BOV @ Idle ??
BOV @ Idle ?? Ok, so I read ALOT of conflicting info on this subject.....
On a Turbo car, should the BOV be open at all at a base idle?
At first I assumed it would stay shut at idle and crack just during decel, but I also see alot of guys say that at idle it should be open and air blowing out? One or the other must not be set up correctly...
Keep in mind this is a Turbo application....
What are the FACTS?
On a Turbo car, should the BOV be open at all at a base idle?
At first I assumed it would stay shut at idle and crack just during decel, but I also see alot of guys say that at idle it should be open and air blowing out? One or the other must not be set up correctly...
Keep in mind this is a Turbo application....
What are the FACTS?
i would also like to know, and being that im running a 2 bar SD tune, i cant start my car to test any of this stuff 
i took a mity-vac and put it on the BOV and adjusted it so it starts to open at 15" which is what my motor idles at. hopefully that will get me close enough for dyno time
i took a mity-vac and put it on the BOV and adjusted it so it starts to open at 15" which is what my motor idles at. hopefully that will get me close enough for dyno time At idle you'll be in vacuum so there should be no air blowing out of it. It should be open and sucking in.when you hit boost it will push the bov closed and pressurize your intake piping, then when you let off the vaccum in your vaccum line sucks it open and relievs pressure.
Curious if this is the case on a BOV on a Procharged car as well. Should it be blowing air out at idle, or just under decel and at faster engine speeds, such as while cruising.
Mine chirps at steady cruise and whoooshes at decel. At idle, it is not venting anything.
Mine chirps at steady cruise and whoooshes at decel. At idle, it is not venting anything.
Staging Lane
Joined: Sep 2008
Posts: 99
Likes: 0
From: MI
Depends on the setup....if the BOV is after the air meter sensor, the bov will have to be closed at isle otherwise unmetered air is being let out of the charge pipes with the bov being open at idle, causing a rich condition, idle surge and will probably stall out.
if the bov is before the air meter sensor, it doesn't matter because what ever has escaped the charge pipe with the open bov is not taken into account until it gets to the air meter...so the ECU compensates for it
the lighter the spring the better reaction time it will have, blower guys need it open at idle (and part throttle cruising) to avoid pumping losses and making positive pressure at idle
if the bov is before the air meter sensor, it doesn't matter because what ever has escaped the charge pipe with the open bov is not taken into account until it gets to the air meter...so the ECU compensates for it
the lighter the spring the better reaction time it will have, blower guys need it open at idle (and part throttle cruising) to avoid pumping losses and making positive pressure at idle
Depends on the setup....if the BOV is after the air meter sensor, the bov will have to be closed at isle otherwise unmetered air is being let out of the charge pipes with the bov being open at idle, causing a rich condition, idle surge and will probably stall out.
if the bov is before the air meter sensor, it doesn't matter because what ever has escaped the charge pipe with the open bov is not taken into account until it gets to the air meter...so the ECU compensates for it
the lighter the spring the better reaction time it will have, blower guys need it open at idle (and part throttle cruising) to avoid pumping losses and making positive pressure at idle
if the bov is before the air meter sensor, it doesn't matter because what ever has escaped the charge pipe with the open bov is not taken into account until it gets to the air meter...so the ECU compensates for it
the lighter the spring the better reaction time it will have, blower guys need it open at idle (and part throttle cruising) to avoid pumping losses and making positive pressure at idle
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Verdad Gallardo Depends on the setup....if the BOV is after the air meter sensor, the bov will have to be closed at isle otherwise unmetered air is being let out of the charge pipes with the bov being open at idle, causing a rich condition, idle surge and will probably stall out.
if the bov is before the air meter sensor, it doesn't matter because what ever has escaped the charge pipe with the open bov is not taken into account until it gets to the air meter...so the ECU compensates for it
the lighter the spring the better reaction time it will have, blower guys need it open at idle (and part throttle cruising) to avoid pumping losses and making positive pressure at idle
if the bov is before the air meter sensor, it doesn't matter because what ever has escaped the charge pipe with the open bov is not taken into account until it gets to the air meter...so the ECU compensates for it
the lighter the spring the better reaction time it will have, blower guys need it open at idle (and part throttle cruising) to avoid pumping losses and making positive pressure at idle
SO...I still see contradicting answers here...some say closed some say open. I could see especially on a Procharged setup it needing to be open due to such positive displacement of the charger...but at idle does a Turbo move enough air that it needs to be released by the BOV?
Maybe a sponsor that builds turbo applications often could chime in?....
Last edited by LS1Silverado05; Sep 16, 2009 at 11:10 AM.
Staging Lane
Joined: Sep 2008
Posts: 99
Likes: 0
From: MI
Interesting observation...
SO...I still see contradicting answers here...some say closed some say open. I could see especially on a Procharged setup it needing to be open due to such positive displacement of the charger...but at idle does a Turbo move enough air that it needs to be released by the BOV?
