ethanol removal

[raytoews]

When I was at Oshkosh in 96 there was a guy from a university who was obviously pushing ethanol. He had an RV3 and was running it on pure ethanol. When I asked him about mixing fuel he was quick to point out it was pure ethanol he was running.
I can believe ethanol will increase the octane (resistance to explode).
Light a can of gas and WHOOSH.
Light a can of ethanol and you get a pretty light blue to clear flame.

How would one go about doing some real world testing?
Set an engine up on a stand, crank the timing up until it spark knocked and then try different fuels?
I haven't heard an engine (pinging) since the 70's, EFI engines won't allow it with their knock sensors.
I have never heard an airplane engine ping, not sure you would hear it over all the other noise.

Would be nice if someone with a test cell and dyno would try it and post the results here, the way EAA did when they were STC'ing auto fuel.
Probably never happen, impossible to keep the lawyers at bay!

There are numerous companies developing av fuels but from what I have read they are limited production and would never release their findings to a bunch of crazy experimenters. Besides, no money in finding a simple solution like adding a little two stroke oil?

Ray

[wyoranch]

When I was at Oshkosh in 96 there was a guy from a university who was obviously pushing ethanol. He had an RV3 and was running it on pure ethanol. When I asked him about mixing fuel he was quick to point out it was pure ethanol he was running.
I can believe ethanol will increase the octane (resistance to explode).
Light a can of gas and WHOOSH.
Light a can of ethanol and you get a pretty light blue to clear flame.

How would one go about doing some real world testing?
Set an engine up on a stand, crank the timing up until it spark knocked and then try different fuels?
I haven't heard an engine (pinging) since the 70's, EFI engines won't allow it with their knock sensors.
I have never heard an airplane engine ping, not sure you would hear it over all the other noise.

Would be nice if someone with a test cell and dyno would try it and post the results here, the way EAA did when they were STC'ing auto fuel.
Probably never happen, impossible to keep the lawyers at bay!

There are numerous companies developing av fuels but from what I have read they are limited production and would never release their findings to a bunch of crazy experimenters. Besides, no money in finding a simple solution like adding a little two stroke oil?

Ray

(M)Ethanol is higher octane, but contains less energy(BTUs) than gasoline. I would run ethanol in my 600 CID 11.5 to 1 Chevy. Specific fuel consumption goes through the roof with Ethanol, but I have no issues with pre-ignition on a supercharged engine putting out over 1000 horsepower. The downside is that for correct air fuel mixture it requires about 30% more fuel over gasoline. As a side note it also fires cooler whether that is an advantage is up to you. I have no clue about how it affects an aircraft engine but I wanted to pass on the facts as I understand them about (M)ethanol.
Rick
P.S. please feel free to correct me if I am mis-informed!!!

[FlyingRon]

EFI engines will certainly run poorer when they retard to avoid the pinging. Clearly you could measure this (and frankly the electronic controls could tell you a pretty good estimation of "octane" as a result).


I'd avoid reinventing the wheel though. THere's already a ton of stuff out there on 100% ethanol in RVs and lots of info on flex fuel in auto engines.

[Mike M]

Very interesting thread. Why has no one tried to get an STC to use ethanol fuel in a small (low powered) airplane?

http://www.embraer.com/en-US/Imprens...-a-etanol.aspx

[Dana]

I can believe ethanol will increase the octane (resistance to explode).
Light a can of gas and WHOOSH.
Light a can of ethanol and you get a pretty light blue to clear flame.

Ethanol has higher octane, yes, but it's not "resistance to explode". Octane rating is a resistance to "detonation" (pinging). The reason ethanol doesn't go "WHOOSH" like gasoline is not because of its higher octane rating, but its lower vapor pressure (2.3 vs. 8-15 for gasoline) and higher flash point (55F vs gasoline's -45F). Though I suspect the flash point may be related to the octane rating (I'm not a chemist). Flash point and vapor pressure are certainly related.

[PaulMillner]

Ethanol has higher octane, yes, but it's not "resistance to explode". Octane rating is a resistance to "detonation" (pinging). The reason ethanol doesn't go "WHOOSH" like gasoline is not because of its higher octane rating, but its lower vapor pressure (2.3 vs. 8-15 for gasoline) and higher flash point (55F vs gasoline's -45F). Though I suspect the flash point may be related to the octane rating (I'm not a chemist). Flash point and vapor pressure are certainly related.

Flash and octane rating re unrelated... At any given flash point, there are zero octane and 100 octane molecules available.

Paul

[FlyingRon]

Flash and octane rating re unrelated... At any given flash point, there are zero octane and 100 octane molecules available.

Octane rating has nothing really to do with "octane" molecules. It's a measurement of detonation resistance compared to a pure octane source. Ethanol has zero octane molecules in it. Propane which has a very high octane (and very low flash point as well) and no octane moledules in it.

Another property, probably more related to octane rating is the auto-ignition temperature. For gasoline it's up around 280C where diesel is down around 260 an ethanol at 360.

[PaulMillner]

I have to question your comment with my common knowledge. Adding kerosene or diesel fuel to gasoline does not make it easier to ignite,,,it makes it harder. Throw gas on a fire and you have an explosion, throw diesel fuel on and you have a bigger fire.

Octane is all about slowing down the burn.

A gas engine will run on diesel/kerosene. I have personal experience. During the war farmers ran their tractors on diesel, started it on gas then switched to diesel.

Back in my younger days when we couldn't always afford gas we would "occasionally" siphon gas out of a field tractor and drive on that. We always had a little can of gas along to start the old low compression chevy.

I believe paraffin would gum up the injectors or carb jets??

Just adding fuel to the fire

Ray

ray,

octane rating is is about resistance to detonation under pressure... Mid-process in the combustion process. Your Unpressured bonfire experiments are not parallels. Jet or diesel have an octane rating of about 50... Which might be adequate in the 5:1 compression ratio tractors you cite. Not so good in a 8.5:1 aircraft engine.

Paul

[PaulMillner]

Octane rating has nothing really to do with "octane" molecules. It's a measurement of detonation resistance compared to a pure octane source. Ethanol has zero octane molecules in it. Propane which has a very high octane (and very low flash point as well) and no octane moledules in it.

Another property, probably more related to octane rating is the auto-ignition temperature. For gasoline it's up around 280C where diesel is down around 260 an ethanol at 360.

Ron,

In fact octane rating is defined by the properties of a very specific iso-octane molecule, 2-2-4 trimethyl pentane. So octane rating is very much related to octane molecules... That's how it's defined. I think what you might be meaning to say is that a hydrocarbon mixture need not contain octane to have an octane rating, and that's certainly true.

Autoignition temperature is a good predictor of whether you have gasoline, jet, or diesel... But not of octane rating. Normal heptane and iso-octane have nearly identical autoignition temperatures. But n-heptane has an octane rating of zero, and certain i-octane has an octane rating of 100...

Paul

[FlyingRon]

In fact octane rating is defined by the properties of a very specific iso-octane molecule, 2-2-4 trimethyl pentane. So octane rating is very much related to octane molecules... That's how it's defined. I think what you might be meaning to say is that a hydrocarbon mixture need not contain octane to have an octane rating, and that's certainly true.

I should have said the "presence of octane molecules." You were the one who mentioned such presence which implied that it somehow had relevance.