Out of this world boost creep.

[aaronmatusz]

Hello folks,
I'm trying to run about 16psi, but I can't seem to manage it
even with the setup you see below.
At some point I'd like to safely remove the restrictor I have in
the exhaust. When I pull the restrictor out at present, it
creeps to 25psi at 3200rpm and shows every indication of
going higher if I stay on the gas. I don't want to see how
much farther it will creep for fear of damaging my new motor.

Pertinent setup specs:
FP exhaust manifold
FP 68HTA turbo with EVO III exhaust housing fully ported for
flow and enlarged waste gate opening.
Custom O^2 housing with Tial MVS WG
Full race 3" turbo back (with 1" restrictor plate at the tail to
keep boost creep sane)
2.3L stroker 8.5:1 pistons

I can't remember why I traded the original exhaust housing
for an EVO III unit and now I wonder if that was a mistake.
Perhaps it now flows TOO well?

Any thoughts?

 

[hurricanecris24]

You could just tune at 25psi. I had the same problem on my car with the e3 16g creeping 20+ only thing I could do to stop it was putting my cat back on for restriction which helped controlled boost.

 

[TSITurbo95]

When you went external off the o2 housing, did you port out the wg hole as large as possible?

 

[GRAVEDIGGER]

Are you sure you have the wastegate connected properly? Where are you getting your boost source from? You should be going from the compressor cover to the bottom port on the wastegate with the top port on the wastegate left open to atmosphere.

 

[thilaksharma]

i faced the same kind of issue on a green, i doubt the mvs is flowing enuff

 

[JusMX141]

These issues always seem to present themselves on turbos with Evo III turbine housings.

I recently installed an Evo III 16G on a customer car with a catless 3" turbo-back exhaust, Apexi N1 at the end. I knew creep would be a problem so I ported the wastegate hole until there was only about a 3/16" ridge around the outside for the flapper to seal, and I also shaped the inside of the housing to direct airflow toward the wastegate hole. Rock-steady boost at 10-12psi until he gets fuel mods....no creep whatsoever. This is also with an o2 dump on the car.

 

[aaronmatusz]

For the time being, I'm running a hose directly from a Dejon compressor outlet elbow to the bottom port on the MVS.
As for porting, I got a little skittish about removing all that metal. That EVO III housing is cast so thin, I felt as though I might grind right through it if I made it the way I wanted.
...I a thought I had just this moment:
I don't suppose the WG hole needs to round, does it? The hole is already as wide as I dare make it, but I think it could be made 'taller' without making parts of the housing paper thin.

 

[JusMX141]

You'd be surprised how large and unusually-shaped I've seen some wastegate holes on turbine housing where the flapper has been removed. Definitely doesn't have to look pretty- go for function over style.

Another thing is to shape the inlet of the turbine housing to direct airflow out of the hole instead of toward the turbine wheel a little. You can "D" the housing a little above the hole, leaving a small shelf beneath which does wonders for routing exhaust flow out the hole.

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[aaronmatusz]

Hmmm....
What you say makes perfect sense, so I will make the WG hole larger.
It's too bad the housing was already ported for maximum flow to the turbine.
Now there's very little material left to direct flow to the WG opening... I hope this doesn't come back to haunt me.