how does a BOV work?
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how does a BOV work?
im trying to figure out how it works
my new car has a turbo.. but doesnt have a BOV... so just wondering on wiring and all sorts of stuff
my new car has a turbo.. but doesnt have a BOV... so just wondering on wiring and all sorts of stuff
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compressed air enters the intake tube with an open throttle. when the throttle is closed, compressed air continues to fill the intake piping. the blow off valve "senses" the increase in pressure, thus overpowering the spring holding the valve shut and prevents air backflow into the turbo by venting it to the atmosphere..
at least, thats how it was explained to me..
at least, thats how it was explained to me..
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Rep Power: 338 its an audi.. the vdubb 1.8t uses a diverter valve.. which is similar to a BOV.. but goes before the turbo...
same thing with the r32.. and its an old *** audi.. with a 5cyl..
ill get pics sometime.. not sure when tho
same thing with the r32.. and its an old *** audi.. with a 5cyl..
ill get pics sometime.. not sure when tho
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Originally Posted by thebigjap
golf r32?
Originally Posted by WannaBFast
its an audi.. the vdubb 1.8t uses a diverter valve.. which is similar to a BOV.. but goes before the turbo...
same thing with the r32.. and its an old *** audi.. with a 5cyl..
ill get pics sometime.. not sure when tho
same thing with the r32.. and its an old *** audi.. with a 5cyl..
ill get pics sometime.. not sure when tho
The R32 is not boosted!!! It's an all-motor VR6 with 240HP, AWD, and a 6-Speed tranny. I think the first release of R32s had 255 hp, but I test drove one less than a month ago and was considering buying it. My civic would roast it once it's off the line. They aren't as fast as hyped up to be. But the instant and low end response is just amazing.
But yeah, 1.8Ts use diverter valves. I heard that the 1.8Ts aren't reccommended to have BOVs unless there's extensive modification done. Food for thought.
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I heard that the 1.8Ts aren't reccommended to have BOVs unless there's extensive modification done
The problem is the way the MAF functions.After being sucked through the filter the MAF measures the amount of air, now lets say you have a BOV and you shift gears, the BOV will release a certain amount of air into the atmosphere from the piping AFTER the MAF sensor. That means you are releasing air that had already been calculated into the computers fuel equations. So while the BOV is going off you will be running very rich.
Some people have no problems what so ever while some people experience stalling after letting off the gas quickly as well as stalling at idle.
Cars with MAF sensors are usually required to redirect the air from the BOV back into the intake piping or the intake manifold so that all the measure air actually gets used.
The reason we (Hondas) can have BOV's without any problems is because our air is measured via a MAP (Manifold Absolute Pressure) sensor in the intake manifold. So you could vent all the air you want, the only air that is taking into the calculations is the air thats just about to enter the engine.
Last edited by Got Boost???; Aug 13, 2004 at 02:59 AM.
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From: In a Box
Rep Power: 342 To answer the orginal question:
On a turbocharged car you usually have a about 1.5 feet of intake piping from the turbo to the throttle body. When you let off the gas the throttle plate in the throttle body closes. However that 1.5 feet of intake piping is already filled with compressed air. The problem is that the compressed air will slam into the throttle body and begin to back up. It will back up all the way into the turbocharger, where after a long time can cause damage to the turbo because the turbo will be straining trying to work against the backed up air.
A BOV fixes this problem by releasing the compressed air from the intake piping after the throttle plate has closed. The air is usually vented into the atmosphere.
On a turbocharged car you usually have a about 1.5 feet of intake piping from the turbo to the throttle body. When you let off the gas the throttle plate in the throttle body closes. However that 1.5 feet of intake piping is already filled with compressed air. The problem is that the compressed air will slam into the throttle body and begin to back up. It will back up all the way into the turbocharger, where after a long time can cause damage to the turbo because the turbo will be straining trying to work against the backed up air.
A BOV fixes this problem by releasing the compressed air from the intake piping after the throttle plate has closed. The air is usually vented into the atmosphere.
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Rep Power: 338 ok.. well the new whip dont have a BOV.. it does have a digital boost display.. it reads in BAR as opposed to PSI... but ive been doing some number crunching.. and i did get it up to 1.3BAR which is pretty close to 19psi... HEHEHHE i wanna hear that thing go PSHHHHH
You'd also need to connect a vacuum line to the bov. And it is NOT a matter of the bov spring only holding shut for so much pressure, otherwise, you couldn't ever hit a boost spike 
Anyways, the spring is regulated by your vacuum source, not the spring itself. The bov doesn't really have anything to do with how much boost you make, it only relieves built up pressure when you let off of the throttle (which it senses from the vacuum source.) Boost you make is controlled by the wastegate alone.
Anyways, the spring is regulated by your vacuum source, not the spring itself. The bov doesn't really have anything to do with how much boost you make, it only relieves built up pressure when you let off of the throttle (which it senses from the vacuum source.) Boost you make is controlled by the wastegate alone.
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Rep Power: 318 Lots of wrong info…oy…lets clean up the mess…
If the BOV “senses” there is “more” boost why wouldn’t the blow off valve release the air when you run more psi? I’ll tell you
When you let off the throttle, the pressure inside the manifold quickly changes from compressed air to vacuum, as soon as that happens the valve in the BOV opens…it only senses vacuum…it does that by an air(vacuum) line connect from the intake manifold to the bov.
The bov can be placed anywhere between the TB and the Compressor outlet, wherever there is room or for connivance sake…if placed right before the TB, the vacuum line is short and will have better response.
