91 octane with 10% ethanol vs. 91 octane pure gas

[imxz28]

91 octane is the best I can get around here but pure gas is available at a premium price.
Which is better for a boosted application?

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[AZ18yote]

I would take the little bit of e over no e any day. Help with cooling even a little and knock.

 

[WildHorse]

yep. the more E the better. I've seen 94 E10 make more ponies than 91 E0 + octanium on the same tune.

 

[ahl395]

Take the E. Ethanol is not bad for your car like many people seem to think. The only benefit of non-ethanol fuel is for older cars with fuel systems that weren't made for it.

 

[WildHorse]

Ethanol is not bad for your car like many people seem to think

That's the old school guys.. like me. But I realized in the 80's the potential of Ethanol.

 

[Dfeeds]

A lot of people also seem to just look at the gas mileage and go "zomg I get 1 less mpg with E it sucks never again."

 

[WildHorse]

A lot of people also seem to just look at the gas mileage and go "zomg I get 1 less mpg with E it sucks never again."

They'd lose their collected minds if I showed them I gained almost 1 mpg using 94 E10 over 91 E0. More timing = better efficiency, better efficiency = better MPG. Something these 87 octane lovers seem to forget.

 

[imxz28]

In my research, I found this:

http://www.superchevy.com/how-to/car-care/1509-everything-you-need-to-know-about-octane

 

[AZ18yote]

A lot of people also seem to just look at the gas mileage and go "zomg I get 1 less mpg with E it sucks never again."

Well put

 

[AZ18yote]

They'd lose their collected minds if I showed them I gained almost 1 mpg using 94 E10 over 91 E0. More timing = better efficiency, better efficiency = better MPG. Something these 87 octane lovers seem to forget.

I'm a strong advocate of e. I run e54 at min (Phx has very little e and it's mostly flex fuel) , with the e85-90 (literally only 2 stations I know of in the county that have this high consistently) for the more fun times. I will concede that on the occasion I run 91 for maintainance (we don't even have 93) that the mpg are much higher but a willing trade off for the cooler temps and more timing from the e.

 

[imxz28]

I discussed this with some technical people I know. Here are some other thoughts


1) I dont think 10 percent ethanol is going to cool your fuel charge enough to notice, imho. Besides, the ethanol mix varies at the pump and with pure gas you do not have to deal with any ethanol drawbacks. Ethanol does not contain as much energy. But really, we are talking things you'd have to measure on instruments. Fuel mileage would be slightly noticeable. Get a busy pure gas pump, though. Higher octane to prevent detonation is king, though. Guys run e85 to get cooler fuel, which is a huge difference than the e10 stuff that we use.

2) Honestly though, its splitting hairs. As long as you can run the octane that prevents detonation and your motor is not pulling timing running the octane it was tuned for (due to knocking), you are good.
100% Ethanol has 30% less energy content than does 100% Gasoline on a per unit volume basis. Additionally, Ethanol has a lower flame temperature than Gasoline. So, Ethanol doesn't cool an engine more than gasoline, it just doesn't burn as hot as gasoline does resulting in a lower engine operating temperature.

So that makes sense to me. 91 octane at E10 vs. 91 octane at 100% pure gas:
both have 91 octane so they are equal in theory. the pure gas has more energy.
is it really that much cooler or better. IDK. they are probably too close to call a winner.

 

[ENPhoto]

1) Ethanol does not contain as much energy. to prevent detonation is king, though.

2) Honestly though, its splitting hairs. As long as you can run the octane that prevents detonation and your motor is not pulling timing running the octane it was tuned for (due to knocking), you are good.
100% Ethanol has 30% less energy content than does 100% Gasoline on a per unit volume basis. .

As stated above:

Run tank almost empty. Put in gas with NO E%.

Flash your tune, start the log and do some driving


Repeat with the E 10%.

Pick the one that you see better results from (ECT and Timing/Knock)

I should really do a comparison for the gas here in Canada. It's all over the place with Pure 92, 94 and blended 92/94.

 

[K4fxd]

I get 4 MPG better on pure 93 than I do with E10 93.

1/4 mile trap speeds are the same. I'd rather have pure gas and the better efficiency.

 

[WildHorse]

I should really do a comparison for the gas here in Canada. It's all over the place with Pure 92, 94 and blended 92/94.

91/93 standard tune 3rd gear pull 2000-7000 rpm shell 91 E0 the KS was always -3 @ WOT settled @ 24 degrees then +0 to 7000 rpm. Husky 94 E10 +3 settled @ 27 degrees @ WOT then +0 to 7000 rpm. What's that 3 degrees worth? 20 hp?

 

[Nuked]

91/93 standard tune 3rd gear pull 2000-7000 rpm shell 91 E0 the KS was always -3 @ WOT settled @ 24 degrees then +0 to 7000 rpm. Husky 94 E10 +3 settled @ 27 degrees @ WOT then +0 to 7000 rpm. What's that 3 degrees worth? 20 hp?

On a N/A going from 24 degrees to 27 is probably a solid 25-30whp difference.

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