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Discussion Starter #1
So I am building my turbo kit and I purchased the ZZP 50mm Stattama blow off valve. It is pressure fitted so I assume its a good BOV for the money:dontknow:

ZZP says it is set to 9psi... So I would need my wastegate to run at least 9psi?:hmmmm:

Can someone chime in on how the BOV and Wastegate function together? Thanks!
 

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The wastegate works off of positive pressure(psi). The BOV, or surge valve, works off off vacuum. When you let off the throttle instead of that boost still trying to force it's way into your engine(it can't so it surges the turbo), the BOV pulls open and releases it into the atmosphere due to the pressure differential betweek the turbo/TB and the intake manifold. The wastegate bypasses pressure either back into the system(recirculating wastegates dump into the downpipe) or into the atmosphere(open wastegate). BOVs can have qualms with the MAF.
 

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Discussion Starter #3 (Edited)
Thank you, but why would the BOV be set to 9psi? and is there a desired wastegate setting for this psi??
 

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I edited my last response to better explain the BOV. The wastegate is controlled by springs. Your BOV is set to .6 BAR. 9psi is kind of high for a BOV. I have mine set to 7psi in the waverunner. What happens is when there is beyond that pressure the BOV opens and you get that distinct hissing sound. It stays open until the pressure drops below that.

The wastegate doesn't deal with the surge and can be set to whatever your system can run safely. It is designed to safely bleed off excess boost so you don't overpower your engine.
 

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Discussion Starter #5 (Edited)
Thanks, I appreciate the post. But why wouldn't we want the BOV set to like 1 or 2 psi? since when we floor it the air bypasses the BOV anyway as it enters the engine? If it is set to 9psi any wastegate setting under 9 would essentially make my BOV not function right?
 

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If your wastegate is under pressure compared to the BOV then yes you will hemorrhage boost when you want it. You should NOT be below 7 psi on a turbo on a 3800 II. The reason you want your BOV above that small amount is when you're part throttle and just a bit in boost, you want that boost going in your engine to help with power. If you have the BOV set that low then you lose it. When the turbo is fully spooling there is far more air moving than the engine can take so bleeding it off past 7psi is completely fine. Do you know what bar spring your wastegate has?
 

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The 9 psi spring in the BOV means that it will take 9psi more pressure in the charge tube than what is in the vacuum hose running to the BOV in order to open it. Any time your throttle is fully open, you should have the same amount of pressure in the charge tube and vacuum hose. When you let off the throttle, the intake and vacuum hoses quickly go into vacuum. If there is 10psi boost in the charge tube and 22"(11psi) of vacuum in the intake, that is a difference of over 20psi and the BOV will open fully to release the boost in the charge tube. This is important in order to keep the turbo from surging. The reason the turbo would surge is because the exhaust pressure driving the turbine wheel quickly drops, but the boost pressure stored in the charge tubes and intercooler still exists. With no exhaust to drive the turbo, the boost pressure quickly stops the impeller and the boost pressure flows backwards out of the turbo and through the air filter. The BOVs job is to release the pressure in the charge tubes to prevent this situation.

The reason you wouldn't want to run a low pressure in the BOV, such as 2psi is that the BOV would then be open at idle, allowing un-filtered air into the charge tubes. Having the valve open at light throttle will also delay the early on-set of boost and make the car a little less responsive. For these reasons, the BOV is usually set up with a spring that is near or slightly higher than the engine vacuum at idle. In this case, a 9psi spring(18") usually works well on the 3800.
 

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My BOV knowledge has been updated!! BTW, Matt as in the guy with the record holding now single turbo race car?
 

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Nice. We tried to replace the IHI t3/t4 with a Precision 6765 on my Honda Waverunner and drop her down to 14psi. Lasted a whole hour before wasting the engine. But DAMN did that thing have some serious nuts. Probably could have used your experience to make the engine last a bit longer :( Good luck with all your plumbing and keeping mopeds out of the turbo inlet of that beast.
 

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You put a 67mm turbo on a waverunner?! Holy crap. And here I thought I was crazy...
 

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1235cc liquid-cooled dry-sump inline four, 4 valves per cylinder. I flogged it unmercifully. Fairly sure I was at least 80mph before the engine went. Gotta cut it up since I don't have a title :(
 

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Discussion Starter #13 (Edited)
I am running an adjustable 14-18psi wastegate w/ E85 103 plugs and a 160 stat. Hopefully KR free. Is 14psi a safe range for the factory upper intake? I'm only running a 59 trim...
 

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What do you mean? Are you running a gutted M90, F-Body UIM or standard FWD L36 UIM? All of the above will take 20psi safely TMK. The part you need to be careful with are your gaskets. You need Aluminum LIM gaskets and need MLS head gaskets.
 

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Discussion Starter #15
Its a grand prix gt. The upper intake I heard was weak.
 

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Its a grand prix gt. The upper intake I heard was weak.
Compared to what? Solid aluminum? It will flex yes, but break?? I highly doubt it. Not at 14psi anyway. I guarantee I could remove the hood and stand on that thing without any ill effect and I'm 225lbs.
 

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Hey Brandon!

How about if I stood on your shoulders to make it 450lbs! I weigh only 225 lbs. also!:)KEV
 

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Hey Brandon!

How about if I stood on your shoulders to make it 450lbs! I weigh only 225 lbs. also!:)KEV
Lets do this!!!!! Every aspect of the 3800 II platform is pretty solid, not high performance but solidly built, EXCEPT the rod bolts. They are 100% garbage and a major fail point of the entire platform!

If you're new to turbo charging then 14psi is PLENTY!!! That's actually kinda overkill to be honest. 14psi will pretty much get you in front of 99% of the other vehicles on the street.
 

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Discussion Starter #20
sweet! I just got my water to air intercooler tonight boo-yah!
 
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