Stuck Waste Gate, or just a boost leak?

[sixpatch]

On my 87' 7mgte, I'm spooling right at 6psi (according to the stock gauge) at 3100 rpm, but then it begins to bleed off as RPM's increase. I'm hearing a loud hiss the whole time I spool, but since I'm not familiar with the Supra's, I don't know how much of that is normal.
I've grabbed my wastegate actuator rod and tried to move it by hand, but it doesn't move at all (front to rear). Again, I'm new to supras and not even sure if the gate actuator should allow movement by hand or not.
I'm not hearing any blow off when I occaisonally tip over the 6psi mark, and not even sure if I should hear anything at all. Help!

 

[MDCmotorsports]

You need to physically inspect all the boost hoses for cracks, tears, or rips. Also, inspect the bypass valve. If you can blow through it, its toast. Report back.

 

[sixpatch]

I've visually inspected all the hoses I can, and found nothing that would produce the loud hiss that I hear while spooling. I'll be sure to check out the bypass valve tomorrow.

 

[hvyman]

Put a wrench to all your ic pipes.

 

[sixpatch]

Yeah, all the clamps are snug.

 

[sixpatch]

Im still wondering about some things. In normal operation, should I hear the famous "TISS!!" when I shift?
Should I maintain 6.25psi from 3100 to Redline? How much drop off should I see?
Is this what they call a "Recirculating System"?
Should I be able to operate my waste gate by hand (while still connected to the bypass valve) using the actuator rod?

 

[GrimJack]

Im still wondering about some things. In normal operation, should I hear the famous "TISS!!" when I shift?
Should I maintain 6.25psi from 3100 to Redline? How much drop off should I see?
Is this what they call a "Recirculating System"?
Should I be able to operate my waste gate by hand (while still connected to the bypass valve)?

Not if you are using a stock bypass valve.

Depends on what gear you are in, and what kind of boost gauge you are using. If you're relying on the stock gauge, well, it's better than guessing, but not by much.

Yes.

Your wastegate should not be connected to your bypass valve. The bypass valve is on the air intake. The wastegate is on the exhaust side. You will not be able to move the wastegate by hand. Hooking it up to a bicycle pump and increasing the pressure to ~10psi should make it open, however.

Lastly, IMO you need to pressure test your intake to find boost leaks - either that or completely remove it from the car for a physical inspection, and that's a lot more trouble than it's worth. Usually the plastic pieces are starting to split along the seams under boost, and heat from the exhaust manifold has cracked the turbo compressor exit hose.

 

[sixpatch]

If it turns out to be the IC hard lines, is there a good source for OEM versions of those, or am I going to be stuck aftermarketing this stuff?

 

[GrimJack]

It's cheaper to go aftermarket. And they work better, too. Kind of tough to justify OEM parts in this case.

 

[lumpy]

I used an EVAP smoke machine at work to find my boost leak. There was about a two inch tear in the hose right off the compressor housing just after the clamp. There was no way for me to physically see it. I remember another kid came in last year for the same hose and it retailed for like $135.... Bogus. At that price it's very hard to justify going w/OEM.

 

[sixpatch]

Sounds about right. It's just that the car is entirely original, and my intitial intention was to keep it a "Survivor". Looks like I may have to adjust that idea.

 

[lumpy]

And you can keep it all original if you want unless the piece you want is discontinued (you can still get oem intercooler pipes no prob). Even then you can find usually something somewhere. Pretty much comes down to what you want to do w/the car and your budget/time avail.. You still gotta figure it out..

What do you have on the car for exhaust, intake? any boost controller (is it supposed to be over 6-8psi for some reason? that's about right for stock boost pressure wise if it's ALL stock..)? The factory bypass valve shouldn't make much noise between shifts, unless you have an open element filter (K&N), but even then it shouldn't be very audible. And if you do have a k&n-type filter it may be the normal spool sound you're hearing. Does the car feel like it's got no balls or struggles to make the 6psi? Just tryin' to think outside the box here. Any way you can get a vid or audio of it??

 

[sixpatch]

It's not so bad actually. It's just one of those things that feels a little off. I've got nothing aftermarket on the car. No K&N or anything. It just seems like it doesn't hold the boost like it aught to (Boosting up to 6psi or so at 3200rpm, and then immediately bleeding down to 5psi by 4000rpm and continuing to drop as rpms increase). Then the amount of hissing I'm hearing seems to be way too loud for a stock setup. I really just need to drive a Mk3 that's in good shape so I've got a baseline comparison. Too bad I'm the only one I know with one.
It's got balls, just not quite what I think it should have. Maybe I'm just used to my brothers boost happy Non STI, Turbo WRX (220 stock hp)

 

[lumpy]

It's pretty easy to do at home if you've got air. Take off your air filter/intake hose etc. and tape the inlet of the turbo shut then carefully blow air into the nipple on the "3000" pipe where the bypass valve goes. be quiet and listen for the hiss. Hope that helps!

 

[sixpatch]

Ok. Here's an update. Looks like the waste gate actuator was in fact sticking a little bit. I spent an evening just moving the actuator arm around (in all directions) and felt it catching some. Whatever was sticking eventually smoothed out, and I'm hitting 7psi (on the stock boost gauge) sometimes. Still need to check for some boost leaks, but my "sticking" issue seems to be resolved. Thanks for all the help.