Naif al Hilali
FULL MEMBER
- Joined
- Nov 5, 2016
- Messages
- 324
- Reaction score
- 24
- Country
- Location
Blogs
Ethanol in Motor Gasoline
Eat it, drink it, or burn it as fuel?
By Kevin Cameron December 1, 2016
Cycle World
Technical Editor Kevin Cameron shares his wealth of motorcycle knowledge, experiences, insights, history, and much more.
The introduction to a book on bartending once began, referring to ethyl alcohol, “Mankind has been systematically poisoning himself for 50,000 years.” To this we can add the present controversies over E15 and higher-percentage gasoline-ethanol blends. Plastic Ducati gas tanks have absorbed ethanol sufficient to swell, making it almost impossible to free them from the frame rails. Plastic or rubber fuel system parts can do the same, causing carburetor or fuel quantity floats to sink and possibly resulting in leakage. Upon removing carb float bowls, we may find sludgy green deposits. Operators of passive-fuel-system engines (those that cannot automatically adjust their own mixture) say they’ve had “ethanol lean-out”, leading to overheating and seizure. How? Ethyl alcohol contains only 2/3 as much energy per gallon as gasoline hydrocarbons do, so the more alcohol you add to motor gasoline, the leaner your mixture becomes. With E10, the lean-out effect is 1/3 of the 10% ethanol, or 3.3% - easily covered by the safely rich condition of most street-operated carburetion. Carburetors had to be set rich enough to be safe in the coldest anticipated conditions (air density increases but fuel density remains constant, which is a lean condition), so they operated comfortably rich in warm weather.
But with E15 and higher levels of alcohol addition, the percentage of lean-out becomes greater and the cooling effect of excess fuel is lost, causing combustion temperature to rise. This is the problem of carbureted engines run on E15 and higher.
Clearly, if E15 is a pump option only, the buyer can take care to select a fuel safe for his/her vehicle. But a fear exists that availability of E15 signals a Federal trend away from fuels (E10) that are relatively safe for engines with passive fuel systems. This would imply a future in which such vehicles could be operated only on expensive specialist fuels such as racing gasoline.
There are limits to ethanol use even in the case of fuel injection. As we add ethanol, the mixture leans, but the oxygen sensor in the exhaust detects the change and enriches the mixture in proportion. Sounds good – where’s the problem? The problem is that vehicle makers size their fuel injectors for the anticipated fuel. If the fuel changes so that greater volumes must be injected, eventually the flow limit of the injector is reached. Beyond that point, the oxy sensor, computer, and fuel system can no longer keep up with the drop in fuel energy as we add more and more ethanol. Again, the result is enleanment. To cover this possibility, vehicle manufacturers generally forbid the use of alcohol blends higher than E10.
Some vehicles are not limited in this way – the so-called ‘Flex-Fuel’ vehicles. Their fuel systems are designed to be able to cope with high-alcohol blends such as E85. The added cost of this fuel flexibility is buried in the generally higher price of such vehicles. As you may have noticed, Flex-Fuel vehicles are often large. Normally, if a maker wants to produce a high-profit luxury SUV which uses twice the fuel of the usual econobox, it must comply with CAFÉ standards (CAFÉ = Corporate Average Fuel Economy) by producing a great many more economical vehicles so that the average economy of that maker’s fleet averages out to meet the standard. But a deal was made; if the heavy vehicle was built as Flex Fuel (making possible operation on lower-emissions alcohol-rich blends such as E85), then 100 such heavy vehicles could legally be counted as a smaller number. Who could resist?
But wait – how did we get into adding ethanol to motor gasoline in the first place? Back in the late 1970s and early ‘80s there were hundreds of thousands of old carbureted vehicles on the nation’s highways. In their carburetors, fuel metering needles and the orifices in which they operated had worn in use, making fuel mixtures richer and increasing emissions of unburned hydrocarbons. Was there a way to fix this? Yes there was – to dilute motor fuel (especially in smoggy urban areas) with a low-energy-content ether – MTBE. Thus began the use of so-called “oxygenated fuels”. What this term actually means is that such fuels are partially burned (that is, partially combined with oxygen), somewhat reducing their content of chemical energy.
The MTBE program began with great enthusiasm and purpose, constructing specialized plants for making the stuff. Then came a terrible blow; MTBE was not decomposed by soil bacteria as normal fuel hydrocarbons were. It persisted in ground water for long distances, appearing in drinking water. Screech, the MTBE program was quietly halted. In its place was put ethyl alcohol.
Ethanol is an excellent fuel which strongly resists detonation. The power gain achieved on 100% alcohol (which has long been used in Australian motorcycle racing) comes not from its energy content, which is low (see above), but from its high heat of evaporation. As alcohol evaporates, it takes heat from the air with which it is mixed, refrigerating that air and increasing its density such that a greater weight of fuel/air mixture will fit into engine cylinders.
Although alcohols cause slow swelling of the familiar plastic ‘Plexiglas’, they are listed as very compatible with nitrile rubber, a common seal material. This apparent easy solution is denied us by the fact that gasolines now contain large percentages of aromatic compounds (toluene, xylene, xylidene) which are not compatible with nitrile rubber. Choice of fuel system elastomers is tricky.
