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Old 04-01-2015, 03:53 PM   #1
k_duraman
Scooby Newbie
 
Member#: 139843
Join Date: Feb 2007
Chapter/Region: International
Location: in front of an evo
Vehicle:
2006 sti 2,5 ppp
blue

Default what cr should i go for on my build?

Hi everyone. I live in greece and we have 100 octane pump gas here. I am building my 2006 2.5 sti with
pistons ????
manley 83mm crank
pauter rods with arp625
Arp 625 headbolts
Fully built supertech kit heads
Rcm 11mm oil pump
gtx35
aps 725 fmic
2006 lega 2,5 long runner inlet manifold
Id1000 injectors
etc. I have pinned the block and
ported and polished the heads

My dillemma is what compression pistons should i go for? I don't want to rebuild the engine every 20k. I want a 600+bhp dd. I want compression i don't want to go for 8,8,5cr. So should i go 9.1.0 or 9,8.1.0 ?
Thanx in advance
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Old 04-01-2015, 04:36 PM   #2
user1029
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Member#: 57064
Join Date: Mar 2004
Vehicle:
2008 STi IAG built
HTA86, Meth, 272s, Cos IM

Default

600bhp, just go with stock compression. Keep it simple
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Old 04-01-2015, 04:51 PM   #3
some dude
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Member#: 100300
Join Date: Nov 2005
Chapter/Region: MWSOC
Location: MIC|-|IG/\N
Vehicle:
06 WRX
CGM

Default what cr should i go for on my build?

Why try to run high compression when you have a turbo? I agree, keep it simple, keep it knock free. Use your turbo to make power.

Since you already have your turbo, can't you calculate the optimum compression ratio you want using the turbos compressor map?
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Old 04-02-2015, 03:14 AM   #4
GuyGc8
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Member#: 417014
Join Date: Mar 2015
Vehicle:
1999 WRX
white

Default

I'd go 9.1.0

it's higher than stock,
still knock friendly,
and should help reaching full boost quicker.
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Old 04-02-2015, 10:18 PM   #5
Razgeiz
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Member#: 358782
Join Date: Jun 2013
Chapter/Region: MWSOC
Location: Springfield, Illinois
Vehicle:
2013 STi
DGM

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Run stock compression and let the turbo do the work man. That gtx35 can do it and then a bit more
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Old 04-03-2015, 06:29 AM   #6
k_duraman
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Member#: 139843
Join Date: Feb 2007
Chapter/Region: International
Location: in front of an evo
Vehicle:
2006 sti 2,5 ppp
blue

Default

Thanx guys I have decided to cancel the order on the 83mm crank and stick to the oem 79mm. And use 8.9cr ceramic coated custom je pistons. It will give me a bit more rev range I think.
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Old 04-03-2015, 07:45 AM   #7
user1029
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Join Date: Mar 2004
Vehicle:
2008 STi IAG built
HTA86, Meth, 272s, Cos IM

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^^^I approve
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Old 04-07-2015, 12:10 AM   #8
JSTOUMBA
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i have had no problems running 9:1 cp for my build however keep in mind that spark knock will creep up on you pending on your boost level.... e85 and lower boost solved that for me but be aware
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Old 04-07-2015, 01:35 AM   #9
subi400
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Join Date: Jul 2009
Chapter/Region: NWIC
Location: Hayden, ID
Vehicle:
1996 Impreza outback
Green

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Quote:
Originally Posted by k_duraman View Post
Thanx guys I have decided to cancel the order on the 83mm crank and stick to the oem 79mm. And use 8.9cr ceramic coated custom je pistons. It will give me a bit more rev range I think.
How high are you wanting to rev? If you are not revving higher than the stock 7k redline or whatever it is, then the 10mm pump would most likely be sufficient for your engine build. If going higher than stock redline then yes the 11mm oil pump will be the ticket since your engine has the single avcs on the intake cams.
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