Hey all first off i want to thank you for reading this and helping me!!
Anyaways., im going to the city tommorow and i was gonna stop by home depot. and i just wanted to know what parts i need to make one. i cant find one on this fourm for the life of me.
i just want to make sure i get the right parts when i go down there tommorow. like whats a good spring to use. would i have to replace the hoses?
anyways thanks again.
1990 Legacy Sedan LS AWD 5-MT 162k miles Slate Metallic (Sold to Brother)
There are several different types of boost controller you could build. This post won't have all the answers and detailed lists of parts, but maybe it'll give you the search terms you need to find the relevant threads that already exist.
The simplest manual boost control would be just a tension spring stretched from something on the compressor housing to the wastegate flapper rod. It's hard to get the right spring on the first try, so you might need to buy a few springs, and/or adjust springs by cutting coils off and reshaping them or something.
If you make a pneumatic one instead, you can reuse your stock hoses (assuming they're in good shape) if you use a 3/16" barb for the inlet and a 1/4" barb for the outlet. You'll be going through the stock union fitting thingie. It's not clear whether that's desirable, undesirable, or irrelevant. If you do want to put new hose in, just get a bunch of 1/4" hose and use 1/4" barbs.
The two general types of pneumatic boost controllers are bleed valves and ball-and-spring valves. A bleed valve is basically just a flow restriction of some type and a needle valve through with air bleeds out of the hose. Last time I built one of these, I used an 1/8" pipe tee, a couple of hose barb fittings that threaded into two ports of the tee, and a small needle valve that threaded into the remaining port. I made a restrictor by drilling a 1mm hole in a short piece of 1/4" aluminum rod, and stuck this restrictor into the hose.
A ball-and-spring valve is a little harder to build but often gives better results. You make a seal with a ball bearing against a barb fitting (hammer it down to deform the brass), and use a pipe tee as the body. You need a spring that cups the ball bearing, and a bolt to tension the spring. I have had good results with retapping 1/8" pipe threads to 1/4"-20, and also with just soldering a nut to the end of the pipe tee. A locknut or jam nut of some type is a good idea. You'll have to experiment to find parts that fit together well. If you find them at Home Depot maybe you could post the part numbers since they'll be pretty standard.
"Just reading vrg3's convoluted, information-packed posts made me feel better all over again." -- subyluvr2212
That thing with cutting and tapping the coupling, though, seems like a lot of effort and might not even work depending on the particular shape of the coupling you find. I say just solder a nut to the end or retap the pipe threads into straight threads, like I described above.
Something you can do to improve the safety of this type of MBC is to put another ball bearing on the other end of the spring. Make it big enough that it can't escape through the hole the bolt threads into. Then, if the bolt backs its way out, you'll end up with low boost rather than uncontrolled boost.
"Just reading vrg3's convoluted, information-packed posts made me feel better all over again." -- subyluvr2212
I used the site IronMonkeyL255 posted to build the MBC for my RX. The only real change I'd suggest is to buy a brass "bushing" from the plumbing department which completely eliminates steps 1-3 (as that's exactly what steps 1-3 have you making on your own and the bushing and coupler are virtually the same price anyway)...just make sure the adjustment bolt you buy has the same thread as that of the inside thread of bushing you buy, though. FYI: the bushing I used came from the left over installation parts that came with one of my Autometer gauges, so you could get one that way as well.
I like the bleeder valve. It's easy to make and adjust.
Have used both style of MBC and the spring on the wastgate. Never had a problem with any of them.
