Is my MBC toast!??

[tsi1991awd]

So I have been getting fuel cut due to my boost going too high. I had it set at 15psi and it was doing it just fine. Once I upgraded my intercooler and this and that, it started to give me fuel cut. Well, I turned the MBC all the way closed and it is still boosting all the way to 20. And it fuel cuts. So is my MBC toast or is there another problem???

Have a GT Concepts Evo 3 GT turbo, 34mm wastegate, ported inlet and atmospheric O2 dump.

 

[OEM]

How do you have your mbc hooked up? (which ports are you using)

 

[tsi1991awd]

I have it hooked up the same as it has always been. There's nothing wrong with how it is hooked up. It worked fine and was set at 15psi. Now it doesn't matter what I do, I have the damn thing completely shut and it still overboosts

 

[RadDsm]

Have you checked your wastegate?

 

[turbodsm007]

make sure there is no cuts in the vacuum lines and also remember ....MBC more boost is CLOCKWISE, less boost COUNTER CLOCKWISE...hopefully this helps.

 

[tsi1991awd]

What do I check on the wastegate? How do I test it? The MBC is closed all the way, for sure...its a Hallman Pro, pretty much idiot proof. Has the - and + and arrows showing which way to turn, haha.

 

[92dsm1]

My boost controller is doing the same thing. I turned mine all the way out on nearly the last thread holding it in and it still hits 20 psi. with a new wastegate actauator. I am going to try a different wastegate actuator and see if that helps.

 

[odysseybiker1]

Boost Creep??? My brother had a Evo 16g and it would creep to 20psi. Then he got an external wastegate. It sloved everything.

 

[spammy123]

make sure all vacuum lines running to wastegate and boost controller are sealed and not leaking. I had this same problem and found out there was a hole in my vacuum line leading to the MBC

 

[tsi1991awd]

I will check both vacuum lines to the MBC, hell I will just replace them tomorrow or Thursday. It COULD be boost creep but why would it just all of a sudden do it? It has never done it before. I did put in Delta 272/272 cams, maybe that is causing it to creep?

 

[92dsm1]

My car still has a 14b ported. I do not see mine being boost creep being it jumps straight to 20 psi. and not "Creeping" to 20 psi., also all vac. lines are new along with the wastegate actuator.

 

[odysseybiker1]

My brothers car didnt really "creep". It would go straight to 20psi and then just stop. I talked to the people at Slowboy and they said it was creeping. It was on a 16G with a Buschur exhaust.

 

[tsi1991awd]

I think it is the wastegate actuator that is shot. After I installed my knock sensor, I was letting the car idle...I heard what sounded like an exhaust leak, and I was checking under the car around the cat and it sounded like it was coming from the downpipe. So I felt around the downpipe/O2 housing to see if I felt exhaust coming out and I didn't.

It was getting dark and I had a flashlight, I was shining it around (and it's freezing outside) and I noticed "fog" coming from the dump in the O2 housing. I got under the car and saw it coming out, WHICH THIS HAS NEVER HAPPENED BEFORE. I was listening and heard that it was coming from there...went back to the engine bay and could hear it coming from around the turbo area.

I checked all the hoses for the MBC and everything checked out. Looked at the actuator and saw that it is partially cracked open. I remember the arm being closer "in" and the flapper arm being centered...now it is pushed off toward the drivers side some.

I am pretty certain that this is the problem....the wastegate is probably stuck partially open and it doesn't blow all the way open, so the boost keeps going up. Does that sound about right? Here are some pics...you can tell in the first one the best (flapper arm pushed toward drivers side):

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[Red97Eclipseboy]

Every MBC I had, turning the knob down increases boost. Didn't you think it was odd that it went up after that?!?!

 

[rush2252]

You might check the vacuum line running to the WGA. On the TD05 turbos (14b & 16g) the nipple is at a strange angle. If you dont bend it slightly it can kink the boost source line, thus acting as a restrictor (working like a MBC) and actually cause creep/spiking/overboost. I had mine do this after my s16g install and took me awhile to track down the issue.

If the vacuum hose/line is kinked where it slips over the nipple on the WGA just bend the nipple slightly and see if that doesnt solve your problem. WGA dont go bad very often. The stock WGA shouldnt hold much more than 10-12psi fully extended. And the arm being pushed slightly to the driver side would leave the flapper slightly open making it leak boost so that wouldnt be the problem.


Also if you are tightening the screw in the MBC and its a ball and spring type then you are increasing boost. The MBC restricts boost to the WGA allowing the flapper to stay closed longer thus building more boost. Unregulated the WGA shouldnt hold more then 9-12psi If you are hitting 20psi with the screw/knob turned all the way out I would check your boost source to your wastegate actuator like mentioned above.

 

[EclipticalGS]

Take the mbc off and do a pull like that, if it still creeps up past the wastegate spring, then its creep/ wastegate malfunction. If taking the MBC off fixes everything, then you either have it set wrong, (this does happen), or theres a leak in the line running to it.

 

[tsi1991awd]

I will check over everything once I get home from work today. How do I fix the wastegate from staying slightly open? It hasn't been like this before. I can hear exhaust coming from it and visually see it stuck slightly open (pictures dont do justice)

 

[EclipticalGS]

Unbolt your open dump, pull that off. Visually inspect. It could be stuck open due to carbon build up.

 

[tsi1991awd]

Just went out and checked over the MBC and it is fully OPEN (less boost)...not sure why I said closed earlier. Took it for a drive to make sure I wasnt crazy, still boosting 20.

Someone recommended unplugging the MBC to see if it still does it....do I just run the line from the J-pipe to the wastegate actuator or what?

 

[KKneipper]

Take off the MBC.

You need to run the line from the j-pipe to the wastegate actuator. Along that vacuum line, you need to put a t-fitting on to run another line to the stock boost controller (wastegate solenoid). The other line coming out of the wastegate solenoid goes to your air intake line.

I don't know about 1g, but on my 2g, the wastegate solenoid is on the passenger side of the engine bay, towards the front, kinda below the fuse box.

Hope this helps.

 

[tsi1991awd]

Wow man, you're 7 months too late.

 

[KKneipper]

Wow, I guess I was too late. It just showed up in the forum, and I didn't even take the time to look at the dates. Did you ever get it figured out?

 

[tsi1991awd]

Lol thats funny....but yea I figured it out. It ended up being boost creep. The cams added too much air and the wastegate never allowed it to escape fast enough.

The one main problem I found was the actuator arm had too short of travel. The flapper barely moved when I applied pressure via air compressor. When I disconnected the WGA from the flapper, I noticed the preload was too much and there was no way to fix it.

I bought a stock 16g actuator and cut the arm in half. Used a die and made threads in each half of the arm. Then I used a hex coupling so the rod length could be adjusted...then used jam nuts on the ends after it had the correct preload (half a hole)....didnt encounter the problem after that. Maintained 15psi just fine.

 

[KKneipper]

Good to hear, you seem to know your shit. I'll keep you in mind when I ever run into a problem. Tag this as RESOLVED so that others with the same problem may be able to find out how to fix it.

 

[tsi1991awd]

Still learning man....the problems my old DSM threw at me were just the beginning. We have some of the same old problems with this new one and some brand new problems as well. Learning experience.