Will a MBC help my situation?

[jawsgst]

Ok i am running All intake pipes, Greddy type S, Intercooler pipes, Stock side mount, FPBig28, and Apex N1 exhaust and my turbo is Boosting 22psi w/o a boost controller and it is causing me to hit what i figure is Fuel cut at WOT at anything above 4-5k rpm and also makes my CEL come on when i hit the fuel cut. I just installed a Walbro 255 to see if that might help a little along with a new fuel filter. I want to get a MBC to turn the boost down but i don't know if that could help since for some reason the Wastegate is not bleeding boost off until 22 right now. So someone pls tell me what you recommend i do in my situation. I really want the boost lowered so i don't detonate, i want to run 15-17 on the street. And i really want my fuel cut gone cause i can't even think to take my car to the track with my problems. I am taking the recommended upgrade paths so i plan to get everything eventually but right now i just want to know if the boost controller will let me lower my boost to see if that can take care of my fuel cut right now. Thanks for reading all of my post!

 

[Zexell]

Where is your Waste gate line currently hooked up to?

 

[blcknspo0ln]

common misconception is that an MBC can turn down boost. it can, but not past what the WGA regulates it to. you're better off just hooking up the WGA to a pressure source.

 

[oldman]

How is it boosting 22 psi?

1. All out boost : boost hitting 22psi immediately and stays there. (wastegate/actuator related)

2. Boost pike : boost hitting 22 psi immediately and settle down to another level. (vacuum source/vacuum line/bcs related)

3. Boost creep : Boost hitting a specific level first then increase as rpm increases. (exhaust related)

They're all very different situations and requires different approach.

 

[jawsgst]

It is a FPBig 28 turbo with the stock wastegate actuator. The turbo spools up and hits full boost at around 3-3.5k rpm at some how measured 22psi at my mechanic who used two different guages to make sure. When it is boosting 22psi and goes over 4.5k to 5k rpm it Cuts out bad which i think is fuel cut. I need some way to turn the boost down. Like i said i have no boost control other than stock boost control solenoid which is what is currently hooked up to the wastegate. I opened up my intake tract and put that exhaust on there and now the boost has skyrocketed to 22psi. I just want to make good power but don't want the fuel cut or detonation.

 

[CanadianTSi]

Hook up a line directly from a pressure source(BOV line or some other) straight to your Wastegate. If your boost doesn't lower then your actuator is probably bad.

 

[jawsgst]

Ok just for the heck of it i went and spent the money and made a leak tester, hooked it up at 20 psi and amazingly NO leaks detected. I dont know how the actuator could be bad, it came new with the turbo, but i would like to try your idea but im not following how to do it. Do you mean unhook the wastegate actuator from the solenoid and plug it up to what line? If i can understand what you are saying better, i would like to try that. Also i was just out driving again and if i stay out of the throttle just a tad i won't fuel cut but if i press the pedal just that little bit more, BAM, fuel cut again. I am lost!?

 

[Zexell]

Take your current waste gate line off. Take your BOV line and T it off. WIth your extra line you have created, plug it in to your waste gate.

 

[oldman]

I dont know how the actuator could be bad

By not opening when it should. You will be able to determine if the problem is the actuator or a defective bcs bleeding off too much pressure by doing exactly what CanadianTsi and Zexell had suggested. If problem persists, you either have a defective actuator or you actually have boost creep and you misrepresented it. If you get a solid boost of about 10-12 psi, you have a defective bcs, in which case getting a mbc will solve your problem.

 

[jawsgst]

Ok before i do this i want to make sure that the BOV line you are talking about is the one that goes to the intake manifold right? I will try this and see how it works out.

 

[oldman]

Ok before i do this i want to make sure that the BOV line you are talking about is the one that goes to the intake manifold right? I will try this and see how it works out.

You can just take the line from compressor housing, disconnect it from the T before the bcs and connect that to the actuator nipple. Or "yes", T from the line that goes from the intake to BOV.

 

[jawsgst]

Ok i unhooked the BCS from the T and capped that part off so there was a direct connection from the compressor housing to the actuator and Boost bled off to a solid 15psi by my guage. So apparently the BCS was bleeding off too much pressure. Now is it ok to leave the BCS unhooked and leave the actuator hooked directly up to the compressor housing so that It will keep bleeding off at 15psi until i get a MBC? Also since boost wasn't hitting 22psi i had no fuel cut all the way to red line from 1-4th gear as so i tested. Thanks a lot for all the help guys. Just let me know if leaving it setup like this is safe for a bit.

Jawsgst

 

[CanadianTSi]

Yes that will be perfectly fine, infact alot safer than how it was before.

Ok i unhooked the BCS from the T and capped that part off so there was a direct connection from the compressor housing to the actuator and Boost bled off to a solid 15psi by my guage. So apparently the BCS was bleeding off too much pressure. Now is it ok to leave the BCS unhooked and leave the actuator hooked directly up to the compressor housing so that It will keep bleeding off at 15psi until i get a MBC? Also since boost wasn't hitting 22psi i had no fuel cut all the way to red line from 1-4th gear as so i tested. Thanks a lot for all the help guys. Just let me know if leaving it setup like this is safe for a bit.

Jawsgst

 

[oldman]

so that It will keep bleeding off at 15psi until i get a MBC?

Once you bypass the bcs, you're no longer bleeding anything off unless the hose from the compressor to the actuator is damaged. I suspect you still have boost creep, questionable actuator or the hose needs to be replaced as you should not be boosting more than 12psi with just the actuator.

 

[jawsgst]

Well i am not sure if it is the regular 12psi actuator for the T-25 becuase it came with the FPBig28 that i bought. I am not perfectly clear if they use the stock 12psi actuator or the 17psi actuator that they sell on their turbos, i never asked them. The car is running much better but i still get some poping out the exhaust but i think that is from the diameter of the exhuast. I just read up on boost creep and exactly how it worked and all and I guess i am getting some and that is probably a 12 PSI actuator but the creep is from the N1 exhaust as what most people have said, putting a big, non restrictive exhaust, w/o porting the O2 housing will cause creep. Im not too worried about the creep atm though, It is only to 15psi and i will be getting a ported O2 housing to help soon thanks for all the help guys!