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Unread 2012-03-16, 10:01 AM   #1
Dart_SI
 
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Default Turbo gurus, need advice on boost issue.

The issue: I have a gt2871 internally gated. Boost picks up kind of slow.

Im tuned for 26 psi. The turbo holds 26 psi until I hit roughly 5300 rpm, then it goes down to 20. There are no boost leaks.

I THINK I may not have enough reload on the wastegate. Anyone agree or have a different opinion?

Its a 2010 cobalt ss.

This turbo is proven to hold full boost till 6700rpm.
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Unread 2012-03-16, 01:01 PM   #2
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figures nobody has a clue. lol.
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Unread 2012-03-16, 01:33 PM   #3
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Or they are all at tx2k12 lol.
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Unread 2012-03-16, 01:59 PM   #4
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bov?
exhaust flow?

if you remove the cat/muffler and try it will it hold boost or still fall off? how is it "proven to hold boost" someone elses setup?

< been playing with turbos since the mid 1980s
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Unread 2012-03-16, 02:01 PM   #5
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Originally Posted by Pny Pwr View Post
bov?
exhaust flow?

if you remove the cat/muffler and try it will it hold boost or still fall off? how is it "proven to hold boost" someone elses setup?
the turbo isnt so small that boost tapers up top like on a stock turbo.

my exhaust is 3" straight pipe with no cats, mufflers, or resonators.

here is a video of whats going on. dont have an MBC or EBC, its the stock solenoid.

http://www.youtube.com/watch?v=NMi4HmpULyg
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Unread 2012-03-16, 07:23 PM   #6
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Your past the turbo's limit. Look at a compressor map....

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Unread 2012-03-16, 07:56 PM   #7
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Its not a true gt2871. Its actually a BNR2871, which is a k04 hybrid. It will hold 26psi to redline. It does on 4 other cobalts with it.
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Unread 2012-03-16, 08:03 PM   #8
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Its not a true gt2871. Its actually a BNR2871, which is a k04 hybrid. It will hold 26psi to redline. It does on 4 other cobalts with it.
Probably helps to explain everything then.....

what bov?
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Unread 2012-03-17, 06:51 AM   #9
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I'd get a manual boost controller and see if the problem still exists. Sometimes you can not have enough tension on an internally gated wastegate also causing the flapper to be pushed open under high boost.
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Unread 2012-03-17, 06:03 PM   #10
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swapped to an MBC and problem went away. my turbo spools a little slow tho, may be a tune issue.
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Unread 2012-03-23, 04:06 PM   #11
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swapped to an MBC and problem went away. my turbo spools a little slow tho, may be a tune issue.
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