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Old 01-27-2019, 09:10 PM   #1
turboedbug
Scooby Newbie
 
Member#: 155981
Join Date: Aug 2007
Location: Graham Washington
Vehicle:
1969 vw bug
ej20k ems stinger 4424

Default Compression ratio

Hey everyone. I am going through some math here and would like a second set of eyes to verify what i have going on.

So this is a ej257 factory new block.

Ej251 heads with volume at 49.5

At tdc i verified the total volume at 25cc

The combustion chamber of my sohc heads is 49.5

So combined volume of 74.5

Stock sti head gasket .6 gasket bore 100

Piston bore 99.5

Stroke 79.

When i punch these numbers in i get 8.7 to 1

Does this sound right? Its been quite a few years since i have calculated a comp ratio
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Old 01-29-2019, 11:25 AM   #2
Savrioreca
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Member#: 497071
Join Date: Jan 2019
Default looks correct

I may be new here, but your math looks spot on.

Especially since it looks to have an almost identical configuration to the EU STI.

The EU Sti has a compression ratio of 8.7:1

Reference:
https://en.wikipedia.org/wiki/Subaru_EJ_engine#EJ257
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Old 01-29-2019, 03:13 PM   #3
CarmelValleyWRX
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Member#: 453872
Join Date: Sep 2016
Vehicle:
2005 wrx wagon
48w

Default

i got 8.75:1
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Old 01-29-2019, 07:48 PM   #4
turboedbug
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Member#: 155981
Join Date: Aug 2007
Location: Graham Washington
Vehicle:
1969 vw bug
ej20k ems stinger 4424

Default

Ya i got a tad more than 8.7 as well.

Thanks guys. double checking stuff as i go.
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