3SGTE: Can a missing VTV cause boost creep on External WG?

[farvaric]

my WG setup:

1. the WG gets signal from "hot" IC pipe (pipe after my hot pipe which the BPV is on).
2. missing VTV
3. seeing slow boost build up and boost creep to 12psi by redline in 3rd with an 8psi spring
4. MBC is removed, running only on WG.
5. turbo is 57 trim T3/T4 .50 comp side and .63 hot side
6. intake, dp, exhaust, ic, no cats

theory, is it possible that since i do not have a VTV in that my BPV is staying open causin a boost leak that is also bleeding the signal needed to open the WG all the way or fast enough which is causing the creep??? granted my gauge does read 12psi at redline, but is this a possibility???

[countyboy3188]

Ii don't think the VTV is causing your problem.
Running the VTV with a boost controller can cause instant boost spikes so you are supposed to block it off or get rid of it when you install one.

[farvaric]

you know better than that

VTV = Vacuum Transfer Valve

not talking about the T-VSV

I am missing the piece that controls the Bypass valve

I do have the TVSV currently plugged off, however i typically run it with my HKS FCD. what other ideas?

Keep em coming.

[countyboy3188]

oh my bad lol i didn't think about it before i posted that ha.

hmmm i still don't think that would be your problem though. of course i still don't know too much about external wastgates. that could be your problem then since the wastegate would need vacuum to work properly.

it seems like you have it hooked up right since you have a boost reference line from your hotpipe. And after looking at the stock BPV im pretty sure you would need the VTV for it to work properly or it might leave it open. thus giving you your slow boost problem...

I don't think they are that expensive you can get on use or one from toyota for around $30-$40

I hope this post helps you out more lol

[countyboy3188]

so that is the piece that you are missing.

[farvaric]

double post deleted

[farvaric]

it does help

EDIT: and that is the piece I am missing, well, it broke, then i threw it away as opposed to just trying to d a temp fix like superglue

I am looking for the part now, but am wondering the possibility of finding a one way vacuum valve restrictor. I see some online at napa and some other crap places, but that is only online, and i would want to look at it if it doesnt come from toyota to be sure.

The main thing is I want it now as opposed to waiting for shipping as I have been on a business trip in the philippines for 3 months and didnt get to drive my car all season...and it is expected to snow this weekend

life sucks without boosted happiness...granted almost all cars are boosted in the philippines now...and I have to go on another business trip in a few weeks to India and then back to the philippines for like 3 weeks.

ah well, the car is sitting at the shop right now getting some work done, hopefully i get it back before the weekend and cna find or acquire a new VTV by then and get my car boosting right and set it to 12psi on my t3/t4

[countyboy3188]

i do have my stock BPV still. I don't need it anymore because of the set up im running currently has the blow-off on the cold pipe.

I will send you a pm.

[CJMR2T]

I've thought about this more and if your WG signal is after the BPV, then it is going to be referancing system pressure after the leak. Your intake manifold is after the leak too so if your intake is seeing 12psi, then your WG should seeing 12psi also thus no boost creep due to BPV leaking....

System pressure is system pressure no matter how you look at it. If the pressure is 12psi, then everywhere in the system is at 12psi or slightly higher (pressure drops due to other items) but nothing is going to be lower...

Im thinking that your idea of it causing a different (lower pressure) is coming form the idea of a bleed type boost controller setup but the problem with that theory is in the case of a bleed type (controlled leak), you are leaking only the air in the sensing line and no where else.. This is a small leak in a very small volume that is only going to the wastgate. In your case, you are possibly leaking air before the sensing port plus its a small leak in an otherwise large volume that is making up the entire system.... now if the leak was in the sensing line itself, they yes I would fully agree with it causing the creep.

Think about this, IC's always induce a pressure drop. So if your engine itself is seeing 12psi, then the hot pipe will deffinitly be higher the 12psi. Its laws of physics... there is no way that the intake mani can be at 12psi and the hot pipe be lower. The WG sensing off the hot pipe has to be seeing the pressure in the pipe unless there is a leak in the sensing line itself or in the diaphram of the WG or lastly if there is a leak between the sensing port of the BPV and the outlet flow port of it (i.e. the actual port that vents the air from the hot pipe)..

