mbc wont work
 

ok well my car will not hold constant boost i have tryed 2 mbc's and both have done the same thing..

i have my mbc set at 0 psi turned all the way down and it still goes past 20psi on my gauge. i have it tapped into the bov like its spose to be. i have tryed changing the wg actuator but still doesnt work.

what else could i try

Re: mbc wont work
 

Do you have a pressure source on the turbo?

Just run a vacuum line from the pressure source like the intake mani or turbo and run it straight into the wastegate actuator. That should run the same boost pressure as the wastegate spring, 10 lbs or whatever.

If that doesn't hold boost down then it's the actuator or flapper not opening when it should.

Re: mbc wont work
 

Does it go to 20psi right away or does it slowly go up there as the RPM increases?

Re: mbc wont work
 

Tell us more about your setup. What kind of MBC? Are you sure you are adjusting it the correct way?

Re: mbc wont work
 

jet- it will hit 20+psi almost right way less than 50% throttle

kracka- its a turbo xs mbc and yes i am adjusting it the right way.. the car is on a 14b stock side mount 3" exhaust all free mods done thats about it

Re: mbc wont work
 

What doe sit do with no boost controller? Just a vaccum line from the wastegate to a boost source?

Are you sure the lines to the MBC aren't backwards? Turbo XS boost controllers often work the opposite way off most boost controllers. Make sure there aren't any holes/cuts in your vacuum lines too.

Re: mbc wont work
 

I bet you're getting insane boost creep, my 1G did this too when I installed a turboback exhaust on a stock turbo/o2 housing (back in 2001). Check what Shane suggested first and if thats not it I bet its creep.

Re: mbc wont work
 

i know it is hooked up right thats for sure...

im gonna try and run a line from the jpipe to a wg and see what happens

Re: mbc wont work
 

Your wastegate flapper may be stuck also. Try moving the linkage with a pliers.

Re: mbc wont work
 

ok well i tryed running wg boost and that did not work, it spooled alittle slower but still 20+psi..

Re: mbc wont work
 

Boost creep, stuck flapper, or bad wastegate actuator.

Re: mbc wont work
 

ok im gonna go check some things ill let you guys know

Re: mbc wont work
 

well the flapper is not stuck and the actuator seems to be working its not getting stuck or anything.. iv already tryed 2 actuator's but ill try one more.. what would give me such bad boost creep?

Re: mbc wont work
 

The restrictive stock turbine housing and stock o2 housing with a free-flowing turboback exhaust. Time to do some porting (or upgrade stuff)!

Re: mbc wont work
 

my hot side is ported

Re: mbc wont work
 

Is your O2 housing ported for better boost control? What turbo is it? Does it have a stock size flapper on it still?

Re: mbc wont work
 

in running the 14b... i have the manifold and housing ported but not the o2 housing. still stock flaper

Re: mbc wont work
 

You could also disconnect the flapper arm from the actuator, that would force the flapper open 100% of the time. I accidentally did this once and I could only get 8 or 9 lbs of boost by redline on my internally gated 20g.

Someone correct me if I'm wrong, but if it still goes over 20lbs then it's insane boost creep, right? And if boost stays low then the actuator isn't opening the flapper properly?

Re: mbc wont work
 

Did this start when you put the new exhaust on? If so, it is just boost creep.

Re: mbc wont work
 

no it was doing it befor the new exhaust.. befor i had to set the boost controler at almost 0 and it would go to 15-16 psi.....