6G Celicas Forums

Hello doctors, get your surgical gloves on, because i need help.....
i have asked this question before with no solutions, so i will try again, maybe someone will pick up something i missed, hopefully!!!!!
basically, my 94 celica gt, which i swapped a st205 into, was up and running last may ( 2011 ), ever since then, my boost climbs to around 19-20psi, i have hit fuel cut twice, and smacked my face into the windshield the first time ( seatbelt safety ),
anyways, in order to stop hitting fuel cut, i have to let off around 5500-5700rpms, because im right on 18psi, and dont want to keep hitting fuel cut....cant be good
so heres what ive trouble shooted so far:
hooked air compressor up to wastegate with 15psi pressure....opened perfectly, quickly and smoothly
have an XS Power DP, checked to make sure the actuator clears the DP flange....it does
there is a line that comes off the wastegate and goes behind the bottom of the intake manifold to a sensor called a VSV valve???? i think its called, anyways, hoses are hooked to that and return up front, cant remember where the line goes up front though??
thats about it, kinda outta ideas

I was thinking of purchasing a manuel boost controller, but isnt that for turning up boost, or can you turn down boost as well ( explain please )
If that doesnt work....is there some sort of a bleeder type valve i can buy, to vent some pressure, or does that screw-up vaccum

Thanx, hope one or alot of you have an answer to my problem 6GC

just buy a manuel boost controller and turn it down. when you plug the controller in it will already be at its lowest setting and you will have low boost.

when i first hooked my manuel controller, ( without a gauage) i could tell that my car was slower then what it was when the OEM boost controller was hooked up. i would think that would solve the problem.

Easiest solution...get a boost controller. I personally have the Apexi Avc-r and it works very well. u can up your boost or down it. U can control it and set it as u prefer.
On the other hand if you dont want one, well u have to check everything again. There is a turbo hose under the car. When its connected directly u may often overboost. Its complicated for me to explaion that as im just an amateur lol

you may be having boost creep issues which are common with the st205's due to the size of the downpipe...too much boost bypassing the wastegate door...

I think the problem here is not being addressed. Wastegate hoses should be hooked up as follows ; compressor nipple > wastegate port 1

Wastegate port 2 > TVSV

If your tvsv works just hook up everything and enjoy stock boost .

Another route you can take which I also took ; cap off wastegate port going to tvsv and cap off line going to tvsv and hook up manual boost controller between compressor nipple and wastegate port 1 and adjust boost to whatever pressure you want.

Last option is same as above, but you omit the boost controller and just run off the wastegate spring. 9-10 psi .

ok i think most things have been hit but not in any detail to actually help you solve the problem other then just get a boost controller. assuming all hoses are connected correctly, as neon said yes the 205 is extremely prone to boost creep, WHEN you have a 3" downpipe and exhaust. most downpipes available (except Berk Tech) sometimes have problem with the wastegate port opening all the way i know you said u checked if it cleared the flange but they have problems hitting the inside, so i would check to see if there is any marks in the carbon on the inside of the DP to see if its making contact. most guys on alltrac.net will say that a 2.5" DP and 3" exhaust is the preferred setup for a street use/stock turbo setup. if the wastegate IS opening all the way and you have 3" all the way back then you can either go smaller with the DP or put a reducer at the end of the DP. my car does the same thing except it holds strong at 1.1bar (just under 18psi) if its cold or i get on it real hard you can see the needle on my boost gauge bouncy back and forth as the wastegate is trying to keep up. in the end yes you can get a boost controller and it should help with the problem.

boost controller is not going to fix this. they are good for making more boost not less. the problem is with your down pipe the waste-gate cant bleed off enough to keep boost at a certain level. the best way to fix this is to machine out the holes that the wastegate open up.

Evo lution, already tried capping off wastgate to tvsv, still building same #s in boost applications ( 19 - 20psi ). Put it back to stock set-up after a couple weeks of driving, nothing changed....same, this was back in August, thanx anyway....
From what i can see on my exhaust, there is a reducer on the end of the DP, its a section about 4inch long before the 3" exhaust, but the reducer piece is still quite big, 2.3/4inch,
When you say machine the holes in the wastegate, are you talking about the ports where the flapper opens up, if so, is there an easier route then that???

Go with an external wastegate...probably your best bet.

Please explain external wastegate, prototype X, I know its pretty self explanatory, but what do they look like, and where would they go on our cars system....

an external wastegate is just that. it looks just like a BOV but instead of pressure it bleeds off exhaust allowing the turbo to slow down. they look something like this

the only problem changing to external requires some serious fab work. you need to block off the ports inside your turbo housing. then fab up a new port for the external gate to hook up to

My God!!!!!! dont think I can do that Smayy, beautiful pic of the external though, very nice, can clearly see how the external works and where it would go.....I just dont have the resources or the steel fab ingenuity to do this, I need to keep trying though, I just started my first of 4 shifts, ( 2 days/2 nights ), will finish last shift on Saturday morning, will be jaking car up " high! " to start with peoples ideas on how to beat this problem....there has to be a way

With my Apexi Avc-R i can lower my boost and run more boost. I ran 0.4 bar on full throttle 7000 rpm on 3rd gear. When i increased it i ran 1.25 bar on 650 rpm. A good boost controller can do both, lower and increase your boost mate.

Rav, is your boost controller Manuel or electronic, and will both do the same job?? ( lower pressure/raise pressure )

Capping of the wastegate to tvsv port would allow you to run wastegate spring pressure (8-9 psi) if you were going past that then I believe your wastegate flap wasn't opening all the way with the downpipe on.

[quote name='injection' date='Nov 30, 2011 - 8:19 AM' post='942361']
Rav, is your boost controller Manuel or electronic, and will both do the same job?? ( lower pressure/raise pressure )
[/quote

The Apexi AVCR is electronic. But normally manual boost controllers also allow you to open the tap or close it. But the electronic one is more precise in calibrating boost. And they can both control the solenoid. If u want one for a very long period of time, get the electronic one.

Concerning manual boost controllers, not all of them allow to lower boost. At least i can confirm u that AVCR allows me to lower it.

i have an AVC-R in my 7th gen. again it will only let you go as low as the wastegate will allow. for example if you have an 8lb spring in the wastegate, you cant lower it to make 4 lbs of boost. it dont work that way.

the OP is having boost creep issues meaning he cant bleed off exhaust fast enough. so a boost controller wont help here unless he wants to raise boost

i dont understand how i made 0.4 bar then:(