[farvaric]

this is a good theory, going to read it again actually

but take this into consideration:

1. the bpv signal is coming post throttle body
2. the boost gauge is post throttle body, so both the bpv and gauge are or should be getting IM pressure
3. the WG is not seeing IM pressure as it is pre throttle body or IM
4. if there is a small leak in the charge pipe which is also pre TB/IM then it is possible that the turbo is overcompensating to make up for the small leak, however if that same small leak is effecting the signal source to the WG, could that explain the creep???

well i guess that may actually justify your point which is if i am reading 12 at the gauge, the WG should be reading 12 regardless if not more, the line could be suspect.

hmmmm what else could be suspect, i have ran a different source from post TB and it was the same issue, but i was checking boost increase only at that time and not creep....dammit, frustrating since i dont have my car right now...

EDIT: my WG is a 38mm and the turbo is a 57trim 50 comp side and 63 hot side. i could try going to a larger WG, but i think it is a leak somewhere.

[CJMR2T]

unless the leak is in the exact same location as the WG signal port then yes... other then that, your over analizing this...

Your intake can not have a higher pressure then the rest of the system, its physically impossible....

Now yes, if you have a big enough leak, there will be a drop in system pressure and the WG will decrease opening to spool the turbo more to compensate thus bringing the system back up to pressure...... Again, the only way that a leak could be effecting the WG and not the rest of the system is if its in the WG signal line (i.e. bleed type boost controller)....

Your 38mm gate is size is not the problem. A 38mm gate can support exhaust flow on a 350 to 400hp engine and 12psi on a 3s is not 350 to 400hp... It could be how the WG is in your setup... IIRC, you said somewhere that your WG is coming from the WG port of the T3 turbine housing, correct? This in itself can and does cause creep.

Here's another question, What kind of WG is it??? Be honest here as this is very important.

[farvaric]

oh, i agree with you, i actually stated that in the end of my post

I understand pressure drop from boost source vs IM. My reasoning is that i dont believe the WG is getting the appropriate signal. which to your point you are absolutely right and i was off, the hotpipe would at least contain enough pressure as what is in the IM and not less, this narrows it down to the signal line or the WG itself, as you stated.

for whatever reason, i may just trying to justify reasoning that my issue may be a simple/cheaper fix

I am so rocking an ebay special WG

so yes, that could be a possible issue, diaphram or spring.

the question is, how can i test to narrow down the issue, I guess I could just try to run without the wastegate on and see if i dont get any boost...

I have read that sometimes the turbo is responsible for the boost creep and may need to port the WG port, however if i do the above and dont get boost, that should narrow it down to the WG being inadequate or an issue with the signal source.

It may be the signal source or line though.

so the missing vtv would/may explain my slow boost increase (if it is keeping the bpv open). could this be part of the creep issue, bascially the slow onset as opposed to immediate onset? I also am not running my MBC inline at the moment, only WG.

[CJMR2T]

Originally Posted by farvaric

oh, i agree with you, i actually stated that in the end of my post

I understand pressure drop from boost source vs IM. My reasoning is that i dont believe the WG is getting the appropriate signal. which to your point you are absolutely right and i was off, the hotpipe would at least contain enough pressure as what is in the IM and not less, this narrows it down to the signal line or the WG itself, as you stated.

for whatever reason, i may just trying to justify reasoning that my issue may be a simple/cheaper fix

I am so rocking an ebay special WG

so yes, that could be a possible issue, diaphram or spring.

the question is, how can i test to narrow down the issue, I guess I could just try to run without the wastegate on and see if i dont get any boost...

I have read that sometimes the turbo is responsible for the boost creep and may need to port the WG port, however if i do the above and dont get boost, that should narrow it down to the WG being inadequate or an issue with the signal source.

It may be the signal source or line though.

so the missing vtv would/may explain my slow boost increase (if it is keeping the bpv open). could this be part of the creep issue, bascially the slow onset as opposed to immediate onset? I also am not running my MBC inline at the moment, only WG.

Ok!!!!! now knowing (which i had a feeling you going to say) ebay or SSAC wastegate, my money is the whole problem is in the wastegate....

