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Old 11-08-2001, 02:26 PM   #1
Tainted
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Question Compression ratio?

What compresion ratio does my engine run at?
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Old 11-08-2001, 02:33 PM   #2
DanzBorin
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10:5:1 if I'm not mistaken...
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Old 11-08-2001, 02:51 PM   #3
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Default check your owners manual...

That info is in there too, along with other vital information.

LaterZ!
Darren!!
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Old 11-08-2001, 03:15 PM   #4
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I know the 01 RS's are 9.7:1, I would be suprised if it was higher than ten for the 2000 model.

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Old 11-08-2001, 03:24 PM   #5
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I thought the compression ratio for the 01 rs was 10:1?!?!
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Old 11-08-2001, 04:49 PM   #6
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9.7:1 for 98-99, 10:1 for 00-01 (and probably for 02).


Ben
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Old 11-08-2001, 06:48 PM   #7
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It is indeed 10:1 for the MY02 RS. The recent car and driver issue has lots of specs you might want to know.
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Old 11-09-2001, 02:05 AM   #8
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the 02 RS's are 10.0:1 as well as the MY00-01. They made no changes because they have gotten what they wanted out of the motor.

Jeremy
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Old 11-14-2001, 04:03 PM   #9
cakagan
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Question

What would the compression ratio be for the Phase 1.5 motors? My '98RS has DOHC heads w/ SOHC block.

Thanks,
-Chris
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Old 11-14-2001, 04:53 PM   #10
bsquare
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Changing the heads on the EJ25 doesn't change the compression ratio. You'll still be at 9.7:1.


Ben
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Old 11-14-2001, 04:56 PM   #11
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Thumbs up

Cool, thanks.

-Chris
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Old 11-15-2001, 08:53 AM   #12
Richard L.
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Quote:
Originally posted by bsquare
Changing the heads on the EJ25 doesn't change the compression ratio. You'll still be at 9.7:1.
Actually, changing the heads could change the compression ratio. Compression ratio is a function of cylinder bore, stroke length, cylinder head volume, deck height, head gasket thickness.

--
Richard
http://www.whitetyphoon.com/impreza/
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Old 11-15-2001, 11:01 AM   #13
cakagan
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The tech that installed my new engine thought the compression was raised, since the SOHC engines are higher now. I hope not. I think I'll ask him to find out what it is when I drop my car off to fix the valve chatter. It wasn't a problem on my original DOHC engine, but this new Phase 1.5 engine is loud as hell.

Btw, nice Typhoon Richard! When I finally buy a house in the mountains and need an SUV, I'm buying a Typhoon...

-Chris
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Old 11-15-2001, 11:19 AM   #14
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I believe the heads do affect the compression ratio. 98's and 99's(all 99's, that I am aware of) are both labeled as 9.7:1 compression. and since the block changed mid-99, but the compression did not, it is not something to do w/ bore or stroke. The only other option is the pistons themselves, which did get redesigned, but the heads were a more significant change...
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Old 11-15-2001, 01:29 PM   #15
bsquare
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I believe they changed the pistons. Can someone with detailed knowledge comment?

I am aware of how compression ratio is calculated, but I sepcifically said that THIS head swap on THIS engine shouldn't change the ratio.


Ben
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Old 11-15-2001, 01:32 PM   #16
cakagan
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Actually, I think Subaru changed the block mid-98, as mid- to late-98 2.5L owners have the Phase 1.5 from the factory.

-Chris
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Old 11-15-2001, 02:09 PM   #17
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I thought the block changed in 99... I could be wrong about that... i also realized my other mistake... I think they went to SOHC in 99, not 00, right? 00 was the year they switched to MAP... sorry, my bad
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