BOV on b21ft w/ T3

[Super1800GTR]

Is it worth doing?? Or are they just noisemakers? If I did put one on where is the best location? I've seen them on the passenger side before the IC & drivers side after the IC. How exactly does it hook up? The hose coming from it goes to... CBV? Do I block off the CBV? Soo many questions!!! Sorry all this is a bit confusing to be being a turbo virgin and all.

Rob

 

[boostdemon]

I'll start this off:

Ditch the myth - my BOV as did Pats, Dougs, Pauls, and some other west coasters all worked fine on a k-jet b21ft.

what it fixed was the sluggish delay in power after a shift at full throttle. Why there was a second of no power im not sure, probably something to do with the combination of the turbo stacking as well as the ignition retard functions being confused - not certain there. But everyone i've talked to with 12psi or more on k-jet knows what im talking about between 2nd and 3rd gear.

You want to mount it as close to the TB and possible - why? because thats where the pressure changes happen first. Why's that important? because i can shift faster then a BOV can release (enough) air on the turbo side of an intercooler.

Hows it work - the BOV is a big spring loaded valve with a diaphram in it that wont let it open until its literally pulled open first. Its pulled open by the vacuum hose to the intake manifold. Now it wont open until there is pressure in the pipe and vacuum in the manifold (e.g. just closed the throttle after boost) that leftover boost pushes the spring up (now that the diaphram is open) and releases the air until either the spring load is stronger the the pressure in the pipe and pushes the valve closed again, or you release the pressure by opening the throttle again. The way you set the spring initially is to watch the valve and rev the motor... as it opens you set it to seal shut as the throttle snaps back down to idle. I personally got pissed off at this going up to VT as everytime i let off the throttle it would pssssh even when not boosting. so i cranked it down till it was only opening in positive pressures.

What i have on my car, mainly to keep me from stuffing it with socks when it gets annoying is a hybrid propotional bov. Its called a Stealth FX made by GFB out of australia and costs about 2x what a normal bov costs. In the end its well worth the extra money imho. Its basically a bov with two vents, one to atmosphere and one to a plumbback fitting thats routed back into the turbo inlet - much like a CBV does under boost release (cbv's also let air past the turbo for better spoolup as well iirc). Then you can also set the proportion of how much you want to either side... i.e. 50/50 to each, or 100% atmo for loud and fun, or 100% bypass for quiet and good metering.

hope that helps.

[edit] heres the pics http://forums.turbobricks.com/viewtopic.php?t=15929

 

[boostdemon]

oh yeah, and unless someone swapped the b230ft turbo setup on your b21ft and T3 you dont have a cbv.... when volvo pioneered the homologation of intercooled turbo cars for the public they couldnt think of a better way to vent the increased turbo pressure other then a rather annoying valve in the throttle plate that opened at like 17psi ... so when you closed the throttle and it stacked up it would open up and release a pound or pressure or two.

 

[coondog240]

yeah go for it mine works great and i have yet to get sick of the noise, in fact it brings a smile to my face every time

 

[slugger89]

i have a 1988 740 turbo where would i put the bov? and how would i take out the cbv? thanks

 

[EricF]

Just to help you visualize, that delay happens because when the throttle plate closes and [air] rushes back at the compressor, it drastically slows or even in some cases starts the compressor spinning the other way... Then there's the delay because the spool-up process needs to start over again pretty much... Though it is a short delay, as you're WOT well within your powerband

BOV just vents that air rushing back and allows the compressor wheel to continue to spin forward, giving instant boost when you get back on it.

Though the CBV has the same function, but on a B21 with a T3, you need not worry about them


edited to put back in words I left out...

 

[Chigga 744SE]

curious on the cbv part too, do I just leave it there? or should I block it?

I'm getting a TurboXS RFL in couple of weeks.

 

[Super1800GTR]

Thanks for the info. Looks like I don't need one unless I plan on running high boost. I'll keep this information in mind when I get to that point!

Rob

 

[boosted]

well heres what i did.... i removed the 1" id hose from the cbv to the i/c pipe, then i removed the entire cbv with bracket. then i TIG welded the aluminum bov on the exsisting peg in the i/c pipe. THEN i turned the i/c pipe around so the peg faces down and at the strut housing. then (for a closed system) it was a short peice of hose from the bov to a 90degree fitting, then the stock 1" hose, down to another 90 degree fitting, then to the stock pipe.


the probably sounds really fucking confusing... ask for pictures and you shall receive.

 

[slugger89]

yah can we see pics please thanks.

 

[Hank Scorpio]

Sam, you ricer

If you have a Mistu turbo with a CBV, block that crap. Yes you can run both, but theres really not much point in that.

Oh, Justin, Ryan, Noah, Paul, countless dudes at volvospeed, across the country, and WORLD have all had no issues.

Dana, rocking article btw

 

[Hank Scorpio]

Something pretty cool for mistu owners, thanks to Mopar and the SRT4

http://www.volvospeed.com/vs_forum/index.php?showtopic=15984

 

[Chigga 744SE]

so I can just use that block off kit on my wack ass CBV???

even know its a tiny whippy woopy 13C??

 

[G96nt]

doesn't Seem worth it...

if you're re-circulating the BOV correctly, taking amient-temp. Air, and you're dumping it pre-turbo, and pre IC. condition, which means it's not Really hot To begin With...


unless this is Something COMPLETELY different?

 

[FlatWagon83]

Sorry I'm a little late on this one, but what was the concern with a BOV on K-Jet? Didn't it have something to do with the system going full rich when the BOV opened? I would love to get some of that lag eliminated in the lower gears, always thought a BOV would do it?

 

[boostdemon]

im under the assumption that the k-jet system is too slow to change enough of the fuel enrichment to cause any negative side effects. I have had no change in gas milage or problems with normal driving (e.g. non wot driving). I have for all intents a stock k-jet fuel system running 95% perfectly.

 

[DecalServiceBrett]

im under the assumption that the k-jet system is too slow to change enough of the fuel enrichment to cause any negative side effects. I have had no change in gas milage or problems with normal driving (e.g. non wot driving). I have for all intents a stock k-jet fuel system running 95% perfectly.

To answer this question, Yes it does. I have a wideband in my b21ft(k-jet ), and it goes pig rich (11.5:1) when I let off the throttle and hit the BOV.

(thread resurrection!)

 

[GabAlmighty]

BOV sound cool, they make you cool, and they make people ive you funny looks cuz it's a volvo with a BOV. They make you feel alot cooler when you drive and shift and you hear that nice sound... imo

 

[The Plague]

I'm glad to see this thread because I too was told that BOVs are garbage on K-Jet cars. I have seen a handful of K-Jet cars and the guys driving them say they run like crap so I kinda assumed that the BOV was some of the problem. I was about to adapt a 740 CBV onto my KJet 245ti.. maybe I'll see about a BOV instead. Thanks for the heads up guys.

 

[MrBill]

I had a k-jet 240 turbo and a greddy BOV and it ran like a champ. No wideband or anything, but it never stalled or did anything stupid.