The R32 isn’t turbo. It has 3.2L flat 6 with 11.3 :1 compression, DOHC and 4 valves per cylinder.
If the BOV “senses” there is “more” boost why wouldn’t the blow off valve release the air when you run more psi? I’ll tell you
When you let off the throttle, the pressure inside the manifold quickly changes from compressed air to vacuum, as soon as that happens the valve in the BOV opens…it only senses vacuum…it does that by an air(vacuum) line connect from the intake manifold to the bov.
The bov can be placed anywhere between the TB and the Compressor outlet, wherever there is room or for connivance sake…if placed right before the TB, the vacuum line is short and will have better response.
The R32 isn’t turbo. It has 3.2L flat 6 with 11.3 :1 compression, DOHC and 4 valves per cylinder.
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Originally Posted by Prod
as for MAF's they suck! I wanted to run a turboxs rfl on my DSM.. NOPE.
I'd have had to buy a 1400 dollar fuel system JUST to run it.. it was gay.
I'd have had to buy a 1400 dollar fuel system JUST to run it.. it was gay.
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it does that by an air(vacuum) line connect from the intake manifold to the bov.
To put it simply when you let off the gas and the throttle plate closes, the pressure inside the Intake piping begins to rise far above normal boost levels. These levels are enough to force open a spring and plate and allow the air to escape before it backs up into the turbo
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A MAF is the single most accurate device to measure, air pressure, density, velocity and temperature. Any maf is allot more accurate then the best MAP system out there. It has its draw back, when you hit 500+hp it becomes restrictive
I saw a vid of a nitroused 350Z that had its MAF pop off while going down the track. Halfway down the track he had a hole in his block about 5 inches across
Originally Posted by Got Boost???
Thats not entierly correct, both the HKS SSQV BOV and the TurboXS RFL BOV, as well as many other BOV's have no lines going to them. Thus theres no way for them to measure a vaccum. I believe your refering to a diverter valve. Its the only thing thats hookd up to any vaccum lines. If a BOV has ANY lines attached to it, its most likely for a MAF car where the air needs to be redirected back minto the intake manifold.
To put it simply when you let off the gas and the throttle plate closes, the pressure inside the Intake piping begins to rise far above normal boost levels. These levels are enough to force open a spring and plate and allow the air to escape before it backs up into the turbo
To put it simply when you let off the gas and the throttle plate closes, the pressure inside the Intake piping begins to rise far above normal boost levels. These levels are enough to force open a spring and plate and allow the air to escape before it backs up into the turbo
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Originally Posted by Got Boost???
I saw a vid of a nitroused 350Z that had its MAF pop off while going down the track. Halfway down the track he had a hole in his block about 5 inches across
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Originally Posted by andyman97
but based on what you're saying, the spring reacts directly to how much boost you make, right? If that's the case, how can you change your boost setting? According to what you're saying, the spring is set for a certain amount of resistance and once it sees that amount, it opens. How would you be able to boost over that resistance? How does the bov know that the throttle plate has been closed or when it needs to bleed out the air? I've dealt with quite a few different bov's and the ones that I've seen have all been on Hondas but they all have needed a vacuum source connected to them, otherwise they wouldn't blow off.
Originally Posted by WhiteCastle
No he’s somewhat right, all bov have a spring that you should tighten according to your psi level, for example there is a guy running 4 psi, he needs to loosen the spring so when the bov opens it can open all the way and freely to release the air, the guy next to him is running 14 psi, he need to tighten the spring, so then it wont open below 14 psi, but the bov still needs a vacuum source to know when to open.
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Rep Power: 342 Ok let me elaborate.
There are 2 kinds of ways to battle compressor surge, you can get a BOV or a CBV (compressor bypass valve)
Andyman what your refering to is a CBV, its opens and closes via a spring that is regulated by a vaccuum line. When the time is right it opens and routes the air into the intake manifold.
A BOV works the same way but via a spring inside the unit, nothing else, a BOV can either vent to the atmosphere or route the air back into the manifold.
Some CBV/BOV's are easily adjustable via tightening/loosening, some require you to take the unit apart and change out the springs.
CBV's/BOV's are not designed to regulate boost but can be used to do so.
Lets say we have a BOV and we install an extremely soft spring. it will eliminate all compressor surge because it will open easily. But because of that it will also hinder you from running higher boost levels.
We could install a mediem strength spring, that won't open under light boost but will allow us to run more boost.
Or we could install a stiff spring that won't open under light or medium boost but we can run the highest amount of boost with it.
There are 2 kinds of ways to battle compressor surge, you can get a BOV or a CBV (compressor bypass valve)
Andyman what your refering to is a CBV, its opens and closes via a spring that is regulated by a vaccuum line. When the time is right it opens and routes the air into the intake manifold.
A BOV works the same way but via a spring inside the unit, nothing else, a BOV can either vent to the atmosphere or route the air back into the manifold.
Some CBV/BOV's are easily adjustable via tightening/loosening, some require you to take the unit apart and change out the springs.
CBV's/BOV's are not designed to regulate boost but can be used to do so.
Lets say we have a BOV and we install an extremely soft spring. it will eliminate all compressor surge because it will open easily. But because of that it will also hinder you from running higher boost levels.
We could install a mediem strength spring, that won't open under light boost but will allow us to run more boost.
Or we could install a stiff spring that won't open under light or medium boost but we can run the highest amount of boost with it.
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