cant run over 14 psi or adjust psi

[allrice4g63]

Ok heres my problem i have a 98 talon tsi with a 14b swap. When i have everything hooked up like stock i run 8 psi. when i hook my mbc my friends mbc and his friends mbc i can not adjust the pressure at all it just spools to 14psi no higher no lower. i have boost leaked test a number of times and there is no boost leaks. I checked the wastegate with a pressure source the wastegate opens fine the turbo spools to 14 quick but doesnt seem to have full power until about 4-5k. even if i leave the vaccum lines to the wastegate it runs 14psi if i pinch them off or block them i run 14psi would anybody beable to tell me why it is doing this thanks.

 

[lo_boost]

Is it a new MBC? Sounds like somthings jamed in it.

 

[allrice4g63]

I have tryed a brand new mbc and i have used two of my friends mbcs

 

[lo_boost]

Are one of the air ports plugged up? there has to be a reason why air is ubstructed.

 

[allrice4g63]

what do you mean bye one of the air ports

 

[lo_boost]

you have the 2 on the MBC. than one on the turbo by the intake, and one on the wastgate.

 

[allrice4g63]

no they are not plugged because i checked the wastegate and tested all of them

 

[grnchevyz]

Let me get this straight....

1. Wastegate nipple to vaccuum source = 14psi
2. Your MBC and 2 other MBC's (I assume setup the same) = 14psi
3. Stock setup using stock BCS= 8psi

correct until there??

If so I would be assuming a 14psi wastegate spring and the MBC's setup either to 0 (meaning use spring only) or they are not routed correctly...what brand MBC are they?

Let me know if I missed something here but it does sound like a 14psi spring in there.

 

[cano86]

Did you connected your MBC in both ways to check if is backwards. I had made a thread with the same problem it wouldnt go over 14 or less no matter what and when I finally figured it out the MBC was backwards good luck

 

[viprez586]

I Believe he is talking about the bleeder valves or "holes" on the MBC itself.
I had a similar problem and just took apart the MBC and cleaned it, you can take a peek at my tech article if you need to.

Some things to note: Pressure source for the wastegate should only run to that, no other items(BOV) should be "T"ed into the the line. I drilled and tapped my J pipe and put in a brass nipple and coated the fitting with a light coat of RTV. The other line runs to the wastegate as you can imagine.

I would get horrible boost creep with a internal gate, 3in downpipe compared to stock exhaust. I later found out the wastegate flapper was only sealing about 70% because it was so cracked and out of adjustment somehow. I'd imagine you would've saw this before installing the turbo however. Point is upgraded exhaust will cause you to have boost creep, esp. now that its getting cold(well here at least) and the air is more dense.

 

[viprez586]

If so I would be assuming a 14psi wastegate spring and the MBC's setup either to 0 (meaning use spring only) or they are not routed correctly...what brand MBC are they?

Let me know if I missed something here but it does sound like a 14psi spring in there.

MBC springs don't change your "static" or "zero adjustment" boost level. Your thinking of an external wastegate spring which directly effects what your zero adjustment boost pressure is set to. IE: 1bar spring = 14.7psi and you cannot drop your boost level below this setup.

 

[allrice4g63]

Ok i had a ebay mbc and two differnt style hallmans i believe they were hooked up and i tryed hooking them up two differnt ways there is no other splices in the line that goes from the nipple on the jpipe to the wastegate nipple. when i do a boost leak test the wastegate opens at 12 psi with the mbc hooked up but i run 14 psi when driving doesnt make sense to me either. I can not adjust the pressure at all i did notice that the exhaust side of the turbo where the wastegate flapper hole is has cracks in it.

 

[grnchevyz]

Viprez, not flaming at all but I clearly state the wastegate spring and not the MBC spring in my post.

=========
Originally Posted by grnchevyz View Post
If so I would be assuming a 14psi wastegate spring and the MBC's setup either to 0 (meaning use spring only) or they are not routed correctly...what brand MBC are they?

Let me know if I missed something here but it does sound like a 14psi spring in there.
==========

 

[grnchevyz]

Ok i had a ebay mbc and two differnt style hallmans i believe they were hooked up and i tryed hooking them up two differnt ways there is no other splices in the line that goes from the nipple on the jpipe to the wastegate nipple. when i do a boost leak test the wastegate opens at 12 psi with the mbc hooked up but i run 14 psi when driving doesnt make sense to me either. I can not adjust the pressure at all i did notice that the exhaust side of the turbo where the wastegate flapper hole is has cracks in it.

hmm...if you have a vaccuum source from the J-Pipe nipple to the WG, with a 1bar (14psi) spring in the WG, you will only get 14psi period. The MBC has to break that connection...one side to the J-Pipe, other to the WG.



Input Side of the MBC goes to J-Pipe, Other side to WG

 

[allrice4g63]

well its a stock 14b with a ported 02 housing do you think that the cracks bye the wastegate flapper could be causing this

 

[grnchevyz]

How did you hook up the MBCs? Did you leave the vaccuum line from the J-Pipe -> WG in place?

 

[allrice4g63]

i have the mbc hooked up like line from nipple on jpipe hooks to mbc and then runs from mbc to wastegate nipple the pressure source is hooked up so it is pushing the ball and the ball pushes against the spring which pushes against the turn nob. if that makes sense

 

[grnchevyz]

Ok, so you remove the vaccuum line attaching the J-Pipe to the WG actuator Nipple and hooked it up like the pic below?

If so, I would assume a bum or incorrectly set MBC. If the MBC is set to '0' with a 1bar (14psi) spring in the WG, you will only ever get 14psi out of it.

 

[allrice4g63]

that could be because i have almost that identical mbc except mine is all gold looking and the car that this mbc was on was running 17 psi street and 27 psi at the track so maybe it does have a 14psi spring but how come when i unhook the mbc and just leave the lines not hooked to anything i run 14psi or if i pinch the lines off i still run 14 psi

 

[allrice4g63]

the only time i have ever got over 14 psi is when i ran a piece of pipe from the jpipe straight to the throttle boddy then i way over boosted to 22psi but i did a boost leak check alot of times and found nothing.

 

[viprez586]

my bad i missed that key word.
It was a looong weekend.

 

[grnchevyz]

If there's a 14psi spring in the WG, you will always get 14psi no matter what. Any vaccuum source to the WG will result in 14psi no more, no less. At this point what I would do is this:

1.Ensure the stock BCS' vaccuum lines are removed from their destination end NOT at the BCS itself
2. Remove j-Pipe AND WG nipple vaccuum lines
3. Run J-pipe DIRECTLY in WG nipple (check for boost level 14psi I'm sure)
4. Remove vaccuum line from WG nipple side and attach to correct MBC port
5. Add another line from second MBC port to J-Pipe
6. Make sure the MBC is zero'd out and check boost (should be the same as in step 3)
7. Increase MBC level by 1 or 2 clicks and check boost level again (should be slightly higher than step 6)

Now, if you run ABSOLUTELY NO lines to the WG at all, you still only get 14psi...if that's the case then your WG flapper might be always open hence not allowing ANY boost control whatsoever. If the steps above do not work, I would see about putting 14-16psi on the WG nipple via an air compressor and see if the actuator arm moves. If there is no movement, you have a stuck open WG.

 

[grnchevyz]

my bad i missed that key word.
It was a looong weekend.

no worries....recuperating myself hehe

 

[allrice4g63]

when i run a line from the jpipe nipple directly to the wastegate nipple i get 12 lbs

 

[cano86]

can you post up some pictures of it to see how you have it set up maybe we'll be able to help you a little better thank you