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Old 02-26-2008, 10:40 PM   #1
Scooby Specialist
Member#: 127704
Join Date: Oct 2006
Chapter/Region: TXIC
Location: TX/Austin
2013 Hybrid
Needs an 05STI

Default Suggested Max boost at different altitudes

Running an 06 STI, Dominator one with supporting 'bolt' on upgrades.

Currently at sea level 0n 91 oct with a little TORCO - usually target will be 21 psi, have run it at 22psi and it is fine, i.e. no log knock, (I get a little knock light action in the 4500-52500 area intermitantly at 22psi, still no recored log knock) correction etc, fueling is good, but do you think at 4500 ft this is running a little more then it should? just opinions, Im interested in how you more experienced guys would set your car up boost wise?

Part two, moving to sea level and 93 oct (no TORCO) assume 22 psi then would be a good max? again opinions, presuming my car run fines at 12.5 atm with 21psi
I know the total pressure will change etc but whats your guys personal preference
As ever
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Old 02-26-2008, 10:52 PM   #2
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Member#: 47145
Join Date: Nov 2003
Chapter/Region: MWSOC
Location: Henderson, KY
2012 Gas Saver


93octane @ near sea level I run 24psi daily w/ a TD05H-20G on a 2.0L, no knock with AFR of 11.4:1 at full load.
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Old 02-27-2008, 12:52 AM   #3
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Member#: 122595
Join Date: Aug 2006
Chapter/Region: NWIC
2005 LGT Wagon


Are you running a MBC?

If you're using the ecu to control boost, the ecu will automatically adjust your target boost. The only problem that might arise is if you are running a very high WG actuator spring. In that case, you will need to adjust your WGDC atmospheric compensation table.
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Old 02-27-2008, 02:21 AM   #4
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Member#: 140163
Join Date: Feb 2007
Chapter/Region: MAIC
Location: 3MI Racing
03 STi


all the stage 2 stis in denver/boulder are maxing out around 16-17psi. my friend who's a tuner out there has his bugeye with a gt30r only running 16psi of boost on e85.

Last edited by nhat; 04-02-2008 at 02:25 PM.
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Old 02-27-2008, 02:49 AM   #5
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Member#: 94490
Join Date: Aug 2005
Location: Australia

maxing out what? sorry noob question!
i am running 22psi through a vf34/p20 with 3" zorst+avcr on an 02STi with 11.4AFR also.
everything else is stock. my tune is getting there. and 300g/sec is a bees foreskin away.
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Old 02-27-2008, 03:40 PM   #6
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Member#: 36033
Join Date: Apr 2003
Chapter/Region: SCIC
Location: Tuning Lab
CEO PhatBottiTuning
2006 STi GTX3582 + Meth


I run 23-24psi on my 16g'd 02wrx on 91 octane at 3000ft.

I have also run 23-24psi on my green'd 06STi on 91 octane at 3000ft.
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Old 02-27-2008, 03:51 PM   #7
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Chapter/Region: RMIC
Location: SLC
2013 Wrx Hatch


I sit at 4,327 and run 17lbs on the TD04. Knowledge of BCS tuning is critical at higher altitude.
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Old 03-01-2008, 02:23 PM   #8
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Join Date: Dec 2006
Chapter/Region: NESIC
Location: six- one-seven

A compressor map will let you know what the compressor RPM will be at various pressure ratios. This will tell you exactly how much boost you can run.
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Old 04-02-2008, 12:10 PM   #9
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Member#: 28291
Join Date: Oct 2002
Chapter/Region: RMIC
2015 WRX


nail on the head apex... the TD04 (assuming that the 13T picture floating around is what is actually in the wrx) has a max pressure ratio of ~2.63 @ approx. 0.15m^3/s... in my experience at 7200ft, i traverse the left side of the compressor island, somewhere in the 73% efficiency region (look at the map, you'll see what i'm talking about). i am currently running 13psi max boost, and when atmospheric pressure here is ~11.4, that translates into a pressure ratio of 2.14 -- well under the limitations of peak efficiency of the turbo. i say find a map of the turbo you are running, check IDC's, and tune boost based upon a combo of your IDC and max pressure ratio...
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Old 04-02-2008, 12:20 PM   #10
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Chapter/Region: International
2003 JDM STI
World Rally Blue


^^ Wow, couldn't have read a better explanation. I run a IHI VF30 and its a b!tch to find compressor maps for it
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Old 04-02-2008, 03:26 PM   #11
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Chapter/Region: NWIC
2005 LGT Wagon


Even though compressor maps are based on PR, the ecu altitude compensation is based on percent reduction of the MAP target. You can change the modeling though. Some ecus use a table but some use a linear equation.
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Old 04-03-2008, 12:54 AM   #12
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Join Date: Jun 2007
Location: EVO 8 built 2.4L
I Parted out WRX
for my Pilots License :)


Kinda of depends on how you want to look at this... for example, I live at 6700ft altitude.. my vf39 WRX is making 18 maybe 19 psi on my boost gauge... however when logging, the actual manifold pressure my engine is seeing relative to sea level is in the 15psi (about 14.5psi at redline) area... So... I run my turbo as hard as I want to based off the gauge, even though of course at this altitude it's not making the same power, the turbo itself is still working very hard...

And yes.. it sucks living up here, however, there are a few things you can get away with.... im running 93% IDC now after I put on an STi TMIC, so I now need injectors, but I was "getting away" with stockers for a while... my driveline doesn't see quite as much abuse...clutch will hold a higher level of mods.... yet, when I go to the drag strip, I can slap LS1's around like nobody's business.... even though my times arn't as impressive
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