About 3 weeks ago I installed the Forge Unos MBC and it's been working great! The other performance mod I have is a full 3" TBE. I used the stiff spring and with 5 clicks I was holding boost at ~21.5 PSI all the way up to redline. Actually boost spiked to just below 23 PSI and instantly settled to below 22 PSI. When I installed the MBC I started with no clicks, and boost went up to ~15PSI. From there I started raising the boost until I reached 5 clicks.

As I said it worked great until 2 or 3 days ago that I started experiencing pretty high boost spikes. I haven't done anything to my car since the MBC installation, just an aftermarket amp (which doesn't have anything to do with the mechanical part of the car). Well, whenever I am at 3,000 RPM and floor the car, boost now spikes to 25 PSI (or even more) so I just let off immediately. I've tried a couple of times to see where it settles and it goes down to about 23 PSI. I thought weather could be the issue, but here in Miami there is never bad weather, now in winter temperature is around 80F during the day, so weather was discarded. I thought the BOV could be the problem, but I wasn't sure. Today I decided to decrease the boost pressure just to be safe, so I gave the MBC 1 click less (now I'm at 4 clicks from the lowest possible setting). I took the car for a spin and the problem remained, same boost spike, same PSI. I decided to bring the boost to the minimum possible, so I took the MBC's knob all the way to the minus (0 clicks now), drove the car again... and the boost problem persists!!! If I floor the car it spikes to 25 PSI or so and then drops to 23 PSI with no clicks!

When I changed the spring 3 weeks ago I made sure that the spring sat well on the MBC, and since the MBC worked great for these 3 weeks I know for sure that it was installed correctly.

What could be causing this problem? Could the spring jump inside the MBC after being installed correctly? Could a bent/crushed/punctured hose cause this issue? What other thing could cause such a high boost pressure with no clicks on the MBC?

Thanks in advance for any help.

 

Do you have the bost controller sourced from the blow-off valve line or directly from the turbo outlet nipple?

 

Did you check all the vacuum lines? Have you taken it apart to check the spring...or tried putting in the soft spring to troubleshoot further?

 

The MBC is connected to the turbo outlet nipple as suggested, I did not mess with the BOV line.

Since I checked this at night I didn’t have a chance to check vacuum lines or anything, just the MBC settings. I’ll check all lines and the MBC’s spring tomorrow during the day, but I posted my question hoping to find someone who experienced this same problem.

When I set the MBC to 0 clicks I was thinking about replacing the spring to see the difference, but when I drove the car and found that it still spiked at 25 PSI with no clicks I thought that something was wrong. I think it's pretty hard for the spring to move within the MBC, so the only thing I can think of is a crushed vacuum line. Am I right?

 

You must have had the spring come off its nipple

Take the unit apart and re press the spring onto the nipple it is suppoed to sit on

I will do it for free for you when i come down to FL this weekend

 

Thanks a lot Al for your offer, however I have to drive my car the whole week to and from work, and then on Saturday for the flash session (pretty long drive from Miami), so I think I'll check the spring ASAP (tomorrow morning). My question is, how can the spring come off of its nipple once it was seated properly?

 

It's a mechanical piece - either it's failed (internally) our you're magically flowing a lot more air. Check the valve first!

 

The only "failures" we've experienced with these units thus far is the spring not being seated properly inside the body of the unit.

I don't know if you did or didn't seat it properly when installing the stiffer spring or if it's just come off it's seat, but it would seem as though that's the most likely scenario at this point since the unit is connected to the turbo outlet nipple (as recommended) and not to the BOV line.

Another possible, but somewhat more unlikely, situation is that the OEM wastegate actuator (which I am assuming you're still using) has "failed" in some way.

(I don't like the words "failed" or "failure" as they're just generic terms for usually a very specific problem with any individual component.)

