[RESOLVED] D.I.Y. MBC Questions

[dj_remy]

Okay read a few threads and still am a little unclear, so I'll give you guys as much info as I can.

For starts, I made the MBC controller from links found here, had trouble picking out a spring (don't really know how tense it should be). Took me a while to install it right, while making small adjustments. This is how I have it setup now:

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It was at this after i did the restricter removal:

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After MBC install its at this:

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Gave me couple psi more, which is good, but the tension screw is almost all the way down, not much room for more adjustment, only about 11-12 psi.

Did boost leak test, found one at SMIC, fixed it for the most part. (think the IC itself is leaking, but don't take that as the word of god), but my boost gauge wouldn't increase during test so not sure if I even did it right, heard that leak, didn't hear any others.

Any advice? Is my 2g stock BOV not letting me go any higher? It's not the wastegate, it is letting me increase.

BTW, I couln't drill the bleeder hole in the MBC for lack of drill bit, but the FAQ said that it would have trouble boosting over 15, and since my goal for now is 14, I didn't think it would matter, is this my problem. Thanks in advanced.

 

[snowborder714]

You have that installed backwards.

http://www.dsmtuners.com/forums/articles-turbo-system-intercooler/237982-best-way-install-mbc.html
http://www.dsmtuners.com/forums/problem-diagnosis/3175-mbc-install-merged-10-7-a.html

 

[dj_remy]

No... I drew them backwards, I'm an ass. Okay fixed the pic, now what.

 

[dj_remy]

I think I figured out most of the problem. I put in a spring with a slight more resistance and it spiked up to 13-14 range and held good at 11.5, but, I apparently tapped the tightening screws hole a bit at an angle, and I can't tighten the screw anymore than that, soooooooo.....I'm getting a new one and tapping that one straighter and that should solve my problems.

At least I know now thats its not my wastegate or anything else keeping me from 14-15 psi.

 

[tkelly27]

If you pull the spring out so that it's deformed into a longer spring, you should be able to get some more juice out of it. That's not a replacement for a new spring, but it might help for now.

 

[dj_remy]

I tried that with the first one, to no avail. But thanks. Luckely I bought three springs with different tension for trial and error purposes. I'm confident this one is the spring, just need a new coupling to tap straighter, doing this tomorrow, let you guys know how it goes.

 

[JusMX141]

Spring tension is key.

It's the same issue that plagues so many of the eBay MBC's....you'll be at 12psi with a target of 15psi, so you turn the adjuster in 1/4 turn until you get to 14psi, then you turn it in 1/8th of a turn and you're now sitting at 18psi.

 

[dj_remy]

Agreed 100%. I'll post some pics/progress tomorrow for anyone else having this issue.
I'm sure I've got the right spring/tension this time.
What about the bleeder hole? Neccesary? Or not?
(Don't plan on boosting over 15psi)

 

[bastarddsm]

you have to have a bleeder hole....its essential...if the ball doesn't seal 110% perfectly, than the mbc dosn't work right.

 

[dj_remy]

you have to have a bleeder hole....its essential...if the ball doesn't seal 110% perfectly, than the mbc dosn't work right.

Thanks man, I really needed to know that. Guess I'll be buy a 1/32 bit and do some drilling also.

 

[Mr Peepers]

The bleeder hole is used to keep it(a ball and spring mbc) from acting like a check valve.

Lets say you boost up to 12 psi, then let off. The spring will push the ball back to its seat and the pressure in the wastegate actuator will have nowhere to go, keeping the wastegate open and hurting boost response(transient response) along with some erratic boost control. Having a bleeder hole in place gives the pressure built up in the wastegate actuator somewhere to go and let the wastegate close again after you let off/shift/whatever so it's ready to build boost once again.

 

[dj_remy]

More helpful knowledge. Thanks guys I really appreciate it. Hopefully tomorrow I'll be boosting 14-15 by 1:00 pm!

 

[dj_remy]

Thanks alot guys, got the problem solved!

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1. Bought new coupler, retapped perfectly straight.

2. Pulled new spring out a little to add tension.

3. Drilled bleeder hole at 3/32.

4. Holding 14.5 psi at around 87-92% throttle and no more spiking.

Thanks alot, again.