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Old 03-14-2001, 09:11 AM   #1
Scooby Newbie
Member#: 4511
Join Date: Feb 2001
Question Compression Ratio for 98-01 RS

I noticed that the pre 2000 RS has a compressio ratio of 9.8:1 while 2000+ has a CR of 10.0:1...how come?
My question is assuming both engine's displacements are the same with the same number of cylinders, would the engine with the higher CR not produce more power than the one with less CR? If so how come the 2000+ models are still listed at 165hp/166lb-ft?
Just curious....
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Old 03-14-2001, 09:24 AM   #2
Scooby Specialist
Member#: 358
Join Date: Oct 1999
Location: Dallas, TX
2005 Xterra


there are a lot of things to consider there.

The pre-2000's were all MAF sensored rather than MAP on the 2000+.

Also, in 98' and I believe very few 99's have DOHC rather than SOHC which is apparent in most 99's and 00-01's. Could be something there also.
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Old 03-14-2001, 10:28 AM   #3
Scooby Guru
Member#: 114
Join Date: Jul 1999
Chapter/Region: MWSOC
Location: Wichita, KS and Whoring, OT
'03 Evo, Rice White
'01 Erion CBR 929


98 was DOHC, but the difference between a 99's 9.7:1 and 00+ 10.0:1 is the piston.
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Old 03-14-2001, 02:19 PM   #4
Scooby Newbie
Member#: 3056
Join Date: Nov 2000
Location: Etobicoke, Ontario, Canada
2001 Impreza 2.5RS
Blue Ridge Pearl


And because of this and the head design, the Phase II SOHC engines produce more torque over a broader range than the Phase I DOHC even though the HP and torque ratings are the same.

[This message has been edited by jetfreak (edited March 14, 2001).]
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Old 03-14-2001, 03:00 PM   #5
Sean McElderry
Scooby Specialist
Member#: 526
Join Date: Nov 1999
Location: Beaverton, OR, USA
1995 Supra Turbo


In 2000, Subaru raised the CR and changed the EFI and air intake systems for better emissions.

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