Regards Bov to Air
Apr 14, 2004 | 07:37 AM
#31
Originally posted by seattle944t
It depends on the blow off valve. The vacuum pressure is what causes them to open. The line that goes into the top of the valve is manifold pressure. When your boosting it puts pressure on the valve, in addition to the spring pressure, to keep the valve closed. If the spring is too weak then boost will leak out, this is one reason why people upgrade the valve.
Anyways, when you come off the throttle and the throttle body closes, the intake manifold goes into a vacuum state - even thought the rest of the intake tract is pressurized. This vacuum pulls against the spring pressure in the blow off valve to open it and allow it to either vent to atmosphere or direct it back into the intake. If the sping is too weak then it will be open under idle vacuum pressure. Conversly, if the spring pressure is too high then the valve will not open when needed, and the pressure wave of the boost will bounce off the throttle body, back through the intake, and back to the compressor wheel in the opposite direction of the flow. In extreme cases that can actually damage the compressor wheel, but most often just stalls/slows the turbo compressor. This effect will also make the car buck/surge briefly when getting out of the boost.
It depends on the blow off valve. The vacuum pressure is what causes them to open. The line that goes into the top of the valve is manifold pressure. When your boosting it puts pressure on the valve, in addition to the spring pressure, to keep the valve closed. If the spring is too weak then boost will leak out, this is one reason why people upgrade the valve.
Anyways, when you come off the throttle and the throttle body closes, the intake manifold goes into a vacuum state - even thought the rest of the intake tract is pressurized. This vacuum pulls against the spring pressure in the blow off valve to open it and allow it to either vent to atmosphere or direct it back into the intake. If the sping is too weak then it will be open under idle vacuum pressure. Conversly, if the spring pressure is too high then the valve will not open when needed, and the pressure wave of the boost will bounce off the throttle body, back through the intake, and back to the compressor wheel in the opposite direction of the flow. In extreme cases that can actually damage the compressor wheel, but most often just stalls/slows the turbo compressor. This effect will also make the car buck/surge briefly when getting out of the boost.
Apr 14, 2004 | 01:57 PM
#34
Originally posted by SSKILLA
does this alsomean that we should t off that small port of the greddy to the waste gate?
does this alsomean that we should t off that small port of the greddy to the waste gate?
NO!!!! That will cause fluctuation in boost. Never tap the WG for VAC. Plus, the bottom nipple on the BOV is for a boost source after the turbo. You'll need to tap a new one but I highly suggest not using the boost source after the turbo that goes to the BCS.
Last edited by Coolguy949; Apr 14, 2004 at 02:00 PM.
Apr 14, 2004 | 05:06 PM
#36
Evolving Member
Joined: Jul 2003
Posts: 494
Likes: 0
From: U.S.M.C.
why wouldnt u tap it from a boost source......wouldnt the 2 springs cause it to have enough tension to keep it closed????
i have the single spring mod and i think its leaking under boost
can any one help here?
i have the single spring mod and i think its leaking under boost
can any one help here?
Oct 30, 2008 | 02:28 AM
#38
i seen people have there bov on top pipe going into the intake manifold
then the plug the bottom stock intake pipe where it use to be for stock n
why would you do that and is it bad to have the bov relocated to the top piping
then the plug the bottom stock intake pipe where it use to be for stock n
why would you do that and is it bad to have the bov relocated to the top piping
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nine4surfah
Evo Engine / Turbo / Drivetrain
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