Compression ratio?

Tainted · 11-08-2001, 02:26 PM

What compresion ratio does my engine run at?

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DanzBorin · 11-08-2001, 02:33 PM

10:5:1 if I'm not mistaken...

Penphoe · 11-08-2001, 02:51 PM

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

LaterZ!
Darren!!

Graham · 11-08-2001, 03:15 PM

I know the 01 RS's are 9.7:1, I would be suprised if it was higher than ten for the 2000 model.

Graham

Jademonkey · 11-08-2001, 03:24 PM

I thought the compression ratio for the 01 rs was 10:1?!?!

bsquare · 11-08-2001, 04:49 PM

9.7:1 for 98-99, 10:1 for 00-01 (and probably for 02).

Ben

jhonas · 11-08-2001, 06:48 PM

It is indeed 10:1 for the MY02 RS. The recent car and driver issue has lots of specs you might want to know.

HndaTch627 · 11-09-2001, 02:05 AM

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

cakagan · 11-14-2001, 04:03 PM

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

Thanks,
-Chris

bsquare · 11-14-2001, 04:53 PM

Changing the heads on the EJ25 doesn't change the compression ratio. You'll still be at 9.7:1.

Ben

cakagan · 11-14-2001, 04:56 PM

Cool, thanks.

-Chris

Richard L. · 11-15-2001, 08:53 AM

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/

cakagan · 11-15-2001, 11:01 AM

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

mrbell · 11-15-2001, 11:19 AM

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...

bsquare · 11-15-2001, 01:29 PM

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

cakagan · 11-15-2001, 01:32 PM

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

mrbell · 11-15-2001, 02:09 PM

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

11-08-2001, 02:26 PM	#1
Tainted Scooby Newbie Member#: 7996 Join Date: Jul 2001 Location: Phoenix Vehicle: 1980 Human Biped Flesh tone.	Compression ratio? What compresion ratio does my engine run at? * Registered users of the site do not see these ads.

11-08-2001, 02:51 PM	#3
Penphoe Friendly Neighbourhood Moderator Member#: 269 Join Date: Sep 1999 Chapter/Region: VIC Location: Burnaby, B.C., Canada Vehicle: 2005 ABP LGT LTD BP6 00 Impreza RS GM6 RIP	check your owners manual... That info is in there too, along with other vital information. LaterZ! Darren!!

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Jademonkey Scooby Specialist Member#: 9213 Join Date: Aug 2001 Location: My grandma was 6' 6" Vehicle: 2000 RS Red	I thought the compression ratio for the 01 rs was 10:1?!?!

11-08-2001, 04:49 PM	#6
bsquare Scooby Specialist Member#: 1911 Join Date: Jul 2000 Location: Seattle, WA, USA Vehicle: 2000 Impreza 2.5RS Silverthorn Metallic	9.7:1 for 98-99, 10:1 for 00-01 (and probably for 02). Ben

11-08-2001, 06:48 PM	#7
jhonas Scooby Specialist Member#: 9015 Join Date: Aug 2001 Location: one boring place, WA Vehicle: 2002 Impreza 2.5RS Platinum Silver Metallic	It is indeed 10:1 for the MY02 RS. The recent car and driver issue has lots of specs you might want to know.

11-09-2001, 02:05 AM	#8
HndaTch627 Scooby Guru Member#: 6551 Join Date: May 2001 Chapter/Region: MWSOC Location: Carol Stream, IL Vehicle: '01 GC8 Dinged STM '09 Concours 14 ABS Black	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

11-14-2001, 04:03 PM	#9
cakagan Scooby Newbie Member#: 251 Join Date: Sep 1999 Location: Chicago, IL Vehicle: 1998 Impreza 2.5 RS Black	What would the compression ratio be for the Phase 1.5 motors? My '98RS has DOHC heads w/ SOHC block. Thanks, -Chris

11-14-2001, 04:53 PM	#10
bsquare Scooby Specialist Member#: 1911 Join Date: Jul 2000 Location: Seattle, WA, USA Vehicle: 2000 Impreza 2.5RS Silverthorn Metallic	Changing the heads on the EJ25 doesn't change the compression ratio. You'll still be at 9.7:1. Ben

11-14-2001, 04:56 PM	#11
cakagan Scooby Newbie Member#: 251 Join Date: Sep 1999 Location: Chicago, IL Vehicle: 1998 Impreza 2.5 RS Black	Cool, thanks. -Chris

11-15-2001, 11:01 AM	#13
cakagan Scooby Newbie Member#: 251 Join Date: Sep 1999 Location: Chicago, IL Vehicle: 1998 Impreza 2.5 RS Black	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

11-15-2001, 11:19 AM	#14
mrbell Scooby Specialist Member#: 1871 Join Date: Jul 2000 Location: Salt Lake City, UT Vehicle: 2000 Impreza 2.5RS Blue Ridge Pearl	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...

11-15-2001, 01:29 PM	#15
bsquare Scooby Specialist Member#: 1911 Join Date: Jul 2000 Location: Seattle, WA, USA Vehicle: 2000 Impreza 2.5RS Silverthorn Metallic	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

11-15-2001, 01:32 PM	#16
cakagan Scooby Newbie Member#: 251 Join Date: Sep 1999 Location: Chicago, IL Vehicle: 1998 Impreza 2.5 RS Black	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

11-15-2001, 02:09 PM	#17
mrbell Scooby Specialist Member#: 1871 Join Date: Jul 2000 Location: Salt Lake City, UT Vehicle: 2000 Impreza 2.5RS Blue Ridge Pearl	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