So I have a stock WRX turbo, which runs at what, 12 PSI? How do I drop that down to about 4 PSI? All the boost controllers I've seen hold off the signal from the waste gate so you can raise boost, but I haven't seen any way to lower it.
Well, you are right about the WRX running 12 psi, but you are wrong in the fact that the wastegate doesn't open @ 12 psi. The WRX uses an advanced method of boost control to vary at different temps and altitudes, therefore the standard internal wastegate isn't the only device used to control boost.
The WRX internal wastegate open, I have seen, anywhere from 4 psi to 8 psi. I have a friend with a 1.8L L Turbo, and his opens around 6 psi. There is another guy, Darshu on i-club I believe, and the wastegate on his WRX turbo doesn't open until 4 psi. So, as you can see, it differs. Kind of strange isn't it?
My friend who is a Subie tuner/technician vaccum tested a WRX turbo and the wastegate was measured opening @ 8 psi.
So, my advice is put the turbo on and see what happens. You DEFINETLY won't get 12 psi, but it could be as high as 7 or 8 psi.
I know others have had similar complaints about the WRX turbo, but no one can seem to find new wastegate springs for the wastegate's.
Hmm, that is weird, thanks for the info. So does this mean that it could fluctuate anywhere up to 8 PSI whenever? Or will it open at whatever PSI it likes, say 4 PSI, then I could safely assume that it wont go over 4 in the future?
Whatever PSI you initially see on your gauge is what your FINAL boost will ever be, unless of course you find other means to raise it (i.e. MBC, EBC, external wastegate).
Another thing I forgot to mention; the reason the people whom I know that are running the WRX turbo and seeing different pressures could be from the engine. Like my friend with the 1.8L turbo, he see'e around 7 psi. Maybe it has something to do with the litre of the engine and exhaust flow keeping the wastegate closed earlier, I don't know. The guy with the 2.5L only saw 3.5-4 psi, so I don't know.