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Old 03-14-2001, 09:11 AM   #1
Delhi
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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
SCOOBYSHAG
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Join Date: Oct 1999
Location: Dallas, TX
Vehicle:
2005 Xterra
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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
ColinL
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Join Date: Jul 1999
Chapter/Region: MWSOC
Location: Wichita, KS and Whoring, OT
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'01 Erion CBR 929

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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
jetfreak
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Join Date: Nov 2000
Location: Etobicoke, Ontario, Canada
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2001 Impreza 2.5RS
Blue Ridge Pearl

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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
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1995 Supra Turbo
Red

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

Sean
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