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Date: Mon, 08 Oct 2001 06:54:33 GMT
From: "sg" <steveginnnopsamail.com>
Subject: Re: 87 or 92 Octane in a 97 SE Turbo?


Car and Driver magazine (USA) has an article (November, 2001) on this very subject. Tech stuff: Combustion should be "slow" rather than an explosion (engine knock) and can last up to 60 degrees of crank rotation in some engines. Modern gas has about 200 different hydrocarbons. Of those, isooctane resists burning and n-heptane promotes it. 87 octane = 87% isooctane and 13% n-heptane. The Test: They tested on the dyno and the drag strip. Cars and recommended octane: Saab 9.5 2.3 Turbo (91) (knock sensor) BMW M3 (91) (knock sensor) Honda Accord V6 (87) (knock sensor) Ford Mustang GT V8 (87) (knock sensor) Dodge RAM PU w/ 5.9 liter V8 (87) (no knock sensor) With 87, performance was down 10% for the Saab and 7% for the BMW. The Honda dropped 2.6% hp with 91 which was a mystery Dodge had an hp increase of 3.8% with 91 The Mustang gained 1 hp with 91 The conclusion ..."for most cars, there is no compelling reason to buy more expensive fuel than the manufacturer recommends." Also: .... If a car starts to knock on it's recommended octane, it's time for a tune-up. They make no mention of causing harm by using an octane rating about the recommended level. They say that few cars calibrated for 87 are capable of advancing the timing enough to gain advantage from using 91. Steve "Brian" <Witch*Drnopsamnospam.net.ru> wrote in message news:ts10mclnjo9d28nopsam.supernews.com... > I just purchased a 97 900 SE Turbo and I was wondering if octane is a > significant Turbo enhancer? The manual states that 87 octane is fine and > I've driven with both Super and Regular Unleaded and can't notice any > difference in boost or performance. For now I'm happy just pumping in > regular unleaded but I'm wondering if Super is really called for? > >

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