"Grainger valve" is just a nick-name for a simple ball & spring check valve with
adjustable spring tension. McMaster-Carr sells them as part number:
The above set up is adjustable and you will get to see if you like the quick spool up. If you do like it then you should add the simple parts below to make a 2-stage controller. Then you go from one boost level to another with the flip of a toggle switch.
Please note that the unused vacuum barb on the solenoid valve is blocked off! I represented the block with a black rectangle. You must cap off this nipple. Again, there is a small (about .020") vent hole drilled into the output barb of the Grainger valve to act as a vent.
Because of several requests, below you will see a fully manual "high-low" boost setup with adjustable "high", and adjustable "low" settings. The bleed to adjust "low" acts as the vent. If you're gonna run around with the low setting closed a lot, then add a vent anyway! The Grainger valve controls the "high" setting.
solenoids flow the same. Some flow much more than others. Apply 12Vto one at a
time, and blow through them with your mouth. Use the ones that are easiest to blow through.
Solenoid valves cannot hold back high pressure that exceeds their spring power; at some point pressure will leak past the closed valve. Get a Mityvac and apply pressure to the center barb while12V is applied to it. Since you have capped off the top barb, it shouldn't let any air through, and it should hold a pressure equal to your highest boost setting. If you want to run 18 psi boost, but the barb leaks at 12psi (for example), then pressure-test the OTHER bottom barb, and whichever one holds MORE pressure is the one you want to face the yellow restrictor in the diagram.
Take it from here, and put it
THERE! Then screw on a brass barb fitting.(McMaster Carr part number) 5346K51
Drill a tiny hole (about .020") in a brass barb first... (90degree brass barb is part # 44555k142)
Then bang the barb into the hole with a hammer. It should be in there really tight!
Then assemble the whole thing, and the finished product
looks like this.
The barb with the orifice drilled in it (the 90^ barb) has to face the wastegate actuator, and the un-drilled barb (the straight one) has to face the source of boost (intake manifold or turbo output nipple)
The knurled knob turns to make
the valve body shorter or longer. The lock ring stops the movement after
adjustments are made. The vent orifice needs no filter, as it never sucks
air in. Making the valve longer LOWERS boost, while making the
valve shorter RAISES boost.
If you don't want to make your own, DarrenDawes is making and selling these controllers.
Here is a schematic from a factory T2 sticker that shows one possibility of tapping into existing lines.
A late model T1 set up, like my 89's.
It has been noted that spiking seems to be minimal when the lines are kept short, and the vent hole is kept small. Try .020" - .022" for a vent hole.