I'm switching to e85 soon, and was curious if anyone has tested the e content in any regions, or logged flex e content?

Researching e85, it's often confusing to understand the e content specs, with SOME regions allowing different content levels of ethanol winter and summer. Winter specs being allowed much lower (~40%?). Every time I read an article on specs, it's seems to be superseded by another. Not working now (refinery ops), I don't have super easy access to the wealth of knowledge (Hhmm...I can make some calls though).

I imagine (from decades of refining experience) they are going to blend low octane crap with any e85 blend content, as octane is not the spec. It's only needed for vapor pressure specs, etc for cold starting. I sure they use a straight run naphtha, or any hydrotreated sweet low octane blend stock. No reformed or higher octane stuff. I'd like to make my own blend (using 91 RON+MON/2) and have it tuned for it...?

I tested the one station I have near me, and it was 85 & 86% e on separate pumps. Quite pleased with that.

I'm going to test it for a bit. Curious to see what my winter numbers will be.
I'm in the Bay Area, Northern CA.

TIA

 

Test it all the time here in Lincoln,Ne. Highest I have ever seen is 83% and usually around 70% and seen it as low as 40 something. We have on station that is constantly around 75-80 so everyone try's to use that same pump lol.

 

The low numbers - is that winter only?

 

No, if you are testing 75-80% on an e sensor that is good. Legally in Nebraska E85 only has to be like E65, so finding a station with close to 80 is good. This also varies on states and ethanol plants in those states. Also you can not accurately measure E content with out an E sensor, the vials can give bad readings...

 

Here's a link from the U.S. department of energy. Looks like it can range anywhere from 51-83%, I think there is a state wide limit also but I may be wrong.
https://afdc.energy.gov/fuels/ethanol_e85_specs.html

 

the place I buy mine from the lowest it has ever been was 80% and is usually 85% or higher for most of the year

 

Just curious: do you folks see any big difference in power with ethanol content, either on a dyno or SOTP? I only ask because I was recently watching some YouTube videos of fuel tests that the tuning school had done and they were saying that once you’re over 50% ethanol or so, there’s no real difference in power? Sounded strange to me, so that’s why I’m asking.

 

I've never seen it below mid 70% E here, usual it's low 80's

I've heard the same Sammy.. I mean, at some point octane isn't limiting you anymore so going to higher E content doesn't seem to do much. I just run straight E85 all the time these days since it's easier than trying to keep it blended and E50'ish or anything like that

 

In the Chicagoland area it ranges from around 80% - 87% on the high end. Sometimes I go to the Myers in northwest Indiana where it’s always 85% -88%. I generally keep (4) 5 gallon pales in the garage, especially around the end of the season.

 

Some stations have different percentages but are mostly consistent. The holiday normally has E83 in the summer while kwik Trip has E75 in some locations. Lowest Ive seen it is E52 in winter

 

this is how I understand it as well, not a significant power difference but you do gain an octane advantage the higher the ethanol content which is a good thing for us... mine stays pretty consistent so I can't say I've noticed a power difference but if it swings too far either direction and you aren't on a flex setup then your afr will change accordingly

 

it is consistently e70 here.

 

So, is everyone in *semi* agreement that if the e content is >50%, that's enough octane to keep tables/power at ~ROUGHLY the same as up to ~85% e? Same to similar power as e85? Good news if that's the case...

I was trying to find tables or calcs for octane numbers at 50% e blends. I know for a fact that straight run naphtha - or any sweet gasoline blending component will be about 80 to 84 octane...and I highly doubt they'll spec reformed/isomerate/alkylate or higher octane blend stock to ensure a higher octane. In fact I was reading some material that the oil companies were trying to find a way to limit the octane give way ($$$).

When I get the HC specs for the varying E content blends I'll report back here.
TIA

 

You could be really rich or lean if you don’t watch it though. That’s why it would be good to have a wideband if you don’t have flex fuel. If you tune on say e83 and you go somewhere that has e72, you’ll be rich. If you get tuned on e70 and then fill with e85, you’ll be lean. That’s why it’s good to find a station that is offers consistent ethanol and try to stick with it.

