Max boost keeps changing.

[Deadly BlaZe]

Mods: Hard intake pipe w/kn filter, boost gauge, bcs restrictor removed.

Since I've gotten my boost gauge, it says i've been boosting 13.5 psi, sometimes (very rarely) spiking to 14.5 and dropping back to 13.5. Couple months later, I've noticed my max boost dropped down to 10 psi for like a day. The next day, it went back up to 13.5. Another month later (today), max boost dropped back down to 10 psi (no spiking or creep).

When it's at 13.5 psi, it'll spool by 3k, and when it's at 10 psi, it'll spool by 2.8k. I've done a boost leak and I have no leaks. I feel no hesitation or unnecessary lag under both circumstances. I highly doubt it is the gauge itself because even the stock gauge reads lower boost than usual when i'm hitting 10 psi. Anyone have ideas? Wastegate maybe?

 

[Blackmitzu]

wastegate is bad, the stock wastegates are junk. Its really nothing to be worried about untill you get into running alot more boost.

 

[Deadly BlaZe]

That's what I thought. Is that the only thing it could be though?

 

[KingAWD]

well, it may not be the only wrong with it... How is your maintence w the car, up to date w all the tune ups? Most likey it is the wastegate, seems to be a common occurance with our cars.

 

[Deadly BlaZe]

Car is maintained very well and have done all necessary maintenance.

 

[Dream On]

Get a MBC and see what happens. May have something to do with modding the bcs.

 

[Deadly BlaZe]

I was gonna buy an mbc after i got the gauge, but then i realized i'm already hitting the boost that i wanted (13.5).

I also wanna add, when it hits 10 psi, the needle starts vibrating slightly back and forth really really fast (at 10 psi) as if it's trying to creep up as i go higher in the rpm's.

 

[oldman]

Remove your BCS and see if boost stays at 10psi. If it does, the problem is the bcs. If it still flactuates, you have a bad gauge or leaks leading up to the gauge. I don't see how a defective actuator can cause the problem you're describing.

wastegate is bad, the stock wastegates are junk. Its really nothing to be worried about untill you get into running alot more boost

Please explain because it doesn't make sense to me. What bases do you have that stock wastegates are junk, first I ever heard of. Are you talking about it's ability to hold higher boost levels (which would have nothing to do with the topic at hand) or are you implying that it won't maintain steady lower boost levels?

 

[Deadly BlaZe]

I'm glad you chimed in Oldman, i'll check the bcs tomorrow. If the bcs works fine, what's supposed to happen to the boost?

Also oldman, why do you think the boost gauge needle starts vibrating back and forth once i hit 10 psi?

 

[garrett21]

There are a few questions you need to answer, what brand is the boost gauge, is it new or used? who installed it, where is it tapped from? have you tried swapping in a different gauge? Is there any reason you should be getting boost spike? Was the boost controller installed right? I would look at some tech articles if you have yet to and see if they help you. Just some thoughts, good luck!

 

[garrett21]

Oh, and as far as I know if awastegate was going bad it would not allow you to build any boost, not make the boost rise. If the wastegate was jammed or the flap is stuck then you could have a problem building too much boost.

 

[oldman]

I'm glad you chimed in Oldman, i'll check the bcs tomorrow. If the bcs works fine, what's supposed to happen to the boost?

If the bcs is fine, bypassing it shouldn't solve the problem.

Also oldman, why do you think the boost gauge needle starts vibrating back and forth once i hit 10 psi?

My best guess would be either a bad gauge or leaks near the gauge. Garrett21 is right, I would like to know which gauge? Condition of the gauge? What type of vacuum line used? Where is it connected to? What is your vacuum reading at idle? How much pressure were you able to register on the boost gauge during your last leak test?....etc.

 

[Deadly BlaZe]

If the bcs is fine, bypassing it shouldn't solve the problem.


My best guess would be either a bad gauge or leaks near the gauge. Garrett21 is right, I would like to know which gauge? Condition of the gauge? What type of vacuum line used? Where is it connected to? What is your vacuum reading at idle? How much pressure were you able to register on the boost gauge during your last leak test?....etc.

