BPV Open at Idle...

By my research the bpv is supposed to be closed at idle, yet mine is staying open until the throttle is pushed. This is a stock bov.

 

05 lgt

5eat

Stage 2, currently on infamous rev1.

 

Is this a vac problem or a faulty bypass valve? I am hearing a boost leak on and off while in 4th or 5th under high boost during wastegate cycling. I am thinking that maybe the valve is leaking just enough to open a hair cause the air to whistle. All other connections are tight. I am running a FMIC. Thoughts?

i thought it was normal for the bpv to be open at idle ?

Possibly. I assumed that they were supposed to be shut at idle, but my searching has not yielded much from it aside from a few threads saying it is supposed to be shut.

bpv is closed at idle/accel.

Thanks for confirming. It is staying closed while accellerating. In numerically higher gears under load I hear a squeeking noise and then the car will bog down ever so slightly (around 100rpms), then work its way up only to rinse and repeat. Does a bov leak usually cause this? My search terms must be too specific, because I am finding no results.

Whistling is a boost leak like a hose. Arent you from mass? Did you do a boost leak test after the fmic install? Im going to guess no, its quite important to boost leak test after any intercooler changes. Your probably loosing boost since its leaking and whistling. Theres youtube vids of lgt boost leaks

Whistling is a boost leak like a hose. Arent you from mass? Did you do a boost leak test after the fmic install? Im going to guess no, its quite important to boost leak test after any intercooler changes. Your probably loosing boost since its leaking and whistling. Theres youtube vids of lgt boost leaks

 

Nope, Im in NE Ohio. I had a boost leak that I previously fixed. This time it is on and off while the wastegate cycles. I'll have to do a leak test tomorrow I suppose.

 

Found a vid of what is going on. Didnt think to search for vids! Comments say it is surge and the bpv is at fault. I will have to confirm this, but this sounds exactly like my problem.

 

[ame=http://www.youtube.com/watch?v=6nAW7fABKgk]Odd noise = boost leak? - YouTube[/ame]

do you have a stock bpv? if not, increase the tension or the spring rate

Stock bpv. My buddy has a blitz that I am going to give a try. I believe it is recirculating and adjustable.

did you notice the uploader of that video is scoobydoobie, he's a member on this forum, maybe you should ask him what the problem was

Good catch. I'll PM him and see what he did to fix it, and direct him to this thread for closure.

 

Assuming the bypass valve is the culprit, have any good BPV recommendations? Maybe an OEM of some sort? Really just want to stick with a full recirc, but would not rule out a hybrid if I find one used. Brands to stay away from? Dont care about noise, I just need a reliable one that I wont leak and hopefully wont break the bank. I come from a jeep background, so I've yet to fully learn what is good and what is not in the subaru world. I dont know what psi I am running right now, but I am only on Revision 1 so I am assuming it will only get higher.

 

I apologize for all of the questions. Dont have enough time to scour the internet in search of clues. And thanks for the help thus far!

The problem is surge. You need an aftermarket BPV to tune it out. I still have the surge to some degree in certain gears/throttle positions (I haven't been able to fully get rid of it). FWIW I am stage 2 w/FMIC as well and never noticed the problem at all when I still had a TMIC.

 

Here is my thread about the issue: http://legacygt.com/forums/showthread.php/wtf-noisei-148152.html?t=148152&highlight=wtf+noise

 

As far as brand of BPV goes, many people seem to like the GFB. I am happy with my Cobb as well.

The problem is surge. You need an aftermarket BPV to tune it out. I still have the surge to some degree in certain gears/throttle positions (I haven't been able to fully get rid of it). FWIW I am stage 2 w/FMIC as well and never noticed the problem at all when I still had a TMIC.

 

Here is my thread about the issue: http://legacygt.com/forums/showthread.php/wtf-noisei-148152.html?t=148152&highlight=wtf+noise

 

As far as brand of BPV goes, many people seem to like the GFB. I am happy with my Cobb as well.

 

This is great to hear.... sort of. Thank you for chiming in! Glad it is happening now and I can catch it before the tune is done.

Got a GFB Respons Hybrid on the way! It'll be nice to have something that is adjustable. I will report back to confirm problem solved once i get the bpv on and properly set.

the stock bpv is open at idle and cruse.

the stock bpv is open at idle and cruse.

 

This is correct.

 

Vacuum pulls the valve partially open. It closes when you blip the throttle, because manifold vacuum drops and the spring forces the valve all the way shut.

 

The valve is partially open any time there is significant manifold vacuum.

i wonder how many inHg it takes to pull a 20psi rated spring up

Springs aren't rated in pressure.

 

Force of a spring is the distance compressed times the spring constant.

 

Vacuum "force" is the differential pressure times the surface area of the diaphragm (so the area of the BPV).

I'm talking about my bpv, forge, with a 20psi spring. still think engine vac is enough to open it at idle?

Not enough information to let you know. What's the surface area of the plunger?

 

The stock bpv is definitely open at idle, which is what the OP was asking about.

Well then that puts my concerns regarding that at rest. Still, the new bov will allow me to deal with the surge issues. It seems that my car is developing rough idle issues and pops more often with letting off the throttle. When I have a chance I am going to reset the ecu remove the banjo filters and make sure they are not clogged. I am also hearing quite a bit of chatter from the valves.

I'm talking about my bpv, forge, with a 20psi spring. still think engine vac is enough to open it at idle?

 

 

the thing with a bov is when you floor it and boost fills the intake that boost also fills the actuator side of the bov, the only thing the spring does is give a bit of bias bov's could be made to work with out the sprng completely.

 

the most amount of vaccume possible on this planet is 14.7 psi.

the stock bpv if you remove the hose from and block it ( the hose ) and drivei t you will be limited to about 5 psi. that is the bias of the spring.

 

you can try your 20 psi thing but aslo unplugging the vaccume hose and see what boost it will open at if its anything more than about 10 psi the bov would be pretty much unable to open unless you have a serge of boost.

 

there are different therorys on whats better with bov, if they should be open at idle and cruse or not.

 

in my case of blow through maf after bov and i have to atmosphere valve. i have it closed during idle and cruse only if there is a surge of pressure it will open, main reason is the pcv and crank case vent would be always blown out during idle and cruse. so basically oil and fumes coming out of it all the time.

 

on the stock tmic i think it would also be benificial for the bov to be always closed because it would reduce the amount of hot air being blown into it. that is a contribuiting factor to heat soak.

If the bpv is closed during idle would that not help with throttle response and spool? I know it probably takes just a fraction of a second for the valve to close. What I am finding is people tend to adjust their valves to be shut during idle. WHy they do this, I have no idea.

shut during idle would reducce the amout of heat being pushed into the intercooler from the turbo.

 

depending on the setup some turbo build pressure at idle and others don't

for example when cold the lgt stock the turbo will push a lot of air! but when hot and at normal idle the turbo is bearly pushing anything.

 

you can think of a vaccume, if you block the intake or exhaust of the vacume it will speed up do to no air or very little air being moved through. and the centrifual effect of the turbo looses its chain reaction. so by having the bpv closed and slightly higher idle with retarded timming the turbo could be at a substantially higher speed to begin with. before you even give it a shot of throttle.

Interesting. I doubt it is worth messing with on a DD. It could potentially be fun, though.

 

Thank you for the info, Frank and BAC. When I get this GFB installed I will report back confirming that the new bpv has laid my surge issues to rest.