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BIG Boost Creep

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95RedRS

15+ Year Contributor
491
1
Feb 2, 2005
Dirty Jerzee, New Jersey
I have a small 16g. 2g ported exhuast manifold. Hallman MBC, 2g O2 Housing, Walbro 255, FIC 650's, Buschur 3in Turbo back, Pacesetter Downpipe 3 inch, GM MAF w translator, On a stock sidemount and wastegate.

When I got the car it was set at 17psi...Held steady nicely until a couple days of normal driving and occasional hard boosting i noticed it would hold at 17 then creep to 19-21 and hold there.

Lowered Boost to 14 and it held at 14 then Creeped BACK to 19 - 21 and held again. Lowered boost AGAIN and had the same dilemma. Took off the MBC and ran just the wastegate. Held at a steady ten until 4500 RPMS then it CLIMBS QUICKLY to 20psi and it would keep going if I wanted to push it.

I thoguht boost leak but that usually drops boost not make it gain that aggresivly. Couple trubo buddies of mine suggested there Might be a hole in the vacumn line and or the vacumn line is not big enough.

I perosnally think my wastegate just won't hold after a certain RPM and it gives out under the boost Load.

Anyone have a clue?
 
95RedRS said:
I have a High Flow cat.
Doesn't matter, every car is different. My old small 16G use to creep to 24+psi by 6k with 2.5" exhaust and 2.5" hi-flow cat. Proper porting of the turbine housing inlet should take care of your problem, this has been done many times.
 
Understood. Seems simple enough. Good thing i know a professional porting guy ;)

I take it this is the process of a Ported and clipped turbo?
 
95RedRS said:
Understood. Seems simple enough. Good thing i know a professional porting guy ;)
Nothing to do being a professional porter or not, the area of porting for boost creep is very specific for DSM application only, knowing where to port is the key. Follow the two links posted above and you will be fine, most people I helped out on the site on the same issue starts off with an already professionally ported turbo as they mainly deal with increasing spool and flow rather than boost creep controlling. Myself started with a $200 3piece porting job by TurboTrix two years ago, ended up re-porting all three pieces again myself.

I take it this is the process of a Ported and clipped turbo?
Not quite sure what you meant here.
 
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