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mbc installed, boost stuck to 5 psi

Posted: Sat May 24, 2008 10:52 pm
by flatoutfred
First, Hi everybody, I'm new here and this is my first message.
Just bought a legacy turbo 92 and I started doing some little mods .
Borla Stainless Steel Cat-Backā„¢ System Aggressive, coffe cup and more coming.

Anyway, I've installed a mbc yesterday following the instructions in the library and after the boost got stuck at 5 psi. Could it be a kind of limp mode ? I've double checked the routing and connections and it did'nt change a thing so I replug the stock solenoid with the mbc on the intake pressure hose and now I'm boosting 10 psi no matter how much I adjust the mbc :? ?

Anyone ever experienced something similar?

What's going on?

Posted: Sat May 24, 2008 11:17 pm
by aspect
~5psi is "wastegate pressure", ie your MBC is not doing anything but directly connecting the wastegate to the charge pipe. If you just took the wastegate hose and plugged it into the pressurized section of the intake with no boost controller whatsoever, you would get the exact same effect.

If you hooked the MBC up correctly (between the pressurized side of the intake and the wastegate), and you couldn't get anything but 5psi no matter how tight you adjusted it, then your MBC is probably jammed open. Try taking it off the car, tightening it down, and blowing through it. If air goes through, it's busted.

Posted: Mon May 26, 2008 10:49 pm
by BXSS
You may have hooked the MBC up improperly.

See SubaruNation's post on how to hook a e-bay MBC up.