hey every1,
So my boost used to be controlled by a home depot MBC, worked fine for a few months, then it stopped giving me 10psi...OK, so i threw that away and put in a Turbo XS MBC (the little blue one), tuned it and it held 10psi for a good year. Now this weekend im back at 10psi in the x-over pipe and 8psi at the UIM (typical 2psi pressure loss for the stock IC) and turning the adjustment screw does nothing. What could it be? The line from the y-pipe to the MBC to the wastegate actuator is good. The turbos have 30k miles on them, so i doubt it would be the actuator...but at the same time how could i "break" two MBC's in a year?

any help would be appreciated cuz im stumped.

-Zach

 

zack you just answered your own question verifying that you dont have a leak

arent there nipples on the front turbo compressor housing? put one side of the vacuum line there and the other to the left nipple on the wastegate actuator and cap the right side.

if this doesnt work then id say you need to get another boost controller. Id suggest a profec it really is that nice.

 

yeah i know i didnt have a leak, but what im saying is that the MBC doesnt affect the boost anymore...its just running at 8lbs off the wastegate spring. Checked the lines to and from the MBC and theyre good, all the other nipples off the comp housing are capped so no leaks there....but it doesnt change the settings. I doubt its the wastegate actuator on a turbo set with 30k miles. Do i just have bad luck with MBC's? (broke two in a year?) I took apart the TurboXS one, and there's no ball and spring in it

 

Maybe the Bonez cat is collapsing, and that's why you can't get the boost you previously had?

 

Bonez cat has 13k miles on it so i know its not that

It's not a constant problem either...Its come and gone once and its back again after a year. It's specifically a problem with the WG Actuator and/or MBC, but i dunno which or the reasoning behind it.