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what happens if I'm switching from ethanol to non-eth

Old 12-04-2008, 07:24 AM
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what happens if I'm switching from ethanol to non-eth

there is a gas station near my house that has ethanol free gas but it's the only 1 in my area so I don't use it all the time. Will switching from ethanol to non ethanol all the time cause any confusion in my ecu? I've been doing a bunch of data logging lately and have found my AFR's to be jumpy while doing a single gear WOT pulls. Just wondering if this might be a cause for the inconisitency in readings.

here's a chart of the afr going all over the place. used ethanol fuel
Attached Thumbnails what happens if I'm switching from ethanol to non-eth-3rd-gear-wot.jpg  
Old 12-04-2008, 09:53 AM
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you will get better gas mileage
Old 12-04-2008, 10:20 AM
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Ethanol has a lower BTU content than straight gasoline. Yes, economy and horsepower should increase with ethanol free gas.
I'm not an expert on this, but the jagged AFR line in your graph is most likely due to intake ports opening or the different fuel injectors turning on as the RPM increased.
Old 12-04-2008, 12:54 PM
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Originally Posted by zoom44
you will get better gas mileage

it's about 15 cents more per gallon so i'm going to assume the price will work out the same per mile.

kind of funny to think that when you go through all the extra processing, shipping and exchanging of hands the ethanol fuel is cheaper

Last edited by Mr.&Mrs.Magic; 12-04-2008 at 12:59 PM.
Old 12-04-2008, 12:58 PM
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Originally Posted by alnielsen
Ethanol has a lower BTU content than straight gasoline. Yes, economy and horsepower should increase with ethanol free gas.
I'm not an expert on this, but the jagged AFR line in your graph is most likely due to intake ports opening or the different fuel injectors turning on as the RPM increased.
just seems that most other charts are much smoother with their afr.

not too worried about the hp numbers what would you be looking at 2-3 hp differance-shift faster and smother.
Old 12-04-2008, 01:44 PM
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Your car will be happier.
Old 12-04-2008, 04:45 PM
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ok I know all the benifits of using ethanol free gas better mileage, more hp, happy motor all that good stuff. I'm looking to see if anyone knows if switching back and forth will keep the ecu in a learning state.
i.e. like when you reset all the fuel tirms your car drives like **** and has to relearn over a period of driving. You have more hp because it runs learner under WOT due to trims being relearned. So what i'm asking is the differance minimal .1-.2 AFR and not confusing the ecu making it jumpy.

just trying to cover a few angles
Old 12-05-2008, 06:12 PM
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I don't believe it will do anything with to the ecu it just has to retard and advance the timing by small amounts but it shouldnot hurt anything that is the reason it is there let it do it's job and enjoy.....also idk if the 15cents more will be accomidated with MPG you might see 1 mpg
Old 12-05-2008, 06:28 PM
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ah see you thought I didnt answer you fully. maybe i should be more clear- the only effect switching from oxygenated gas to non oxygenated gas will have on your gar is the one i gave in my previous post- #2 of this thread
Old 12-05-2008, 06:39 PM
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fair enough
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