boost fluctuating

[kenuwine4g63]

Alright guys did some searching and nothing specific. I just purchased a Hallman ES mbc, im runing 15psi on a 16g. My boost keeps fluctuating like it will go to 15 then back to 12 then back to 15 very rapidly threw 2nd all the way out to 5th gear. Has this happened to anyone and if so please tell me how u fixed it. I do have a smaller vacuum line from the nipple on the wg to the side of the mbc and a bigger vacuum line from the boost source to the feed of the mbc, but i dont know if that is the problem

 

[LiquidX]

As usual, have you performed a boost leak test at all?

Do you have larger injectors or just the SAFC?

 

[kenuwine4g63]

Oh yes i have performed boost leak test just to verify. If I take the boost controller off it will hold 10psi to redline and I would hit full boost at 3400 rpms. Theres absolutely no leaks. I dont have the safc anymore but still have injectors. Im thinking the spring in the mbc may be kinked or my wastegate.

 

[Benshooter]

Eliminate the BC and narrow it down.

 

[pj91gsx]

You probably have your boost controller hooked up wrong. On line from boost source off the turbo, to the MBC, then to the WG. Dont T it into another line.

 

[kenuwine4g63]

well my pressure source is from the intake manifold, then another hose to the wastegate. Nothing is T'ed off. Im starting to think it could be boost creeping, but boost creep wouldnt fluctuate right??

So i took off my mbc, took it apart and put it back together just to know how "I" put it back together. One thing i kind of believe is that i didnt have the spring pressed against the ball all the way so that it would just bounce back and forth giving me a fluctuating boost. Any more things you guys can think of and I'll try them out

 

[pj91gsx]

Its not boost creep. That is when your boost rises when you increasing in rpms, because the wastegat area isnt flowing well enough. It happens when you have a 3" exhaust and no porting to fix the creep. Some of the flow problems is in the o2 housing and some in the hotside.

 

[kenuwine4g63]

Oh Ok great explanation, i completely understand it. Im goin to try it out tomorrow and see what happens also have some new bpr6es's to go in it too

 

[sexystover]

why are you running boost source from the mani? i was always told run it off an intercooler pipe or compressor housing

 

[kenuwine4g63]

you dont have to always run it off the compressor housing or the j-pipe or intercooler. All of my DSMs i've had i ran from the intake mani, Any thing that sees positive boost except the bov. On top of that i never ever had a nipple of the comp housing, intercooler, or j-pipe since i've owned DSMs and this one is my 5th.

 

[pj91gsx]

you dont have to always run it off the compressor housing or the j-pipe or intercooler. All of my DSMs i've had i ran from the intake mani, Any thing that sees positive boost except the bov. On top of that i never ever had a nipple of the comp housing, intercooler, or j-pipe since i've owned DSMs and this one is my 5th.

You are right, but it is more responsive to get boost pressure closest to the turbo, because that is where the boost increases the soonest. Your more likely to have boost spike from having the boost source at the manifold. Boost spike is when the wastegate does not open soon enough, so boost shoots up to 20 or so then goes back down to normal boost level.

 

[kenuwine4g63]

OK well that rules out the boost spike theory. Because its set at 15 and goes to 13 back to 15 and so on. Hopefully sealing that ball down will help since it wont have any slack against the spring, so we'll see

Ok still having the same problem. If i take the mbc off it holds boost fine, dont tell me hallman makes faulty products im really not understanding this at all.

 

[kenuwine4g63]

alright guys guess what. I have a boost leak at the boost gauge you can hear it cleanly. I will be fixing this tomorrow and hopefully that will be it, no more leaks