Alright, I found my boosting problems. Wasn't what I thought it was. Originally I had diagnosed the problem as a dead boost solenoid on my EBC. So I bought an MBC.. no cigar. That of course led me to a massive search for boost leak. Of course, it was a coupler.. the damned gash was literally hidden from the naked eye, the only way I found it was by feeling around.

Anyway, fixed the coupler problem and plugged my EBC vacuum hoses back in (I didn't mess with a thing. Merely unplugged and plugged back in the hoses to the solenoid). Took it out for a spin.. EBC turned down all the way.. BOOM, 1.5 bar. I was shocked. Car was fine, didn't act weird or anything.. but woah.. 1.5 bar was incredible. So I tried a couple of different settings on my EBC to no avail, then tried my MBC in the same fashion to no avail.

Which led me to only one conclusion: wastegate. I have a TiAl 40mm with a .5bar spring.

Here's my thought-process (I might be completely wrong, that's why I'm posting): Because I was still, technically, pushing a shitload of boost (just wasn't making it all the way because of the coupler), I might have worn the spring in the wastegate out? Does this sound like a fair assumption?

Ideas please!

Thanks,
Mark

 

I don't think springs wear out very easily

 

maybe the wastegates just to small. I ve had issues before with a .4bar setting on internal wastegate which peeked 1.3bar. I always thought tial 44mm was the size to go for on t4 turbos.

 

That's what I was thinking at first, too, boby... but it has had this wastegate its whole life and I've never run into this problem. Maybe it's time for an upgrade anyway?

pwwatkins: I didn't either.. but I am out of ideas. I can't think of anything that would cause my symptoms short of what bobybeach said.

 

the wastegate may be too small. thats the prob im having right now until i switch to the tial next week. with the boost controller off does it hold at .5 bar for a minute before jumping up? thats what mine does. i have the hks 38mm right now bc they discontinued the 50mm and hks said the 38 would be plenty big enough. not the case tho. you may need to go with a bigger wastegate.

 

too small of a wastegate or bad wastegate placement

if the spring is worn out, which i've never heard of this happening then the wastegate would open early....

 

See.. this all makes sense and stuff.. but it was running perfectly fine before this boost leak.

It was running 19 psi on C16.. exact same setup.. no creep or anything.

I guess I'll just get a 44mm TiAl instead. Hell, it can't hurt anything.

Bigcox: It doesn't hesitate at all, it just goes. I'll bet if I didn't let off it'd keep goin' until the motor decided to stop going with it. :P When it was pushing 1.5 bar it didn't feel like it was going to let off.

 

One more thing... the wastegate is routed back into the downpipe, right?

One of the screws on the bracket connecting the bottom of the wastegate to the route to the downpipe is missing. It didn't appear as if it was causing any problems, though. There wasn't a noticable gap. But, now that this is happening I'm starting to wonder if I should get under there and take another peek.

 

You may have leak in the line to the wastegate.

Your wastegate may be binding partway open or even stuck partway open. If it is binding before full open it will act like a small wastegate and give boost creep. If it is stuck partway you will get the boost creep and late boost onset.

 

I have checked both lines (top and bottom) coming from the wastegate.. they're both in tact.

Could you elaborate more on that concept, 13BT?

 

A manual boost controller is basically a controlled leak in the wastegate line. If the pressure never gets to the wastegate it can't open. If it doesn't open the energy gets extracted by the turbine and ends up as more boost.

There is one more place there could be a leak. The wastegate diaphram. That could have gotten hot and cracked.

You may want to take the wastegate off and pressure test it's operation. Record displacement vs psi. Your wastegate is basically fully open once the displacement exceeds 1/4 of the poppet seat diameter (From: Pi*D²/4 = Pi*D*H). So if you have a 40mm manifold wastegate flange opening all you need is for the poppet to move 10mm or more and it is fully open.

You may also want to see if you can find some calibration instructions for your wastegate. Not too important though.

 

To cover all the bases...

Where did you connect the top line? Before the turbo?

Where did you connect the bottom line? After the turbo?

