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post #1 of 8 (permalink) Old 05-29-2013, 09:40 PM Thread Starter
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E91 octane

I will be getting a tune for my 05 Balt 2.2l base coupe from trifecta and was told for best results i should run on e91. Will this hurt my vehicle? What are thes pros and cons (besides more money)


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post #2 of 8 (permalink) Old 05-30-2013, 05:17 PM
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Im on e91 no problems just more power. What mods do you have?

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post #3 of 8 (permalink) Old 05-30-2013, 10:12 PM Thread Starter
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post #4 of 8 (permalink) Old 05-31-2013, 01:41 PM
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....

Quote:
Originally Posted by gypsy08 View Post
Im on e91 no problems just more power. What mods do you have?

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THIS IS A COMMON MISCONCEPTION .....using a higher octane gas results in a smoother burn which intern allows you to safely burn more fuel....you will actually lose horsepower if the tune is not set to run the 91 at all times ....

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post #5 of 8 (permalink) Old 05-31-2013, 07:38 PM
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But if its set to run 91 then its more power that just means only 91 goes in tank or thats just what i go by

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post #6 of 8 (permalink) Old 05-31-2013, 08:15 PM
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Originally Posted by gypsy08 View Post
But if its set to run 91 then its more power that just means only 91 goes in tank or thats just what i go by

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maybe ,....you can allow for more timing .....doesnt always equal more power.....not sure for a cobalt..... but i run on mid grade always and my car runs good..put in 91 and just eats gas =0

---------- Post added at 10:15 PM ---------- Previous post was at 10:08 PM ----------

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maybe ,....you can allow for more timing .....doesnt always equal more power.....not sure for a cobalt..... but i run on mid grade always and my car runs good..put in 91 and just eats gas =0
before getting a tune you can an ecu learn by ridding all the cheap fuel....unplug the battery for a couple hours....put in mid grade shell gas...drive like 5 miles and it will adjust itself.....worked well with my mods

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post #7 of 8 (permalink) Old 05-31-2013, 08:42 PM
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THIS IS A COMMON MISCONCEPTION .....using a higher octane gas results in a smoother burn which intern allows you to safely burn more fuel....you will actually lose horsepower if the tune is not set to run the 91 at all times ....
Really?

Because...

These cars (or any car for that matter) could knock. Knock retard pulls timing (tuned or not), that in turn yanks off about 5~ WHP for each degree. If the car knocks on 87, but not on 91...regardless of the tune...the higher octane will net more gains because the PCM isn't pulling timing. Yes, higher octane will LOSE horsepower...but you have to be running some dumb high octane gas for that, think 110+. 87 to 91 isn't going to make a damn difference, hell...even ultra 94 in some places probably won't matter. Is it overkill? Yeah. More expensive? Sure. But will it kill the Cobalt you're driving? No...and it might help performance anyways. A little bit, but not anything you'd notice. It would be however more beneficial to your fuel system and valvetrain, as higher octanes...like you said...burn cleaner...and keeps things clean. I run 100% gasoline, no ethanol blended, 92 separate pump BP in my car for that reason.

The problem you get with gas these days is the ethanol drowning effect of the 8-12% gas companies mix into their gas. Ethanol normally lowers MPG's by a few percent when mixed in, hence why 100% gasoline is more expensive than the watered down crap. Another issue is not every car on the planet, especially older models are flex fuel capable...and over use of gas with mixed ethanol will cause issues down the road for older cars. Not saying it'll happen in a 2005 base Cobalt...but's possible. Ethanol is corrosive...it'll eat plastic and melt it. Seen that...fuel filters just turning to mush on the inside.

So, running E85/91 will net gains...you'll sacrifice MPG's for it, and you'll need to ramp up the ignition timing and lean the car out quite a bit to see gains from it. Probably isn't worth while either, unless you were going for an N/A HP record or something.

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post #8 of 8 (permalink) Old 05-31-2013, 09:27 PM
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Quote:
Originally Posted by bluegtp91 View Post
Really?

Because...

These cars (or any car for that matter) could knock. Knock retard pulls timing (tuned or not), that in turn yanks off about 5~ WHP for each degree. If the car knocks on 87, but not on 91...regardless of the tune...the higher octane will net more gains because the PCM isn't pulling timing. Yes, higher octane will LOSE horsepower...but you have to be running some dumb high octane gas for that, think 110+. 87 to 91 isn't going to make a damn difference, hell...even ultra 94 in some places probably won't matter. Is it overkill? Yeah. More expensive? Sure. But will it kill the Cobalt you're driving? No...and it might help performance anyways. A little bit, but not anything you'd notice. It would be however more beneficial to your fuel system and valvetrain, as higher octanes...like you said...burn cleaner...and keeps things clean. I run 100% gasoline, no ethanol blended, 92 separate pump BP in my car for that reason.

The problem you get with gas these days is the ethanol drowning effect of the 8-12% gas companies mix into their gas. Ethanol normally lowers MPG's by a few percent when mixed in, hence why 100% gasoline is more expensive than the watered down crap. Another issue is not every car on the planet, especially older models are flex fuel capable...and over use of gas with mixed ethanol will cause issues down the road for older cars. Not saying it'll happen in a 2005 base Cobalt...but's possible. Ethanol is corrosive...it'll eat plastic and melt it. Seen that...fuel filters just turning to mush on the inside.

So, running E85/91 will net gains...you'll sacrifice MPG's for it, and you'll need to ramp up the ignition timing and lean the car out quite a bit to see gains from it. Probably isn't worth while either, unless you were going for an N/A HP record or something.
it doesnt knock on base gas,...... though ive done plenty of data logging on different types of fuel....and you do lose horsepower with 91 ....at least i do without a tune .....i know plenty about kr....people expect race gas = race car and its soooo not true....they dont even sell pure gas in houston to my knowledge only time ive seen it is in Louisiana.....i do know i run better on shell...=) as far as octane ratings go its usually a little higher than listed BECAUSE of all the ethanol they try to shove in it ....so if you not tuned right any car can lose horsepower , hence having to run much larger injectors with an e85 tune....i do not talk out my ass sir...if i say it ..there is a reason -_-

---------- Post added at 11:27 PM ---------- Previous post was at 11:24 PM ----------

Quote:
Originally Posted by cobaltune View Post
it doesnt knock on base gas,...... though ive done plenty of data logging on different types of fuel....and you do lose horsepower with 91 ....at least i do without a tune .....i know plenty about kr....people expect race gas = race car and its soooo not true....they dont even sell pure gas in houston to my knowledge only time ive seen it is in Louisiana.....i do know i run better on shell...=) as far as octane ratings go its usually a little higher than listed BECAUSE of all the ethanol they try to shove in it ....so if you not tuned right any car can lose horsepower , hence having to run much larger injectors with an e85 tune....i do not talk out my ass sir...if i say it ..there is a reason -_-
and as far as timing = power...well ive tried advancing it on my v8 supra and nothing ....and then eventually lost power ....

0-60....tooloonggg......Someone Wanna tune me =)
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