I've got a Greddy R type blow off valve actuating 3.5" tubing from a T-trim through a ATI 3 core intercooler. The blow off valve is actuated by both vacuum and pressure. The vacuum side is directly from the intake and the pressure is sent from just in front of the intake. My delema is that pressure likes to open the valve at different intervals depending on spring pressure.
I don't like the "chirping" of the SC with the back pressure nor do I think that it's very good for the impeller but I'm trying to find solution.
Right now I'm maxing out pressure at 12-13#s going into a 355ci motor with I/E .525/.510, 224/230, lift .3500/.3400 cam. Pully combo is 7/2.5 41.5" 8 rib pully. The valve just seems to open. I can vary the max pressure from 5#s to 12#s with the twist of the spring but the chirping just gets louder and louder under part throttle.
Any suggestions? (I know I'll here a few like "get rid of the ricer blow off" and such but would like to hear some solid feedback)
TIA,
BTW-You might want to see the sig for what it's in.

 

I used a GReddy type R with great sucess. It's a good peice, but I'm not sure how your trying to use it, your using it to limit the pressure of the blower??? Under boost conditions in the intake manifold the valve should never open. Looking at the valve there is a port under the silver cap part in the aluminum body, that should be hooked up to a place after the blower, but before the throttlebody, the other port on the silver cap should be hooked up to the intake manifold. Check the connections. Under WOT conditions you should have the same pressure on both sides of the actuator diaphram with the spring being the only thing holding it closed. When you lift the throttle the vaccum from the manifold will be on top with the spring and the pressure from the blower on the bottom will open the valve quickly releaving pressure from your intake tract, and hence the "woosh" noise.

Bill

 

Thanks Bill, I'm using it as a blowoff valve. But when I set it to a point where the blower no longer "chirps", it opens up under WOT. I've got it set now to where it chirps lightly under part throttle but will still open once the intake is pressurized at approx 8-10#s of boost. This blower combo should make somewhere around 13-16#s of boost conservatively. (T-Trim with 7/2.5 pullies and a brand new belt.)
The top line is going to a verified vacuum port on the intake, the lower line is going to the intake tract 9"s in front of the throttle body.
My biggest regret is that I cringe every time the chirping starts up under part throttle. I end up taking it out of gear almost every time. Quite bothersome.

 

What do you mean by "chirping"?

 

Compressed air surging against the impeller of the supercharger.

 

That "chirping" is probably the valve lifting slightly under part throttle operation. Mine does this all the time (I run a Turbonetics Godzilla BOV now) It likes to do this at part throttle because there is a vacuum in the intake, yet your blower IS putting out positive pressure before the throttle blades, All it is doing is releaving press to the atmosphere and should be nothing to worry about at all. For your compressor to go into surge conditions you would need to be at a very high pressure ratio with very little CFM flow thru the blower, it isn't going to happen cruising around.

 

According to Greddy, you should only have the port connected to the intake manifold. The other is a vent..

I have to screw the adjusting nut almost all the way in on mine at 12 psi to keep it from opening under boost. I think the stock spring is only good for around 14 psi, but they do sell heavier ones.

 

I tried it like that (with only one hose connected) and it never worked like a normal BOV does, it opened realy lazy and i never got any noise from it so I never knew if it was working. Hooking it up as I described, which is how every other BOV gets hooked up made it work fine. It vented every time I let off the gas and made noise so I knew it was doing its job. The valve comes with 2 threaded holes and 2 hose barbs, I doubt the other hole is just a vent, if that was the case why would they take the time and money to thread it?

Edit: just looked at the install instructions, and it shows both ways in a pictoral diagram, no explaination though, its all in Japanise.

 

It may respond different on a s/c; with my turbos I have boost at 1/4 throttle, and if I let off the gas, it makes plenty of noise!

It should only operate when the throttle is closed while under boost. That is the way it is designed, and at low boost, light throttle you will not hear much out of it.