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Old 02-12-2001, 12:53 PM   #1
Scooby Newbie
Member#: 775
Join Date: Jan 2000
Location: usa
Post Octane rating for Turbo's

How is it I can't import a whole WRX engine and put it in my car without running at leat 97 octane, which we can't get in the states without ocatne boost. Yet, you all turbo your cars and run fine on 91 octane? what am I missing?

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Old 02-12-2001, 12:54 PM   #2
Scooby Guru
Member#: 329
Join Date: Sep 1999
Chapter/Region: Tri-State
Location: NJ
1995 325i
Arctic Gray


The way we measure octane is a little different from other countries, so our 94 octane we get at the pumps is close enough.
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Old 02-13-2001, 01:31 AM   #3
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Member#: 775
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Location: usa

What? How is it they measure octane differently?

We only get 91 in Colorado.

"close enough" is something I can live without.

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Old 02-13-2001, 07:45 AM   #4
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Join Date: Oct 2000
Chapter/Region: MAIC
Location: Media, PA
2006 WRX Wagon


I don't think that the measurements are different, but the components that make up the gasoline (ethanol) are different from country to country (for emmisions requirements) and lead to different ratings.

I certainly dont think an engine designed for a minimum of 97 would run too well on 94. The engine would probably knock like crazy. Thats one of the reasons why it takes so long for cars like the WRX to get introduced over stateside. The car has to be tuned to the [much] lower octane rating (91 is the minimum requirement for the WRX, correct?).

I know for a fact that you can get higher than 94 at a service station. My company markets 100 octane at a number of its outlets in the Delaware Valley. Its not very common, and at around $4.00 per gallon, you'd prolly only fill up before an auto-x ($4x10 = $$$$$$$). This is still better than the 11$ bottle of octane booster cause the 100 is still a higher rating and better blended. (I think its 2 bottles of octane booster to get over 100... dont quote me on that though.)

0.02$ USD
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Old 02-13-2001, 04:38 PM   #5
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Join Date: Jun 1999
Location: New York

You can run the JDM/Euro motors here without a problme...not sure about on 91 octne gas though, as that is a bit low. The rest of the world uses a different measuring system than the US (ala metric vs. U.S.). As such, 91 octane here is NOT the same as 91 octane "over there". I researchd this heavily when shopping for the motor in my car now (almost done!), and found that 94 Sunoco, which I have always used anyay, is equla to 98 RON (the JDM/Euro rating). Since my motor is from an STi 4, I will be fine..the STi4 ecu's are much better at compensation for lower octane than the V5's, from what I am told....due mainly to the V5 running a bit highr boost, and ignition timing a little higher than the previous STi's. When turning up the boost significantly (over 21 psi) I will use either booster, but probably av gas, or race gas
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Old 02-14-2001, 05:44 AM   #6
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Location: Lansing, MI
1999 Impreza 2.5RS
Rally Blue Pearl


The issue is that in Europe and Japan they just use RON (Research Octane Number), whereas the States use the RON+MON/2 formula (MON is Motor Octane Number, and is lower than RON). Hence, our ratings are an average of the two numbers and are lower than the numbers you see overseas.
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