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Discussion Starter #1
I have used only Shell 93 Octane (10% Ethanol) since taking delivery of my GT.
A new Shell station opened a month ago and they have an 87 Octane (Ethanol Free) Gasoline. Says it is NOT a Shell product.
Just wondering what your thoughts are regarding the two fuels.
Thanks,
-Paul
 

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I would never run personally anything less than what I'm tuned for. Even stock tune I would not run 87 unless I'm on a flat hwy trip. I get 93 Conoco ethanol free at my location. Done lots of logs with it and it is super legit. If you can get 91 or 93 in no ethanol run it. Most people cannot get it. It's called "Clear" btw.

I have run only 93 Clear with VP Racing Octanium for 8 mos straight. That is 101 plus octane btw. ;)
 

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Not really sure what your question is?

Octane rating is octane rating regardless of how much ethanol is in the gas. You will make more power with 93 octane than with 87 octane regardless of the ethanol content because the engine can run more timing.

The higher octane rating allows the engine to add more timing before detonation. More timing means more power.

The ethanol content only changes how much volume of fuel is needed to be injected to produce the proper Air Fuel Ratios. The ECU reads the AFR's from the O2 sensors and adds or reduces fuel as necessary to make sure the AFR's stay in the range they are supposed to. The only time the ethanol mix will make a difference is if there is so much ethanol that the ecu cannot add enough fuel to keep AFR's in the right place. This is one of the reasons why you need to make changes to your fuel system if you want to run E85.
 

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Discussion Starter #4
Thanks guys.... was just wondering if Ethanol free was better. Haven't found any higher than 87 around here and was just curious about the pros and cons between the two.
Your posts were very informative. I'll stick with 93!
Thanks,
-Paul
 
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91 octane v power from shell is ethanol free. At least here it is. If you have a tune for higher octane and have access to the higher octane fuel with no ethanol then do that.

87 is too low for these motors and ethanol in fuel is just junk because it burns less efficiently and contaminates the purity of the fuel obviously. Pure gasoline makes the most power and does so most efficiency.
 

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Not really sure what your question is?

Octane rating is octane rating regardless of how much ethanol is in the gas. You will make more power with 93 octane than with 87 octane regardless of the ethanol content because the engine can run more timing.

The higher octane rating allows the engine to add more timing before detonation. More timing means more power.

The ethanol content only changes how much volume of fuel is needed to be injected to produce the proper Air Fuel Ratios. The ECU reads the AFR's from the O2 sensors and adds or reduces fuel as necessary to make sure the AFR's stay in the range they are supposed to. The only time the ethanol mix will make a difference is if there is so much ethanol that the ecu cannot add enough fuel to keep AFR's in the right place. This is one of the reasons why you need to make changes to your fuel system if you want to run E85.
Larger injectors will fix that. I run 93 with 10% ethanol and it works for me. Why do people make a big deal out of ethanol ?
 

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It's "best" to go full e85/e70 etc. or stay straight clear pump. Mixing creates inconsistent fuel and or tuning. Are you testing that ethanol content at every fill up? Reason? Because corn has different stoich than regular pump.

Yes, the ecu will correct/compensate to a degree. You need to run logs from the station/s you use for fuel. Your tuner should dial in best he can.
 

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It's "best" to go full e85/e70 etc. or stay straight clear pump. Mixing creates inconsistent fuel and or tuning. Are you testing that ethanol content at every fill up? Reason? Because corn has different stoich than regular pump.

Yes, the ecu will correct/compensate to a degree. You need to run logs from the station/s you use for fuel. Your tuner should dial in best he can.
The difference between E10 and ethanol free is less than 5% in fuel volume needed. Your ECU compensates more than that with air temperature changes regardless of the tune. E85 needs around 30% more fuel. That requires tuning.