Maybe a sponsor that builds turbo applications often could chime in?....
SO...I still see contradicting answers here...some say closed some say open. I could see especially on a Procharged setup it needing to be open due to such positive displacement of the charger...but at idle does a Turbo move enough air that it needs to be released by the BOV?
Maybe a sponsor that builds turbo applications often could chime in?....
Thats what I was wondering since technically some guys have even gone without a BOV (I wouldnt, but I know its been done)...
So Im starting to assume it will WORK either way....but maybe a certain way is better?....There are obviously guys running open and closed both...
This seems way harder than it has to be...LOL
So Im starting to assume it will WORK either way....but maybe a certain way is better?....There are obviously guys running open and closed both...
This seems way harder than it has to be...LOL
8 sec potential, 12 sec slip
iTrader: (50)
Joined: Apr 2002
Posts: 4,092
Likes: 2
From: Savannah, GA
I was always under the impression a BOV is supposed to be closed at all times except when it sees a sudden surge of backpressure, then it is supposed to open to release the air built up in the system on decel. A BOV is for turbo applications for this reason that turbos won't create positive pressure at lower (idle) speeds.
A BPV is supposed to be open at all times unless under boost to allow the system to pressurize, and then open once the throttle is let up which causes the system to go back into vacuum. This is for supercharged cars primarily, but can be used for turbo cars as well.
A BPV is supposed to be open at all times unless under boost to allow the system to pressurize, and then open once the throttle is let up which causes the system to go back into vacuum. This is for supercharged cars primarily, but can be used for turbo cars as well.
Staging Lane
Joined: Sep 2008
Posts: 99
Likes: 0
From: MI
Thats what I was wondering since technically some guys have even gone without a BOV (I wouldnt, but I know its been done)...
So Im starting to assume it will WORK either way....but maybe a certain way is better?....There are obviously guys running open and closed both...
This seems way harder than it has to be...LOL
So Im starting to assume it will WORK either way....but maybe a certain way is better?....There are obviously guys running open and closed both...
This seems way harder than it has to be...LOL
if air meter is before the bov - bov needs to be closed at idle
if air meter is after the bov - it doesn't matter
one is not better than the other as long as the BOV is functioning
I was always under the impression a BOV is supposed to be closed at all times except when it sees a sudden surge of backpressure, then it is supposed to open to release the air built up in the system on decel. A BOV is for turbo applications for this reason that turbos won't create positive pressure at lower (idle) speeds.
A BPV is supposed to be open at all times unless under boost to allow the system to pressurize, and then open once the throttle is let up which causes the system to go back into vacuum. This is for supercharged cars primarily, but can be used for turbo cars as well.
A BPV is supposed to be open at all times unless under boost to allow the system to pressurize, and then open once the throttle is let up which causes the system to go back into vacuum. This is for supercharged cars primarily, but can be used for turbo cars as well.
It will be irrelevant on my car as far as the metered air as I will be tuned in SD...
Last edited by LS1Silverado05; Sep 16, 2009 at 01:33 PM.
You need to keep in mind vacuum is what keeps the valve open (sucking) and it shuts when positive is applied. Another way to test it is disconnect the vacuum hose going to the blow-off valve and watch it shut. Thats why you see alot, if not all, running a MAF they have the blowoff valve before the MAF.
8 sec potential, 12 sec slip
iTrader: (50)
Joined: Apr 2002
Posts: 4,092
Likes: 2
From: Savannah, GA
On a MAF tune, it really shouldnt matter if its sucking air in thru the BOV/ BPV or blowing excess air out, the point is, the metered air that has gone thru the MAF will not be the same as whats going into the engine as expected by the computer if the valve is after the MAF. So just to keep things on par, if you are running a MAF tune, put the valve BEFORE the MAF measures it.
And BTW, I don't really see any way of air being drawn IN to the intake tract thru a BOV or BPV, it should be spewing excess air OUT of it..
And BTW, I don't really see any way of air being drawn IN to the intake tract thru a BOV or BPV, it should be spewing excess air OUT of it..
Staging Lane
Joined: Sep 2008
Posts: 99
Likes: 0
From: MI
Vcious04
I agree 100%
how does a blow off valve work
OFF VACUUM!!!!! if the car is at idle or decel their will be vacuum on the the throttle body and if you have a vacuum line going to the bov it will pull it open in less you have the spring in the BOV way to tight
I agree 100%
how does a blow off valve work
OFF VACUUM!!!!! if the car is at idle or decel their will be vacuum on the the throttle body and if you have a vacuum line going to the bov it will pull it open in less you have the spring in the BOV way to tight
IN my opinion the bov should be before the intercooler if you have one, that way you dont heat soak the intercooler with the charged air thats being blowed right back out when not under boost