socalwrench New Reader
12/2/09 5:11 p.m.

Anyone know what the stock blow off pressure is for the early VR-4 BOV? or any early turbo 3000GT BOV?

snipes Reader
12/3/09 9:44 a.m.

Socalwrench, From the way you asked the question, I think you may have some trouble with your understanding of the components in the turbo system. Please ask your question again. What are you trying to do or fix. And just to be clear a stock VR4 would have a Bypass Valve not a BOV.

The spring used in the valve is only to keep the valve closed under vacuum (idle). The BOV or BPV has nothing to to with boost pressure. If I did not understand your question please ask it again, so I can try and help.

Edit: "The spring used in the valve is only to keep the valve closed under vacuum (idle)." I an not sure his is true all the time.

socalwrench New Reader
12/3/09 10:02 a.m.

Yes, some call it a BOV, others call it a Bypass valve since it doesn't vent to atmosphere. When I've used the BPV term before many haven't understood what I was saying.

Perhaps I need to be more clear. The BOV, BPV in this case, has a spring that at a certain pressure will open. This is one of the two functions. I am not referring to the quick release on the top (which is for sudden closing of the throttle). I am simply trying to figure out at what pressure (boost) the internal spring will open up.

Further information: 2.0L, 14b, 8 psi (wastegate)

dansxr2 Reader
12/3/09 11:30 a.m.

91-93 VR-4 was set at 9psi,. the newer 94-99's is 11psi. (measured at the wastegate) If you look on the pass side firewall, you will see a ton of solenoids and relay's. The one for the boost pressure has the hoses on top of eachother of the same solenoid. When you remove the hoses you will see a small restrictor in it, remove it wil a woodscrew and whala... 2 extra psi.

93gsxturbo Reader
12/3/09 12:15 p.m.

If its a 2.0L (4 cylinder) 14B car, is it a DSM, Galant VR4 or a 3KGT VR4 or Stealth RT/TT?

3KGT VR4 and Stealth RT/TT never had a 2.0 and 14B from the factory.

Stock 1G (metal) DSM/GVR4 blowoff valves are good to 15-20ish PSI without mods. Plastic junk BOVs used in the 2Gs (and 3kGTs VR4s?) are barely good for stock 11ish PSI.

bluesideup New Reader
12/3/09 12:19 p.m.

You mention 2.0L and 14b which indicates you are talking about a DSM or Galant VR-4 since the 3000GT VR-4 was a 3.0 V6.

On a 1st gen DSM the BPV starts to leak around 7 or 8 psi of boost. The valve doesn't have a stiff enough spring by design to help prevent overboost. The valve can be modified to work better and hold higher boost without leaking.

The stock valve begins to open for venting at about 5 inHg vacuum.

Dr. Hess
Dr. Hess SuperDork
12/3/09 12:37 p.m.

A BOV, like this one (on my car)

doesn't open at some fixed level of boost. It opens when the throtle plate(s) close and vacuum shows up, indicating that the boost isn't going anywhere and the turbo is going to stall. Then it opens (WHOOSH).

93gsxturbo Reader
12/3/09 7:14 p.m.

Some open at a fixed level of boost (if they are junk, and leak at high boost levels)

socalwrench New Reader
12/4/09 12:19 a.m.

Turbo is a 14b, off a 1st gen Talon AWD; TSi I believe (yes, the 3000gt was a 13g). The BPV is off a 3000gt VR4, and it is a small black plastic one- looks similar to the one Hahn racecraft sells in their kits.

Seems like I need to get a different BPV, or BOV, if it's going to open at 9-11 psi. Current research says that the stock internal wastegate on this 14b is 11 psi. Basically, they may not be matched. I guess I will find out when I fire it up. I can always change out the valve later.

Thanks for the info.

UPDATE: I may run 10-11 psi with the factory wastegate pressure (from the 14b).

xci_ed6 Reader
12/4/09 1:15 a.m.

They open under pressure differential. When the difference between charge pipe pressure and manifold pressure is large enough to overcome the spring tension.

If the valve is in good working order, but it is still opening boost at WOT, then the problem is actually charge pipe restriction. If it is opening at partial throttle, then you do need to increase the spring tension.

To test it, you need a vacuum gauge, pump, and a factory service manual should have the specification.

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