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Old 03-11-2009, 09:41 PM   #1
vanillajuice
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Default compression ratio

so after asking around, everyone seems to have a different answer, does anyone actually know what the compression ratio for a 2.5 litre block with wiseco forged pistons(stock bore) and the 2 litre heads and sti head gaskets?
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Old 03-11-2009, 09:46 PM   #2
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You will be near 9.0:1

However.... what are those rated at??? I need that info to know... It will be higher always
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Old 03-11-2009, 09:48 PM   #3
vanillajuice
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what are what rated at?
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Old 03-12-2009, 03:06 PM   #4
FuJi K
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Quote:
Originally Posted by vanillajuice View Post
what are what rated at?
those pistons, what's their advertised compression ratio??? advertised for STi EJ257?
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Old 03-12-2009, 03:42 PM   #5
AWDWRXLOVER
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here is what Maxwell Power told me based on 8.2 cp s
8.95:1 with factory HG
8.57:1 with 0.040"
8.38:1 with 0.051"

if you get ots weiscos they are 8.9 so it would be higher than that.
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Old 03-12-2009, 03:48 PM   #6
andya
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I think he just soiled himself... What pistons did you get again? I did not pay attention..
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Old 03-12-2009, 07:22 PM   #7
vanillajuice
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wiseco 99.5 bore
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Old 03-12-2009, 08:17 PM   #8
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its about 9.1-9.2. Advertised by wiseco for an sti is 8.9. But with a stock sti headgasket with wrx heads, it is going to be between 9.1 and 9.2. And your gonna love it. I have this setup and LOVE it. I got off the cometic gasket about 5 months ago, and I'll never go back.

DK

I have the 100mm bore so my CR is even a little higher
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Old 03-12-2009, 08:20 PM   #9
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Quote:
Originally Posted by vanillajuice View Post
so after asking around, everyone seems to have a different answer, does anyone actually know what the compression ratio for a 2.5 litre block with wiseco forged pistons(stock bore) and the 2 litre heads and sti head gaskets?
depends on how much you've decked the block and heads

seriously...its nothing but math depending on the previous two questions, beyond what you've supplied.
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Old 03-12-2009, 08:51 PM   #10
vanillajuice
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decked the block and heads? the hell does that mean? lol
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Old 03-12-2009, 09:10 PM   #11
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The block was new... the heads????? MYSTERY!
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Old 03-12-2009, 09:15 PM   #12
vanillajuice
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haha oh god those heads, lol....btw ^^this guy is da man!
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Old 03-12-2009, 09:17 PM   #13
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get the 98-99 legacy outback 2.5 NA twin cam motor headgasket. it is really thick and will help bring down the CR
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Old 03-12-2009, 09:25 PM   #14
vanillajuice
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oh i dont want the CR down...i want it UP! about 9:1 is around where i want it :-D
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Old 03-12-2009, 11:34 PM   #15
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Quote:
Originally Posted by andya View Post
The block was new... the heads????? MYSTERY!
Quote:
Originally Posted by vanillajuice View Post
haha oh god those heads, lol....btw ^^this guy is da man!
then just cc them...that's what you'll ultimately have to do with them anyhow to get a 'true' CR
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Old 03-12-2009, 11:54 PM   #16
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Quote:
Originally Posted by Homemade WRX View Post
then just cc them...that's what you'll ultimately have to do with them anyhow to get a 'true' CR
It's an inside joke.. They were ported/butchered by original owner, re-worked by one machine shop, then worked again by our local machinist. They are as good as they can get without turning them into Top Fuel drag heads. The chambers were just cleaned up a little and minimal material removed.
I like giving Josh a hard time about them and he's a good sport. After all he now has a running hot rod!
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Old 03-13-2009, 12:29 AM   #17
vanillajuice
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^^haha yea...this thing picks up alot quicker than the 2 litre did. loving it so far!
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