I feel like sort of a *** for asking this but my brand new GReddy BOV doesn't seem to be doing it's job. I must qualify this however.



Engine is brand new, breaking it in currently. I have a big single turbo. I'm keeping boost to about 3kg/cm2 and revs below 4K rpm. I get surging when I let off the gas abruptly and the BOV is adjusted all the way out, ie. screw is about to fall out. Vacuum source is being taken from just behind the throttle body and vacuum line connects to the top port on the BOV, the bottom is left open as per GReddy's instructions.



My initial thought is that I must have the stiff spring in there and I need to swap it out for the standard spring...anyone else ever experience this?



My current thought is that it should still open when the engine returns to vacuum regardless and the spring determines how much boost it'll hold peak as in the standard may start to leak at say 15psi whereas the heavy duty will hold 40. Random numbers. I've pulled the BOV off and checked to see that the valve did move.



I've tried two different vacuum sources with the same result. Perhaps I need to reference the bottom port to a source before the throttle bodies? Thanks in advance.

 

i only have one vacuum port hooked up and it works fine. low boost it flutters when it releases high boost its fine. how much boost ?

 

Same as Vosko.

 

mine works no problem

 

make sure you run the vacuum line to it directly, and not t'd into anything. Run the shortest line possible.

 

We're talking 3-4kg/cm2 tops, about 5-6psi by 4k rpm. Short line, direct, no tees. Flutters at that setting, doesn't seem to open at all. I may add a smaller BOV on the other side as I still have a Type S lying around, just need another flange and a bit of welding. Just seems sort of strange that it wouldn't open under low boost load. Should have purchased the HKS

 

is this BOV new or used? if used, open her up and check the diaphram inside.

 

The Greddy really is not designed to run at those low levels, they are designed for high cfm turbos such as the TO4 and larger. If your planning to go to a single turbo then by all means keep it, or if you plan on turning up the boost. The flutter is because there just is not that much air to disperse when it opens, the rapid pressure drop then build up causes the valve to flutter like that, where with a large cfm boost level it will dump a lot more air in that short amount of time. Basically you overkilled on the BOV for your current modifications.

 

mine won't flutter at 5-6psi. it flutters at about 1-4 psi....... anyway. try tightening it and running more boost lol

 

hmmm..... not to steal the show but, I have the hks ss bov, and its flutters on my buddies mkIII supra turbo @ 15#s.... And another supra owner had it and it made a short loud burst sound. So is this the same thing? I thought it was suppose to sound that way, the hks unit..