Quote:
Originally Posted by Jay2TheRescue
Ethanol does not have the same amount of BTU's per unit of volume as gasoline. Ethanol will therefore reduce the MPG of a vehicle. Ethanol is used primarily for 2 purposes. It is an effective way of "watering down" the gasoline, and it is used as an oxygenating agent. It helps reduce the unburned HC level in the exhaust.
-Jay
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This is correct, but it's far from telling the whole story behind the power and MPG potentials of Ethanol.
The main loss in MPG people are seeing is because there's less power per cubic foot in ethanol versus gasoline. But there's MANY factors here that people are either ignorant to, or not talking about.
Ethanol can create MORE power than gasoline. Just talk to some serious drag racers. Ethanol is very similar to methanol, but much less corrosive, meaning rubbers and metals that are ethanol friendly are a bit easier to come by.
Why can it make more power? Stoichiometric ratio. The stoichiometric ratio is where a fuel makes the most complete burn. Gasoline's stoichiometric ratio is 14.7:1, and realistically is above 15:1 if you want to use every last molecule of gasoline, and closer to 12:1 if you want to use every last molecule of air. E85 (not even pure ethanol) is around 9.765:1. That's a LOT more fuel at the stoichiometric ratio, meaning more power.
Understand that engines are air pumps, and throttle controls air, not fuel. In an engine designed for gasoline that's now running E10, it's not running as much fuel as it can, thus there's normally a power reduction.
But wait, am I saying that once calibrated for E10 my car will get WORSE gas mileage still? Yup, but there's MORE!!!
Ethanol is EXTREMELY detonation resistant, and detonation (or knock) is the main factor engines are designed around. It's the whole reason engine compressions in the 60's went down so much when leaded gasoline was banned. The lead additive in gasoline prevented knock, allowing companies to run much higher compression getting more power out of every cubic inch of engine volume, and every molecule of gas.
Another huge factor, is that ethanol is extremely versatile on the air/fuel ratios. It can run much leaner and much richer than it's stoichiometric ratio. So, though it needs much more fuel for a given air volume to reach stoichiometric, it can safely run much leaner, and richer depending if you're going for economy, or performance.
Right now, the highest compression production engines are around 11:1. Ethanol only engines can run upwards of 16:1, even as high as 18:1.
If an engine was designed to use E85 there's VERY little data showing weather it would be less or more efficient. Like always, it comes down to too many factors. My personal believe is that it will be a wash either way. Ethanol has more versatility as a fuel, and I think at best it might get a couple % extra efficieny than gasoline, but the offset is that it will be able to create much more power on demand.
As a complete motor head, this is the first "green" tech to ever come along that I've been excited about. For the most part I find tree huggers and the like to be idiots, and rather annoying. They pay little attention to real facts, and make thier own assumption on the way science works.
Ethanol right now takes more energy to make.
I could care less though, because to me at least that's money not going to the middle east right? Even importing sugar can from south america is better than giving the billions we do to the middle east. Though statistically, with sugar cane for every gallon you put into the farming process, you'll gain about 11 gallons back in ethanol. Not a bad conversion.
It might sound like magic, but it's that basic magic of agriculture that we live on every day. You always get more out of the ground than you put in. Obviously it's more complex than that once you add in fertilizers and such, but my point is that even a kid can watch a kidney bean grow to much greater sizes than the origonal bean.
Another thing I like about ethanol is that it's a technology that is still seeing rapid improvement. Oil refining hasn't changed much, and won't change much in the forseeable future. There's lots of possabilities for ethanol.
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