BOV's what fits a STOCK legacy turbo??

inzomniac · Post by **inzomniac** » Sun Mar 30, 2003 12:54 am

Anybody know what will fit/be made to fit a Legacy turbo in stock trim (in terms of the turbo and with a lack of intercooler) pushing around 10psi ( I don't know why it does.. it just does ) what will fit if anything?!?! I'm just craving the sound and I'm getting sorta antzy and I don't want to wait until I get around to putting an intercooler on it (plus I have plans for this as a rally car and doing the I/C will mean open class

) Any advice would be very helpful.

-K- · Post by **-K-** » Sun Mar 30, 2003 7:19 am

Any with a 1in or 25mm hose connections should work. Not the type that bolt to a flange. And make sure it's going to work with a MAF. As far as what brand I don't know. The piping might need some mods.

vrg3 · Post by **vrg3** » Sun Mar 30, 2003 1:23 pm

If you switch to atmospheric, you'll have to cap off the pipe in the little corrugated elbow that the stock valve goes to.

You'll also run rich momentarily unless you tweak your engine management to handle the situation.

The stock valve is kind of weird... There is a big hose going to just before the throttle body, and a big hose going to just before the compressor. These make sense tot me. There's also a small hose going to the intake manifold, though. Does anyone know exactly what it does? Does the valve not actually dump pressure until manifold pressure drops too? That would be a cool feature to prevent boost loss through the blowoff valve.

At the least, if your new blowoff valve doesn't have that connection, you'll have to cap that off too.

inzomniac · Post by **inzomniac** » Sun Mar 30, 2003 3:50 pm

This is the one I'm thinkning about getting... it seems to be able to solve all of the issues wiht running rich and such, also has the quiet mode... great for me with the police in the town I live in.

http://www.mrtrally.com.au/performance/ ... 0Flyer.pdf

vrg3 · Post by **vrg3** » Sun Mar 30, 2003 4:57 pm

Well, I think you would have to run it in quiet mode to avoid the rich condition.

If you use that valve, it should fit, and you'll have to cap off or plug the other two hoses. You may want to use the longer hose from your old valve for the new valve rather than the shorter one, since you'll probably want to relocate the valve a bit.

mile hi · Post by **mile hi** » Sun Mar 30, 2003 7:30 pm

The little hose goes to the manifold and opens the valve when the manifold goes to vacuum. I have two of the stock valves and one Bosch valve with 1" fittings for sale if anyone is interested.
AL(CO)
al@iwtu.net

vrg3 · Post by **vrg3** » Mon Mar 31, 2003 12:56 am

Al, really? That's cool! That's what I thought it might be... Does that mean that the valve pretty much won't leak boost, since it requires both a high pre-throttle pressure and high manifold vacuum to open?

mile hi · Post by **mile hi** » Mon Mar 31, 2003 2:03 am

From what I understand some valves will leak, probably due to the type and construction because they have optional springs available. I have run 20lbs and don't see any difference from the Bosch valve and the Forge valve with a red spring that someone said I should have.
AL(CO)
al@iwtu.net

inzomniac · Post by **inzomniac** » Mon Mar 31, 2003 4:11 am

Ok, this may be a stupid question... but other then the backfires... is there any other problems with running another "loud" blowoff valve?? backfires I can handle..

91White-T · Post by **91White-T** » Mon Mar 31, 2003 4:36 am

I found that when I ran with the stock BOV with the recirculating hose disconnected, it ran really really rich(ALL the time), and after a while it would get real sluggish.

vrg3 · Post by **vrg3** » Mon Mar 31, 2003 6:05 am

When you disconnected the recirculating hose, how did you cap it off? If it wasn't sealed right it could have caused a boost leak which would mean rich mixtures during boost.

Oh, and backfires can be really bad with a turbocharger in place; in bad cases they've actually blown the turbocharger right off the engine.

-K- · Post by **-K-** » Mon Mar 31, 2003 8:00 am

The problem with the stock valve as a blowoff is, it isn't made to. It will open when there is vac in the manifold (idle, no boost driving) You are making a big vac leak so it should run like crap. I have always heard them refered to as bypass valves. The small hose to the manifold is also supposed to keep it shut under boost, the pressure in it holds the valve closed. The problem with them is you are releasing air that is metered, but if you get a blowoff that is for MAF cars it will only happen when you shift or come off the gas fast. It running rich there is fine, some people think it might keep the turbo spooled some during shifting, but I don't know.
JUST make SURE it's for a MAF car, or else it might be a big vac leak.
That one looks good, and you can send most of the air back into the intake so it should run good. And you don't have to plug the return line with that one because it is used.

vrg3 · Post by **vrg3** » Mon Mar 31, 2003 2:01 pm

Huh, -K-, what you say is interesting. The stock valve is actually open during idle? I would have thought it would operate as a check valve that opens above a certain pre-throttle pressure (say 6psi), with the additional requirement that the manifold vacuum be high before it actually opens.

