Pure-Gas: For How Long?

[rxcrider]

Just my personal experience, but when the E-10 hit the market, I noticed a 20% drop in MPG on my bike, (Harley Electra Glide) and the car (Ford Explorer). Also, the engine in my tiller burned out, had to buy a new riding mower after the valves fried. If 10% ethanol translated to 20% loss of mileage, I'm actually burning more gas. Now, with the R1200RT, the manual says avoid ethanol, and the Subaru seems oblivious. Still, whenever I can, I use real gas.

20% is high, but plausible assuming a carbureted or open loop FI engine with no effort made to adjust the mix for the new fuel.

To the orginal point, I still have one local filling station with a 91 octane ethanol free pump. I get it for 2 stroke mix and for things that will sit for quite a while, like the generator.

 

[swall]

Rxcrider--my fuel management strategy is similar to yours. I'm a little more anal on generator fuel, though. I put a mix of Coleman fuel and toluene in my generator fuel tank for long term storage.

 

[rxcrider]

I just keep ethanol free in it for a year at a time with marine Stabil in it. If it hasn't been used, I run it for a while, the transfer out the fuel for use in the mowers, fill it with fresh and run it again for a bit before putting it away again.

 

[Omega Man]

Stebe--in the U.S. , ethanol is produced by using yeast to ferment a mixture of water and ground corn kernels. In Brazil, ethanol is produced by fermenting molasses squeezed from sugar cane. The second stage of production is to distill the fermented mixture to remove the ethanol. At that point, the ethanol from corn is indistinguishable from the ethanol from sugar cane. The final stage is to dehydrate the distilled product to remove the residual water content. In Brazil's earlier efforts, this step was not performed and the engines were run on this "neat" ethanol, which is 95% ethanol/5% water. In the U.S. a 99.5% ethanol product is required because it is blended into gasoline. If the water were not removed, a phase separation would occur, which is not a good thing.

For your consideration-
Keep an eye out for an odd discoloration, a blotchy almost "over-spray" looking substance near the flip close gas cap covers on cars, especially a white car. A friend of mine brought this to my attention and has theorized it is a mold growth caused by the fermentation mentioned above. I'm inclined to agree as I have seen the same.
Ethanol hasn't done anything good for my engines.
OM

 

[rangerreece]

FWIW, I have seen a marked increase at least, in my area, of non-ethanol gas products at the local gas stations. Maybe our activism is seeing results.

 

[36654]

20% is high, but plausible assuming a carbureted or open loop FI engine with no effort made to adjust the mix for the new fuel.

To the orginal point, I still have one local filling station with a 91 octane ethanol free pump. I get it for 2 stroke mix and for things that will sit for quite a while, like the generator.

If the fuel has nominally the same heat energy (i.e., BTU's / volume) and octane rating how would your carburetor or FI system know the difference?

 

[pglaves]

If the fuel has nominally the same heat energy (i.e., BTU's / volume) and octane rating how would your carburetor or FI system know the difference?

Ethanol alcohol has approximately 30% fewer BTU per unit volume than does real gasoline. Thus with a 10% mix, the BTU content of the adulterated fuel is approximately 3% less. But in actual use, mileage decreases seem to decrease by between 5% and 10%. I can document many tanks with a 9% or 10% reduction im mileage. (40 vs 44 in a K75, for example) The 20% mentioned is extreme, but probably a carbureted bike.

 

[AKsuited]

If the fuel has nominally the same heat energy (i.e., BTU's / volume) and octane rating how would your carburetor or FI system know the difference?

Sorry, but you are way off. Gasoline has way more energy content than Ethanol.

Look at it for yourself: http://www.afdc.energy.gov/fuels/fuel_comparison_chart.pdf

That is why fuel economy goes down when perfectly good gasoline is contaminated with ethanol.


Harry

 

[rxcrider]

If the fuel has nominally the same heat energy (i.e., BTU's / volume) and octane rating how would your carburetor or FI system know the difference?

Say you designed an engine to run on a carburetor. You've chosen this route for cost reasons. As such you would also like to avoid spending the money on a catalytic converter. So you jet your carburetor to meet the current emissions standards and in order to meet these requirements you run it leaner than the engine would like. You know it won't be the most efficient and make the most power, but it runs well enough. As we know from oilheads, running on the lean side of life can cause all sorts of weirdness; surging, misfiring, reduced power and despite the fact you are feeding the engine less fuel, reduced fuel economy. Now take this engine that you designed to run on the fuel standard at the time and push it a few years down the road to E10 fuel. You may have now push the enveloped from marginally lean to substantially lean and problematic. Keep in mind that Ethanol not only gives you less hydrogen per unit, but also adds oxygen to the mix giving you two nudges to the lean side. The fuel injected bike next door with an O2 sensor can adjust its trim, but the lowly carburetor you chose needs to be rejetted.


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[52184]

Sorry, but you are way off. Gasoline has way more energy content than Ethanol.

Look at it for yourself: http://www.afdc.energy.gov/fuels/fuel_comparison_chart.pdf

That is why fuel economy goes down when perfectly good gasoline is contaminated with ethanol.

Harry

And also why jet sizes for pure alcohol-fueled engines require roughly 2.15 times the cross-sectional area of comparable gasoline engines. Which in turn begs the question of how--or if--European manufacturers, where gas is pure, program into an EFI system some form of compensation for our alcohol-polluted gasoline. Knock sensors telling the EFI to richen up and spark timing to retard when detonation occurs? Crude, but effective--at the expense of mileage. Or are they doing more, and if so--what and how?

Best,
DG

 

[36654]

Sorry, but you are way off. Gasoline has way more energy content than Ethanol.

Look at it for yourself: http://www.afdc.energy.gov/fuels/fuel_comparison_chart.pdf

That is why fuel economy goes down when perfectly good gasoline is contaminated with ethanol.


