another mbc/bov problem, please help!

[800_Speed]

Alright everyone, I just bought an MBC from a friend's car that was in working condition. I also have a Greddy Type RS blow-off valve that was working just fine before I installed the MBC. Now that I installed the MBC, my boost spikes immediately to 20PSI regardless of where I have the knob set. Also, the BOV flutters no matter how tight or loose I set it. I've got the MBC T-ed into the BOV and run to the wastegate... I've included a couple pictures that I hope someone can make something out of, I'm pretty sure I installed it correctly. The line marked with red on the boost controller runs to the wastegate actuator, I originally had the lines switched the other way, but I get the boost spike problem either way... Any opinions on why the MBC is doing this based on what you see here??? It's my daily driver so I need to have this fixed asap, thanks!

 

[absolute_DSM]

Sounds like a bad MBC, specifically the spring. Anyone else?

 

[Isphius]

try switching the vaccum lines and see if it works. If not, just replace the MBC.

 

[91 Turbo Mitsu]

You need to get rid of that boost controller. They are no good. If you search here or on vfaq there is a story as to why these dont work. You need one that is a ball and spring design. You can actually build one yourself for about $10.00. I think it was vfaq that had a story as to how to build it and what you need for parts.With this design you cant get the fine adjustment that is needed to control your boost. Travis

 

[hewhoisknot]

http://www.geocities.com/chmwatson/FAQs/mbc.html That is the site to build one yourself, yes it works I have done it. Is that turbosmart MBC? I used to own one and had sort of the same problem. If i remember correctly there is a line on the MBC that points to the direction to rotate to make it build boost, on mine I actually had to turn it the opposite way to build boost, like I mean alot the other way, so try back it all the way out, and try turning it all the way in and see what happens.

BUN

 

[VanIsleDSM]

you shouldn't be using your BOV line for your MBC anyway.. could be part of your bov problems.. use a boost source from the compressor housing on the turbo.. where the BCS source comes from.

 

[absolute_DSM]

^^^ X2

You shouldnt rob your BOV source anyways.

 

[800_Speed]

Okay i switched the lines so its running from the j-pipe now... and its controlled a little better. I'm getting a leak now though, I'll boost to about 15psi no matter where I set the MBC (I guess its just a crappy one, ill have to put my old one back in) and itll drop off to about 5 by 6k RPMs. Thanks for the advice guys.

 

[4SFED4]

^^^ X2

You shouldnt rob your BOV source anyways.

I have ran mine form the same source as the BOV for years on many cars with no problems, even with my current setup running two BOVs. I encountered problems sourcing the compressor housing.
I use Hallman MBCs, second to none IMO.