Boost not adjusting?...

[1GjGST]

(Downpipe connected)My boost will stay at 15 no matter how much i put back on the MBC. The boost will jump to 18-19 then drop back to 15psi and hold it there..(Open downpipe) My boost jumps to around 18-20psi and holds 17psi no matter what the MBC is set on.
I researched and cant find any answers on this. The only thing i can come up with is that the actuator flapper is stuck open?.. I have no boost leaks. What other causes could there be other than actuator flapper stuck open?.. How do I check if the actuator flapper is stuck open? Can i check without removing the O2 housing?..

 

[LiquidX]

(Downpipe connected)My boost will stay at 15 no matter how much i put back on the MBC. The boost will jump to 18-19 then drop back to 15psi and hold it there..(Open downpipe) My boost jumps to around 18-20psi and holds 17psi no matter what the MBC is set on.
I researched and cant find any answers on this. The only thing i can come up with is that the actuator flapper is stuck open?.. I have no boost leaks. What other causes could there be other than actuator flapper stuck open?.. How do I check if the actuator flapper is stuck open? Can i check without removing the O2 housing?..

Remove the boost controller and run a vaccume line directly to the waste gate. What psi does it open at? Sounds like you have a very mild case of boost creep. You can check the wastegate by getting an air compressor and blowing air into the wastegate. Watch the arm travel and see if the arm is rubbing/catching anywhere and check to see if the flapper opens. You can slip off the actuator arm from the flapper and move it freely by hand. I would suggest disconneting the arm and let the flapper free while you drive around trying to build boost and take a note of what psi you are able to hit. That is a big indicator of seeing if it's boost creep.

The 16gs are notorious for boost creep. Some are worse than other as mine after extensive porting will creep somewhere above 20psi(max on gauge) and it's connected directly to wastegate.

 

[1GjGST]

But if it was boost creep wouldnt the boost rise instead of holding 15psi?... I think i am getting more of boost spike since the boost will jump past the set destination and then drop back and hold what it is set on. You see but for some reason the boost will stay at 15psi even if i dial back the MBC all the way and that is my problem... Why cant i adjust my boost with my MBC anymore?.. It worked fine before. By the way is boost spiking bad?...

Possible Problems i have come up with:
MBC Is no good or Actuator is stuck open

 

[LiquidX]

But if it was boost creep wouldnt the boost rise instead of holding 15psi?... I think i am getting more of boost spike since the boost will jump past the set destination and then drop back and hold what it is set on. You see but for some reason the boost will stay at 15psi even if i dial back the MBC all the way and that is my problem... Why cant i adjust my boost with my MBC anymore?.. It worked fine before. By the way is boost spiking bad?...

Possible Problems i have come up with:
MBC Is no good or Actuator is stuck open

I must have misread then, yes, if it's jumping then dropping down to the preset boost level then it is boost spike. Have you tried a different MBC? Also, without larger injectors and a way to tune, you shouldn't be boosting more than 15psi anyway.

Spike isn't as bad as creep but it's still not good either if you don't have the right fuel modifications to handle the now lean condition.

 

[dsmjay]

But if it was boost creep wouldnt the boost rise instead of holding 15psi?... I think i am getting more of boost spike since the boost will jump past the set destination and then drop back and hold what it is set on. You see but for some reason the boost will stay at 15psi even if i dial back the MBC all the way and that is my problem... Why cant i adjust my boost with my MBC anymore?.. It worked fine before. By the way is boost spiking bad?...

Possible Problems i have come up with:
MBC Is no good or Actuator is stuck open

I would say that your MBC is junk. I'm not sure what kind you have or if you made it yourself...but I have had similar problems back in the day with cheap ones. No matter how many times you adjust it, it makes no difference.

Get a new one...you should be good to go

 

[1GjGST]

My friend will be bringing me his boost controller later to test it. What causes a MBC to be work good then just not work at all?.. Spring gets weak i am assuming.. Besides the MBC being bad what other causes could there be?.. Is there any way that the wastegate is clogged or stuck?.. Would a vaccum leak be a cause of spiking?..

Thanks for the help also guys

 

[LiquidX]

My friend will be bringing me his boost controller later to test it. What causes a MBC to be work good then just not work at all?.. Spring gets weak i am assuming.. Besides the MBC being bad what other causes could there be?.. Is there any way that the waste gate is clogged or stuck?.. Would a vacuum leak be a cause of spiking?..

Thanks for the help also guys

Could have bad o-rings, spring or something got stuck in the MBC. I've mentioned how to test the waste gate. Get an air compressor with a blower end. Insert the tip into a vacuum line off the waste gate and pressurize it. If you can watch the actuator arm move, then the waste gate is fine. Search boost spike and you'll find your answers.

 

[1GjGST]

I took my MBC apart and the spring looks shorter than it was before and does seem to get stuck in the threads of where the bolt adjuster goes... could be the cause of it not letting the adjustment work. Where are there o-rings in the MBC?..

 

[LiquidX]

Some have o-rings and others (most) just use the "block" with a ball and spring in the middle and a threaded rod pushed down on the spring so there wouldn't be a need for the o-ring.

 

[1GjGST]

I think mine is the one without o-rings in it. I am going to replace the spring to a 1" medium duty spring and see if that makes a difference first and going to hook up a compressor to check the internal wategate

 

[LiquidX]

If your friend is coming by with another MBC, I'd wait until you try that one to see if it fixes anything.

 

[1GjGST]

New question....

Should the arm on the wastegate actuator be able to move with ease back and forth?... I just went outside and checked to see if i could move the arm and it would not move back or forth... I think the flapper might be stuck or having trouble opening....

SHOULD THE ARM MOVE WITH EASE OR DOES IT TAKE SOME UMPH TO BUDGE IT?..

 

[LiquidX]

It take a bit of effort to move it. I take it you don't have a compressor? You can pop the arm off and move the flapper freely, it's fine. It may take a bit for you to pop it back together though depending on how tight it is.

 

[1GjGST]

I am at work right now so now compressor on hand. Will a 12v tire compressor work? Is the arm supposed to move away or towards the wastegate?.

 

[LiquidX]

You need to be able to pressurize the the wastegate through the vaccum line nipple. If you have an attachment to use to blow the air it should work. The arm will travel away from the wastegate and move roughly a quarter inch.

 

[1GjGST]

Would the actuator being stuck be a cause of me not controlling the MBC and the spiking?.. I am going to find a adapter so i can check with it pressurized

 

[LiquidX]

Would the actuator being stuck be a cause of me not controlling the MBC and the spiking?.. I am going to find a adapter so i can check with it pressurized

I can rule out that it's sticking. If it was stuck shut you would be constantly building boost. Still test it to see if it catching or rubbing on anything that would slow it down. How do you have your MBC plumbed in? Is if teed off the bov line or from the compressor housing/IC pipe?

 

[1GjGST]

It is hooked up from the compressor housing and the wastegate... It worked good before with no problems or spiking until i ran stock open downpipe. It started spiking and ever since then it has been spiking with open or closed downpipe and i have no control over the MBC

 

[LiquidX]

Whole exhaust is stock right? I can understand with the open dp allowing a lot of free travel for the gasses.

 

[1GjGST]

So with open downpipe spiking is normal?.. Yeah stock exhaust but the catyilic converter is gutted?...