Possible Problem

[mig233]

hey dsmers. Recently i installing a boost and a/f gauge. Stock, i noticed that when dropping a gear or in between shifts my car would spike to 15 psi, then bleed down and hold at 10psi. i put in a turboxs mbc, and the same thing happens only with higher boost. Spikes to 20 psi, then holds at 15 psi. Is there a problem here or am i just paranoid? Also, is it safe to be spiking to 20 psi, on stock fuel components? Because i know that the fuel system can handle 15 psi. Please help, any feedback is appreciated. Keep boostin!

 

[ZachM31]

still the stock T-25? spiking to 20psi probably isn't such a good thing, i put a MBC on because of that, when you spike does your A/F gauge go to "lean"? anyways, how do you have your MBC wired up? bottom to BOV line, side going to the Wastegate Actuator? i was gettin 25 psi when i had it hooked up using the compressor signal instead of the BOV line, swapped it around, screwed it all the way out, and took it on the road and got it set... now i spike to 15 and drop to 14, and go to 10psi near redline .. damn T-25's....

 

[mig233]

zachman, i think you're on to something. Actually the bottom, blue nipple of the mbc is hooked up to the wastegate actuator, and the side is teed into the bov line. i used the instructions from turboxs, but whatever. Thanx a lot, let me try that, then i'll get back.

 

[ZachM31]

hey man, that's how i had mine hooked up too one time, my boost pressure was spiking all over the place where i didn't want it (i had a leak from my BOV at the time) but i fixed the leak and swapped the 2 ends around, and set it, and am fine now... speaking of instructions, you should see the instructions Qboost sent with my MBC, the written one said bottom to the compressor nipple, and side to the actuator, and the picture had the exact opposite..... no wonder however far i turned it out or in, i was always overboosting extremely bad ... went to vfaq and saw the one about the MBC install and looked at that....solved ALL of my problems, i hope that swapping the 2 ends around works better for you..

 

[mig233]

ok zach new problem, maybe you can help me. My mbc was leaking thru the o-rings. i got new o-rings, and now it doesn't leak. But i have the mbc hooked up and i can't adjust it past 10 or 12 psi. This is how i have it hooked up. Bottom nipple on the mbc is hooked up to the wastegate actuator, the side nipple on the mbc is hooked up to the bov line. The nipple on the compressor housing on the turbo is blocked off, and nipple on the boost control solenoid is also blocked off. WTF is going on!!!!!! Please help!

 

[oldman]

Heads up for both of you. Due to the fact that the turboxs mbc is a bleeder type valve, it's not a good idea to tap the pressure source from the bov because it will create a vacuum leak and suck in un-metered/un-filter air whenever you're not in boost. A better source would be the compressor housing.

 

[mig233]

thanx a lot oldman. I'll try that. That is the exact information that i was looking for.

 

[oldman]

thanx a lot oldman. I'll try that. That is the exact information that i was looking for.

You're welcome. Can you describe your boost problem again? I didn't quite understand your description above, I may be able to help you there.

 

[mig233]

ok well, i hooked up the side nipple of the mbc to the compressor housing on the turbo, like oldman said. The bottom nipple of the mbc is still hooked up to the wastegate actuator. But guess what the same problem is occuring. It's only letting me boost to like 12 psi. I turned the adjustment screw on the boost controller all the way up. It's only letting me boost to 12 psi. I don't know what to do. Oldman...any suggestions?

 

[ZachM31]

isn't all the way out the lowest boost setting you can have? the spring tension is least at that point, what happens when you turn it in? 12 psi?

 

[oldman]

1. So the spiking is gone after you switched it to the compressor housing? Is that right?

2. No matter how you adjust the knob, boost stays constant at 12psi? right?

3. Just checking, you did cap off the T off the BOV line, right?

 

[mig233]

the spiking is gone, and the tee is blocked off on the bov line. And the side nipple of the mbc is connected to the nipple on the compressor housing. I'll try turning the adjustment screw in, but the directions on the mbc, say turning the screw inwards lowers boost, and turning it outward raises the boost. Any other suggestions?

 

[oldman]

the spiking is gone, and the tee is blocked off on the bov line. And the side nipple of the mbc is connected to the nipple on the compressor housing. I'll try turning the adjustment screw in, but the directions on the mbc, say turning the screw inwards lowers boost, and turning it outward raises the boost. Any other suggestions?

Not familiar with the bleeder valve set up on the Turboxs unit. Typically, a ball/spring type would be in=increase and out=decrease, you best follow the instructions given. I'll wait for your test result with the mbc before I post my next suggestion.

 

[mig233]

ok correction. I just tried turning the adjustment screw inwards. No matter where i adjust the screw, the car only runs 12 psi. It doesn't quite hold steady, it bleeds down to like 10 psi. I don't understand it! No matter where i adjust it, it runs like 12 psi, then bleeds down to about 10psi.

 

[mig233]

olman, do you have a screen name or something, i think it would be easier if i talked to you in person.

 

[oldman]

ok correction. I just tried turning the adjustment screw inwards. No matter where i adjust the screw, the car only runs 12 psi. It doesn't quite hold steady, it bleeds down to like 10 psi. I don't understand it! No matter where i adjust it, it runs like 12 psi, then bleeds down to about 10psi.

1. Test run with the actuator nipple open by removing the hose between the mbc and actuator and cap off the mbc side. The desired result would be all out boost so control the throttle accordingly, let off at 15psi. If In fact you get all out boost, the mbc is defective because it's not bleeding off enough air. If problem persists, go to 2.

2. Perform a boost leak test, fix all leaks till system hods 20psi for 30+ sec. If this doesn't fix your problem, the turbo would be the suspect.

I believe it's more likely that the mbc isn't doing it's job because you were able to boost past 12psi before. Also, even if you're able to confirm the mbc is defective after performing #1, doesn't mean you don't have boost leaks so it wouldn't hurt to do the test anyway.

 

[mig233]

ok i'll try that, let you know what happens, i'll post back in like 10 mins.

 

[oldman]

olman, do you have a screen name or something, i think it would be easier if i talked to you in person.

Sorry don't do IM, I think and type too slow.

 

[mig233]

am i pissed! Ok oldman, did what you said, it boosted fine, i let off the throttle at around 15psi. i checked for boost leaks, ie bov. i tightened the bov, put the mbc back in, with the same results. I guess it means the mbc is broken. I am pissed!!!!!!! Thanx a lot for your imput, i appreciate your time. Any suggestions on what i should do now?

 

[oldman]

Any suggestions on what i should do now?

Return it and exchange if possible, with a ball and spring type mbc like a JoeP or Hallman and the likes.

 

[mig233]

well my friend gave it to me for free, now i know why it was free, . Ok i'll see if i can pick up a ball and spring boost controller. now, if it's a ball and spring should i tee it to the bov line, or could i keep in on the compressor housing as is. Thanx

 

[mig233]

oh also, where could i get a joe p, or a hallman? i heard dejon tool is pretty good also.

 

[oldman]

now, if it's a ball and spring should i tee it to the bov line, or could i keep in on the compressor housing as is. Thanx

You're welcome. It would make much of a difference unless you have boost leaks some where in between. BTW only way to find leaks is through a real boost leak test posted above, no visual inspections.

oh also, where could i get a joe p, or a hallman? i heard dejon tool is pretty good also.

Have not heard anything bad about the Dejon Tool unit, I'm sure it will work fine. Most of our site sponsors should carry both JoeP and Hallman.