Blow off valves

Cory9584 · 02-02-2005, 09:10 PM

I'm looking to replace the stock bov with one that vents to the atmosphere but cant find any to fit a 951 unless I get a flange welded on the IC pipe. Is there any bovs out there that just clamp and still have decent quality?

awilson40 · 02-03-2005, 05:45 AM

I bought one that installed in the stock location, then you add a plug
to the unused port in the 'J' boot.
It worked fine, but I got tired of the sound so I replaced it with stock.

Lawrence Coppari · 02-03-2005, 07:41 AM

Why do you want it to vent to atmosphere?

Cory9584 · 02-04-2005, 01:20 PM

I just always liked the bov sound, Im not looking for something rediculously loud but just makes a little noise.

DannoXYZ · 02-24-2005, 02:29 PM

Take the stock one, loosen the upper-hose clamp on the intercooler pipe. Pull the valve out of the J-boot and rotate the upper hose 90-degrees up. Plug up hole in J-boot with a big cork or something. Instant atmospheric BOV!!!

docsafi · 02-24-2005, 08:20 PM

He he hehehe, He wants to blow into the atmosphere! Thats cool.

rucool · 02-25-2005, 06:42 PM

Don't be a ricer, keep the power under cover then blow the ricers away.
its more fun that way.
safe driving
Russell

Cory9584 · 02-25-2005, 09:27 PM

maybe ill just get an upgraded recirculating one and vent it once in a while by turning it and plugging the hole so i can choose. Right now ive had the boot plugged and the valve venting to the atmosphere but it doesnt make any sound whatsoever, it pronably doesnt even work

Every once in a while ill get a nice sound out of it. Does that mean its probably shot and only works occasionally?

Lawrence Coppari · 02-26-2005, 02:47 AM

You can test valve by applying vacuum to nipple at top of valve. If nipple does not hold vacuum, your diaphragm is leaking. The nipple sees both positive pressure to hold valve closed (in addition to spring) and vacuum to open valve and let compressed air back into compressor.

What does your boost gauge say at full boost? About 1.8 is stock. Anything less means something is wrong or gauge is bad. If you have leaks in small tubing that goes to top of recirculating valve, you will be low on boost.

DannoXYZ · 02-27-2005, 02:32 AM

"Every once in a while ill get a nice sound out of it. Does that mean its probably shot and only works occasionally?"

Besides the test of the diaphram that Lawrence pointed out, check the vacuum hose going to the BOV's nipple. This hose has shared Ts with a lot of other things like the FPR and fuel-dampener. If there's a leak anywhere in the system, it'll prevent proper operation of those components and the BOV.

Unhook the hose at the BOV and plug a vacuum gauge into it. Should read 18-20 inHg. at idle.

Cory9584 · 02-28-2005, 11:57 AM

I checked my bov today and sure enough the diaphram is shot. Now I definately got to replace it soon. Does anybody know of any valves that fit because all of the ones people want to sell me require a flange being welded on and i dont think there would be enough room to fit the valve.

DannoXYZ · 12:22 PM

The Forge valves from Stratmosphere are a direct replacement for the stock unit. It's is of aluminium instead of plastic and the internal diaphram is all metal with O-rings for sealing (rebuildable). The spring is also replacable with one of rate you want (different spring needed for BOV compared to CBV function).

Lawrence Coppari · 03-01-2005, 03:09 AM

Dannoxyz, what does CBV mean?

Cory9584 · 03-01-2005, 07:51 PM

can i use the first one on the page thats for a 1.8t without changing anything, and will it fit between the ic pipe and expansion tank? or do i have to use the one on the bottom of the page thats for a saab which is identical to ours? Id like to use the 1.8 one because its fully rebuildable and just looks nice

DannoXYZ · 03-01-2005, 09:05 PM

CBV = compressor bypass valve

This is the stock configuration where it vents pressurized air from the turbo-outlet back to the inlet when you shift. Otherwise, this pressurized air wil slam into the closed throttle-plate and stop. Meanwhile more air keeps on slamming into that 1st piece of air and stops. The point of stopped air builds up to intense pressure and works its way back to the trubo. This pressure-wave is like the point where traffic accumulates from rubberneckers and moves backwards into traffic. Just like rear-end collisions are really dangerous in this situation, the pressure-wave working its way back to the turbo's compressor wheel and stops it from spinning, even shatters the wheel and bends the axle.

So by venting this pressure back to the turbo-inlet, it allows the turbo to keep on spinning. When you finish the shift and open the throttle again, the turbo will spool up back on boost faster than if it had to start from a standstill. On the J-pipe I build for my MAP kits, I angle the return-pressure from the bypass-valve to aim direclty at the compressor wheel, to really keep it spinning .

Cory9584 · 03-08-2005, 07:09 PM

Does anybody have the forge 006 valve on their 951. I want to order it but dont know if its going to fit where the stock bypass valve goes. My whole intake system is original right now. Can somebody let me know if this is going to work or im just wasting my money?

DannoXYZ · 03-08-2005, 10:18 PM

I haven't used the larger 006 valve, but it may fit. I got the 007P which is about the same as the stock one. Get the stiffer spring if you are going to vent to atmosphere, otherwise, it'll leak and vent while driving through parking lots and cause surges and stuff.