Car won't boost over 11-12 psi

[wvturbo2]

I turned the boost controller way up and it still won't let the car boost over 11-12 psi. What could the problem be ?

 

[ROOKIE1]

How does it run ? Boost leak test ? Have you done any throttle body work ? The gaskets are different from other years on our beloved 90s .

 

[wvturbo2]

I might have a few small boost leaks, but it pulls pretty hard. I'm going to have my friend do a leak test and we are going to fix the leaks. Last time we checked they were small still seems like it should pull more than that from time to time or less from time to time

 

[Mike1992]

Any leak is a leak and your turbo has to work harder to make up for it. A leak will also cause you to run richer and run higher idc's. Case and point, leaks are bad fix them asap

 

[oldman]

1. TurboXS MBC is different from a typical ball and spring, how is yours hooked up? Which direction are you turning the adjustment knob?

2. Test run with the actuator fitting open, expect uncontrollable boost so let off at about 18psi. If you're able boost past 12psi, the problem is MBC related. If problem persists, the problem is either exhaust leaks, boost leaks, defective wastegate or a dying turbo.

 

[wvturbo2]

Its hooked up as directions said, bottom goes to boost source top goes to vacuum. If i remember correctly. My friend is going to do a boost leak test today hopefully and we will fix the leaks. Turbo shouldn't be dying, but i wouldn't doubt the wastegate could be an issue. It might have changed after the gm maf install i really dont remember I'll see what happens after boost leak test.

 

[Spooling99]

I turned the boost controller way up and it still won't let the car boost over 11-12 psi. What could the problem be ?

By turning it up you mean screwing it down? Because screwing it down creates more boost. I made this mistake on mine the first time. What is your boost source and vaccum source?

 

[oldman]

TurboXS often tells their customers to tap the BOV line for boost reference which is a big no no, especially with a TurboXS mbc, double check how it is hooked up. The fitting perpendicular to the body goes to compressor housing or licp, the fitting opposite but inline with the adjustment knob goes to the wastegate actuator, neither should see vacuum. The adjustment knob direction is also opposite of a typical ball and spring, CW (in) = less boost, CCW (out) = more boost. The reason I think the issue is mbc related is because 11-12psi = stock actuator spring rating which indicates the MBC isn't doing its job, the chance of issues like leaks, wastegate, turbo....etc. resulting in a steady 12psi is slim, not that doing a boost leak test is ever a bad thing.

 

[Spooling99]

I have a Joe P and its hooked up like Bruce has said. It works great and the shorter lines make boost response better as well.

 

[oldman]

I have a Joe P and its hooked up like Bruce has said.

I hope not!! Your inlet and outlet fittings are completely opposite to his TurboXS.

 

[wvturbo2]

The one facing out goes into the same vacuum tee as the bov vacuum, the other goes to the wastegate act. i do believe

 

[oldman]

The one facing out goes into the same vacuum tee as the bov vacuum

Well congrats , you have boost leak, vacuum leak and possible idle and compressor surge, restore your BOV line as a dedicated line from manifold to BOV, take your reference from the compressor or j-pipe/licp.

You still have not answer which direction are you turning the knob to get more boost. Be detail so we don't go back and forth with the same questions.

 

[Spooling99]

Ok bruce I must have misread. My boost source is the compressor housing and my other line routes to the LICP.

 

[wvturbo2]

I turn the knob to the side with a + sign to add boost and a - sign to get less boost. I don't think my new J-pipe has a nipple and I know my lower intercooler piping hasn't go anything to hook it up to. What should I do ?

 

[romeen]

Ok bruce I must have misread. My boost source is the compressor housing and my other line routes to the LICP.

Are you sure you didn't mean to say WGA instead of LICP?

 

[Spooling99]

Exactly. Haha I'll get it right sometime today.

 

[oldman]

I turn the knob to the side with a + sign to add boost and a - sign to get less boost. I don't think my new J-pipe has a nipple and I know my lower intercooler piping hasn't go anything to hook it up to. What should I do ?

Drill and tap the J-pipe with a 1/8 npt to 1/8" fitting, that's what most people do. Don't forget to do that test run on your way to BLT I mention above in my first post, ask questions if you're unclear about it.

2. Test run with the actuator fitting open, expect uncontrollable boost so let off at about 18psi. If you're able boost past 12psi, the problem is MBC related. If problem persists, the problem is either exhaust leaks, boost leaks, defective wastegate or a dying turbo.

Ok bruce I must have misread. My boost source is the compressor housing and my other line routes to the LICP.

Opposite as in the orientation of inlet and outlet fittings on the mbc itself. In other words, his inlet fitting is the one perpendicular to the body, yours is the one inline with the body. Damn it Beavis!

 

[wvturbo2]

Its not the turbo, because i used to spool up to 15 and sometimes creap up to 16 psi. I guess i'll have my friend do that as well.
So one end goes to the wastegate act. and the other to the jpipe ?

 

[Spooling99]

Did this happen when you installed you MBC or just recently. If it just recently started I'd do a boost leak test as Bruce stated. If you've never done one prepare to be amazed.

 

[wvturbo2]

My car has has had its fair share of boost leak tests and it actually has a couple or one small leak right now. It ran 15 psi for awhile and my friend thinks its the mbc and not they way its hooked up, but we are going to fix it on monday when he has time. As for now I'll enjoy my 12psi and leaking air.

 

[oldman]

My car has has had its fair share of boost leak tests and it actually has a couple or one small leak right now. It ran 15 psi for awhile and my friend thinks its the mbc and not they way its hooked up, but we are going to fix it on monday when he has time. As for now I'll enjoy my 12psi and leaking air.

I expected your friend to argue about the BOV line issue, don't give in no matter what he said. Did you test run with the actuator open to atmosphere to see if you can boost past 12psi without the mbc?

 

[wvturbo2]

I will when i get off work, and yes he said it shouldn't matter that much, but it only makes sense. I don't doubt that leaks are playing their roll, I actually pushed the throttle to the floor for once and it went up to 14 or something and dropped back. The turbo wants to keep going but is just getting beat down.

 

[evogst97]

Well congrats , you have boost leak, vacuum leak and possible idle and compressor surge, restore your BOV line as a dedicated line from manifold to BOV, take your reference from the compressor or j-pipe/licp.

You still have not answer which direction are you turning the knob to get more boost. Be detail so we don't go back and forth with the same questions.

With all my idle problems I never thought of this. My vacuum reading is at 10hg when it should be at 20. I am running on one line and not using the J Pipe. Also I have idle probles. Could this be the problem? Also I feel stupid asking this but I loosen the mbc (joe p) by twisting to the left. Is this the correct way to gain psi or lose? I always thought that if I tightened it, It would be at higher boost but now I think its the opposite.

 

[romeen]

I'm not familiar with all of the different types of MBC's. But I was under the impression that turning the adjustment knob clockwise (inwards towards the body of the MBC itself) will further restrict the air passage between the inlet and outlet of the controller leading to higher boost since the air pressure going to the WGA is delayed from reaching the necessary opening pressure.
I would like to know for my own information if this is accurate. Bruce?

 

[oldman]

That is correct for ball and spring type MBCs, the more you turn it in, the higher the pressure of the spring, the higher the boost level. A bleeder type like the TurboXS Standard on the other hand is opposite, the more you turn it in, the smaller the bleeder hole, the lower the boost. The more you turn it out, the larger the bleeder hole, the more boost.