Further, quoting from the Owen and Coley “Automotive Fuels Handbook”, “Methanol and ethanol are corrosive to many of the metals that are used in conventional fuel systems such as terne plating used in fuel tanks (a lead/tin coating on steel), aluminum, copper, brass, magnesium and die cast zinc. “Elastomers and plastic components can also be attacked. Carburetor and fuel gage floats are often made of plastic and have been known to swell and stick. Fiber gaskets can be softened and fuel hoses and pump diaphragms can swell or harden and crack.”
What this means is that the nature of motor gasoline should not be arbitrarily changed by government administrators without the most detailed consultation with the vehicle industry. Because motorcycles are greatly outnumbered by cars, it is possible that this consultative process may not include their manufacturers.
Why not just require all vehicles made after a certain date to be Flex-Fuel? First of all, any added system adds cost. An engine optimized for E85 would have a compression ratio too high for operation on ordinary gasoline, but with compression set at the high limit for gasoline fuel, when running on E85 we’d be throwing away some fuel economy which higher compression could have delivered. A vehicle returning a fuel mileage of 30-mpg on gasoline would deliver more like 22-mph on E85. The take-away here is that engines cannot be optimized across the range from common E10 to E85. A compromise is always present.
We have recently seen a proposal to build engines which could break this compromise – engines able to vary their compression ratio while operating. Certainly this is possible – the standard laboratory CFR knock-test engine has had this feature for seven decades – but it would add substantially to the cost, weight and complexity of engines.
The following label has been approved by EPA for placement on pumps capable of dispensing E15 fuel:
Cycle World
E15 fuel label.
Like so many other things, the E15 controversy has acquired political aspects. Quoting from a USDA site; “Strong demand for ethanol production has resulted in higher corn prices and has provided incentives to increase corn acreage.”
Another USDA site gives figures for 2016 averaging just over 38% as the fraction of US corn now devoted to ethanol production.
You get the picture. Environmentalists are delighted at this use of corn because it satisfies their desire to see renewable energy sources replace fossil sources. The petroleum industry sees a gallon of fuel ethanol as 2/3 of a gallon of gasoline they don’t sell. A factory farming organization will naturally seek to increase the percentage of ethanol in motor gasoline. Think of being a Congressperson, deafened by the roar of all this lobbying. Is there any such thing as “right”? Or has right come to mean “what I want” while wrong means “what my opponents want”?
Still others see conversion of corn to ethanol as the institutionalizing of hunger in the form of “burning food.” Could it be, as claimed by some big-picture pundits, that the world-wide rise in food prices in part cause by conversion of corn to ethanol led to the social unrest and revolutions now referred-to as “Arab Spring”?
It’s giving me a headache. What do we do? We read and understand what it says on the pump before filling up. We write to our Congresspersons to let them know our concerns.
Happy motoring.
Ethanol in Motor Gasoline
Eat it, drink it, or burn it as fuel?
By Kevin Cameron December 1, 2016
Cycle World
Technical Editor Kevin Cameron shares his wealth of motorcycle knowledge, experiences, insights, history, and much more.
The introduction to a book on bartending once began, referring to ethyl alcohol, “Mankind has been systematically poisoning himself for 50,000 years.” To this we can add the present controversies over E15 and higher-percentage gasoline-ethanol blends. Plastic Ducati gas tanks have absorbed ethanol sufficient to swell, making it almost impossible to free them from the frame rails. Plastic or rubber fuel system parts can do the same, causing carburetor or fuel quantity floats to sink and possibly resulting in leakage. Upon removing carb float bowls, we may find sludgy green deposits. Operators of passive-fuel-system engines (those that cannot automatically adjust their own mixture) say they’ve had “ethanol lean-out”, leading to overheating and seizure. How? Ethyl alcohol contains only 2/3 as much energy per gallon as gasoline hydrocarbons do, so the more alcohol you add to motor gasoline, the leaner your mixture becomes. With E10, the lean-out effect is 1/3 of the 10% ethanol, or 3.3% - easily covered by the safely rich condition of most street-operated carburetion. Carburetors had to be set rich enough to be safe in the coldest anticipated conditions (air density increases but fuel density remains constant, which is a lean condition), so they operated comfortably rich in warm weather.
But with E15 and higher levels of alcohol addition, the percentage of lean-out becomes greater and the cooling effect of excess fuel is lost, causing combustion temperature to rise. This is the problem of carbureted engines run on E15 and higher.
Clearly, if E15 is a pump option only, the buyer can take care to select a fuel safe for his/her vehicle. But a fear exists that availability of E15 signals a Federal trend away from fuels (E10) that are relatively safe for engines with passive fuel systems. This would imply a future in which such vehicles could be operated only on expensive specialist fuels such as racing gasoline.
There are limits to ethanol use even in the case of fuel injection. As we add ethanol, the mixture leans, but the oxygen sensor in the exhaust detects the change and enriches the mixture in proportion. Sounds good – where’s the problem? The problem is that vehicle makers size their fuel injectors for the anticipated fuel. If the fuel changes so that greater volumes must be injected, eventually the flow limit of the injector is reached. Beyond that point, the oxy sensor, computer, and fuel system can no longer keep up with the drop in fuel energy as we add more and more ethanol. Again, the result is enleanment. To cover this possibility, vehicle manufacturers generally forbid the use of alcohol blends higher than E10.
