MBC not stopping boost

[2bclutch]

Since my previous thread kind of got hijacked and since I have a new problem I thought I would start a new thread. Here's what happened:

Here's the whole story. My clutch burned out and I had an ACT one installed. The car has an S-AFC-II and we did disconnect the battery. It looks as though it has kept all of it's settings so I'm not so sure it's that. The Blow off valve is making a loud clunking noise and we are unable to untighten it to adjust it. Basically what's happening is you'll get up to about 3,000 RPM and start to build about 2-3PSI of boost and the blow off valve will release the pressure. We checked all over for other leaks but didn't find any at all. Could this simply be the BOV being busted?

Here's the current problem I'm having now:

I replaced the TurboXS H34 BOV with a new one and now the car is holding boost but won't stop boosting. It'll boost all the way to 30PSI and max out then the blow off valve will go off. It's like the MBC isn't able to keep the car from boosting past whatever I set it at. SO I replaced the MBC with a new TurboXS Standard MBC and it's still doing the same thing AND leaking from the TurboXS MBC. We checked the WG Actuator and it looks to be tight/in place. Is there any chance the actuator could be stuck or what would be causing this?

 

[2bclutch]

Just wanted to add that it's pretty much giving infinite boost. Going to check the WG actuator tomorrow to see if it may be stuck closed, thus creating the infinite boost. Any other ideas?

 

[ddavisaf]

Yeah, run a compression test. If you hit 30 psi in your car (which there is no possible way you could have...) then you're in some trouble.
Run an air compressor to the fitting on the wastegate actuator. If it doesn't open it's bad. If it does, it's good and your MBC is your problem.
The new MBC sounds like it's a bleeder type MBC. They're supposed to leak. That's the way they function.

 

[2bclutch]

Well the gauge spiked close to 30 so I doubt it actually really got that high, the BOV goes off before it gets there of course. But basically it's just giving inftinite boost. Didn't realize that was the bleeder type MBC, that makes more sense now.

If the wastegate doesn't open what are the possible ways of fixing it? Am I going to have to just buy a new turbo or just get a new wastegate itself?

 

[Highwayrun]

Could it be that the original BOV didn't have enough washers inside it, and you adjusted the MBC to maximum to get some boost? Then, when you changed the BOV you got 30 psi because the MBC was still set high.

Try adjusting the MBC fully in the opposite direction and start from there.

I use six washers in my H34 BOV. The clunking noise indicates the BOV's brass piston was moving freely and not jammed--it's supposed to clunk. Open it up and add/subtract washers to have it open around 15 inHg of vacuum applied to the nipple on the top.

 

[2bclutch]

Well before we swapped out the H34 for a new one (which was clunking whenever I hit a bump or something, that doesn't sound normal) the car wouldn't build boost at all. Then when we put in the new one it now does infinite boost. We put 3 washers in the new H34 and I switched out the old rusted crap MBC with a New TurboXS Standard MBC and no matter what we set the new MBC it just keeps giving me unlimited boost. We checked the wastegate and apparently it's working fine, opening and closing. I have a Super AFC 2 computer but it's all still set to the -22% etc. etc. correction for the RPM, but I don't think the Super AFC 2 would have anything to do with allowing the car to build unlimited boost.

There are no leaks that we can find, it's crazy. WTF

 

[Maverick3169]

Make sure that you didn't hook up the MBC backwards... that would cause what you're going through.

 

[Highwayrun]

Make sure that you didn't hook up the MBC backwards... that would cause what you're going through.

I thought of that too, but from the TurboXS website, they seem to be hinting that their MBC (I assume 2bclutch is using the base model) doesn't have a one-way valve in it.

2bclutch, it is definitely worth verifying your connections against the user manual, as Maverick3169 suggested.

Are any of the pressure lines blocked or damaged?

On a side note, three washers in the BOV seems too little to me. You'll likely have bucking issues on the highway as a result. It's best to set the BOV using a vacuum pump.

 

[PFXGSX]

not trying to jack your thread like the last one did....

im having the same problem that he is except my MBC which is a TurboXS says there is a right and a wrong way to hook it up ive done it both ways and it does the same thing once i see the needle to up to or past 20 psi i push the clutch in and dont take it anymore....i pull over and adjusted i followed the directions w/ the MBC then i fully tightened the coarse adj screw still did the same thing so i came back home and took it off

now with the MBC off and the vac lines going to the WGA it will only let me go to 16-17 psi before it spikes and feels like the fuel cut off kicked in....

now if that is fuel cut at 17 psi y would i be able to go to 20 + now and nothing at all happen? its just really getting on my nerves and ive been told that since its an internal wastegate im going to have to buy a new turbo, is this true?

 

[2bclutch]

Well here's my update.. The WG Actuator opens and closes fine. I talked to someone about it and they said since I'm running no Cat with a straight pipe 3" and a 3" Apexi N1 that it's effecting it. But I don't know, this stuff wasn't happening before. Guess I'm just going to have to take it in and have some people take a look at it. I'm completely baffled... I was kind of thinking maybe a seal got blown out or something but that would cause it to loose boost. I'm totally lost on this one.

 

[2bclutch]

I thought of that too, but from the TurboXS website, they seem to be hinting that their MBC (I assume 2bclutch is using the base model) doesn't have a one-way valve in it.

2bclutch, it is definitely worth verifying your connections against the user manual, as Maverick3169 suggested.

Are any of the pressure lines blocked or damaged?

On a side note, three washers in the BOV seems too little to me. You'll likely have bucking issues on the highway as a result. It's best to set the BOV using a vacuum pump.

Yeah I wish it was as simple as a backwards installed MBC. Yeah it's just the standard TurboXS boost controller. Will double check the connections of course.

I checked all the pressure lines and they seem okay. Will double check them.

I plan on adding another 3 washers to the BOV and see what that does. If all else fails I'm going to attempt to drive it to MachV and have them take a look at it. Because I have no freakin idea what the problem is, mainly because it never did any of this before and we did nothing to change anything except putting a new clutch in it.