BOV Discussion Thread
 

I have one but i haven't turboed my car yet. still waiting on the intercooler. But What I was wondering is how the bosch BOV sounds. Does it have a whistle to it or is it just a WHHooooosh? Cuz if it doesn't I want one that does.

Re:Bosch BOV
 

So are you looking for a whistle or the woosh?

Re:Bosch BOV
 

mine is very quiet with a wooooosh. but i dont think it lets enough air out because i get a nice loud compressor surge churp. ???

Re:Bosch BOV
 

projecteg has a bosch, on a B16 and its not loud but its a nice whosh.....

Re:Bosch BOV
 

it has a nice deep whoosh sound and flutters somtimes

Re:Bosch BOV
 

Stock dsms give off a nice throaty wooosh when you take off the piping and give the accelerator calbe a quick turn.. every BOV acts differently to every engine/turbo setup.

Re:Bosch BOV
 

Alittle trick to vent the Bosch into the atmosphere is to install a one way valve from a septic/well system on the end.The Bosch valve is a bypass valve,not a true BOV.It bleeds air just above idle.

Re:Bosch BOV
 

i think all BOVS are open at idle?

Re:Bosch BOV
 

So you are saying that when at idle it is sucking in unfiltered air. That would mean that I would be loosing boost when it gets boosted or not? Would the positive pressure of the boost on the vac line close it when boosted?

Re:Bosch BOV
 

BOVs aren't supposed to suck in air at idle or any other rpm range, DSM bov's definately don't.

Re:Bosch BOV
 

dsm bov suck in air at idle, cover the compressor and you will see, you can even look in the end and see that its slightly open.

cheers

Re:Bosch BOV
 

hes right, at least mine did

Re:Bosch BOV
 

Thats because they are a "Bosch" style.They are not BOV's,they are bypass valves.They are meant to be vented back into the air intake down stream so yes if it is vented into the atmosphere it is leaking boost out.

Re:Bosch BOV
 

they dont leak boost out, they close as soon as there is no vaccuum in the intake manifold

Re:Bosch BOV
 

They suck in air at idle,but leak under boost.They actually work better than a blow off because during shifts the air is recirculated and some pressure is kept in the pipes.That keeps lag down.The BOV's create a overly rich condition when they blow off as well.

Re:Bosch BOV
 

yes, they do 'suck' air at vacuum, but like stated above, that doesn't leak boost b/c it closes at 0 vac. they're aren't really loud, but they do have a nice flutter/whoosh to them, they actually sound better at low boost, like 5 psi. or so. i have one and for the price, it works and if you're getting a bov just b/c of the sound, you're a ricer ;)

Re:Bosch BOV
 

im glad somebody said it. :P

Re:Bosch BOV
 

You don't really need a blow off unless you're running 1.5 bar or more on a big turbo....

Re:Bosch BOV
 

Not all BOV suck in air...the OEM's and single diaphragm do...that's why they make dual diaphragm BOV....so it won't open at idle....
Every bov is closed when boosted cause the pressure in the intake pipe and manifold is the same....I think some of you guys need to go back to high-school ::)

Re:Bosch BOV
 

Well I kinda am a ricer. So what? I want everyone around here to know that I will kick the ---- out of there car who thinks its fast. We have a really bad rice problem here in lincoln. Just today I saw a guy in his white cavalier with spinners on it. Hubcap spinners that is. And with some wack stickers in his rear window. He had his windows rolled halfway down and was just pimping it by himself. But we have worse than that. My car is clean rice. Not dirty rice. Haha. thanks for the info guys

Re:Bosch BOV
 

the dsm valve is not a blow off valve, its a diriviter valve, at low idle when the turbo is not making enough pressure the engine is asking for more air then the turbo can supply. then the diriviter valve with a pop-et type valve allows air pressure to enter the intake tube. then when no more pressure is needed it closes. when you let your foot off the gas abruptly the popet valve goes up from the pressure and give you your WOOOOSH sound. releasing to the atmosphere or back to the tubo inlet, what ever you wanted it to... if you have a "bov' from a stock car, its acctually a DV valve and i suggest you add i filter to the end to you dont suk ---- into your motor.

Re:Bosch BOV
 

highschool, you need that.

