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Old 04-19-2005, 09:41 AM   #1
GotTurbo
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SOON BMW STEEL GREY

Default compression test!!!

hey i wanted to know if any knows the stock compression of a 2.5 dohc engine in my 1998 legacy 2.5 gt. any ideas cause i was thinking of doing a compression test to see if they are all upo to par.

-matt
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Old 04-19-2005, 11:30 AM   #2
fastenova
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Not your usual 1997
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Mine were all ~140 psi after I had a valve job done and replaced the HG. More important than what number they all are (generally!) is that they are all +/- 5-10% or so of each other, i.e. if one is 150, then 140-160 is not a bad range for the others to have. They should wear about the same, so if three are 130, and one's 110, you may have an issue on that cylinder.

I believe our engines have a compression ratio of 9.7:1, so that means you should see 9.7 times atmospheric pressure, which is 14.7 psi at sea level, so that would equal a compression level of ~143 psi at sea level.

-Aaron
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Old 04-19-2005, 11:33 AM   #3
GotTurbo
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thx alot for that help.
-matt
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Old 04-19-2005, 02:00 PM   #4
MY99 2.5GT
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Thats strange mine were all 193 and one around 195.
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Old 04-21-2005, 06:47 AM   #5
fastenova
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I dunno how they'd be that high. SOHC EJ25s run 10.1:1 I think, which should only be around 150psi. If you were running high compression pistons, like 13:1, that would make sense... but otherwise, I don't know how your numbers could be that high...

-A
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Old 04-21-2005, 08:27 AM   #6
MY99 2.5GT
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NO wonder my head gaskets keep leaking. I have 13:1 compression
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Old 04-21-2005, 08:27 AM   #7
MY99 2.5GT
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No I don't really have 13:1 compression pistons.
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