Does E85 run cooler and make more power than traditional gasoline because a website says so? No, it’s because science says so. And while you can, in fact, argue with science, rarely will you win.
“The key player here is the heat of vaporization,” explains Zachary J. Santner, technical specialist at Sunoco. Heat of vaporization, also referred to as enthalpy of vaporization, refers to the amount of energy a liquid absorbs from its surroundings as it changes from a liquid to a gas.
“When things evaporate,” Santner explains, “they actually absorb heat from the surroundings.” As each molecule flies away and leaves the nest, so to speak, it takes some energy with it. As a result, the liquid left behind has a lower average energy.
All liquids have an enthalpy of vaporization. For gasoline, it’s about 150 btu per pound. For ethanol, that figure climbs to 360 btu. (For a real-life example of enthalpy of vaporization at work, notice how rubbing alcohol cools the skin as it evaporates.)
Then add in the fact that an engine requires 30% to 40% more E85 than traditional pump fuel to make combustion–so that’s even more cooling at work. “So anywhere ethanol evaporates, it’s cooling,” Santner adds.
Ethanol can make more power, too, since it contains more oxygen–about 34% oxygen by weight. “More oxygen means more fuel,” Santner explains, “so more horsepower.”
[E85 Ethanol Fuel: How to corn your way to more horsepower]
But this isn’t a free lunch. Not only will the engine drink more E85, but that E85 can be trickier to store because it wants to evaporate and absorb moisture quicker than gasoline. A closed container–and closed vents in a fuel cell, if so equipped–are paramount.
Santner points to a possible suspect for E85’s bad rap regarding its short shelf life: the gasoline component of the mixture. Pump E85 is required to contain only 51% to 83% ethanol, and the gasoline component could well be 83 octane. Sunoco E85-R, he notes, always contains 85% ethanol along with Sunoco race fuel–so about 100 octane for the petroleum part.
Comments
jimgood
New Reader
8/25/21 10:04 a.m.
In reply to jimgood :
Just look for the flex fuel emblem on the back of your vehicle. I'm seeing it more and more often. Including 2 recent Toyota Prius.
Or if you're ordering a new vehicle spend the $99 it costs to order it. My truck saved me that back in lower fuel costs in the first month.
In reply to jimgood :
Yeah, there are definitely applications in which ethanol works best, and we actually touched on that when we upgraded our Corvette Z06 project to run on E85:
E85 Ethanol Fuel: How to corn your way to more horsepower
As much as I'd love to just start pumping my lowly Honda Fit full of ethanol, that would probably do more harm than good for me.
I was unable to get the oil temperatures in my first daily/HDPE car down in midsummer - of course, the fact that I was trying to track a 4500lb 470whp AMG E63 in central Texas might have been to blame. Adding a massive oil cooler didn't do the trick, but installing a standalone E85 flex fuel sensor and kit (basically just waited for a fuel pulse, checked the ethanol content, and kept the injectors open x% longer) dropped the temperatures down just enough.
20% worse fuel economy wasn't a great side effect, but it was a lot better than overheating the oil!
Colin Wood said:
In reply to jimgood :
Yeah, there are definitely applications in which ethanol works best, and we actually touched on that when we upgraded our Corvette Z06 project to run on E85:
E85 Ethanol Fuel: How to corn your way to more horsepower
As much as I'd love to just start pumping my lowly Honda Fit full of ethanol, that would probably do more harm than good for me.
No you cannot just add the fuel to your gas tank. You have to have the sensor to detect what percentage of ethanol you have and adjust the engine accordingly.
But if you did have the sensor telling your car, you would gain power, Lose about 20% fuel mileage, but still save money.
On my truck I get 24 mpg ( V8, 4x4 using 87 octane @ $3.09/9 ) when I use E85 @$2.09/9 I get about 21-22 mpg. ( it's sooooo tempting to feel the extra power ) Save about $20.00 a tank full but lose about 40 miles of range.
So my understanding has generally been that E85 is for knock-limited engines and it was a means to increase boost or advance timing. I always thought that if your engine wasn't knock-limited (e.g. naturally aspirated Wankel) then there wouldn't be any benefits. This thread and some quick Google-ing seems to suggest otherwise in that there's still a small power benefit to be had. Thoughts?
In reply to infernosg :
There is a site here where GRM showed that properly jetted any car gains from E85.
It's when they tested fuels. Including Race gas. Methanol made the biggest improvement. ( but that stuff is toxic ) E 85 next and way below it was racing gas.
Now 10% is not earth shaking gain. But more power for less money? What's wrong with that?
In reply to frenchyd :
For modern vehicles that are essentially already prepared, sure. In my specific case to run E85 I'd need: some new fuel lines, higher-flowing injectors, a flex-fuel sensor and maybe a fuel pump to facilitate the extra flow. Then there's setting up the sensor with the ECU and adjusting the tune. I'm not sure if this is difficult or if the sensor takes care of the enrichment based on ethanol content alone. Since I wouldn't likely be advancing timing and don't have forced induction it's not like I would need multiple maps. If the benefit after all that is around 10% I'm okay with leaving it on the table, for now. The lower running temperature is actually more enticing to me if it can reign in oil temperatures like someone else mentioned. I'll have to add this to the list of nice-to-haves eventually just like drive-by-wire throttle control.
I splash in a couple gallons of E85 on a mostly full tank on my turbo tercel when I stop by the gas station near the track. No flex sensor, just overly rich toyota tuning that I take advantage of. I do not rely on it, but I use it for a touch ofknock insurance due to no intercooler atm
infernosg said:
In reply to frenchyd :
For modern vehicles that are essentially already prepared, sure. In my specific case to run E85 I'd need: some new fuel lines, higher-flowing injectors, a flex-fuel sensor and maybe a fuel pump to facilitate the extra flow. Then there's setting up the sensor with the ECU and adjusting the tune. I'm not sure if this is difficult or if the sensor takes care of the enrichment based on ethanol content alone. Since I wouldn't likely be advancing timing and don't have forced induction it's not like I would need multiple maps. If the benefit after all that is around 10% I'm okay with leaving it on the table, for now. The lower running temperature is actually more enticing to me if it can reign in oil temperatures like someone else mentioned. I'll have to add this to the list of nice-to-haves eventually just like drive-by-wire throttle control.
I'm the last guy to ask regarding these subjects but I've read where the required maps are already on your cars ECM all you need is the sensor and a way to input the feeds
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