Too much boost! help with mbc install

[mrlilguy157]

my BCD from ATP and the 3071r hold boost all the way to 7k... yea.... my car used to haul balls all the way to redline.

you guys cars' doesnt.

 

[tru-boost]

now that i think about it hooking up a MBC in place of the stock solenoid doesnt sound like a good idea. think about it. it should be between the turbo and WGA. if you put it after the WGA and use it like the stock solenoid, the pressure wuld come in from one side and just dump air back into the intake tube from the other side, that is a huge boost leak. no wonder the car doesnt spike anymore.... its working its ass off just to make boost. with the proper set up the pressure comes in one side of the MBC and exits the other side going to the WGA. it is OK for the stock solenoid to bleed into the intake because it is in controlled amounts. with a MBC all the air going through it will be bled out. i suppose if it is a ball and spring only MBC it could work, but i wouldnt trust it. MBC inline with the compressor and WGA is the way to go. if you see spikes or dont hold boost well...your MBC sucks ! turbosmart FTW !!

 

[mooserov]

It is a ball and spring mbc. Very good design IMO.

 

[tru-boost]

since it is ball & spring it will work just like a WGA. it will hold the boost back until it overpowers the spring and then open the WG. that would be fine. if it was a bleeder type valve it would not work out well installed that way.

 

[boost3]

i have turbosmart mbc.im installing it 2morrow.onel ine goes form the wastegate to the top of the turbo smart port.then a line from the turbo to the bottom off the turbosmart port right.is that how its installed.then im adding my atp boost cut defender.hope it all works for me.

 

[Ghetto Mods]

Puzzling this out a bit further, I think you could install the MBC off the TOP hose from the WGA and cap the outlet of the MBC.

No skinned knuckles FTW!!!!!

This should work the same as capping the top outlet of the WGA.

Tru Boost - what do you think???

 

[shadrag]

...cap the outlet of the MBC.

??????

Air pressure needs to go through the MBC for it to do anything.

 

[Ghetto Mods]

O.K. to review:

Standard install:

Compressor through MBC to waste gate actuator INLET, cap waste gate actuator OUTLET.

My suggestion:

Compressor to waste gate actuator INLET (like stock), connect MBC to WGA OUTLET, cap OUTLET of MBC.

Same effect, the MBC bleeds off pressure but the other end is closed off. Leaving that end open major boost leak per Tru Boost's post above.

Clearer now?

 

[tru-boost]

ahhhhh i see ....cap the mbc outlet. i suppose that would work.

 

[RocaLoca]

in temps above 45 degrees i am fine with AFR's that drop to high tens/low
11's. when it is cold the AFR's climb into the 12's and my fuel pessure drops a lot. i am usually at 1700psi or so. in the cold it will drop as low 800psi. a pump upgrade is a MUST HAVE if you want more boost.
yes a map clamp must be wired into the harness. if you dont want to tap in near the ecu you can do it off the map sensor wires directly off the sensor, but it will be a pain in the ass !

are these your afr's at WOT? correct me if i'm wrong but isnt nominal somewhere between 14-15? are you running lean due to excessive boost and not enough gas to feed your monster?

 

[tru-boost]

yes that is at WOT, and you have your numbers mixed up ! higher numbers mean you are lean and lower numbers mean you are rich. 14-15 would equal a tossed rod or melted piston !

 

[RocaLoca]

yes that is at WOT, and you have your numbers mixed up ! higher numbers mean you are lean and lower numbers mean you are rich. 14-15 would equal a tossed rod or melted piston !

my mistake you were right about my numbers being backwards BUT, 14.7:1 is perfect stoichiometric mixture for a gasoline engine (not at WOT) =)

 

[slo4now]

Correct

 

[phillyb]

i know all of the MBC instructions i have ever seen say to place the MBC directly between the compressor and the WGA, then do away with all other hose connections. if it is working out for you, i see no harm in it. the only for sure NO, NO for an MBC on our car is trying to install it with the factory solenoid still in use.

bump...
please elaborate on this...the top of the wga and solenoid should be capped. what happens if i don't cap them and hook up the mbc?

 

[freebird_78]

Well, I hooked mine up per Moose's recommendation. I am running a JoeP Inline Boost Controller, a ball and spring type.

The first way I had it was to have the MBC inlet to the WGA. My thinking was based off Moose mentioning that the WGA ports were straight through, therefore, the boost coming from the compressor, to the lower WGA port was actually a boost source coming out of the top WGA port. This immediately produced 20+ PSI and the setting on the MBC had no effect.

Swapped the orientation of the MBC and it seems to work. With the stock BCS, I'd hold ~11.7 PSI max (I'm at 4000+ft alt). My goal with the MBC was simply to "simulate" pressure I would see at sea level. I figured this was nice and safe, but also a good increase. I figure if I want to go further, I could always clamp.

So I installed the MBC in the correct orientation with the MBC outlet going to the top WGA port and the MBC inlet to the turbo intlet nipple. I'm not sure how this is working, but it seems to be. Where I'd see no more than 11.7 PSI stock, I'm seeing a steady 14.6 PSI now. This is a bit down from what I had started with and actually had to trim a touch of boost as I did encounter boost cut once. Could someone who knows please draw up a diagram on how this is working?

I've heard the whole 18 PSI spike for more than 2 seconds will cause boost cut, but what sustained boost causes boost cut? I'm guessing >15.6 PSI sustained? My spike with the MBC is pretty much eliminated vs stock. The spike is very quick now, about 1/4 the duration of the stock boost control, and stablizes very quickly.