Magown

p0wp0w,

A CBV and a BOV are basically one and the same. The term CBV is used when the valve dumps boost back into the intake and a BOV is used when it dumps boost to the atmosphere. Also the CBV is open at idle, which bypasses the Turbo and the all of the intake track so the engine doesn't have to breath thru 10 ft worth of pipes and intercooler, hence the name compressor bypass valve.

Some blow off valves have adjustable springs and can be set up to work either way. If you are using a stock air flow meter or Maf and you dump to the atmosphere then the A/F will go rich. Jason is using the same valve that I described above. The Forge 006. It is a CBV and should not be used in a BOV configuration.

p0wp0w

ahh, I understand now.
Thanks for clearing that up Stephen!

MachSchnell

Actually, for clarification, I'm using the Forge 007, slightly bigger flow capacity, minor modifications to the J-pipe required (I cut about 1/2" off the bung sticking up out of the Jpipe...seems to work fine, it was just a matter of making it fit under the hood with the rubber vacuum elbow not pinched.

MachSchnell

It's amazing what a putz I am...I can't believe I just MIS-corrected someone on a fact that is actually in my signature. I need longer weekends!
I do have the Forge 006, not 007, the 6 being the larger unit. Just one of those sundays.

Sami951

Since I'm dumb today, could somebody clarify just one more thing: Forge 007, the smaller unit - it fits into stock location with no modifications? Or does it require cutting, in which case I might just as well get the 006?

Bill

I got the Stratosphere Forge 007 DV in stealth black. Direct replacement, no modification needed. It has a steel piston with spring inside (no diaphram) that has an o-ring milled into the body of the valve for the seal. Just a little grease every now and again. Great BOV!

streckfu's

Go with the Forge 007! Great piece. I'll post a picture tomorrow if no one else has.

Daniel

Chas

Correct me if I'm wrong...but doesn't the stock setup blow off back to j-pipe right before the turbo?

I thought to get a really loud "whooshing" sound you have to blow off to atmosphere...

And that totally screws up your A/F mixture during shifts right? Does that matter?

dmoffitt

stupid thought, but don't rally cars and other really prepped/built race cars vent to the atmosphere, and use the extra fuel as a way to cool the engine between shifts? or is this different than the rich condition reported by jason above?

Magown

Yes, the rally cars do vent to the atmosphere and yes the do use fuel to keep the turbo spooled between shifts. I’m not sure if they use it to cool the engine. The rally cars run very sophisticated engine management systems like Motec, which have anti-lag features built in. Basically what I'm saying is, those cars a programed to do it. Our cars can do it (temporarily run rich) by fooling the system (venting to the atmosphere). I think the AFM based system is to slow to react and the car will respond with a brief stumble. I tried this years ago way back in 1998, didn't seem to help any then.

Here's pictures of the 007 Forge Valve that I got from Imagine Auto installed on my '88.

<img src="http://www.lilray.com/porsche/images/DSC00490.JPG" alt=" - " />

<img src="http://www.lilray.com/porsche/images/DSC00489.JPG" alt=" - " />

Chas

where/how does the BOV/CBV get it's pressure signal to know when to dump air?

TurboTime

I bought and installed the Lindsey BOV two months back. Sounds, looks and works great! A little pricey at $190. (I got the modified unit)

It worked a lot better after I installed in the correct horizontal vs. vertical position ;oP

Greg

User 41221

I got the same Forge 007 that Stephen did (and I also got mine from Imagine Auto), and I like it really well. I hold boost better and it seems like I picked up about .05 bar more boost at the same time.

Since my 951 is also red, I won't bother posting a pic of it. Just look at Stephens pic and imagine his car has the KLA strut brace on it.

Regards,

H Dog

I don't understand how some of these aftermarket "Blow Off Valves" work.

First, I suspect that what we're talking about is really the Compressor Bypass Valve. If so, then these shouldn't make all that much noise, unless they're being vented to the atmosphere.

And if this is the case, this should mess up how your car runs. The stock configuration is upon a sudden closed throttle condition(e.g. upshifts), the boost be rerouted from after the intercooler back to in front of the compressor (but after the airflow meter).

The DME is metering fuel based on the air in the intake, regardless of the boost pressure. So once past the air flow meter, the system must be closed. Otherwise, an overage of fuel will be introduced based on a faulty expecation as to the volume (mass) of air in the system.

However, perhaps there's a higher performance issue surrounding this aftermarket arrangement. In the movie "In Car 956", it is clear when the car is accelerating down the Mulsanne Straight that during upshifts the car makes a "fluttering" sound. So maybe the stock setup is a compromise for road cars.

But I still don't get it.

Magown

H Dog, sounds like you've got it down to me. The only thing is, is that it seems most people can't use the correct term to describe their valve, everyone just defaults to BOV. I've been trying for years to set everyone straight. Looks like I've got my work cut out for me.