new BOV spring installed...
Senior Member
Joined: 03-16-2008
Posts: 662
From: Cleveland, Ohio
First this is just my opinion and I do not claim to be a turbo expert. I'm just an engineer who needed to know how this BPV thing worked. I was just intrigued by so many contradictive explaination.
Yes, Agree if you are losing boost on acceleration your valve is bad. After reading all weekend on BPV operation I finally found the best info on this topic. The search was for "Vacume transfer valve". The operation of this value is controller by the size of the air chambers on each side of the diaphram. One air chamber is smaller than the other. So under acceleration the smaller chamber on top of the value pressurization changes faster (needs less air) this pushes the valve closed. So no matter how much boost pressure you are running a BPV should not leak. If your valve opens at steady state (constant boost pressure) your spring is too light. How can you tell this is happening I don't know? Is should be closed at idle.
So changing this spring and increasing the tension will make the valve open later during deceleration and it will stay open shorter as a greater differential is required to keep it open. From a manual transmission point of view this seems like a good Idea - helps your shift points. But for an auto I don't know. It's definatly a personal setting you'll have to try. I wish someone made a set of spring with different tensions. This way you could adjust for your driving style.
Yes, Agree if you are losing boost on acceleration your valve is bad. After reading all weekend on BPV operation I finally found the best info on this topic. The search was for "Vacume transfer valve". The operation of this value is controller by the size of the air chambers on each side of the diaphram. One air chamber is smaller than the other. So under acceleration the smaller chamber on top of the value pressurization changes faster (needs less air) this pushes the valve closed. So no matter how much boost pressure you are running a BPV should not leak. If your valve opens at steady state (constant boost pressure) your spring is too light. How can you tell this is happening I don't know? Is should be closed at idle.
So changing this spring and increasing the tension will make the valve open later during deceleration and it will stay open shorter as a greater differential is required to keep it open. From a manual transmission point of view this seems like a good Idea - helps your shift points. But for an auto I don't know. It's definatly a personal setting you'll have to try. I wish someone made a set of spring with different tensions. This way you could adjust for your driving style.
Senior Member
Joined: 06-12-2008
Posts: 113
From: Lincoln, RI
That exactly what I thought I was finding. The BPV only effects deceleration but the Wastegate effects acceleration. It's the shaft speed of the turbo that is most important.
Senior Member
Joined: 02-20-2009
Posts: 596
From: Charleston, S.C.
My sportscar with a factory turbo came with an OEM valve that has a leak in it. The longer you used it the more it leaked. The car came from the factory making 8.5 psi boost and after a year it isn't abnormal to only be getting 7 psi. If you could change the spring in this valve you would definitely feel and increase on the acceleration side of the curve.
Senior Member
Joined: 11-07-2007
Posts: 1,613
From: Southside of Houston Texas
Bov
BINGO we got us a winner.....But let everyone have their own opinions I and others know it works let those who think it dont let them think that the end result is the one's who have done it will be leading the pack....JFWY LOL have a good one 
Last edited by gcsd3742; Apr 1, 2009 at 03:13 PM.
Senior Member
Joined: 03-11-2009
Posts: 327
From: WI
Not exactly true. If the BOV spring is too light for the amount of boost the turbo is making you will have a leak at the BOV. This affects the rate the boost builds at and also affects the total amount of boost you make.
My sportscar with a factory turbo came with an OEM valve that has a leak in it. The longer you used it the more it leaked. The car came from the factory making 8.5 psi boost and after a year it isn't abnormal to only be getting 7 psi. If you could change the spring in this valve you would definitely feel and increase on the acceleration side of the curve.
My sportscar with a factory turbo came with an OEM valve that has a leak in it. The longer you used it the more it leaked. The car came from the factory making 8.5 psi boost and after a year it isn't abnormal to only be getting 7 psi. If you could change the spring in this valve you would definitely feel and increase on the acceleration side of the curve.
Thread Starter
Senior Member
Joined: 08-18-2007
Posts: 602
From: Warrington PA
And then again, my SS has always ran good from the start.......
I still recorded a 0-60 5.6 sec on my DashHawk....after the BSR Tune.....
and BTW for your information, "it does whatsoever make sense" ...... Mr. OP
Senior Member
Joined: 06-02-2008
Posts: 2,358
From: Fairport Harbor, OH
Spring Installation Pictorial Essay
I don't know why I let you guys talk me into these things...
Especially with no pictures.
First, locate the general target area:
Then loosen the air pipe. Sort-of. Not sure if this helped or not.
Now you can see the cap on the BOV. That off-white plastic thing in the center of the picture. If that isn't it, then I eff'd up big time:
Twenty minutes later, (i'm only halfway there) I have the old spring out and compare it to the new one (right). It's a smidgen (CH) shorter and a bunch stiffer.
I put it in the plunger/diaphram thingy:
Then it goes back into the cap, but needs to be held together just as reported while you re-assemble it:
And after another 20 minutes and scraped up forearms later, It's done. No report on the effects, if any. That will come later. I did check around the block to make sure no toxic fluids were spewing out or red lights flashing. So far so good. BTW, as difficult as it was for me, I don't think I used any of my choice words I reserve for working on the car, (or boat).
Especially with no pictures.
First, locate the general target area:
Then loosen the air pipe. Sort-of. Not sure if this helped or not.
Now you can see the cap on the BOV. That off-white plastic thing in the center of the picture. If that isn't it, then I eff'd up big time:
Twenty minutes later, (i'm only halfway there) I have the old spring out and compare it to the new one (right). It's a smidgen (CH) shorter and a bunch stiffer.
I put it in the plunger/diaphram thingy:
Then it goes back into the cap, but needs to be held together just as reported while you re-assemble it:
And after another 20 minutes and scraped up forearms later, It's done. No report on the effects, if any. That will come later. I did check around the block to make sure no toxic fluids were spewing out or red lights flashing. So far so good. BTW, as difficult as it was for me, I don't think I used any of my choice words I reserve for working on the car, (or boat).
Senior Member
Joined: 02-17-2008
Posts: 287
From: NJ
Installed mine yesterday.
Couple of quick ideas for people with big arms like mine. Remove the 2 bolts on the large plastic piece that goes from the engine bay to the windshield. This allows it to lift up and gives you a LOT more room to work. This makes it easy to completely remove the intake tube which lets you work with 2 hands when putting the 3 screws back in.
Couple of quick ideas for people with big arms like mine. Remove the 2 bolts on the large plastic piece that goes from the engine bay to the windshield. This allows it to lift up and gives you a LOT more room to work. This makes it easy to completely remove the intake tube which lets you work with 2 hands when putting the 3 screws back in.