Re:Bosch BOV
 

I don't remember learning that in high school. In fact all the ---- that I use most I learned on my own or out of high school. except for the numbers and english stuff that I use everyday. Wait a minute :-\ I confused

Re:Bosch BOV
 

i dont even have a filter on my turbo inlet ;)

Re:Bosch BOV
 

that is really stupid, unless you crawl down under your car and cover up the intake/compressor inlet, it is not going to "suck" in anything so there is no need for a filter on it.

Re:Bosch BOV
 

I feel like making this one a sticky for everyone to throw in their 2 cents. Good reading.

Re:Bosch BOV
 

Your right quadnie.This is some good reading.

Sem you are right about the dual diaphram BOVs.

Deverter valve is the correct name for it though.Calling it a blow off valve is like calling a supercharger a blower.If you think about it a bov is just diverting the presurized air into the atmesphere.

True diverter valves like the bosch are used on turbo cars with mas/maf.This is becouse the air needs to re routed back into the charge pipe that goes between the maf/mas sensor and the compressor inlet.


The fact of the matter is that no matter what you want to call them they open at vacume.The diaphram inside works completely opposite of a wastegate wich opens at a set psi.

Re:Bosch BOV
 

I'm kinda having a hard time grasping this "open at idle" thing. Let us use a 2g dsm for reference, since the placement of the MAF and the routing of everything is pretty simple.

If the 2g bov (someone said it was a "bosch style"?) is open at idle then it can't be sucking in any air since all the air flow is being sucked from where the compressor is. Otherwise it would be just fighting for air suction?

And if all thse single diaphram BOVs suck air at idle, man the dsm guys are really ------- their cars up, the MAF is what meteres the air to the computer, the injectors compensate exactly for it. So that means the cars are leaning out at idle?

contribute guys

Re:BOV Discussion Thread
 

Ok, I changed the thread title and made this a sticky (in hopes to get some more input on the issue). I'll leave it stickied for a few days so everyone has a chance to throw something in.

If anyone minds me changing the title, it can easily be changed back.

-ryan

Re:BOV Discussion Thread
 

All DSMs, whether 1g or 2g run their BOV the same. The valve IS open at idle, but the air drawn in by the BOV is compensated for by the MAF. If you look at the pipe coming off the BOV, it is routed back into the compressor intake pipe DOWNSTREAM of the MAF. Thus, whatever air is sucked through the BOV has already been calculated and doesn't cause a lean condition. Because of the way this BOV setup works, a DSM will do one of two things if you disconnect the pipe going from the BOV to the intake pipe. If you just take the pipe off and do nothing, the car will run like complete ---- because there's a big gaping hole after the MAF that allows air to bypass it. Second, if you plug that hole up and disconnect the pipe, it will run a little lean under vacuum, which may or may not matter depending on your setup.
Overall, I'm pretty happy with my 1g DSM BOV. It's got an interesting sound that's not too loud. I've just learned to deal with the constant whining and whistling every time I let off the gas.

Re:BOV Discussion Thread
 

I just want to clarify what he just said only applies to DSM. If you were to put the exact same BOV/DV on a Honda or a custom turbo, IT WILL NOT "SUCK" AIR IN AT IDLE.

Re:BOV Discussion Thread
 

Not true.All deverter valves(bosch,dsm,the ones off of Volvos)will be open at idle.Its not the make of the car that makes it open so it doesnt only aply to DSM cars.Like I said before ALL diverter/BOV valves open at vacume.Th eonly ones that wont suck in air are the dual diaphram ones like Semnos said.

Im using one off of a Vovlo(all aluminum with 8)).It sucks air at idle couse its a single diaphram diverter valve.


Quadnie your right in the sense that cars like My VW passat have sensers that will throw a CEL if it senses a loss in pressure or a change in air volume.They make a BOV/diverter that vents 1/2 of the pressure to the atmesphere and returns the other 1/2 back into the charge pipe.It sounds really low and its really pricey.Not worth it IMO.

Factorys use diverter valves not only becouse of the mas/maf meters but also couse most people would be driven up the wall by the sound of compressed air being released everytime the car goes into vacume.

