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Discussion Starter #1
i'm having a boost creep problem with my sp61gt. it's internally wastergated. i got the boost controller backed all the way out (joe p manual) and i'm still hitting 19psi in thne upper rpms. anyone have any ideas on what this can be from
 

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DO WORK!!
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is your turbo brace hitting the waistgate arm at all? Mine was doing that but I crept up to 24psi

I just put about 5 washers in between the brace and the turbo and that fixed it. I have also heard about the accuator arm not being "pre-bent" and causing problems.
 
J

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If I remember correctly, You are using the BIC DDP. right? When my brother and I installed one on his car, it made the boost creep WAY up. Slammed into spark cut.
We installed an intake, and backed out the screw in the AFM, and still hit spark cut.
Long story short, took the turbine housing off and ported the crap out of the wastegate, nice chamfered flow into into it, and elnarged the outlet.

Fixed the creep issue.

My SP61GT turbine housing is sitting on my floor, along with my manifold.
...getting dremel lovin'
 

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DO WORK!!
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Mabey the boost controller is crap.... or hooked up wrong I had to find a good vac source becasue the compressor port was covered by the waistgate accuator bracket. Seems like you have tryed everything though.... but its gotta be something stupid.
 
J

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Ehhh, look again. The flapper on the SP61GT is HUGE. There is room for alot more porting.
Close the flapper and trace a pencil line around it, then open it... I've removed quite a bit of material...
There could be something else causing your creep issue, but the horrificly efficient nature of the DDP will cause boost to rise.
I'm sure you'd rather not have to take the tubo off again, but, I'd lay money on that being your problem.
 

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Discussion Starter #8
YEA, i really dont want to remove the turbo again.. i'm goin to see if i have a bad boost controller
 

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put a high flow cat and i bet it will solve your problem
 

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Destroyer of Turbos
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might be the wastegate hitting that little plate on the bic ddp and not opening fully causing boost stability problems.
 
J

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I'd be interested in how a high flow cat is going to help the situation in any way?

I'd also be willing to bet he has one, as he has an SP61GT, and a DDP...
 

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Discussion Starter #12
right now i have a test pipe. if it is not my boost controller than i'm going to trade this DDP for a defcon. i called larry and he has no clue
 

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i <3 fitness chicks
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If you are expecting it to peg a certain psi and hold there steady then keep dreaming. It's not an external w/g therefore it won't perform like one. Internal gates will have boost creep.

If you are trying to run, oh say 12psi, and its hittin 19 then check the hoses to the actuator and make sure they are correct.

Also it would be a good idea to pick up an ebc. Mbc's are garbage.
 
J

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Why would you trade the best downpipe available for these cars, for something of inferior quality? You WILL lose HP if you do that.

I know it's alot of work, but porting the wastegate will fix the problem, is free (assuming you have a dremel, I think you do), and you won't lose HP.

Also, internal wastegates are quite good at holding boost at higher pressures.
I'm not sure how anyone came to think one is "better" than the other.
Internal and external wastegates are different, for different packaging, and requirements for different turbo systems.

EDIT: if you still have your stock cat, throw that on. If it fixes it, or partially fixes it, then you know it is because of the DDP...

Why you ask?

Remember when you put your catback on?
Boost went up, right?

Turbos don't run off exhaust, they run off heat and pressure, more specifically the pressure difference in the manifold and the exhaust. When you lowered the backpressure of the exhaust with your catback, you INCREASED the DIFFERENCE in pressure before the turbine, and after the turbine. (exh. manifold pressure stayed the same, exhaust pressure lowered=larger differential)
This makes the turbine wheel more eager to spin=more boost.

What does this have to do with the downpipe?

The stock downpipe (elbow) is a fairly high pressure area, as the exhaust manifold vents directly into it (wastegate).This causes sort of a "pressure equalization" i.e. turbulence. This keeps the pressure difference between the manifold and exhaust small. This makes it more difficult for the turbine wheel to spin, and create more boost. i.e. easier to control.

This is why the DDP is such a good idea, and was used in the group A MK3. It is the most efficient setup possible for an internal wategate, the only catch is: the wastegate has to be big enough to regulate boost. This is also easier when you run higher boost on an internal wastegate. As I said before, internal wastegates are excellent for regulating higher boost levels (~20psi)

If an internal wastegate is good enough for a Group A Supra, it's good enough for me.
...That was quite an edit...
 

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Discussion Starter #15
since when are MBC garbage? i had a profec b spec 2 and that thing was fuckin crap. i'm going to do some more investing and see what the problem is.
 

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wastegate hose is pulled
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Step one would be to remove the boost controller and run a line straight from the compressor cover to the wastegate actuator. See if it will hold wastegate spring pressure then. If so, it is the boost controller, if not, then it is time to investigate the actuator, wastegate flapper, downpipe and any clearance issues between them. The very last resort would be to hog out the wastegate hole in the turbine housing. It will encourage premature cracks in the housing but, may be nessicary as a last resort.
 

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I hand ported every turbo myself. There is no more room for porting those WGs. Those Wg holes are opened up to the maximum. What is interesting about this case is that he told me today on the phone that the first week it did not creep.
 
J

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Or just throw your stock downpipe on. If it fixes it, then porting the wastegate will fix it.
I know I sound like a madman, and maybe someone more articulate could explain it better, but trust me....
Actually could a more articulate regular explain it?
Since I'm a nobody here...
yet...

Also, high EGTs will cause boost creep on internal wastegates...
and so will too much cam related blow-through/overlap...
But that is for another time, young jedi...
for another time...
That is not your problem.

But you could ask me how if you wanted...

But I'm sure an established, knowledgable member of this community could get their point across better.

P.S. if you haven't read "Maximum Boost" by Corky Bell yet, then shame on you!
-not gospel- but some damned good basic info!
 
J

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Larry, that you?

I have the SP61GT you sent me 6' away. Yeah it was ported a bit, but there was definately room for some more, not a huge amount, but significant nontheless.
The biggest improvement that could be made would be to make it easier for exhaut to escape. i.e. chamfering around the hole, maximizing the difference between the area above the top of the hole, and below the hole, and smoothing the area a bit.

Also, porting will not cause premature cracks in the housing, so long as care is taken to eliminate "hot spots"...

It is interesting that it just started up now though....

The wastegate could be getting stuck on the divider...
I'd check it for any marring or contact, you would be able to tell if it were contacting.

I'm just trying to shy you away from losing any HP with an inferior DP as a solution, esp. when you are using such an awesome turbo.
 

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wastegate hose is pulled
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JalopySiR said:
Also, porting will not cause premature cracks in the housing, so long as care is taken to eliminate "hot spots"...
You are wrong there bud. The thickness of the cast iron is key to preventing it from cracking. No expertise nessicary there, just one look at the hot side of a well used CT26. ;)
 
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