I'm using a prosport boost gauge, i bought it a few months ago so it's in excellent condition. Pretty reputable company also i'd say. I installed the guage myself, I'm using the nylon/plastic hose (I know i should probably change it to a rubber one), it's tapped into the FPS, vaccum at idle is 18-20 inhg, and i pressurized the system to 20 psi (which is what it read on the gauge). I have not switched out the gauge with another one to test it out. What I do know is, the stock boost gauge is insanely close and consistent with my prosport gauge. When my gauge started reading 10 psi, the stock gauge started reading a lower boost than usual too. I know the stock gauge isn't accurate at all, but i thought it would nice to point out.

 

[oldman]

Do the bcs test first, Adam (Dream On) probably hit the nail on the head. MBC is not only good for raising your boost level, a good one will also provide precise boost control, remember, the stock bcs is nothing but a electronically controlled bleeder/solenoid type boost controller.

 

[Deadly BlaZe]

Do the bcs test first, Adam (Dream On) probably hit the nail on the head. MBC is not only good for raising your boost level, a good one will also provide precise boost control, remember, the stock bcs is nothing but a electronically controlled bleeder/solenoid type boost controller.

So should i remove the bcs and plug up the vacuum lines?

 

[oldman]

So should i remove the bcs and plug up the vacuum lines?

Remove all the lines including the T fitting then connect a line from the turbo outlet fitting directly to the actuator fitting, this will basically set your boost level to the spring rating of the actuator, 10-12 psi.

 

[Deadly BlaZe]

ok gotcha, and if i do this, what's supposed to happen to the boost (assuming bcs is fine)? Is it supposed to stay at 10, or change a bit?

 

[oldman]

Damn it Arthur, maybe we should make you a new member again.

After the BCS is out of the way,

1. If the boost level stays consistent, regarless what psi, you can conclude that the inconsistent boost level was caused by the bcs bleeding off inconsistent amount of pressure. Get yourself an reliable ball/spring mbc.

2. If the boost level continues to flactuate, regardless what psi, you will then move to the boost gauge side like discussed earlier starting with that platic vacuum line, specifically where it connects to the T fitting on the FPR line.

 

[Deadly BlaZe]

haha thanks old man, i honestly feel like a noob when i'm asking these questions. Honestly i never understood what the purpose of the bcs was if the actuator is what controls the limit of the boost.

 

[oldman]

haha thanks old man, i honestly feel like a noob when i'm asking these questions. Honestly i never understood what the purpose of the bcs was if the actuator is what controls the limit of the boost.

BCS, MBC, EBC.......or any kind of boost controller works by altering the amount of boost the actuator sees therefore delaying the opening of the wastegate resulting in higher boost levels. A bleeder type like the factory bcs achieves this by bleeding pressure off the reference line to the actuator. A ball and spring type (Hallman, Joe p.......etc.) does this by blocking the pressure altogether, only releasing pressure to the actuator once the spring pressure in the mbc is overcomed. Time to hit the book stores.

 

[Deadly BlaZe]

Thanks for the explanation. Let me ask you another question oldman, this isn't related to my current problem but i don't feel like opening up a new thread.

When my car is cold, the car hesitates really bad. I'm talking about lower rpms like 2k-3k. I have enough common sense not to do pulls when the car is cold, but i'm sure if i went over 3k when it was cold, it would have the same effect. Like at 2k while depressing the gas pedal, i'll feel the car pull back a little and then suddenly a second later, it loses the power, then a second later it comes back and drops again and so forth. This is only when the car is cold up to the point where it completely warms up. When it's fully warmed up, it feels absolutely fine. Any ideas?

 

[oldman]

When my car is cold, the car hesitates really bad. I'm talking about lower rpms like 2k-3k. I have enough common sense not to do pulls when the car is cold, but i'm sure if i went over 3k when it was cold, it would have the same effect. Like at 2k while depressing the gas pedal, i'll feel the car pull back a little and then suddenly a second later, it loses the power, then a second later it comes back and drops again and so forth. This is only when the car is cold up to the point where it completely warms up. When it's fully warmed up, it feels absolutely fine. Any ideas?

If it's temperature related, check your plugs and wires, fpr (may be related to your gauge reading problem since you're tapping the fpr line) and engine coolant temperature sensor. Go open your service manual before you ask me how.

 

[Deadly BlaZe]

Go open your service manual before you ask me how.

blah . thanks