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Installed a turbo xs MBC, should I unplug the BCS from the ECU? I'm not getting boost, and it was suggested I unplug the BCS completely. It's bypassed as of now, but still plugged in.

You're not getting ANY boost? Or are you only hitting a certain psi?

Leave it plugged in. The ECU will have a fit if you disconnect it, even though you're running the MBC and no lines are going through the BCS.

If you were boosting fine before then you've done something wrong in hooking up the MBC. Recheck your work and make sure you have all the lines hooked up properly. The BCS should no longer have hoses going to it on the sides. Leave it plugged in or find an auto NA and get the resister that's pugged into that connector and hook it up in place of your BCS and that will prevent the ECU from throwing a code.

I was only boosting to about .05 megapascals before I installed it. So I changed all my vac lines, installed the MBC, and now I'm only hitting .03. there was a line on the bottom of the BCS that was run nowhere before I changed to the MBC, and that concerned Mr, but I can't find anywhere for it to run either. It's really strange.

It sounds like you're only running wastegate boost, which would happen if the MBC is not working and/or tightened enough.

Regarding that bottom line on the factory boost controller, that is the vent line which goes back into the intake. The MBC will not have this.

Check out this vacuum diagram. It shows where everything should go.

http://surrealmirage.com/vrg3/vacuum/ej22t_vacuum.png

Thank you. After looking at that schematic, I missed a couple lines when I replaced everything. Gonna do that after work.

Okay, so the lines are all buttoned up, and still not boosting much past .04 MPa. It's probably .042MPa (about 6 PSi) Here is a crude sketch of how I'm hooked up.

Try switching the lines around that go to the turbo. If that doesn't work or it overboosts, then I think you got a bum MBC.

For most ball and spring MBC's I've seen, the side port goes to the wastegate and the bottom port goes to the compressor nipple. (Opposite the picture)

I've heard this from a few people, however TurboXS states this is how their controller is supposed to be set up. I'll try swapping the lines, but something tells me I am not going to like what happens.

Or you may like it for a split second and then become a boost addict

Update: Okay, old MBC is out, new MBC is in. Working great. New problem. Fuel cut. Either my boost gauge is wrong, or I'm hitting fuel cut WAY early. Any ideas?

First place I always recommend for fuel cut issues is checking the vacuum lines to the MAP sensor and pressure exchange solenoid. Very easy to come off when working around that part of the engine bay.

Also, what pressure do you see it at?

Yeah what pressure are you hitting fuel cut at? Make SURE that the small vac line coming off the top of the brown Pressure Exchange Solenoid on the passenger side strut going into the bottom of the black MAP sensor right below it is connected and in good health (not split or cracked)

The line appears okay, but I'm going to change it anyway. If I'm doing my math correctly (MPa to PSI) I am cutting at just over 10 lbs.

Your gauge is likely off.

Is there a way to re calibrate the gauge(stock WRX gauge)? Or should I just invest in a new one?

You'll fuel cut above 10, so that's pretty normal. Get a HKS Fuel Cut Defender, or one of those cheap vac check valves. Never used one but I can vow for the HKS FCD that it works very well. And it's not too expensive.

As far as calibrating the stock WRX Gauge (small black one?) you can take it apart and bend the spring back to read at 0, but i'm not sure if that's a reliable means of calibrating. There are many shops that can calibrate speedometers and such that i'm sure could recalibrate the boost gauge for you. But the WRX one is kinda cheap, maybe invest into a Prosport gauge?

As Robert mentioned, you'll likely be hitting fuel cut above 10 psi. So the gauge may not be off by much. If you can get a fuel cut defender that raises the fuel cut but doesn't eliminate it, that would be preferred.

I'd rather hold off on doing that until I upgrade my fuel system. Hot spots don't sound like something I want to fix. Thanks for everything guys, I think I have a good plan of attack now.

Sounds good. I think too many people just want more boost and want it now and don't want to make sure there's enough fuel before they go straight to eliminating the fuel cut and cranking up the boost to 16 psi.

Agreed. Supporting mods are key to a reliable engine.