Aaron's ej22t · Post by **Aaron's ej22t** » Mon Mar 31, 2003 8:23 pm

K:

The small hose to the manifold is also supposed to keep it shut under boost, the pressure in it holds the valve closed

What?
all blow off valves or bypass valves have that small hose. that is the vacuum line.
it is sometimes hard not to have idle problems with blow off valves. i would not run a blow off valve on a maf equipped car, it just messes it up makes it run poorly.

if you want a good replacement bypass valve, then get the forge bypass. it is polished chrome, has a straight inlet/outlet like the stock valve but has an adjustable spring for valve tension, it is nice and good for high boost. they cost $130.

91White-T · Post by **91White-T** » Mon Mar 31, 2003 10:52 pm

Aaron's ej22t wrote:they cost $130.

Damn that's a lot of money, here's the free way I did it.

I had to remove mine when I put on my IC, and as far as I can tell, just getting rid of it has had no ill effects whatsoever, plus you get a really loud cool wastegate sound...

boostjunkie · Post by **boostjunkie** » Mon Mar 31, 2003 11:16 pm

Can't say too much for the longevity of your turbo, however.

91White-T · Post by **91White-T** » Tue Apr 01, 2003 1:43 am

Not too worried about that, its got 170K on it and its still kickin out 15psi... Plus if it does crap out it'll just give me a good excuse to get that WRX turbo I've been wanting.

inzomniac · Post by **inzomniac** » Tue Apr 01, 2003 3:11 am

Aaron: Can you send me a link on where to get the forge valve, also this will make the noise associated with a blowoff valve right? The noise what I'm really looking for, along with the better throttle responce/spool time. My stock unit still functions perfectly and with my aspirations to run this car as a rally car (production) there is no point in doing an intercooler setup wich would make mounting the BOV easier.

I'm guessing this is the valve??

http://www.forgemotorsport.com/subaru.a ... =FMDVS013B

would this work?
http://www.forgemotorsport.com/subaru.a ... =FMDVK013A

Austin · Post by **Austin** » Tue Apr 01, 2003 5:06 am

91White-T wrote:I had to remove mine when I put on my IC, and as far as I can tell, just getting rid of it has had no ill effects whatsoever,

The ill effect of removing your bypass valve is that without one, when the throttle plate snaps shut, it sends a huge reverse wave of pressure against the compressor blade. Not only will that slow the shaft down quite a bit, but if it's bad enough you can snap compressor blades.

Better to run an atmospheric venting BOV (even on a MAF car) than no BOV/bypass valve at all.

Best to run a bypass valve on a MAF car.

-K- · Post by **-K-** » Tue Apr 01, 2003 7:06 am

Let me clear it up. The vac line also puts pressure to keep the valve closed, if you disconnect the vac line it will not hold any boost. vrg3 if you have a boost/vac gauge when at idle there is a lot of vac so it is kind of open, hence the rough idle if vented. If it is hooked up like stock, so what if it's open some on idle, the air going into the engine still had to come through the MAF. If you ran a check valve that would hold a few lbs after the bypass valve I think it would idle just fine, still run rich on shifts.
I'm thinking about making something to put in the bypass hose to make more noise, like blowing on a coke bottle.

Aaron's ej22t · Post by **Aaron's ej22t** » Tue Apr 01, 2003 8:07 am

also this will make the noise associated with a blowoff valve right?

inzomniac, yes that is the one. bypass valves and blow off valves essentially sound the same, the only difference is that the blow off valves vents it to atmosphere and it is a loud whoosh, whereas the bypass valve sounds the same but just very quiet.

inzomniac · Post by **inzomniac** » Tue Apr 01, 2003 3:08 pm

Ok, just to clear this up... will both of the links I posted fit my car? Or only the top one pt#: FMDVS013B Just making sure so I don't buy the wrong one.

boostjunkie · Post by **boostjunkie** » Tue Apr 01, 2003 4:18 pm

The top one is the recirc-style (no sound) and the bottom one is the atmospheric venting kind (lotsa sound). Both will work, but I think you'd want the bottom one for sound purposes . . . (but NOT performance).

inzomniac · Post by **inzomniac** » Tue Apr 01, 2003 5:47 pm

Will the bottom one hrut my performance (ie. cause all of the above problems including possible death of turbo) or will it just be similar to stock?

Sorry I've got so many questions, but this is one thing that I really don't know very much about.

boostjunkie · Post by **boostjunkie** » Tue Apr 01, 2003 5:59 pm

The bottom one (loud one) will cause a slight lag in performance after each shift. It's like this:

Instant throttle response after shift for top one (quiet one), a little delay in throttle response after shift for bottom one (loud).

So you trade the cool sound for throttle responsiveness. Make sense?

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BOV's what fits a STOCK legacy turbo??

BOV's what fits a STOCK legacy turbo??