BPV Installation Question [Archive] - SaabCentral Forums

: BPV Installation Question


LDFolsom
12th March 2003, 01:06 AM
I recently purchased a BPV from abbott racing for my 2001 9-3SE. I was wondering if it should be positioned just like the stock bypass valve or not. It didn't come with any instructions and it doesn't fit very well in the stock position. It actually seems to have been made to go the other way around (With the vacuum nipple facing towards the front of the car instead of the left front wheel). When I looked on the abbott racing website the only thing I found was a picture of their air intake pipe and next to it you can see their BPV installed on a Viggen (I assume the basic setup of the SE and the Viggen engines are the same). In the picture it is installed with the nipple pointing towards the front of the car. I have attached the image so you can see what I mean. I installed it like the picture shows and it seems to function properly, but it worries me to see different people installing them different ways. Does it really matter which way it goes? Thanks.


Larkin Folsom

davy913
12th March 2003, 02:03 AM
hrm, from vw's 1.8t knowledge...if that valve is anything like the forge then it should be postioned like the stock one. there are two types of valves, one is the pull type and one is a push type, stock being pull.

LDFolsom
12th March 2003, 11:53 AM
How would I be able to tell if it is a push or a pull type? I know that mine is piston operated, and the way it is currently set up the air inbetween the turbo and the throttle body is pushing up on the bottom of the piston when activated and then escaping back to the intake tube. I also know that the stock one was a diaphram type (I'm not sure how that one works). The forge looks very similar to the one I have, but then I saw the picture on abbott racing's webpage (The one I posted).

davy913
12th March 2003, 07:59 PM
heres some info on the differences http://forums.audiworld.com/tt/msgs/108325.phtml
mainly, the stock dv/bpv is not strong enough to hold boost with the piston side facing pressure

LDFolsom
12th March 2003, 09:13 PM
That was probably the most useful piece of information I have ever seen for BPVs. From what I understood, my BPV is installed correctly, with the high pressure air hitting the bottom of the piston. I guess alot of people have them installed the wrong way (Although apparently piston operated BPVs function in both directions without problems). That was most helpful, and now my worries are gone. Thanks.


Larkin Folsom

TYPE IXXI
12th March 2003, 11:01 PM
I have a forge unit and my nipple faces the wheel well. is this correct?

LDFolsom
13th March 2003, 01:09 AM
According to the site Davy913 provided, it will function either way and thus your current installation is just fine. However it does state that piston operated BPVs should technically be installed the other way, with the nipple pointed towards the front of the car (The high pressure air is thus hitting the bottom of the piston instead of the side). The person who wrote the post on that site had originally installed his in the same position as yours, but decided to turn it around so that the high pressure air now hits the bottom of the piston. It also notes that in theory the BPV that came with the car (and apparently basically all turbo cars) was installed backwards. You should read it and look at the diagrams and pictures he has provided, it will make more sense then.



Larkin Folsom

TYPE IXXI
13th March 2003, 08:19 AM
I read the Document but still perplexed. Which is the high preasure side? My piston faces towards the turbo and the nipple to the fender. Please forgive my ignorance.

LDFolsom
13th March 2003, 12:23 PM
The high pressure is in the piping between the turbo and the throttle body, because the turbo is forcing air into that tube. I think if I explain it you will understand better.

When the throttle body snaps shut, the air in the tubing (And in the intercooler as well) after the turbo is trying to go into a closed throttle body. Keep in mind that the turbo is still spinning and pulling in more air, but there is nowhere for the air to go because the throttle is shut. This is the "high pressure side". The BPV is there because if you don't relieve this pressure, it will go back into the turbo (The wrong way) and cause the compressor to stop spinning. When this happens it means that your turbo will not be spooled up and you will experience turbo lag when you open the throttle again. The BPV diverts the air from the high pressure area back into the intake (Through that thin metal tube that goes from your BPV into your intake pipe), and thus back through the turbo (The correct way). Essentially the turbo is kept spinning by circulating its own air through the intercooler, then through the BPV, and then back into the turbo until the throttle body is re-opened. This results in a large decrease in turbo lag. So, if you look at your BPV you will notice that the high pressure air (The air in the piping between the turbo and the throttle body) is currently hitting the side of the piston until it is opened. In the correct (According to the person that wrote that post that you viewed) position, the air should hit the bottom of the piston. It does say that it will function either way. And since you have the forge unit, they said to install it in the stock positoin, so I don't think there is any problem. But I think that technically it should go the other way.



Larkin Folsom

ERP
13th March 2003, 02:23 PM
I have tried both ways several times and have not noticed any performance difference. The only difference I could detect was the loudness of the exhausting air. My current setup is pictured below and gives a slightly louder note than in the other orientation. This coincides with the Audi guy’s analysis. To most this wont matter thought because they are diverting the air and not blowing it off.

http://www.lehigh.edu/~erp4/saab/Upgrades/BOVin.jpg

TYPE IXXI
17th March 2003, 05:12 PM
Thanks guys. I switched mine around so the piston is towards the manifold. Its opposite of the pic

http://doofdog.homestead.com/files/bypass2.JPG