Anybody use E85?

[MalcolmV8]

I read so much on E85 and know people that use it etc. but never touched it myself till recently. There are only two gas stations near me that have E85 and one is about 15 miles north of me and the other about 15 miles south. Not exactly a setup for a daily driver but non the less I wanted to experiment.

Currently the turbo'd Honda was running 14 lbs of boost on 91 octane pump gas (that's premium in KC) and even at 14 lbs I had to pull a ton of timing out the motor from about 5250 RPMs and higher. In fact look at the dip down on this timing table. This is the secondary table for when VTEC kicks in, only a portion of this table ever gets used hence the small area modified



I'm going to install water/meth injection in the next few weeks so I can add timing back in and turn the boost up but figured hey why not go put in some E85 and see what that's all about.
So I threw a couple gas cans in the trunk, grabbed my laptop and headed off to the gas station. Filled up my two cans and proceeded to drive around the city and burn out the remaining gas. Who would have ever guessed the dang car had such a huge reserve once the fuel gauge hits the E red line. Granted it gets over 30 mpg but sheesh took me over 100 miles before it ran out lol. So by now it's 9pm at night and I finally strand myself on the side of the highway in the middle of no where. A very uneasy feeling not knowing if I can even tune a car for E85 or not. So I dump the E85 in the tank and break out the laptop and much to my surprise it was really easy. I just added 40% to my fuel maps and the car started right up and off I went. Wow that was just to easy. I quickly noticed it was a little on the rich side because it was still mixed with some 91 so I had to pull about 10% fuel out.

Immediately I could tell a difference. wow the car pulled really hard on e85. I use boost by gear and rpm so I can get traction in all gears and it was ripping the tires in 2nd and 3rd on the same boost settings. I added the timing back in I had previously pulled and bumped the boost from 14 lbs to 18 lbs wow did the car come to life. Also not the slightest hint of detonation as monitored by my J&S Vampire. I was really impressed. I can definitely see why people love E85 for performance cars.
I also noticed after hard highway pulls when I let off the car is about 170F where as on 91 it's always around 180F this time of year (about 30F outside) so it runs cooler too.

After I burned off that bit of mixed gas I filled the tank on E85 and had to add about 12% back into my fuel so I'm spraying about 42% more fuel on E85 than I did on 91 pump gas. Over here in KC on that night 91 cost $3.22 and E85 was $2.72 so that makes E85 only 15% cheaper than 91 but it burns 42% more so that makes it 27% more expensive to run E85 over premium. I think in the long run for a daily driver the water/meth on 91 is the way to go.

So anyhow wondering if others play with E85 too? It's definitely great stuff.

[cgrey8]

I experimented with E85 a while back on the 302 and I too found it fairly easy to work with. But in my tunes, I didn't have to add nearly as much. But I'm also not boosted either. And comparing E85 to gasoline requires you talk about conditions since the condition of use matters when retuning for E85.

For simplicity, I'm going to use AFR values of lambda, not actual AFR so I don't have to clarify whether I'm talking about 100% gasoline, E10, or E85 AFR values. Anybody that doesn't understand what I mean by this, read this tech doc I wrote about Wideband O2 sensors a few years back:
Widebands measure lambda (λ), not AFR.

For those that don't want to know more than they have to about lambdas and AFR, the quick-n-dirty conversion from λ to AFR is to multiply the λ value by the stoic AFR of the fuel you are in question about. So a λ of .85 with 100% gasoline would convert to AFR by multiplying .85 by 14.64...12.44 AFR.

Closed Loop EFI systems target AFRs ~1.00λ using the HEGO sensors, which "switch" rich/lean about 1.00λ. At closed loop idle, cruise, & moderate accel, you shouldn't need more than about 30% more fuel over what we call gasoline today.

100% gasoline takes 14.64 parts air to 1 part fuel to attain 1.00λ.
E85 is 9.76 AFR to attain 1.00λ.
That's a 33% increase over gasoline.

However we don't burn 100% gasoline in most places in the US. Most of us have to burn E10 which is 10% ethanol. E10 is 14.08 AFR to attain 1.00λ. So that's only about a 30% increase over E10. And if you targeted the same λ at both closed loop and WOT conditions, you'd still only need the same 30% even at WOT. But E85 needs even more enrichment than gasoline yielding the 40% increase.


Most n/a engines burning gasoline/E10 target between .85-.9λ (~12.5-13 gasoline AFR).
The same engine on E85 would be in the .85-.80λ.

Mildly boosted (< 8 PSI) engines tend to target .82λ (~12.0 gasoline AFR) on gasoline.
The same engine on E85 would be in the .75-.80λ.

Moderately boosted (8-15 PSI) engines tend to target .79-.80λ (~11.5-11.7 gasoline AFR).
The same engine on E85 would be .70-.75λ.


So compare the difference in AFR at WOT on a moderately boosted engine:
Gasoline: .79 * 14.64 = 11.56 AFR
E85: .70 * 9.76 = 6.83

That's a difference of your 40% and why fuel injectors in E85 engines have to be at least 50% larger than they would need to be on gasoline/E10 engines.


Now as for my experience on E85, it burned like premium gasoline other than just taking more of it. Since I still had the stock 19lb injectors in the engine, there wasn't nearly enough injector to run E85 at WOT. And as a result, WOTing onto the interstate ran my injector PWs to wide open by about 3500RPMs. As the RPMs rose above that, the AFRs got leaner and leaner. So I couldn't safely run the engine above about 4200RPMs.

I did test to see if the EGR made any difference with E85. As it turned out, having EGR was even more noticeable than it is with gasoline. When I turned the EGR off, I immediately got worse fuel economy. I added the EGR back, and immediately noticed that I was datalogging a good 1-1.5MPG better. While I did get better fuel economy with EGR on gasoline, it's not quite that big of a difference.

