2G Help with MBC boost spiking to 20+ psi

[darkstar5456]

well i have been having a issue with my boost spiking to 20+ psi before. Was told could be boost seliond so i just went ahead and got a mbc. Well its not spiking to 20 but still will shoot up to 18 WTF. i can not figur it out car has only intake tublar header and apexi turboback. Not having a frontmount is ###### not helping anything either . So i am agian at a brick wall here guys i will post a pic of the mbc hooked up maybe someone can shed some light on the subject.

 

[Altoids94]

Does it stay at 18 or drop? What's your boost set at?

 

[darkstar5456]

well to be honest it seems to vairey from speed. In town lighty building boost its great around 10-12 psi . When the car say is in fourth gear {auto}< i went about half thorttle and bam 18 and stays there. As to setting your boost level how do i do that i have my mbc turned all the way down. And i do belive its hooked up correctly its a ebay bleeder vavle style if that helps. Please help i really dont want to blow my gurl up or damage it. Granted it has been having spiking boost since my buddy got the car and then sold it to me so about a year or so miles are 112k.

 

[schumy]

You say eBay? I have an eBay one also and it does the same thing I just don't go full throttle atm. A picture of how you hooked it up would help.

 

[darkstar5456]

yes it is a ebay mbc scary part is i didnt even go wot just half. BUt i will upload pic in a minute.

edit+ he is a few pics of it hooked up tell me what you think guys. i am pretty sure its hooked up right

 

[c2ypt1c]

When trying to diagnose problems with boost controllers, the first thing you should do (and I keep repeating myself, perhaps a guide is needed...) is run wastegate pressure, to see if in fact the boost controller is the source of the problem...

Bypass the boost controller altogether by running the vacuum line from the nipple on the turbo compressor (or jpipe) straight to the wastegate actuator:

turbo ------------> actuator

as opposed to:

turbo -------------> MBC ------------> actuator

If the problem persists, then you know it's not the boost controller and it's probably the actuator, flapper, or possibly boost creep. This procedure takes all of five minutes to complete and is the easiest way to help pinpoint the problem...

 

[darkstar5456]

well back when it was all stock lines i would get spiking and uneven boost would fall and rise .

 

[AngelOfPassion]

Have you checked your wastegate flapper to make sure it is working/opening all the way? What type turbo is this I don't think I saw you mention it?

 

[darkstar5456]

its a stock t25 turbo sir as to the wastegate question how would i check that ?.

 

[c2ypt1c]

as to the wastegate question how would i check that ?.

One way of checking it is to run wastegate pressure:

When trying to diagnose problems with boost controllers, the first thing you should do (and I keep repeating myself, perhaps a guide is needed...) is run wastegate pressure, to see if in fact the boost controller is the source of the problem...

Bypass the boost controller altogether by running the vacuum line from the nipple on the turbo compressor (or jpipe) straight to the wastegate actuator:

turbo ------------> actuator

as opposed to:

turbo -------------> MBC ------------> actuator

If the problem persists, then you know it's not the boost controller and it's probably the actuator, flapper, or possibly boost creep. This procedure takes all of five minutes to complete and is the easiest way to help pinpoint the problem...

I feel like I'm repeating myself again.

run wastegate pressure and report back...

 

[darkstar5456]

you got like a diagram of that or somthing .

 

[ilco187]

Heres the way for that kind of mbc http://dub-se7en.toyotagtturbo.com/useful_info/MBC/MBC_1.JPG

and another pic http://media.photobucket.com/image/recent/bubblebob88/Mobile%20Uploads/1272082089.jpg

and 1 more http://truestreetcars.com/forums/at...boost-controller-fail-my-part-mbc-diagram.jpg

hope this helps.

 

[c2ypt1c]

you got like a diagram of that or somthing .

run it straight from the turbo to the wastegate (bypass your boost controller, meaning do not connect it, meaning take it out of the engine bay, meaning you don't need it for this test)

turbo ------> wastegate

doesn't get any easier than that.

 

[darkstar5456]

ok afther that then what should i be looking for.Sorry for the noob questions just kinda confused on the wastegate part havent had to deal with them before it could very well be that wouldnt that cause high boost and spiking. Maybe the flapper isnt opening

 

[c2ypt1c]

Maybe I should explain how the internal wastegate works. Think of the wastegate as an automatic door that opens when someone pushes a button. The button in this case is the wastegate actuator, and instead of electricity, it operates on air pressure. As your turbo generates boost, it sends a "signal" to the wastegate actuator, which in turn opens the flapper (door), via a metal rod. The stock actuator will activate at approximately 10-12psi.

