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Back from the Tetons and experience of high altitude driving. Maybe a dumb question, but is E85 good at high altitude? Read a post from Cessna that made me think of mountain states fuel supply.

 

Not much E85 in Wyoming, that I found.  Mostly 85 octane unleaded. A search of e85vehicles produced little on subject of high altitude fuel.

 

Items of interest on subject:

 

1. Higher altitude will increase fuel vapor pressure something EPA concern with.

 

2. Higher altitude air, less dense and as result less oxygen

 

3. Although modern engine controllers will adjust the fuel mix ratio based on available oxygen, still fuel stations in high altitude regions supply low octane fuel. Is this fuel low btu fuel? Being so, because engines can't develop hp.

 

4. Would E85 be a tremendous fuel for high altitude as far as producing power? It appeared this way.

 

 

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this is out of my league scientifically... but historically, ethanol was used a lot for this reason in WWII for high altitude bombers/fighters over Europe...  the internal combustion engines at these very high altitudes were struggling with not having much oxygen for combustion... crews even had to use oxygen masks... adding ethanol to the aviation fuel added some of that oxygen to allow the engines to perform as needed. 

 

It would stand to reason that it would help autos in the mountains then...

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My guess their is something more to this as it's to simple a solution. Higher altitude drivers love turbos for making power. The 4x4 vehicle owners like the big V-8s to get power.

 

If ethanol could solve the low power problem of high altitude driving E-85 would gain much popularity. But, have to say my truck appeared to have no power loss with the high ethanol mix fuel. Go figure?

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i think there is no big difference between gasoline and ethanol or E85 at high and low altitudes.

 

ECU controls AFR by MAF sensor, and AFR always will be correct, at any altitude.

 

ethanol and methanol using in engines (at any altitudes) for other purposes, basically becouse of their cooling properties and high octane rating.

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Back from the Tetons and experience of high altitude driving. Maybe a dumb question, but is E85 good at high altitude? Read a post from Cessna that made me think of mountain states fuel supply.

 

Not much E85 in Wyoming, that I found.  Mostly 85 octane unleaded. A search of e85vehicles produced little on subject of high altitude fuel.

 

Items of interest on subject:

 

1. Higher altitude will increase fuel vapor pressure something EPA concern with.

Vapor pressure is related to the fuel itself (or in general, the liquid / substance)  it doesn't change with altitude.  Reid vapor pressure is measured in a closed cup, so it, too is more of an absolute measurement.

 

2. Higher altitude air, less dense and as result less oxygen

Yep, and less oxygen means less fuel is able to be burned.  Not sure how this would be considered 'good' or 'bad' - though as noted below, it could have a few benefits for E85.

 

3. Although modern engine controllers will adjust the fuel mix ratio based on available oxygen, still fuel stations in high altitude regions supply low octane fuel. Is this fuel low btu fuel? Being so, because engines can't develop hp.

I think you are mixing up a few parameters...AFR, octane and BTU really have no relation to each other.  Low octane fuel is supplied at high altitude because even though the static compression ratio of a given engine remains the same, the pressure developed during compression is lower at higher altitude.  This is simply due to the lower initial pressure of the atmosphere.  Lower compression pressure means lower octane requirement.  So an engine which requires 87 octane at sea level may only need 85 at 5,000 feet.  I guess this may be a negative for E85 - it is needed even less at high altitudes. (assuming all other engine parameters stay the same)

 

If you look at AFR, I'm at ~875 feet here and most engines seem to run around 0 LTFT.  I would suspect an engine at high altitude may run negative LTFT (say -10)  So if one were to convert a car to E85 at high altitude, the ECU would still want to adjust maybe +25 to +30 points in LTFT but instead of starting at 0 and going to 30 (which may set an ECU code) it would start at a negative number and go to maybe +15 or +20 - which should be perfectly acceptable as far as the ECU is concerned. So that might be considered a plus for E85.

 

4. Would E85 be a tremendous fuel for high altitude as far as producing power? It appeared this way.

Well, all things being equal...ie take a stock 'grocery getter' engine from sea level to high altitude, and it's octane requirement drops due to the lower atmospheric pressure. 

 

So it would seem like E85 is even more of a waste in that application.  The engine needs 87 octane at sea level, maybe 85 at altitude, but you'd still be feeding it 105 octane.  If you turbo'd it, you could make more power, but even given 10 psi boost at sea level vs 10 psi boost at altitude, the high altitude would deliver less compression pressure, so again a waste of E85 octane.

 

 

So, all things being equal, it would seem E85 is more of a waste at high altitude.  Instead of wasting 105 octane E85 in an engine which can run 87 at sea level, you are wasting 105 octane in an engine which only needs 85 or even less at altitude.  If you boost to a certain psi at sea level, you still have less pressure in the cylinder boosting to the same psi at altitude - again a waste of extra octane.

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Thanks, guess the percentage hp gain when switching to E85 the same. Meaning at sea level or high altitude. Ethanol has less energy per gallon, but since the fuel has chemical bound oxygen more of it can be squirted into combustion chamber. The overall energy produced per liter of engine displacement higher at a cost of mpg.

 

Since high altitude hp is at a premium, note the big V-8 in Jeeps….E85 should be popular as reports from 5% to 20% gain in hp depending on engine technology just by change over to E85. 

 

Another problem….vapor lock. Gasoline/ethanol blends have higher vapor pressure. The chemistry of the two reacts to produce higher vapor pressure than one would think and higher than each separate component.

 

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