Installed the Hallman MBC, everything works well except that boost still falls off. I have it set ti 19psi and I get that probably until 6k rpms from which it falls off to about 16~17psi by 7k. I am COMPLETELY stock other than this BC, I thought it would hold 19 all the way to redline, but I can't make it do it. Is there something wrong with my setup or is this just the charactersitic of the car being completely stock with an MBC? Any help would be appreciated.

 

if you installed it right, your boost seems in the stock form. Your knob or cockpit adjustment knob must be turned all the way to the left. Drive around turning it half a turn at a time and set it at 20 steady to redline. It will make a huge difference after 5000 rpm. Anything more than 20psi will cause knocking and timing being pulled thus making less power. Hope this helps.

 

Thats just it....when you install the MBC, you the ECU can no longer control boost as you disconnect the stock BC solenoid. I had to turn it up to 19psi already, it just won't hold to redline. I won't go above 19psi on the stock exhaust, seems like too much of a restriction and could cause EGTs to bump a little more than my liking.

 

Your ECU may pull timing if it thinks there's knock due to the turbulence that may cause by the stock exhaust. Get TBE and some air-fuel management and it'll hold steady for you.

 

There could be two issues. One, the stock exhaust is a huge bottleneck. Two, you could have a boost leak somewhere. If the MBC taps it's source at the compressor discharge than it won't compensate for boost leaks such as tapping into the BPV feed line will.

 

I tapped my pressure source from the intake mani. I am thinking it could be a combination of guage error and stock exhaust.