MBC install [Merged 10-7]

[b00sted99-X]

HERE, DAMMIT!

http://www.dsmtuners.com/forums/showthread.php?t=237982


ok n00b question here.. i got my MBC all hooked up fine (dejon tool.. sweet!) i'm just wondering what to do with the stock boost solenoid hoses.. i took the top one completely off (this is the one that was going to my intake pipe.. then capped that nipple on the pipe) .. the one on the bottom, that tees off and goes to both the wastegate and the turbo housing, is still there. i just bent it backwards and stuck it in the bracket that the top hose was at.. its still connected to the solenoid though. is this alright? can i leave it on there like that will it screw anything up?

 

[10minutequarter]

You might not have noticed any difference in "boost spike" but I'm almost positive that your BOV is open under boost. Do not tap the BOV line!!

Glliw, the first 5 turns does mostly nothing on most mbc's.

How do you figure? How is that fixed, also I have a 1g BOV so that should hold more boost right. Sorry to whore your thread.

 

[Glliw]

Ah well I think if I were to add up the turns it was probably 5-7 turns .

 

[oldman]

How do you figure? How is that fixed, also I have a 1g BOV so that should hold more boost right. Sorry to whore your thread.

It's not about the BOV's ability to hold boost, it's about the wastgate pressure relief hole on the MBC bleeding pressure off the BOV line causing the BOV to open slightly under boost as well not opening fully quickly enough after letting off. The solution is to not tap the BOV line.

Ah well I think if I were to add up the turns it was probably 5-7 turns .

Can't really see the mbc in your pictures so can't really tell you if it's hooked up right.

 

[10minutequarter]

Right now I don't have it tapped,
Boost source-------Boost controller--------Wastegate
My boost spikes to 20 and them levels off at 12.

 

[Glliw]

Here's the mbc I'm using. By looking at that, you can see that the bottom nipple is attached to the wastegate and the side nipple is attached to the j-pipe.

 

[oldman]

Is this a ball and spring?

 

[Glliw]

yes.

 

[oldman]

Right now I don't have it tapped,
Boost source-------Boost controller--------Wastegate
My boost spikes to 20 and them levels off at 12.

T25s are well known for spiking before settling, usually about 3-5psi the most. The rest of your boost spike is probably coming from the TurboXS Standard MBC (bleeder type valve), also well known for boost spikes.

 

[oldman]

yes.

Here's the mbc I'm using. By looking at that, you can see that the bottom nipple is attached to the wastegate and the side nipple is attached to the j-pipe.

Then you got it backwards.

 

[Glliw]

D'oh! Well thanks for correcting me .

 

[oldman]

D'oh! Well thanks for correcting me .

No problem. I think the confusion comes from using terms like "bottom fitting" and "side fitting" since you can mount the mbc in 4 different orientations. For a ball and spring mbc, the fitting opposite but inline with the adjustment knob always goes to the pressure source (j-pipe).

 

[10minutequarter]

Thanks also, is a Hallman any different? I have one of those too.

 

[oldman]

Thanks also, is a Hallman any different? I have one of those too.

Your T25 will probably still spike with a good ball and spring like the "Hallman" but it should be less than a bleeder type mbc. Make certain that you're not tapping the BOV line or any manifold pressure source with a bleeder type mbc. The bleeder hole on a ball and spring type will only be exposed under boost after the spring is overcome, a bleeder type like your TurboXS standard will be expose both under boost and vacuum making it a vacuum leak as well as a boost leak. Tapping the BOV line will result not only in BOV opening under boost, it will also change your vacuum reading, A/F ratio and possibly cause compressor surge.

 

[10minutequarter]

Thanks

 

[oldman]

No problem.

 

[Glliw]

Thanks oldman, I just switched around the nipples and it holds 10psi just fine now. Think I hear a boost leak down in there thought. We'll in the coming days when im not working 12 hour shifts.

 

[Glliw]

Update: In gears 1 and 2, I hit 10 and bleed to 7ish psi. in 3rd gear however, it holds 10 all the way. Whats going on here?

 

[Low Impedance]

the load on the engine is different in higher gears. in third gear your engine is exhausting more energy than it does in 1 and 2. that is way you get your highest boost pressure readings at freeway speeds. (taking for granted everything is working as it should)

 

[oldman]

Update: In gears 1 and 2, I hit 10 and bleed to 7ish psi. in 3rd gear however, it holds 10 all the way. Whats going on here?

Boost leak test.

 

[thekellbeast]

Before I put in the switchable boost controller, I had the MBC getting its source from the nipple on the turbo outlet, the bov getting source from the intake manifold, and the boost gauge getting its source teed from the FPS line.

I know that response is a bit late, but I figured I'd throw it out there.

 

[Glliw]

Yea I figure there's a boost leak...I had to order a new one since a friend lost the one I had so its put on hold til wednesday or so. Just to add further, In 5th gear when accelerating in the "full boost rpms" it'll hit like 13-14 psi.....wish the other gears were getting that .

 

[chicagoavenger]

What happens if you don't have the stock j-pipe anymore then where would you tap into?

 

[Auto RS T]

Same spot.

Just remove the outlet and drill and tap an 1/8 NPT fitting into the new outlet. You can mount the fitting near the flange so you can grind off the excess inside the pipe.
(another Oldman tip)

Mine is done this way, but I choose to go farther away from the flange, I was still able to grind off the excess. Here is a pic.

 

[chicagoavenger]

Same spot.

Just remove the outlet and drill and tap an 1/8 NPT fitting into the new outlet. You can mount the fitting near the flange so you can grind off the excess inside the pipe.
(another Oldman tip)

Mine is done this way, but I choose to go farther away from the flange, I was still able to grind off the excess. Here is a pic.

Sorry I meant if you have no J-pipe whatsoever? Some people have 50trims etc that the outlet connects to a FMIC coupler. What do you do then?

 

[denniegst]

Same concept, the jpipe is just part of the intercooler piping section inbetween the turbo and intercooler so tap as close as u can to the turbo or on the turbo outlet itself. ive seen some coupler that actually have npt fitting on them you can buy, but i forgot where i saw it.