Possibly a hole in the diaphram but the more common problem with them is the valve/shaft is too rough / tight in the guide.... This is a very common problem with them...

Overall, they are actually good units if the they are modded... I've had a few local guys with various cars that have had almost this same type of problem. One of them had a small hole in the diaphram, the rest were binding shafts....

Its very easy to solve the problem first off make sure the diaphram doesn't have a hole in it. To do, the best way is with compressed air (about 5 to 6psi wil usually be enough), a shut off valve to trap the compressed air in the gate and a gauge to read the pressure... Basically you pressurise the unit and make sure the pressure doesnt bleed off...

For the shaft fix, you have to dissasemble the unit and chuck it up in a drill to spin it while using various grits of sand papar / emory cloth to polish the shaft. They are machined too course and they get hot and tend to bind and get stuck in the guide... Basically, you want to take off as little material as possible, just enough to knock down the high edge's and polish it.... Every single one that I have done has not had a single problem since then and work flawlessly....

A WG is one of those things that are hard to F-up when designing / building as long as the machining of the moving parts is smooth enough this is where the problems tends to be.

[farvaric]

what I will say is that i was able to use BOTH thumbs to actuate the valve when i got it (had to press with decent force). it honestly seems to actuate smooth enough, but lets just say it wasnt "glass" like polished metal with a sleeve.

I will check this out.

One more thing, just to confirm, is it safe to assume that if I run my car with the WG completely off (IE: uninstalled completely), the car should NOT produce boost at all correct? This technically should point ti the WG for sure.

Let me know if I am crazy, I just want to cancel out the turbo WG port from being the issue.

[CJMR2T]

no, the car shouldn't produce any boost at all if you were to take the wastegate totally off... (might possibly produce 1psi at the most but even that is unlikely)

The valves tend to work fine when new. They get stock after several heat cycles..... Its a very common problem with them..... My guess is yours is stuck partically open thus causing very slow rise but not open enough to keep boost below the nominal 8psi of the spring....

[farvaric]

thanks CJ, you are getting me pumped to fix this nuance.

i am just hesitant on buying a freakin tial in the event it is NOT the issue. but I may need to do that, but i will take it apart once i get my car back.

I also believe I may be making a deal with a board member to get a replacement VTV, just waiting for response from him on the condition of it as it is used.

[CJMR2T]

I might also have a VTV lying around if you need it.... Im not sure though... I'll look thursday when Im over by my storage area by my family where I'll be at for Thanksgiving....

[farvaric]

yea, that would be great if you dont mind parting with it, just let me know.

Thanks again!

[CJMR2T]

back on the topic of the knock off wastegate... The Ebay / SSAC units arent realy that bad... They just need a little TLC to work 100% effectively... My cusin used one on his honda that I build for him... That unit has been on the car working flawlessly for almost 4 years now.... But I did polished the shaft before it was ever ran cause I knew of the problem....

Plus like I said before, I alone have fixed several of them that have gotten stock and or were randomly sticking then freeing up..... I have not had one yet that polishing down the shaft didn't fix it.......

Remember, the valve / shaft itself experiances much higher temps then the body and the guide and thus expands a lot more. Most of them are Stainless material which expands even more for a given temp.... The shaft has to have a good amount of clearance or it will seize.... I've had a couple that seemed fine when they were cold (contracted) but would seize up once they heated up...

Having said the last part, I would take it apart and polish down the shaft regardless of how it seems when you take the unit off, and then try it... If you take apart a good name brand unit like a Tial, HKS, Greddy, Turbonetics, etc... they are all polished very smooth... Look at a Valve in a head, they are polished smooth too... This is for a reason... Clearance is very important too expecially cause of the expansion rate differances of the different materials...

[CJMR2T]

Originally Posted by farvaric

yea, that would be great if you dont mind parting with it, just let me know.

Thanks again!

if I have one and its good, I dont have a problem parting with it seeing as how I have a HKS SSQV on my car..

Im almost positive I have 2 stock BPV's sitting in a box so Im thinking that the VTV's are there with them... One of the BPV's is from a Gen 3 but Im pretty positive that they are the same as the GEN 2 USDM stuff and use the VTV too..