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Old 09-04-2007, 12:16 AM   #1
omdwrx508
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Default 93 stage 2 map with 91 octane

so ive searched this question with no luck.. i just moved to socal for mass. out in mass we have 93 octane so i was running a stage 2 xpt 93 octane map. driving across the country i found that iowa and nebraska only have 89 octane and 90 octane was a treat. now that i live in cali i can only find 91 octane. am i doing harm to my car by using the lower octane, and should i try to flash my ecu to a 91 map? i currently don't have a laptop like back east. so its a bit more of a hassle to do.
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injen cai
3" catless turboback
catless uppipe
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Old 09-04-2007, 06:40 AM   #2
dlh1999
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IMO, you'll probably want to switch to a 91 octane map pretty soon. You're basically making your current map lean out the car a little because it expects 93 octane but you're only giving it 91 (which, I hear, isn't great quality in some parts of California, Nevada and Arizona). It'd be pretty safe going the other way (ie. 93 octane with a 91 octane map) because rich is better than lean, but probably not the best idea vise-versa.
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Old 09-04-2007, 09:55 AM   #3
robert46123
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Cobb has a map designed just for the crappy piss you call gas in California. I'm not sure a standard 91 octane map would even be safe in California.
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Old 09-04-2007, 11:07 AM   #4
rkramer
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Quote:
Originally Posted by dlh1999 View Post
IMO, you'll probably want to switch to a 91 octane map pretty soon. You're basically making your current map lean out the car a little because it expects 93 octane but you're only giving it 91 (which, I hear, isn't great quality in some parts of California, Nevada and Arizona). It'd be pretty safe going the other way (ie. 93 octane with a 91 octane map) because rich is better than lean, but probably not the best idea vise-versa.

octane doesn't have much to do with the AFR. the AFR won't change (much) with different gas. what does change is if the car knocks or not, at a certain RPM it might need more fuel to prevent knock, even though it technically isn't lean, or at least any more lean then before.
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Old 09-05-2007, 07:08 AM   #5
StupidFastWagon
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I have a 91 oct map that runs great if you want it (STG 2)
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Old 09-10-2007, 11:09 PM   #6
dtpebs
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Sign up at osecuroms and you will be able to download a 91 octane map.
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Old 09-12-2007, 11:20 AM   #7
Worxman02
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Quote:
Originally Posted by rkramer View Post
octane doesn't have much to do with the AFR. the AFR won't change (much) with different gas. what does change is if the car knocks or not, at a certain RPM it might need more fuel to prevent knock, even though it technically isn't lean, or at least any more lean then before.
rkramer is right. Please try to post accurate information especially when it pertains to something as sensitive as engine management. /channeling Uncle Scotty.

I can understand where the confusion might come from, however octane has NOTHING to do directly with AFR. Since 91 octane has a lower knock threshold (ie what the octane rating measures) than 93, the ECU will ONLY run richer on 91 than it did with the 93 if it detects the presence of knocks. Otherwise fuel is fuel and the ECU has no way of detecting what sort of octane gas is in the tank BEFORE a knock event occurs.
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Old 09-12-2007, 06:21 PM   #8
kyledooley
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I'm hoping you intend to keep your car registered in Mass. You're going to fail your emissions test in about 4 seconds with no cats, that's if you don't get pulled over by a CHP officer that happens to follow you and not like your stink a$$ exhaust.
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