And not to change the subject but cars with mas/maf sensors are easier to tume for boost.Just a simple chip can up the boost as much as double.......map sensors suck :P

Re:BOV Discussion Thread
 

I have never said they don't open at idle, they do but they just dont' suck in air in most cases.

Re:BOV Discussion Thread
 

Damn Rafeal, all this time I thought you were as smart as a turnip.. who wouldn've known you get them mad skillz.

Anyways, back to the dsm cars. Yeah, I'm familiar with the dual chambered BOVs that recirculate half, vent half. But ---- spending $300 on one, plus I've only seen them made for Subaru cars. See all these DSM guys have this thing for venting.. yeah they have a factory turbo car, no the little peel off badge of GST/GSX/TSI just isn't good enough for them. I'm yet to see the dual function BOVs meant for an eclipse.

So now there are two problems with capping off your bov return flange.. first, the single diaphram bov sucking air into the car at idle, thus raising the A/F ratio (probably not by that much).

The main problem is that the MAF sensor meters air coming in (before the turbo, right after the air filter). And the BOV is meant to reintroduce the charge line's air back into the system (between the turbo and the MAF). When it gets vented instead, the ECU has already compensated for that extra air that just escaped, thus the car puffs some smoke between shifts from the over production of fuel. Worse yet, the cars will stall out at low rpms. Yeah, most of you already knew that, but I'm giving people some heads up anyways since this thread will be going into my newbie FAQ.


My next question is, any of those dual purpose BOVS dual diaphrams?

Re:BOV Discussion Thread
 

Ok dude I dont want to argue but you make no sense.

If the car is on.The throttle plate is closed,so the manifold has vacume(the nature of an internal combustion engine is to want to feed its self to death).Ok now if the manifold has vacume and the diverter is open couse the diaphram is sucked open by the vac line that comes off the mani....you with me.Ok my point is that if the charge pipe is conneted to that throttle body and the diverter is on the charge pipe thats on the throttle body while the engine is trying to suck in air from where ever possible how would the diverter not be sucking in air if its open?

To my understanding it is a dual diaphram.I think it would throw the ecu for a loop if it were open at idle sucking in air from the side that vents to the atmesphere.Thats on the one that I saw for the VW though.

Also I think the DSMs are ok with venting into the atmesphere couse like you said the air has allready been acounted for and they must not have a meter down stream that would tell the ecu like the VWs have that there is more incomming air than necessary.Its only sucking a little more air at idle while its open or durring shifts.Most DSMs that Ive seen run a Greeedy Type S bov.I belive that has a dual diaphream too ???

Oh and quadnie I do actually know a little bit here and there but Im still learning ;)

Re:BOV Discussion Thread
 

I'm not familiar with DSM, but let's just say a DSM bov/dv regardless first or second gen was used on a b18, it will open at idle but air will be coming out, not in. The reason i'm so sure because I have experience with it first hand and have seen others that acted in the same manner.

Re:BOV Discussion Thread
 

How is air coming out? There is not positive pressure in the charge pipes. It is under vaccum, therefore the air is being sucked into the engine.

Try this: hook up a Diverter valve (bosche style bov) to any vaccum source on your car. Don't have the bov hooked up to your charge piping. You can blow through it when your car is sitting there idling.

The reason is that the vaccum line you connected to the bov is "pulling" on the diaphram and the bov opens, when you go into boost it presses on the diaphram closing it.

When you let off the throttle quickly, your going from boost to vaccum. And since these style bov's open at idle, thats why some people say they hear a long hissing after the let off the throttle, because the turbo is still spinning and trying to create boost, but since your engine is in vaccum, the air that the turbo is pushing, is coming out the bov.

Re:BOV Discussion Thread
 

Your car at idle is under full vaccum.Which means,like a vaccum cleaner,it is at full "sucking" power.If the diverter valve is open,then the vaccum in your intake is going to "suck" air through it no matter what car its on.

Re:BOV Discussion Thread
 

my 1g bov blows air out at idle not sucking; but the reason this is ;cause i have a little IHI; it never stops spining ;D

Re:BOV Discussion Thread
 

ok some of this was confusing but just to see if it sucked in air at idle

couldn't you just start you car up and put your hand over it to see if it sucked ???