My Research Assistant working on my next ethanol blend. It may take some time to complete this study, but I'll report back with my findings.
Posted on 12/05/2007 9:29:42 AM PST by Red Badger
A minor inconvenient truth.......
You can’t buy gasoline that would allow a 12:1 compression ratio as auto fuel. For any amount of money. The refineries refuse to produce high octane gas for any purpose other than special racing fuels for WWII piston fighters - and then they bring in those loads of fuel specially to places like Reno/Phoenix. Common piston aircraft engine fuel is the highest octane gasoline you can commonly find — called “100 low lead” or “100LL,” it still has tetra-ethyl lead as an octane booster in it.
Since WWII and the end of the mighty piston engines that required 130 octane fuel, we have seen only crappy, low octane gasoline. After WWII, the Oliver Tractor Company approached the refineries in the 1950’s trying to get higher octane fuel for their X-121 engine project (a 12.5:1 compression ratio engine). They showed (with actual engines and dyno’s, not just theory) that if they could get 120+ octane fuel consistently, they could reduce gasoline consumption by the gasoline engine in a tractor by 20%+. All they needed was higher octane gas.
The refiners categorically refused to produce the higher octane fuel, which killed the Oliver X-121 engine project. Shortly thereafter, Oliver went to diesel engines in tractors.
Currently, most unleaded gas is 87/88 octane at the pump, and has a “research octane” rating of 91, with premium gas having a “research octane” of 95.
Ethanol as a “research octane” rating of 129.
” Hmmm Fuel with less energy will do more work. makes sense to me (as long as you repeal the first law of thermodynamics..”
THat’s assuming you get complete combustion of the fuel source which we know not to be the case in internal combustion engines.
Perhaps at a lower BTU content the fuel combination becomes more efficient as the data suggests.
I am curious as to whether or not this was checked. Ethanol is hygroscopic.
All ethanol will contain some water, that’s why the strongest liquor you can get is only 180 proof, pure alcohol will absorb 10% water by volume from the air alone.
Some engines would need to be redesigned, yes, but they wouldn’t be as heavy as you’d think.
Part of the reason why diesels are so heavy is that most diesels are designed to take 19.5 to 20:1 compression ratios, as well as much higher power densities. Unlike a gasoline engine, many diesel engines are designed to cover a range of HP outputs. The same engine block in my JD 4440 tractor (a 466-cu in inline-6) at 135 PTO HP is in the 4840 tractor at the high end of the line, and that engine is regularly “turned up” to produce 200 PTO HP. Just push in more air with a bigger turbo, turn up the fuel delivery at the injection pump and you increase the HP. Deere designed that engine to withstand the demands of the high end of the power output, then just put on smaller injectors, pumps, radiators, etc as they went down the power scale.
Today, diesels in trucks, tractors, etc - are commonly controlled by a computer. Change the firmware on the computer controlling the fuel injection pump and you change the output. The engine is still designed for the high end of the HP output range. That’s why so many diesels seem so massively over-built.
So designing a gas engine to withstand 12:1 compression ratios isn’t going to result in a block that looks like a Cummins 855 stuffed under your Geo’s hood. More than likely, you could accomplish a compression ratio increase to 11 or 11.5:1 on many engines by changing the pistons and heads and leaving the block in place.
Chevron investigated what would be the worst possible blend ration and found that between 10 & 15% offered the worst gas mileage. This was then the percents that were suggested so that the oil companies did not lose market share (Same amount of oil to go the same number miles). Chevron holds the patents to these blends.
“The new study, co-sponsored by the US Department of Energy and the American Coalition for Ethanol (ACE)”
LOL! In other news, a study co-sponsored by Burger King and McDonalds found that fast food is quite healthy. :)
My guess is it will take about six months to a year of regular ethanol use, in the quantities above E10, for rust and dry rot to begin to plague a non-flex-fuel vehicle.
I find the news in the article good news, however, especially the 15% increase in the Chevy flex-fueler. There are millions of these flex-fuel vehicles in the hands of drivers who are nowhere near E-85, but if blends of lesser ethanol content could deliver that much of an improvement in fuel economy, then the demand for it will soon begin in earnest.
But many street motorcycles have 12:1 compression and run on premium gas e.g 2008 Honda CBR600rr 12.2:1
The thermal efficiency of a common gasoline engine tops out at about 29%.
A typical diesel engine’s thermal efficiency is at least 34%, and when you start putting on turbo’s and including two-stroke diesels with blowers, you can see thermal efficiencies up to 50%.
The reason why is the short extraction stroke on gasoline engines and the longer extraction stroke on diesels.
Another possibility to gain more fuel efficiency out of a gasoline engine would be to ditch the Otto cycle engine and convert to a Miller cycle engine, which would result in improvements without raising the octane, but would get a MUCH more dramatic boost with higher octane fuels.
ch3ch2oh + o2 = co2 + h2o. ch3(ch2)nch3 + o2 = co2 + h2o Same combustion products. besides you can't get any more work out of steam than the energy put into it by combustion.
There are more dynamics at work in a piston engine than the first law. For example, if the ethanol enables the engine to burn the fuel mixture more completely than it does the straight gasoline, you could conceivably get more energy from the ethanol mixture. Not that the gasoline has less BTUs in it, of course, but that you just aren't harvesting all of them inside the cylinder where they can do useful work. We know there are unburned hydrocarbons left over in a straight-gas engine, because something is left to light off the catalytic converter.
I agree, the additional weight if any would be just a factor mitigating against any improvement in mileage; nothing like a Cummins or Deere.
Did you really remember from another post that I drive a 50+ mpg Geo Metro running on 87 octane with a three cylinder engine a strong boy could lift?
My Research Assistant working on my next ethanol blend. It may take some time to complete this study, but I'll report back with my findings.
Can’t copy and paste the graphs; go to link and click the different boxes for the standard test.
http://www.fueleconomy.gov/feg/fe_test_schedules.shtml
Put your hip boots on ping.
.
As Grampa used to say...hooey.
Nope that's assuming that the same engine functions at the same thermodynamic efficiency for different fuels. The thermodynamic efficienly of any cycle is primarily determined by the inlet and outlet temperature differences (very loosely translated into compression) The compression of any given engine is usually fixed by it's mechanical parameters, so there isn't any reason to expect that a mixture of ethanol + gas will burn any more efficiently than gas.
What determines the power output of any engine is three things - the thermodynamic efficiency of that engine, the energy available in the fuel, and how much fuel it can burn in a unit time. That is why turbo and supercharged engines can put out more power for the same displacement. They pack more air and fuel in the same sized engine. Another way to get and engine to put out more power is to design it to be able to run at higher revs. More fuel burned per unit time. None of this would appear to be helping ethanol gas mixtures which have less energy than straight gas develop more HP. I suspect that this "report" is like global warming. Start with the conclusion and alter the facts to fit your conclusion.
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