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Old 05-07-2001, 12:33 AM   #1
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Question Bosche BOV leaks over 7 psi, need recs for BOV for 0-12 psi

Well, after having rides in several other turbocharged RS and WRX, it is becoming clear to me that my Bosche BOV (which is vented back to the intake) leaks at over 7 psi.

I want to replace it with a BOV that will be perfect for my 4-10 psi 2000 Turbo RS, that doesn't leak under boost until I let off the gas. My preference is that the BOV must be recirculated back into the intake to keep noise down, although a little BOV noise is nice to scare off and/or intimidate the r*ceboys who wanna race all the time

I have been told the Greddy would be a good option, but also wonder about what options Blitz, HKS, Turbo XS and others have for my particular turbo setup and needs as above.

My setup: I have an IHI ballbearing compressor with a 2.5" exhaust and two hi-flow cats, 5x4x18 top mount IC and dual TB 480cc injectors, running 4-10 psi (depending on octane of gas and altitude I am driving at), with the stock 10:1 pistons and no timing control. Remember, the absolute compression ratio is 12.97:1 at 8 psi boost at 6,000 feet, which is like 6 psi at sea-level.

Driving above 7,000 feet altitude, 9 psi is easy with 1 bottle of octane booster, and highway cruising in 5th gear is good up to 10 psi. At 5,000 - 6,000 feet where I live and drive most often, I can run 8 psi without detonation if using octane booster added to 91 octane, and I can run 7 psi on 91 octane pump gas if I reset the ECU and train it. We can't get higher than that in Colorado Springs, except 93 at ONE place accross town.

So, a BOV leaking at 7 psi isn't gonna cut it anymore. Especially when I get my water injection done and may see over 10 psi occasionally.

So, any suggestions for BOV?

Larry www.ImprezaRS.com

PS: And, no, I am not installing a timing controller yet because I have someone designing a boost referenced timing controller that we are going to sell, and my car is the guinea pig for testing.
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Old 05-07-2001, 08:14 AM   #2
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Larry,
I have the JC Sports kit and I am running a Greddy type S and have always been, since the Bosch one always seemed to leak. I am running 6psi at Sea Level and have been very happy with it's performance. As to noise and rounting it back in, With the lower pressures we are running the BOV noise is very slight when venting to atmosphere, which is how I have mine set. Hope this helps.
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Old 05-07-2001, 08:28 AM   #3
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I just got a Forge unit for my wrx, I have to say its nice and compact. Its not as loud as the Blitz and Apex in my opinion. It doesnt have a accustically tuned horn like the others in that it has holes around the body of the unit.

alan
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Old 05-07-2001, 10:24 AM   #4
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Yebokmj wrote, "As to noise and rounting it back in, With the lower pressures we are running the BOV noise is very slight when venting to atmosphere, which is how I have mine set. Hope this helps."

I've been hearing that most people have problems with venting the BOV into the atmosphere. Are you saying that you haven't had problems venting it to the atmosphere at all or you had to do something first so your car would not stall?

I have the Bosch BOV and I wasn't aware of the leak issue. How would I know that it's leaking? I bought it because it is relatively cheap. I'm mostly function over form but if it doesn't function up to par, than I might as well get the best of both worlds. Pffffsssssttt!
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Old 05-07-2001, 10:50 AM   #5
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Quote:
I have the Bosch BOV and I wasn't aware of the leak issue.
Yeah, me too. Joshua, how do you know it's leaking? The valve I have is the cheap plastic Bosch diverter valve from an Audi A4/S4. Is that the one you're using, Larry? It's supposed to hold 8psi, IIRC.

Looks like this:
<IMG SRC="http://www.rallystuff.com/images/turbo3.jpg" border=0>
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Old 05-07-2001, 11:41 AM   #6
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I knew mine was leaking because I have always had the BOV blowing off to atmosphere. And both of mine (yes I tried a second one) had air coming out of them at idle making for alot of problems. And yes the one shown in the picture is what I was running. As to how I am venting into atmosphere it's because I am using the the HKS Super AFR. Go to the link for more information and then to features to read about the BOV to atmosphere control. But I can tell you I am having no problems what so ever running my setup this way. Any other questions feel free to ask.
Joshua
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[This message has been edited by yebokmj (edited May 07, 2001).]

[This message has been edited by yebokmj (edited May 07, 2001).]

[This message has been edited by yebokmj (edited May 07, 2001).]
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Old 05-07-2001, 01:47 PM   #7
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I thought I can vent to atmosphere if I wanted because to because I have a MAP sensor, not a MAF. I just dont' want to.

Also, my Bosche BOV is like the photo above, but is mounted the other direction. If that is part of my problem, it is moot point because from what I see above, it would still leask at over 8 psi instead of 7.

1) yebokmjh - you are vented to atmosphere, but will that Greddy type S also vent back to the intake? I will not be runing the low and "quiet" 6 psi pressures you are running.

2) ravnazn - does the forge vent back to the intake?

Thanks,

Larry
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Old 05-07-2001, 02:07 PM   #8
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Another cheaper alternative might be to use the Bosch BOV on Porsches. This is very similiar to the ones on the A4 but I think it might hold more PSI. The price is well under $100 from the Porsche dealer too. Just a thought.

