I'd like to start a post listing any/all Diverter Valves (recirculating valves) listing their limits before they begin to leak - according to pressure testing or even "educated" experience... So here goes nothing... (Corrections and additions are inherently welcome)

Tomei diverter valve 18psi
JDM MR diverter valve 22psi
Works diverter valve 25psi

 

How are you testing this?

 

How bout, according to 1) pressure testing (what others have documented) or even 2) what the manufacturer/vendor claims...

 

Doesn't make sense for the Tomei to open at 18psi, when it's the same as the JDM MR DV, and the JDM MR DV doesn't open unti 24-25psi. I've personally pressure tested 3 stock IXs to 22+psi without the valve budging.

 

plastic stock = 13 psi
IX , MR .... = 24-25 psi
HKS SSQ =30+psi
from what ive seen

 

I don't think this is accurate at all....in order to make this accurate you'll have to take each one of the valves and personally pressure test it. You have no control if you go by what other people say.

 

did you do the test with the vac line on the DV connected to the same boost source? the boost plus the spring pressure is what keeps the DV close under boost, not just the spring itself.

 

I think you were referring to the thread starter , if not Ive test each bov I have listed off the car and even submerged them under water to see any leaks that I could not hear .

 

that doesnt make any sense that the stocker would open at 13 psi because stock boost is 19-20psi.

 

Nah, it still makes sense. Just because the stocker starts opening, it doesn't mean you can't run 19-20psi. It just means that the turbo has to work harder to overcome the small leak and still reach 19-20psi.

My stocker also opened at 13psi during pressure testing.

 

the spring itself might only hold 13 psi, but remember the vac line is connected to the intake manifold, so the total force the bov can hold would be 13psi from the spring and what ever amount of boost is in the manifold.

remember, there's equal amount of pressure on both side of the bov diaphragm, but since the vac line is pretty small, that side of the diaphragm usually see a little less boost. the spring is there to make up the difference in boost and to keep the bov close until the vac in the manifold is strong enough to overcome the force of the spring which is usually around 20+ psi at deceleration.

 

i get the impression that most people don't know how a bov actually work, this site can explain it pretty good. http://www.gofastbits.com.au/index.p...tion=tech_info

"How it works: The usual arrangement is to have the pressure side of the valve attached to the pipe between the turbo and the throttle, and a vacuum hose on the top of the valve hooked up to the inlet manifold after the throttle body. A spring holds the valve shut. When you are on the throttle, the pressure in the turbo piping and the inlet manifold is equal, meaning that the pressure on each side of the valve is the same and therefore cancels itself out, leaving the spring holding the valve shut. When you lift off the throttle, you have high pressure in the turbo piping, and a vacuum in the inlet manifold. The pressure on the bottom of the valve and the vacuum on the top combine to lift the valve open and release the pressure in the turbo piping, since it can no longer go into the engine.

Blow-off valve myth #1: One of the biggest misconceptions about blow-off valves is that you need to tighten the spring to run higher boost. This is totally incorrect (at least, for a GFB valve anyway), as you can see from the last paragraph, at full throttle, the pressure on the top and bottom of the valve is equal, therefore cancelling itself out. So no matter what boost pressure you run, the valve will stay shut.

Leaking factory valves: Having said that, some factory valves have systems designed into them to crack open at high boost, in order to protect the engine from boost spikes. They do this by designing the pressure to be unequal on the top an bottom of the valve, thereby overcoming the spring at a certain pressure.

If you are intentionally raising the boost level, this is bad news as the valve will begin to leak pressure. Examples of factory valves which exhibit this behaviour are the Subaru WRX MY95-98, and MY01-04, Mitsubishi Lancer GSR, and Nissan 200SX to name a few. Replacing these valves when increasing the boost is a good idea."

it seems that the stock evo gsr bov does incorporate a leaking feature as a safety precaution.

 

gotcha.

 

The SSQV is a reverse design... instead of the pressure trying to force the valve open it technically pushes it shut harder. Thats the only reason I bought one... It will hold ALOT of boost. Im yet to see one leak and I have seen plenty of Supras running over 40psi on them.

 

I would say that this statement is quite erroneous and very misleading.

While there is SOME truth to this statement, it is not entirely accurate.

There may be positive pressure acting on both the "top and bottom" of the sealing surface of the valve (be it piston, diaphragm, etc.), but there will likely be different amounts of surface area on which these levels of pressure are acting upon inside the two (sometimes 3) chambers of the valve, and the pressures being referenced are from before and after the throttle body, which will equate to small differences in the actual amounts of pressure acting on the "top and bottom" of the sealing surfaces.

Another thing to consider is the length of the vacuum line referenced to the top of the valve from the intake manifold. A longer length of hose will equate to a larger volume of space that is added to the manifold volume which must fill up with pressure before acting upon the top side of the valve. This extra length of hosing can often times equate to slowed valve response potential valve leaking (with no adjustments to spring tension) which is why the shortest possible valve reference is always highly recommended.

This is why the spring tension (and it's adjustability) plays an essential role in ensuring that the valve stays shut under ever-varying boost levels.