A tuner will set a baseline fuel map in your tune and then rely on the ECU to monitor and adjust AFR's through the O2 sensor readings. There is a short term fuel enrichment process that will add and remove fuel as needed to keep ratios where it needs to be in the transient short term driving. This happens several times per second. If over a period of time, the engine is always having to add or remove fuel then the ECU will make a long term fuel adjustment to move the baseline enrichment process up or down. A 5% change in fuel AFR's is absolutely zero issue for an ECU to adjust for.

Thereaper said:
Larger injectors will fix that. I run 93 with 10% ethanol and it works for me. Why do people make a big deal out of ethanol
Exactly, In modern vehicles (mid 90's and newer) there is zero issue running gas with some ethanol in it. The big deal about ethanol in gas is that when it was first introduced it had the possibility of causing issues in older carbureted vehicles that were still very common in the mid 90's. These vehicles were not able to adjust as easily to the fuel mixtures as fuel injected vehicles and some of their fuel system components would react with the ethanol in the gas. This is no longer the case and newer vehicles have ZERO issues with the percentages of Ethanol in E10 fuels.

E85 is a different story and is much more corrosive than E10 and thus "sometimes" requires changing some components in a fuel system to work properly. They also had to put in bigger injectors, fuel pumps, and fuel lines vs non E85 vehicles (Enter the FLEX FUEL sticker on cars)

This issue was further complicated whenever fuel prices shot through the roof in the mid 2000's and everyone was extremely worried about fuel mileage. It came out that E10 fuel got less gas mileage than 100% gasoline, so everyone again started saying that ethanol fuels were terrible and you should always get 100% gas. Even though 100% gas was costing as much as 15-30% more per gallon than E10 even though only it got about 5% worse fuel mileage. Your driving habits have more affect on fuel mileage than E10 does.

Basically like most stupid things in the world, the bias towards E10 fuels is 100% based on fear and ignorance.


Blazin72 said:
Good question. A lot people avoid E10 but tuning for E85 is popular. Seems counterintuitive.
If E85 was more readily available near me and I was going to forced injection I would go to E85 in a heartbeat. E85 has octane ratings over 100 and is amazing with forced induction.


Having said all of the above, if your ECU can adjust for higher octane ratings (and ours can) your vehicle will make more power with higher octane fuel regardless of it being 100% gas or E10.
 

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HP Tuners is in the process of adding Flex Fuel support to 2011-up Mustangs.

Flex fuel
Thats awesome to hear! Thanks for the update info!

Been waiting to buy mine till I have more time to work on my car. Looks like i'll be picking one up later this year.
 

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Lund already has flex fuel tunes.
Does he have flex fuel tunes or E85 tunes? Those are different things.

E85 tunes are just assuming you are running E85, similar to a 93 only tune.

Flex fuel tunes let you run whatever mix of fuel you want and the ECU is able to adapt. TOTALLY different from an E85 tune.
 

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It's possible SCT has the same support now too but from what I got from that thread they weren't there yet.
I think your right. What I got from that thread was SCT can read the alcohol enrichment tables, but they can't turn them on yet.

Either way, exciting developments!
 

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I think your right. What I got from that thread was SCT can read the alcohol enrichment tables, but they can't turn them on yet.

Either way, exciting developments!
Supposedly with HP Tuners you can turn the switch but the tables either aren't populated or they aren't correct. It means you still have to do your homework but it should allow true Flex Fuel operation. I downloaded the latest update and didn't see any new tables for my 2011 but they probably don't have all of the definitions updated yet.

They are even enabling it for the GT350s.
 

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Sometimes this place rocks, that is some of the best info thanks Fellas. My Brother was telling me to use 91 Shell cuz it's the only premium up here that doesn't have ethanol - which makes sense in the F5 Roadster (750 Holley) and the 04 Sportster ( last of the carb EVO's) but I guess I can happily run Sunoco 93 (10% ethanol) in the Mustang and the FB.


This should be stickied or an FAQ


Scott
 
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