Harry

Harry,

E10 is 10% Ethanol, 90% Gasoline. The BTU difference is 3% between E10 and pure gas.

 

[36654]

Ethanol alcohol has approximately 30% fewer BTU per unit volume than does real gasoline. Thus with a 10% mix, the BTU content of the adulterated fuel is approximately 3% less. But in actual use, mileage decreases seem to decrease by between 5% and 10%. I can document many tanks with a 9% or 10% reduction im mileage. (40 vs 44 in a K75, for example) The 20% mentioned is extreme, but probably a carbureted bike.

Paul,

You calculated the energy content of the mixture. How could that support your conclusion and why would it matter with a carbureted engine? Again, the energy content is similar and the octane is the same. The stuff will ignite the same and has similar heat energy......where's your loss?

 

[pglaves]

Paul,

You calculated the energy content of the mixture. How could that support your conclusion and why would it matter with a carbureted engine? Again, the energy content is similar and the octane is the same. The stuff will ignite the same and has similar heat energy......where's your loss?

My loss is in the miles I can go with each gallon. That is empyrical data. In the real world the mileage difference depends on how well the engine can utilize the different fuels. The energy content in each unit of fuel is one factor. How well the engine uses that energy is another factor. Fuel injection running closed loop, sampling the O2 content in the exhaust almost instantaneously provides one result. Running a crude vacuum operated slide carburetor with no feedback loop may well provide a totally different result - which is one of the key reasons modern vehicles meeting strict emissions and fuel use standards are virtually all fuel injected.

I tend to see a decrease of 3 or 4 mpg with ethanol compared to pure gas on both my K75 and my R1150R. The reported 20% decrease is greater than I have ever experienced. That would equate to a reduction from say 44 down to 36 which I have not seen.

 

[akbeemer]

I was told by a friend who owns a fuel delivery firm that the actual amount of alcohol in some of our local stations can vary a great deal. I don't know if or how closely ethanol content is monitored in general or in our local area.

 

[swall]

GTRider--for engines running higher than 10% ethanol, a sensor is used (I think it is a capacitive device) to determine presence of ethanol. This information then tells the ECU to richen the mixture above and beyond the feed back from the O2 sensor..

 

[pglaves]

GTRider--for engines running higher than 10% ethanol, a sensor is used (I think it is a capacitive device) to determine presence of ethanol. This information then tells the ECU to richen the mixture above and beyond the feed back from the O2 sensor..

That might be true for engines designed to use fuel with greater than 10% ethanol, but certainly isn't true of any vehicle I own which happens to get a dose of mis-mixed crap from a station somewhere. The ill advised farm and agribusiness scam known as ethanol in gasoline (as opposed to actual alcohol burning engines which were developed 75 years ago during WWII) would be eliminated if Congress wasn't on the take.

 

[martyhill]

That might be true for engines designed to use fuel with greater than 10% ethanol, but certainly isn't true of any vehicle I own which happens to get a dose of mis-mixed crap from a station somewhere. The ill advised farm and agribusiness scam known as ethanol in gasoline (as opposed to actual alcohol burning engines which were developed 75 years ago during WWII) would be eliminated if Congress wasn't on the take.

Thank you Paul, I look fwd to meeting both of you some day!

 

[lkchris]

Not really covered yet is the fact that ethanol is the replacement for tetraethyl lead as an octane enhancer. In that role, it's a godsend.

I'm consequently quite suspicious of those claiming to sell alcohol-free gasoline these days, as there has to be some additive to achieve the required octane and it can't be lead, as that's now illegal except possibly at the airport (maybe not, don't know).

Americans seem to be hanging on to the old-fashioned notion of low compression/large displacement engines, but that's a formula for excessive fuel consumption. These days the solution is higher compression and smaller displacement. High compression = higher efficiency. Also fewer cylinders--see the return of 4-cylinder Porsches. And of course turbocharging, which is just another way to create high compression and to maintain the effect more consistently with varying atmospheric conditions, including altitude. All of this requires knock resistance, of course, and that means octane enhancing additives. There is even some talk of phasing out "regular" gasoline by regulation if not legislation. Ethanol has its uses.

Kind of a funny thing ... ten years ago I got to witness a 6.3 liter Mercedes AMG V8 engine being hand built. Naturally aspirated. That engine is now, I think, mostly out of production, replaced by something of smaller displacement and turbocharged. The newer motors make more horsepower. 6.3 badges are still used on the cars, however ... marketing.

 

[Stebe]

20% is high, but plausible assuming a carbureted or open loop FI engine with no effort made to adjust the mix for the new fuel.

To the orginal point, I still have one local filling station with a 91 octane ethanol free pump. I get it for 2 stroke mix and for things that will sit for quite a while, like the generator.

Both were carbureted engines, The car dropped from averaging 24 - 27 mpg down to 18 - 22mpg, the bike from 47 - 50mpg down to 40 - 42. The 20% number was a quick off-the-top-of-my-head calculation that may not completely hold up to scrutiny. Decidedly a loss of mpg, either way.

Your mileage may vary.

 

[52184]

swall, thanks for the info.

On the TEL issue, that was only one of the many additives considered for octane boosting. In spite of pre-existing data showing its extreme toxic effects it was selected anyway, mostly due to profit considerations. In my book, the same consideration pushed ethanol into use.

As for octane rating, much of that is determined at the cat cracker where the fuel is refined. Additives are just a faster, usually cheaper way of getting to the octane rating you want. At the station where I buy my non-ethanol gas both "pure gas" and ethanol gas are marked with the same octane rating, and I can't find anything on the EPA or other sites showing any mysterious MTBE-like additives approved for use. Yet.

Best,
DG