The other thing I noticed about E85 is that cold cranks were much more difficult. It took the engine a good 2 seconds longer on the starter to turn over in near freezing temps...and what I was burning was actually E70 (winter blend E85). But that's common on ethanol concentrations above 50% hence why the EPA requires "winter blend E85" be limited to E70. Ethanol doesn't atomize as well as gasoline. So it takes a lot more of it on crank and takes longer to crank on a cold engine. In Brazil where 100% ethanol is sold at the pumps, vehicles have 1 gallon gasoline starter tanks that is used to crank off of when cold. Once the engine is running the driver flips the engine over to the ethanol tank after about 3-5 seconds. Interestingly Brazil's "gasoline" is actually E25.

I haven't run the 331 on E85 yet. But I did size the injectors so that E85 is an option and I won't have to worry about WOTs maxing out the injectors.

[MalcolmV8]

Chris, I also noticed the cold cranking increase. My car sits in the garage over night which is around 60F and I had to blip the key twice each time so far as I'm so used to just barely tapping it on 91. I'm curious to see how much additional cranking it takes when I leave the car out and it's 20F outside and needs to start.

I use 91 which is E10 over here too. We have a few random BP stations that have true 91 with no ethanol but it's about 35 cents a gallon more than e10 91 that's commonly available. I'd have to do some reading up on the advantage of that 91. I filled up the Cobra with it once a couple months ago but then never got a chance to play with the tune.

As for a/f I run my boosted cars around .80 lambda which is around 11.76. Anywhere between 11.5 ~ 11.8 is fine for me. I have a lean cut out set at 12.3 so if I hit 12.3 it instantly shuts off the injectors which of course kills the motor immediately. You have to let off the gas pedal and press back on it and the car will come back to life. Fantastic safety measure when playing around with tune etc. especially when the weather is changing so much and you're still dialing things in.

You are correct in that the fuel system needs to be able to supply 40% more fuel so injectors, pumps, lines etc. all need to be able to handle the additional capacity. I have more than over sized all of that so I was good in that department.

Another concern is E85 depletes your engine oil much sooner so I guess more frequent oil changes are in order too. I don't plan on running it a lot though as there's no pumps near my house to make it worth it.

Of interest I noticed I can't just add 40% blindly to my fuel maps and it worked correctly all over. I noticed while that worked almost all over I had to pull fuel in random spots like part throttle low load acceleration and certain tip in conditions etc. it went super rich and I had to pull fuel from certain spots. So the two fuels don't behave exactly the same but I suppose that's to be expected.
Of interest too I noticed that on cold start and driving e85 doesn't need nearly as much fuel enrichment as 91 does. Using the same enrichment tables as I use for 91 a cold start and drive on e85 puts me around the 12.5 ~ 13 AFR on light load till the motor warms.

[MalcolmV8]

BTW - how's this for a variation in gas. I didn't realize I'd have so many choices when I went up there

[cgrey8]

E30-E50 are considered the ideal blends from an octane/cost standpoint. E30 has roughly a 91-93 octane rating (depending on the octane of the gasoline its blended with). In the case of this blender pump, it appears its being blended with 89 octane. That's unusual since most places blend with 87 octane. Interestingly, the octane rating doesn't go up linearly. It goes up almost linearly from 100% gasoline to E40. But beyond that, the octane rating starts leveling off. There's very little octane change from E50 to E85. So I'd consider experimenting with the E30 and E40 blends to see how they work as well. My guess is E40 is going to perform much like E85 from a detonation resistance standpoint even with heavy boost and lots of advance. However you won't need to run nearly as much fuel since both the AFR and lambda demands will be much less. So if you do try E40, run the same spark advance as you are running with E85. But back the AFR back and the lambda enrichment back closer to gasoline levels. My guess is you'll find it's a tad more economical.

And BTW, notice the E85 button indicates what I said earlier that it could be as low as E70 (winter blend).

[MalcolmV8]

For some reason that station doesn't even carry 87. All they have is 89, 91 and the various ethanol options. I probably won't try all those other blends. When I put E85 in and crank the boost up I want the most protection possible.
They sell test kits to check the fuel and see if it's really E85 or E70 or wherever in between but from what I've read that's not necessary.

On a side note I also noticed that the smell from the catch can after making WOT pulls in boost (which shut down the PCV system and vent blow by) no longer has that nasty oily smell. Clearly the stink in crank case blow by is from regular gasoline. I never knew that. Always just though that's how hot oil from an engine just smells. However on E85 its almost completely odorless and the tiny smell you do get is actually quite pleasant lol.

[cgrey8]

Ethanol from corn does have a distinctive, almost sweet smell even in the gas can. It certainly doesn't have the distinct petroleum smell that gasoline and oil do. I also noticed the exhaust smell changed while idling too. It reminded me of the propane exhaust smell from forklifts.

It is interesting that station only carrys mid and premium. I also am envious of your gas prices. We are over $3.25/gal for regular here.

BTW here's an ethanol spreadsheet I threw together years ago when I was experimenting with E85:
Ethanol Fuel Economy.xlsx

Notice that there are multiple pages to the spreadsheet for each of the calculators.

I had to post this on EECTuning.org since this forum won't let me upload *.xls or *.xlsx files.

[MalcolmV8]

Very cool spreadsheet Chris, I'm curious to see what my real world mpg numbers are on E85 after running out a couple tanks.

[cgrey8]

I looked over the cost calculator and I remember those numbers meaning something to me at the time, but it wasn't intuitive to me immediately. So I added some notes to the spreadsheet that explain the numbers a bit more. It's uploaded and has replaced the old version.