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Old 05-07-2001, 03:19 PM   #9
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Larry,
The Greddy type S can be routed back into the intake. As to Blkwan's suggestion, I was told by JC Sports when I called about my problem with the Bosch BOV that this was the same one being used by Porsche.
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Old 05-07-2001, 03:34 PM   #10
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There is always the best option...no BOV at all. Stupid little devices they are.

Id rather not have one. Then deal with on.
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Old 05-07-2001, 03:58 PM   #11
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I know your joking but you deffinatly don't want to go that route. I went that way for a short time when my Bosch was junk and I was waiting for the Type S. The noise you get of the air forcing itself through the turbo and back out the intake sounds like death.
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Old 05-07-2001, 10:36 PM   #12
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The bosch bov for the Porsche has a different part # than the Audi A4. If you also talk to any performance Saab and Volvo people, they'll tell you that it is a different unit. Some of them have installed them back to back and have noticed a difference.
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Old 05-08-2001, 06:22 AM   #13
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According to the Audiworld folks who've tried it, the Porsche BOV IS the same as the S4 valve(s). A better upgrade is the Bosch BOV from certain SAABs, which looks identical, but holds more boost. The SAAB version costs about $45.

In terms of the Forge valves, S4 owners are having major problems. Seems that they get stuck open or shut when hot. Obviously this is really bad. Forge is working on the problem, but I wouldn't put one of those in my car until I hear everything is ok.
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Old 05-08-2001, 08:43 AM   #14
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Many AW guys are using the Bailey valve, in both A4s and S4s. They're made by a company in England, and seem to have been better engineered than the Forge valve.
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Old 05-08-2001, 10:23 AM   #15
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Silly me, I was actually thinking of the SAAB's BOV being different than the Audi.(Damn, they all look similiar). The part #s are different but it may be dealer part #'s instead of manufacturers. I heard from Saab crowd that it is just the opposite. Some of them seem to like Porsche(Audi) BOV's better. Go figure. Hmmmm....
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Old 05-08-2001, 11:17 AM   #16
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Actually yebokmj i wasnt joking. Beleive it or not.

A good quality turbo with a 360 ball bearing, and not large enough that it will create a cavatation problem, and your all set. Personally i dont like driving cars with BOV's. Too much turbo lag for my liking.
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Old 05-08-2001, 11:31 AM   #17
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Buck-O, assuming a BOV/diverter valve is functioning perfectly (has a stiff enough spring that it doesn't bleed boost, but opens instantly when the throttle is closed), how could it possibly cause turbo lag?
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Old 05-08-2001, 11:41 AM   #18
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Oh come on Jon, i know you know better then this.

Once the BOV opens, and vents boost pressure out of the intake the turbo has to recover all of that boost presure that was leaked away. And if your running an FMIC, thats a real pain in the ass. Especially when my driving style relys heavily on left foot braking, and working the throttle to balance the car, nothing sucks more then trying to hold a drift, only to hear "PHIIIIIIIISSHHHH!!!!!" and have the engine bog, and turn a nice drift into a nice spin.

BOV's are a joke, they are mearly for turbo preservation. Not for turbo performance. I dont know WHY people assume they actually make your car faster, and the turbo work better.

[This message has been edited by Buck-O (edited May 08, 2001).]
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Old 05-08-2001, 11:51 AM   #19
Jon Bogert
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OK, so it's directly related to the volume of the intake. I can see as the equation would be a little different with a cubic foot or two of volume to fill. Still, I'd rather have a compressor spinning at 100k and no pressure in the tube, than a stalled compressor and a little pressure in the tube. So you bog for 1/2 second instead of 2 seconds.

I suspect the real answer is to either keep in it or spend a coupla grand on an anti-lag system.
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Old 05-08-2001, 07:32 PM   #20
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Well, looks like it is between the GReddy recommended here and by John at JC Sports, or maybe the TurboXS of which I know wnothing about and will continue to research.

I will probably do my water injection at the time I upgrade the BOV.

Larry
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Old 05-09-2001, 12:01 AM   #21
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You know, in all the time ive been around turbo cars (the last 5 years or so), i have yet to see a properly setup car without a BOV have turbo stall. I think when you have larger, and improperly setup turbos there might be a problem with it. But ive never exerienced it, or seen someone experience it. And the couple of time i have seen turbo stall was becuase it was set up TOTALLY wrong. And it wasnt a very good quality turbo.

But anyway, thats one of the reasons why i left foot brake to keep the turbo spooled. But even then you have to feather the throttle a little bit to keep the car in line. And without fail the BOV always rears its ugly head when you drive like that.

For street driving, if your looking at getting several thousand miles out of the turbo, and plan on racing maybe once a month with out ever setting a wheel on dirt...run a BOV. It will save your turbo. But even then, i dont recemend an atmospheric venting BOV. Thats just a noise maker, and really serves no function.

Anyway, my preference is not to run them. I can deal with a little turbo surge.
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Old 05-09-2001, 11:58 PM   #22
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Well, I am waiting to find out if the Forge Motorsports BOV vents back to the intake. I might be testing one of those.

Anyone know?

Larry
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Old 05-10-2001, 11:25 PM   #23
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The Forge Motorsports BV vents to the atmosphere, but they will have a recirc style BOV in a couple of weeks.

Larry
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