If both are connected after the turbo then no wastegate.

If both are connected before then no wastegate.

 

Check the vacuum lines to the wastegate to make sure there is no leak. Check the nozzles that attach these vacuum lines to the wastegate to see that there are no leaks.

I really doubt the wastegate is too small...

I am pretty sure it is a vacuum leak of some sort in the wastegate control system...even if you are running on just the spring it requires vacuum to actuate the wastegate.

 

Something to add:

I recently installed a newer (hybrid) turbo on my Turbo II. The hybrid was equipped with an aftermarket Turbonetics 10psi WG spring... For whatever reason I pressure tested the WG actuator diaphram and the thing leaked.

Not knowing if this was normal, I pressure tested a spare stock WG actuator I had laying around, and it held pressure...

The theory is: If pressure is bleeding off from the leaking diaphram before the WG spring (which opens the WG), then the boost will just spike uncontrolled since the WG door never opens. However, I've been running this turbo and it's leaking WG actuator for about 2 months now, and I only see about 2psi of creep... The reason is that the actuator leak is obviously not a major leak, therefore 95% of the pressure is still able to push on the spring and open the WG. And since it's a sustained pressure, there's no chance for the diaphram leak to actually cause the WG door to shut during boost, from a loss of pressure.

At least that's my personal experience and analysis.

That being said, a great way to help isolate the problem is to simply run no boost controller, and allow the WG to operate on it's spring alone... This will narrow down the problem to the WG itself, and limit the suspect components.

How long have you had the "boosting problem"?

 

Another simple yet destructive failure is a melted line to the wastegate. I would run a new line from the lower wastgate port to the manifold and disconnect the upper port all together. If it still doesn't work take the wastegate off and test it.

 

No it shouldn’t make much of a difference. Since the pressure refill from the vacum hose is much greater than the pressure leak in the wastegate.
The internal wastegate Diaphrams are different design and don’t suffer from that problem.
Some Fuel regs also suffer from this issue. if you test with a syringe they wont hold the pressure, but if you uses a continues source of vacum or pressure flow then they work perfect even with the vacum leek.

I guess it does ultimately depend on the degree or size of leak, but i think what you found on your wastegate is normal and unavoidable.

 

Wow, thanks for all the replies guys. I was about to just call it quits.

13BT, in response to your questions:
1) The top line off the wastegate is plugged into the UIM,
2) Bottom line of the wastegate is plugged either into the Profec's boost solenoid or the MBC,
3) It might also be noted that the "Boost source" for the controllers is a vacuum off of my BOV.

@Erik: The story is the car has been stuck at what was presumably wastegate pressure rate (.5 bar) for a few months. Last night when I was piecing my new intake together, however, I came across a split in one of my intercooler couplers. After sewing it shut with duct tape and test driving, it was clear that this was the problem. But now the boost is unregulated. I've tried an EBC, MBC and no boost controller to no avail... which is why I decided it was wastegate-related.

@cozmo: See? I didn't know that! I learn new things every day. And yeah, I just can't believe that the wastegate would magically be too small after working perfectly for 3 engines at up to 19 psi.

Thanks again for all the replies, I'll try some of the suggestions ASAP.

 

Thats your problem there. The top line should not be pluged in to pressure side. otherwise as the boost gets higher the dipham pressure down fights the wastegate from opening. It shoud be to atmosphere or to vacum like pre turbo between air filter and turbo compressor.

 

Hmm, I understand your logic.. but I tried running it without that line plugged in too. Still was skyrocketing.

 

No lines = no wastegate function.

Use only one hose for a final test.

Connect from the intake manifold to the lower port on the wastegate. Make no other connections. If this doesn't fix it you have a failed wastegate.

 

if the wastegate spring was worn out, it would be opening to EASILY, not sticking shut.

i'm wondering why you havent hooked the wastegate straight up to a boost source with no EBC or MBC and crap.

 

Been there, done that. I'm ordering a new wastegate.

 

You may be able to rebuild for less $. Get a new diamphram and spring. If you don't want to bother though maybe someone would want the old one.