how the bpv works. i know there is alot of post on this but they dont agree.

rickyS4 · 08-04-2005, 11:16 AM

I was wondering if anyone has a good explanation for how the bpv work? I understand that they are normally closed. when you are on the throttle and suddenly let of they let air back into the intake to keep the turbo pressure from going to high. It is controlled by suction from a controller. what does the controller go by to decide when to open? and can the valve open from the pressure from the turbo alone?

thanks

WindyCityS4 · 08-04-2005, 11:21 AM

The BPV's are connected to the intake manifold behind the throttle body. When the throttle body closes, the vacuum in the manifold is used to open the BPV and "release" the built up pressure in an attempt to prevent the turbo from stalling.

vegasS4 · 08-04-2005, 11:24 AM

Leif S4 · 08-04-2005, 11:25 AM

Mike2kS4 · 08-04-2005, 11:25 AM

The ECU opens the valves based mostly on throttle and MAP inputs. XR actually uses the BPV's during part throttle from time to time.

No, the BPV's can not open from boost pressure alone if they're oriented properly (OE). They just close tighter.

ryans4 · 08-04-2005, 11:25 AM

..vacuum sucks, the BPVs open, pressurized air now has a low pressure release back into the non-pressurized intake tract, the air goes there, the turbo is happy the air is going somewhere and you're happy the air isn't going into the manifold since you are trying to slow down (presumably).

It gets real interesting when you design a turbo motor that continues to make boost while the throttle is closed but isn't stalling the turbo. Figure that one out.

rickyS4 · 08-04-2005, 11:26 AM

WindyCityS4 · 08-04-2005, 11:26 AM

When the tb closes, the boost needs to vent or a pressure "shock" wave will bounce back to the turbos and slow them down. The turbo can't push against a wall.

I can't see how a BPV prevents overspins

rickyS4 · 08-04-2005, 11:29 AM

Mike2kS4 · 08-04-2005, 11:30 AM

Air reflects through the inlet piping from the closed throttle plate to the turbo exducer, stalling it. when you get back on the gas the turbo has to start up again from almost no RPM. This is bad for performance and reliability.

Venting that air that would normally cause this problem keeps the compressor spinning.

08-04-2005, 11:16 AM	#1
rickyS4 Junior Member Account #: 94739 Join Date: Jul 2005 Posts: 548	how the bpv works. i know there is alot of post on this but they dont agree. I was wondering if anyone has a good explanation for how the bpv work? I understand that they are normally closed. when you are on the throttle and suddenly let of they let air back into the intake to keep the turbo pressure from going to high. It is controlled by suction from a controller. what does the controller go by to decide when to open? and can the valve open from the pressure from the turbo alone? thanks __________________ ric martin 2000 Black S4 - me 1996 Blue A4 - Fiancee AIM: rikys4

08-04-2005, 11:21 AM	#2
WindyCityS4 AudiWorld Super User Account #: 52314 Join Date: Mar 2003 Posts: 7,550	What i was told... The BPV's are connected to the intake manifold behind the throttle body. When the throttle body closes, the vacuum in the manifold is used to open the BPV and "release" the built up pressure in an attempt to prevent the turbo from stalling. __________________ In a world of constant change, it is the learners that shall inherit the future. For the learned soon find themselves capable of living in a world that no longer exists. Autobahn Country Club (North, South, combined), Blackhawk Farms, Gingerman, Grattan, Mid-Ohio, Putnam Park, Road America, Sears Point, Thunderhill and "The Ring"

08-04-2005, 11:24 AM	#3
vegasS4 Member Account #: 12649 Join Date: Nov 2000 Posts: 4,146	Basically correct but it vent air as to not overspin turbo __________________ L10 AWE Stage III tip

08-04-2005, 11:25 AM	#4
Leif S4 Junior Member Account #: 74922 Join Date: May 2004 Posts: 1,006	They work like an electrical relay (if that helps) with the vacuum activating the "gate"

08-04-2005, 11:25 AM	#5
Mike2kS4 Elder Member Account #: 38083 Join Date: Jun 2002 Posts: 12,104	It is controlled by N249 which is fed by a vacuum reservoir. The ECU opens the valves based mostly on throttle and MAP inputs. XR actually uses the BPV's during part throttle from time to time. No, the BPV's can not open from boost pressure alone if they're oriented properly (OE). They just close tighter. __________________ 2002 S4 Avant, 6spd. Bone stock. <a href="http://www.autospeed.us"> </a> Caveat: Any advice I express regarding potential tuning and such is purely informational. If your knowledge and abilities are not up to the task, no amount of advice can assist.

08-04-2005, 11:25 AM	#6
ryans4 Senior Member Account #: 4359 Join Date: Apr 2000 Posts: 7,314	you decide when to open when you close the throttle body... ..vacuum sucks, the BPVs open, pressurized air now has a low pressure release back into the non-pressurized intake tract, the air goes there, the turbo is happy the air is going somewhere and you're happy the air isn't going into the manifold since you are trying to slow down (presumably). It gets real interesting when you design a turbo motor that continues to make boost while the throttle is closed but isn't stalling the turbo. Figure that one out. __________________

08-04-2005, 11:26 AM	#7
rickyS4 Junior Member Account #: 94739 Join Date: Jul 2005 Posts: 548	i am putting in after maket valves. should i be concerned with how much suction to open them? __________________ ric martin 2000 Black S4 - me 1996 Blue A4 - Fiancee AIM: rikys4

08-04-2005, 11:26 AM	#8
WindyCityS4 AudiWorld Super User Account #: 52314 Join Date: Mar 2003 Posts: 7,550	are you sure??? When the tb closes, the boost needs to vent or a pressure "shock" wave will bounce back to the turbos and slow them down. The turbo can't push against a wall. I can't see how a BPV prevents overspins __________________ In a world of constant change, it is the learners that shall inherit the future. For the learned soon find themselves capable of living in a world that no longer exists. Autobahn Country Club (North, South, combined), Blackhawk Farms, Gingerman, Grattan, Mid-Ohio, Putnam Park, Road America, Sears Point, Thunderhill and "The Ring"

08-04-2005, 11:29 AM	#9
rickyS4 Junior Member Account #: 94739 Join Date: Jul 2005 Posts: 548	yea my dad says they prevent overspin cus the turbos are centrifugal. __________________ ric martin 2000 Black S4 - me 1996 Blue A4 - Fiancee AIM: rikys4

08-04-2005, 11:30 AM	#10
Mike2kS4 Elder Member Account #: 38083 Join Date: Jun 2002 Posts: 12,104	Not true. Vents air to keep turbos spooled/ spinning. Air reflects through the inlet piping from the closed throttle plate to the turbo exducer, stalling it. when you get back on the gas the turbo has to start up again from almost no RPM. This is bad for performance and reliability. Venting that air that would normally cause this problem keeps the compressor spinning. __________________ 2002 S4 Avant, 6spd. Bone stock. <a href="http://www.autospeed.us"> </a> Caveat: Any advice I express regarding potential tuning and such is purely informational. If your knowledge and abilities are not up to the task, no amount of advice can assist.

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