boost creep...any ideas?

[mdss]

Hi guys, sorry to ask for help on my very first post!

I have some boost creep on my r32 gtr.

Its got standard turbos, uprated intercooler, apexi air filters 3" down pipes,
3" decat and full 3" exhaust.
I have removed the restrictor to achieve 1 bar


I read another post about fitting a 2.25" exhaust restrictor to stop the creep so i ordered one from thor racing and although this has helped it has not completely eliminated the creep.

It runs 1 bar but the issue i have is when it comes on boost it hits 0.9 bar and then rises and holds 1 bar when over circa 5500rpm.
I would like it to make a bar and then hold 1 bar.

Is it the cases that if i was to fit standard down pipes i could do away with the restrictor and then i would not have this issue?? Or maybe its the intercooler????

To be honest i am a bit perplexed so any help is much appreciated.
Sorry for the long post.
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[Skym]

Internal wastegates are not opening quick enough or not enough which causes the turbo's to overspeed at higher rpm, which is common with stock internal wastegates. Higher rpm = more air + fuel thus more exhaust gas is created and not enough is being bled off by wastegate hole on back of turbo (stays in exhaust housing driving the turbo's exhaust wheels) at higher rpm.

Adjusting wastegate hole size on back of turbo's + bigger wastegate flap is one way people usually solve this boost creep problem. Another way some solve this problem on single turbo engines is by fitting external wastegate that has a bigger diameter hole.

Boost restrictor helps the stock single solenoid control boost level. I posted a link showing the testing someone did while ago (another thread) with different size restrictors + stock boost control solenoid (proper way to raise boost level is via Nistune / stock ECU, not by removing boost restrictor). The other options is top of the line HKS or Blitz boost controller (has a better solenoid) if remove boost restrictor.

[Dragon Humper]

I wouldn't be all that worried about a 10th of a bar in creep. If you were starting at .9 and climbing to 1.3 and it got worse as you put more load on the motor (ie: grabbing more gears), then I would be concerned. If it becomes a big issue you can take the exhaust housings to a machine shop and have them mill bore out the wastegate holes to just smaller than the flap. The factory holes are pitifully small.



Jon.

[mdss]

Thanks guys much appreciated,
to my knowledge i dont think i had this problem when the cat was still in it only started happening when i removed the cat.
Is putting the cat back in a good option?

thanks again

[Skym]

You're welcome. The cat can become a restriction (creates back pressure), so slows the exhaust gas, turbo down which should reduce the problem (smaller exhaust = similar result's). Turbo's create boost based on rpm, so higher boost level = higher rpm on turbo and more flow = higher rpm on turbo.

Can see how high in rpm turbo's get via looking at this balance test for turbo's -

http://www.turbo.co.nz/alltech/service.php?Page=Turbo

Sport cat is higher flowing (I think was less amount of filter holes but bigger holes) and because internals are made of metal it shouldn't blow the internals out on racetrack. Also can handle higher exhaust temps.