 

I'll be on flex, with the GM sensor.

 

No big difference in power from pump e85. Ours locally is pretty good. Winter is over 70 and summer is close to 85. I have Ignite for extra kill mode though.

 

Does that mean that you may need to adjust the tune for ethanol content changes from say, E50 to E85, even if you have a flex fuel sensor? Should you aim for a different AFR (displayed) based on ethanol content?
BTW: what’s the “ideal” AFR range you should be aiming for with FI on E85, once you have the correct stoich settings in the tune set and you’re using a flex fuel sensor? By that I mean, what AFR should you be looking for on your wideband? My understanding is that once you have the tune and scanner set up properly, the wideband should be displaying roughly the same AFR @ WOT as it would on gasoline (say,11.4-11.6:1), when in fact the tune is fueling the motor based on the stoich tables? Or do you have to switch over to reading lambda instead of AFR on the wideband?

 

As octane goes up, you can bring more timing in if the engine was octane limited, until the point at which the piston/lever is in an optimum position atdc, and that is it. Increasing timing from that point will hurt power and raise peak pressure which could blow a gasket or fracture a piston. On E85 the engine won't audibly 'ping' or 'detonate' during this period, so it may simply explode violently or pop a gasket.
As octane goes up, power potential per unit mass of fuel goes down. So if you switch from say 87 octane to 93, or from 93 to C16 racing fuel, and don't change the quantity (mass) of fuel, power must also go down even though octane is higher, unless the engine was octane limited. e.g. I think most NA engines lose around 5% power. Also it should be obvious that an engine won't run with the same mass of Ethanol as Gasoline and that mass needs to be dramatically adjusted, making this comparison useless for Alcohol.

So if you are already optimal timing on say, 93 octane. Then E85 wouldn't do anything for the spark timing. Any extra power comes from the cooling of intake tract/evaporative nature of alcohol which gasoline does not provide.

How to determine optimal timing?


Unless you have one of those cylinder-pressure testers (above picture) You would be using traditional methods of spark plug reading, EGT/wideband and dyno tuning:
Spark plug method acceptable for stock engines up to 1k rwhp: https://sites.google.com/site/sloppy...ls/spark-plugs


Gasoline is very temperature sensitive. Engine that produce a lot of power per cubic inch will use a lot of gasoline and make a lot of heat, which over time can accumulate in the cylinder, which over time adjusts the volatility of the fuel. In other words, if the cylinder/piston gets hot enough, the fuel will no longer behave the way it did when everything was cool. It could explode immediately (imagine spraying a mist of gasoline onto a hot frying pan) or prematurely (preignition) even without hot spot contribution.

Alcohol acts temperature independent. If a cylinder is getting hot and accumulating heat, it will not affect the rate of the combustion reaction nearly as much as it does to gasoline. The alcohol also brings with it a cooling effect that lasts as long as alcohol is evaporating (just prior to combustion everything gets a cool-down). Alcohol also tends to clean everything it comes into contact with, removing carbon and oil deposits, which help keep compression ratio lower (carbon and oil increase compression which leads to hot spots and pinging etc...)

Alcohol appears to be an ideal racing fuel for racing in which conservation of energy (economy, mileage-distance) is not an issue.

Gasoline is ideal in situations where you need to create a lot of heat, and use that heat to maintain the efficiency of combustion reactions while using the cheapest fuel.
i.e. manufacturers are designing gasoline engines with higher compression, higher coolant temperatures, and increased insulation, all to acquire gains in efficiency/economy/emissions.

 

Excellent explanation and info!
Gasoline (MOGAS) auto-ignite temperature is higher than most fiuels, even with diesel having much more BTU's... Much lower BTUs require much more fuel, which results in more cylinder Cooling, correct?

(FWIW the Flash Point = the temperature at which point a hydrocarbon will give off FUMES that can ignited. The auto-ignite temp is when the fuel will burn (if O2/HC ranges are in proper range).

I was not aware that ethanol has a much higher auto ignite temp than just gasoline...as indicated below.

 

Dupe - not smart enough to understand how to delete a post