grade of fuel for n/a - Page 4 - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


1992-1999 Series I L27 (1992-1994 SE,SLE, SSE) & Series II L36 (1995-1999 SE, SSE, SLE) and common problems for the Series I and II L67 (all supercharged models 92-99) Including Olds 88's, Olds LSS's and Buick Lesabres Please use General Chat for non-mechanical issues, and Performance and Brainstorming for improvements.

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Old 04-20-2004, 10:16 AM   #31
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I still don't buy the fact that the engine has spark/fuel mappings that will take advantage of 91 for a N/A 3800. To get to the bottom of this we'll simply have to ask a tuner who programs the things, thats the only way to get the answer.

How about you take a N/A Bonneville, put it on a dyno with 87, empty the tank, run it on 93 and see how it does? I'd be willing to bet the difference is nada, zilch, zero.
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Old 04-20-2004, 12:48 PM   #32
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Quote:
Originally Posted by CFoote
I still don't buy the fact that the engine has spark/fuel mappings that will take advantage of 91 for a N/A 3800. To get to the bottom of this we'll simply have to ask a tuner who programs the things, thats the only way to get the answer.

How about you take a N/A Bonneville, put it on a dyno with 87, empty the tank, run it on 93 and see how it does? I'd be willing to bet the difference is nada, zilch, zero.
The stock PCM can adapt to a point. If you drive with a higher octane, KR will be reduced. You'll only notice this for the most part at WOT. I can tell you from experience how my own car reacted to octanes ranging from 91-95.5, and it was obvious. Both on the scantool, and by the seatofthepants dyno.
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Old 04-20-2004, 01:20 PM   #33
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Didn't read the novel above, but Octane is just basically the way the gas burns. Not cleanliness. Engines can run with whatever, it just depends on their tuning at the time. You could make an l67 run with 89 if you wanted, it wouldn't be easy with a pcm but you could.

Higher octane= longer burn
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Old 04-20-2004, 02:25 PM   #34
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Quote:
Originally Posted by willwren
The stock PCM can adapt to a point. If you drive with a higher octane, KR will be reduced. You'll only notice this for the most part at WOT. I can tell you from experience how my own car reacted to octanes ranging from 91-95.5, and it was obvious. Both on the scantool, and by the seatofthepants dyno.
Oh I'm sure the Supercharged models love high octane gas -- and I certainly would run the best I could find if I had one. My concern is that the base 3800 doesn't have the mappings it needs. We aren't talking about a Corvette PCM here This base 3800 is a engine that is used in a multitude of models, a lot of which are leased/rental vehicles for fleets.
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Old 04-20-2004, 04:00 PM   #35
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Octane number is relative to the activation energy that a certain fuel needs to ignite compared to iso-octane. Once it ignites, it'll burn at the same rate.

Methanol has less than half the energy than gasoline. It'* average octane number is around 99.
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Old 04-20-2004, 05:59 PM   #36
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I saw the thing about OBD 2 & 3, but do we know what OBD 1 does? (besides take over)

i'm very curious.
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