly when positive (boost) pressure is present in the inlet manifold (or plenum chamber). When on-boost and changing gear (throttle lift-off), a sudden lower pressure condition is created in the manifold and the valve is pulled open again, directing pressurised air back to the turbo inlet.


Blow-off valve (BOV) / Dump Valve / Vent valve
This valve type features an adjustable spring design (spring in compression) to keep the valve closed under idle, cruise and boost conditions (eg 0.5 bar). Only at sudden throttle lift-off (eg 0.8 bar) does the valve momentarily open to vent / dump the pressurised air directly to atmosphere through a specially designed orifice (and wooshtssh).

S13 S I L V I A

One could conclude that the BOV does not react as fast in opening to vent the pressurized air off as fast as the CBV becasue in the case of the BOV a preset has to be over come first for it to work and that means boost must first build up to overcome this threshold whereas the CBV reacts to vacuum and instantly relieves the boosted pressure than can do your turbo damage.

Edit: Your no where near done son

95zilvia

This is a good thread.

S13 S I L V I A

True they can both be recirculated (the CBV will do a better job at it though as in react much quicker and blow off more air for a longer time) but only a BOV can be vented.

Once again this is tottaly false as we know becasue I put the info out there a CBV will remain partially open during idle and cruise (vacuum condition cruise) if you dont believe me unhook your stock CBV and have a look its being held open becasue its made to open during vacuum i.e. idle and partial cruise are vacumm situations and since the engine is working as a huge vacuum pump during this time it will suck in what ever it came, running a CBV open to atmosphere is like punching a hole in your intercooler piping.

S13 S I L V I A

One more thing to note why is it that a BOV has to have a spring holding the diaphram shut, well heres another obvious reason...

so it don't suck unfiltered air in

but why do some BOV come with a filter???

so it don't suck unfiltered air in

and this is another reason why your not suppost to vent a CBV to atmosphere...

Cashizslick

Nobody has yet to mention that HKS's SSQV is a pull type BOV. Its designed that way so it doesnt leak/suck crap into it.

I run the SSQV on my car (uncirc'd) and it drives fine. I get a back fire every once and a while but its nothing along the lines of what you pro recirc's are talking about . . . from the way you describe this it sounds like MAF cars are exploding everywhere due to un-recirculation of intake air.