Another Overboost

[nightracer91]

I have read some threads about overboosting but I can't seem to get anything that adds up to what my car is doing. I have a built engine, fmic, 3" turbo-back exhaust and a Big 16G Turbo. I bypass my MBC and it will pull to 8-9 psi, then creep to 14-15 psi. If I hook up the MBC all the way down it does the same thing. If I turn it up a little bit, it will pull to 10-11 psi then creep to 16-18 psi. I keep running around in circles. I just want some guidance on what to check into next.

 

[oplix]

Is your turbo ported? It might be the turbo that is causing the boost creep. This will often happen with big 16g's and 3' turboback's

 

[nightracer91]

No I don't think it is. Can I port the housing and still use the same flapper?

 

[Chicken Patty]

Hello,

Not to hijack this thread, but I am having the same problem. If you guys can help me out, it'll help both of us fix this issue. I am interested in knowing if for example I bought a 34mm flapper from FP, if you have to port the flapper area of the exhaust housing? Or can it be drilled bigger?> THanks in advance.

 

[TurboAnything]

I just use a carbide cutting burr and open op the hole. I leave just enough material that the flapper seats all the way around. You will also want to shape the hole on the inside of the turbine housing to promote better flow through the flapper hole out to the O2 housing.

 

[RipperXX]

Port the waste gate passage and entrance.

 

[kazzam]

what they said; above. port the flapper hole. or get a ported 2g housing. those can be opened up pretty good. i had 1 on a 50 trim with 0 creep. i moved to a tubular and super happy with it. best

 

[Bud92gsx]

It's been said the 16g's like to creep..Mine like to creep to about 20 psi, all the while still going faster..My MBC is set to stock wastegate pressure, which is what 12psi on these turbo's.. I have also heard that switching to a 38mm external wastgate also helps with creep..And everbody knows that porting will help as well.

 

[JayRolla]

what they said; above. port the flapper hole. or get a ported 2g housing. those can be opened up pretty good. i had 1 on a 50 trim with 0 creep. i moved to a tubular and super happy with it. best

The o2 housing really doesnt have anything to do with creep. Actually a higher flowing o2 housing will cause more creep. Your 50 trim didnt creep because they are not really prone to do it.

Your high flow 3" exhaust is what is causing your creep. The air flows to fast past the wastegate flapper and doesnt bleed off like it should. Like stated you need to correctly port the wastegate passage so its easier for the air to bleed out the wastegate. Running 2.5" exhaust also helps since it slows the air down and more can reach the flapper.