MBC Problems

[v-mac]

i installed a forge boost controller in place of my old ebay one, and it is spiking 15+ psi on one click when i dont even push it half or 3 qtr throttle, im only wanting 10psi right now....how much is spring pressure for the wastegate on a evo3big16g? i was spiking to around 13psi with my ebay BC which was turned about 3 clicks.....so im not understanding why its spiking now. it just came off and srt from the track working perfect all day so i know the MBC is fine.....it is connected by the jpipe source and the wastegate just like my old one was, im just not sure whats going on. any ideas?WTF

 

[dale187]

Is it just me or is your j pipe source teed off to something else other than just your MBC?

 

[v-mac]

yes the right side is going to the wastegate...

 

[TJs91tsi]

If you were able to keep it at 13psi with your ebay boost controller, then its likely the forge has a stiffer spring.

What I dont understand is, if you want 10psi, why are you putting a manual boost controller on for? just run the wastegate.

I dont think you'll be able to run less than 13-15 psi anyway.
Also it does look like you tee'd into the j pipe boost line. did you?

 

[TJs91tsi]

yes the right side is going to the wastegate...

he was asking if you have a tee and more then one vacuum line coming from the j-pipe. to the boost gauge maby?

you should have one uninterupted boost line from the j pipe to the boost controller thats it. having more can cause funky problems, overbossting etc...

Tyler.

 

[v-mac]

yea i do have it teed to the jpipe, but im not sure what the wastegate spring is set to, i have a brand new evo3big16g and idk what the wastegate that came with it is set at if i just ran it with the wastegate and no MBC

 

[TJs91tsi]

Well go to www.v-faq.com and find the correct place to tee in for your boost gauge. Do that first.

You cant make the wastegate open any sooner than the spring pressure on the wastegate will allow. not with a mbc. that only RAISES the boost. If you run just the wastegate with no mbc, you will be running the lowest amount of boost you can. Just run straight wastegate. if you go wot, right where the boost stops rising is roughly where the wastegate spring pressure is. itll probably creep higher though.

It also depends on your mods. with my exhaust and intake, i cant run less than 17 psi on my evo316g.

 

[v-mac]

How do I run without the mbc or make it where I can

 

[TJs91tsi]

You need to run the vaccum hose straight from the j-pipe, (the outlet of your turbo compressor side), straight to the port on your wastegate.

 

[spawn87]

your boost gauge should be ran from your manifold near your brake booster (its the fpr vacuum line.) you never tee off boost signals it gives a ''fake'' signal much like with blow off valves and as for the mbc open it all the way first (or make sure its open all the way if you havent) as for 10 psi thats something (like mentioned before) you can run with the wg.

 

[v-mac]

this is his friend with the SRT that installed it.

he had it T'ed into a line running from the J-pipe to some kind of boost T on the passenger fender well. It had 2 connections on it and a big black hose coming off the bottom.

i told him he should only have one source for the boost controller and that its being T'ed in incorrect.

so my question is what is that weird T in the fender well and does it need to be hooked up?

 

[v-mac]

my boost gauge is nowhere near my MBC lines, trust me on that one...and when i got the car it had a T on it already so i used it in the install of the MBC...what my friends is reffering to is i guess where the source of the vacum line starts that runs to where my MBC is, its on the fender and it has two ports of vacum lines and one runs to my MBC which is th ebottom one and the top one runs off somewhere near the headlight im not sur ei have not messed with it....how should i hook it up then? do i need to get rid of the t? if so im not sure how i would hook up two places "wastegate, j-pipe" with only one vacum line i would need the T i would imagine..

 

[v-mac]

ok i think i see what i need to do now....should i just run vac line from the MBC to the wastegate and then from the other outlet to the Jpipe and leave it like that, from some diagrams that is what i am seeing, and so that would do away with the T that was being used and then i could just plug that old line that wont be used anymore

 

[TJs91tsi]

ok v-mac. im not sure what you mean by the Tee by the fenderwell.

This is very simple. The j-pipe doesnt supply vacuum to anything, it supplies pressure. The nipple on the j-pipe supplies pressure to the wastegate. so as your turbo boosts, the pressure climbs. When your turbo is pushing the same psi that the wastegate is designed to open at, say for example 10psi, the wastegate opens. The mbc goes inbetween the j-pipe and the wastegate blocking the boost to a higher setting 13-14-15psi whatever...


now, thats all it does. NOW, go get rid of any tee in the wastegate line. find out where the line to the headlight goes.

You should have a vacuum line go from the j-pipe nipple to i believe the bottom of your mbc. then run a line from the top of the mbc to the wastegate. thats it.

but if you only want to run 10psi, dont run a mbc, just run a line from the j-pipe to the wastegate.

 

[v-mac]

thanks TSI sorry man i know it seems a little elementary and believe me i thought so too as ive had a few MBC, but i got this car a while back and havent messed with this MBC until now and i got all messed up....thanks for your help tho bro, and everyone who posted on here im gonna fix it in a bit

 

[neoviper]

^^^ It really is as simple as that. The only other thing that would be connected to anything is the BCS which doesnt need to be hooked back up, maybe thats where the confusion is coming from v-mac

 

[TJs91tsi]

neoviper makes a good point, its possible that the previous owner somehow kept the factory bcs plugged in which may explain the tee. let us know. but like he said, you eliminate it with a mbc anyway.

 

[spawn87]

you dont use the factory bcs just put caps on both ends so it dont suck in dust... its simple

nipple from j-pipe---------------------mbc---------------waste gate.

thats it

this is a dsm not an srt so just follow dsm protocol and it will make it easier.

good luck and i hope your get your problem fixed

 

[v-mac]

got it fixed today, did away with the t and plugged the old line and just ran line from the wastegate and jpipe...running good now boostin 13psi