Occasionally, actuator diaphragms can rupture, which will cause an overboosting situation, and on at least two instances that I have seen reported here on EvoM, the two body halves of the OEM actuators can separate from each other which would also cause an overboosting situation.

I don't know that this is the case, nor am I trying to sell you one of our actuators as the OEM units "typically" work quite while, but if you're going to be tinkering in the engine bay checking things out, it can't hurt to take a look at the actuator just for safety's sake.

Good luck and let us know what happens and we'll trouble shoot from there if need be.

 

OK, some news on this problem.

Today I took a look at the MBC and vacuum lines, and everything looked fine. I decided to take the MBC apart and see if the stiff spring was seated correctly, and as I said it was properly installed. As Warrtalon suggested I tried the soft spring and I made sure that it seated correctly on the MBC's nipple. I logged all the clicks I did on the MBC and the boost reached at each level (holds boost perfecly fine like with the stiff spring):

0 clicks -----> 12 PSI
6 clicks -----> 12.5 PSI
12 clicks ----> 13 PSI
20 clicks ----> 14 PSI
30 clicks ----> 14.5 PSI
50 clicks ----> 16 PSI
60 clicks ----> 17 PSI
80 clicks ----> 18.5 PSI
90 clicks ----> 19.75 PSI

At 90 clicks the Forge Unos MBC is at its limit, so I can't raise the boost any more with the soft spring. I'll leave it as is for now while I find solutions to the problem.

Something I noticed, boost comes faster with the soft spring, and wherever it spikes, it stays there (as opposed as with the stiff spring that spiked to some level and then settled ~1 PSI below).

Also, would it be good/safe to lube the stiff spring? I ask this because wear can be seen on both sides of the stiff spring, and on the MBC's interior as well. This may be the reason why I was getting overboosting problems, the spring may be stucked inside the MBC's body. Does this make any sense?

 

I'm not sure what you mean by having wear marks on the "sides" of the spring.

Does that mean the wear marks are on the coils up and down the length of the spring or at each eand of the spring where it meets it's seat and the ball?

With that said, has the original problem gone away?

 

I'm sorry about the confusion, wear can be seen on each end of the spring, not on the "sides".

The problem is gone now that I installed the soft spring, however I can only boost up to ~19.75 PSI. I don't know if I'm wrong, but I think I saw wear marks on the MBC's interior (the sides where the coil travels up and down).

The stiff spring was properly seated on the MBC's nipple, so I don't know what caused this problem. Again, is it safe to lube the spring?

 

Boosting to (roughly) 20 PSI when using the stock actuator is 100% normal for the softer spring. That's the limit of the range that it has.

The wear marks are a "news to me" type of occurance, but I can see how they would happen. When the unit actuates and the spring compresses and the ball lifts with it, the ball and the end of the spring may be moving around as they are not the exact same diameter as the bore inside of the body of the unit. I highly doubt it would create any problems, however.

Maybe try reinstalling the stiffer spring and se what happens.

I can't think of anything else! (plus I'm tired)

 

Today I reinstalled the stiffer spring, and I made sure that it seated correctly on the nipple. I even used a precision screwdriver to secure the spring on the nipple, so it can't be seated any better. The MBC is working like the first time, no complains. I'm holding boost @ 21PSI, I'll drive the car for a week and see how it works, if I don't see any crazy spikes like before (25 PSI or even more) I'll raise the boost a little bit (just below 22 PSI).

 

Help! I just sent a PM to both Warr and Mike about my boost spike to 26psi. I took my MBC apart, but didn't remove the spring from the nipple. Should i try that? Just like JuancaROD, everything was PERFECT, and then today, BAM! 26psi. All i have is the stiff spring as i bought my unit used, so i don't know what to do? From the sounds of it, i should actualy pull the spring off the nipple (it was stuck on there pretty good, so i just let it be) and then put it back on?

 

Try doing what Juanca did at least, since his went back to normal. If yours goes back to normal, then just keep an eye out in case it happens again.