Now, the boost controller is placed between the compressor and actuator. It intercepts the signal (air pressure), and essentially causes a delay, which allows more boost to generate before it passes the signal along to the actuator, ultimately opening the "door" and allowing exhaust gases to be routed around the turbine.

The lowest boost pressure you can run is wastegate pressure (10-12 psi on stock actuator). The boost controller only allows you to add boost, by delaying the signal sent to the actuator.

So, if you run wastegate pressure and the problem still exists, then the cause may be the actuator, flapper, etc...

If the problem goes away, and you are able to run steady wastegate pressure (10-12 psi), then you've determined that your boost controller is the culprit.

 

[99ECLIPSEGSXDSM]

I've herd of even some t25s boost creeping with some downpipes. I would do wastegate pressure first to rule out tho.

 

[darkstar5456]

well i am quite sure it is not my mbc as the problem was there before i even installed it . As to my problems it would spike to 20+ psi then kinda flat out around 16-18 psi but it kinda seemed like boost leak as well if i lightly got into boost . At around 10-12 psi it would kinda fluter up and down as well. So i am kinda ruling out my mbc as it still is doing . I am really leaning towards my flapper is forzen shut and isnt opening? .I was reading up on preloading the wastegate is that a good idea as to help see the problem.

idk i am kinda at a confusing point on it ? .Has anyone had this problem

any thoughts guys on this i am leaning towards my flapper is stuck closed?. As the problem was there before i even bought my mbc so i am thinking its not my mbc as i unhooked it and went back to stock still the same high boost . So i am not sure

ok update i am farily certain its my wastegate flapper not opening. As i said before it has had this problem even before my mbc so i am kinda ruling that out. As to the wastegate problem how would i get the flapper to open i swear its not i will hit 20+ psi when i should be at 12 as my mbc is turned all the way down. somone please help i am so tired of overboosting i mean its a T25 no way in the heavens should i be pushing that much boost. I dont want to blow it up or fry stuff

 

[c2ypt1c]

run wastegate pressure and report back...

Help me help you. I'm not offering any more help until you do this...

 

[96awd16g]

Those boost controllers are garbage! First all if your turning the knob towards the minus on the knob, your raising boost, it's marked ass backwards.

Next good luck with getting it to "control boost" it's either going to be closed off and your going to be overboosting badly, as you are, or if you turn it out it's going to run stock boost. I had one of these "boost controllers" and it was either 20+ psi or 10, couldn't get it anywhere in-between. Throw it in the garbage where it belongs and never look back.

 

[darkstar5456]

you joking me they are backwards>!WTF. As to wastegate pressure i havent done that . Dont i hook up a air comperrsor hose to the intake nipple on boost controller.?

 

[NHerron]

No offense but holy hell man! Just run a hose from the turbo outlet pipe nipple (or ANY port [A,E,P] on the throttle body) to the wastegate like c2ypt1c is saying!

Those type of MBC's are absolute crap! Read this article on your eBay MBC (bleeder type) vs the ball/spring type. Maybe hit up page one too, to learn how boost control works...
Intro to Boost Control - page 4

 

[darkstar5456]

yea sorry about that . I always seem to hop on rite when i get off work . So i have my air head moments .Forgive me on that i will do that on the test and update on it i will check out those pages on the mbc.

 

[NHerron]

It's all good don't worry about it but it will help evaluate the possibility of the MBC being the culprit

 

[greekgodchaos]

Its possible the diaphragm inside the wastegate is shot...but there seems to be quite the lack of actually TESTING previously posted ideas. Hopefully some confirmation regarding everyone's theories will arise soon.

 

[darkstar5456]

i dont think testing at midnight will help . I would more then likey just make a mess in the dark . But as soon as i get up and smoke a cig quick i am on the testing to update. I hope it is my mbc but it did it when it was all stock. So i guess we will find out

OK update guys i did hook up the vac line running from turbo nipple to wastgate. As there wasnt even a line on the nippleWTF my buddy is the one who hook all my mbc up.But i am please to say i didnt hit over 10-12 psi .Granted i have a HUGE boost leak it will flutter between 10-12 kinda like idle surging but no spiking and huge 20+ psi . Ok now the bad new i think all that testing overboosting has took it toll on my poor t25 i check for shaftplay and there is none over spece. Problem is that she is throwing a little smoke out of exhaust could be from the weather getting cold now. But it looked like turbo smoke same color as my 96 tsi when the seals where bad on its turbo .I mean its no where near as bad but still there.Any thoughts on boost leak and seal problems gentlemen