Some vehicles are not limited in this way – the so-called ‘Flex-Fuel’ vehicles. Their fuel systems are designed to be able to cope with high-alcohol blends such as E85. The added cost of this fuel flexibility is buried in the generally higher price of such vehicles. As you may have noticed, Flex-Fuel vehicles are often large. Normally, if a maker wants to produce a high-profit luxury SUV which uses twice the fuel of the usual econobox, it must comply with CAFÉ standards (CAFÉ = Corporate Average Fuel Economy) by producing a great many more economical vehicles so that the average economy of that maker’s fleet averages out to meet the standard. But a deal was made; if the heavy vehicle was built as Flex Fuel (making possible operation on lower-emissions alcohol-rich blends such as E85), then 100 such heavy vehicles could legally be counted as a smaller number. Who could resist?
But wait – how did we get into adding ethanol to motor gasoline in the first place? Back in the late 1970s and early ‘80s there were hundreds of thousands of old carbureted vehicles on the nation’s highways. In their carburetors, fuel metering needles and the orifices in which they operated had worn in use, making fuel mixtures richer and increasing emissions of unburned hydrocarbons. Was there a way to fix this? Yes there was – to dilute motor fuel (especially in smoggy urban areas) with a low-energy-content ether – MTBE. Thus began the use of so-called “oxygenated fuels”. What this term actually means is that such fuels are partially burned (that is, partially combined with oxygen), somewhat reducing their content of chemical energy.
The MTBE program began with great enthusiasm and purpose, constructing specialized plants for making the stuff. Then came a terrible blow; MTBE was not decomposed by soil bacteria as normal fuel hydrocarbons were. It persisted in ground water for long distances, appearing in drinking water. Screech, the MTBE program was quietly halted. In its place was put ethyl alcohol.
Ethanol is an excellent fuel which strongly resists detonation. The power gain achieved on 100% alcohol (which has long been used in Australian motorcycle racing) comes not from its energy content, which is low (see above), but from its high heat of evaporation. As alcohol evaporates, it takes heat from the air with which it is mixed, refrigerating that air and increasing its density such that a greater weight of fuel/air mixture will fit into engine cylinders.
Although alcohols cause slow swelling of the familiar plastic ‘Plexiglas’, they are listed as very compatible with nitrile rubber, a common seal material. This apparent easy solution is denied us by the fact that gasolines now contain large percentages of aromatic compounds (toluene, xylene, xylidene) which are not compatible with nitrile rubber. Choice of fuel system elastomers is tricky.
Further, quoting from the Owen and Coley “Automotive Fuels Handbook”, “Methanol and ethanol are corrosive to many of the metals that are used in conventional fuel systems such as terne plating used in fuel tanks (a lead/tin coating on steel), aluminum, copper, brass, magnesium and die cast zinc. “Elastomers and plastic components can also be attacked. Carburetor and fuel gage floats are often made of plastic and have been known to swell and stick. Fiber gaskets can be softened and fuel hoses and pump diaphragms can swell or harden and crack.”
What this means is that the nature of motor gasoline should not be arbitrarily changed by government administrators without the most detailed consultation with the vehicle industry. Because motorcycles are greatly outnumbered by cars, it is possible that this consultative process may not include their manufacturers.
Why not just require all vehicles made after a certain date to be Flex-Fuel? First of all, any added system adds cost. An engine optimized for E85 would have a compression ratio too high for operation on ordinary gasoline, but with compression set at the high limit for gasoline fuel, when running on E85 we’d be throwing away some fuel economy which higher compression could have delivered. A vehicle returning a fuel mileage of 30-mpg on gasoline would deliver more like 22-mph on E85. The take-away here is that engines cannot be optimized across the range from common E10 to E85. A compromise is always present.
We have recently seen a proposal to build engines which could break this compromise – engines able to vary their compression ratio while operating. Certainly this is possible – the standard laboratory CFR knock-test engine has had this feature for seven decades – but it would add substantially to the cost, weight and complexity of engines.
The following label has been approved by EPA for placement on pumps capable of dispensing E15 fuel:
Cycle World
E15 fuel label.
Like so many other things, the E15 controversy has acquired political aspects. Quoting from a USDA site; “Strong demand for ethanol production has resulted in higher corn prices and has provided incentives to increase corn acreage.”
Another USDA site gives figures for 2016 averaging just over 38% as the fraction of US corn now devoted to ethanol production.
You get the picture. Environmentalists are delighted at this use of corn because it satisfies their desire to see renewable energy sources replace fossil sources. The petroleum industry sees a gallon of fuel ethanol as 2/3 of a gallon of gasoline they don’t sell. A factory farming organization will naturally seek to increase the percentage of ethanol in motor gasoline. Think of being a Congressperson, deafened by the roar of all this lobbying. Is there any such thing as “right”? Or has right come to mean “what I want” while wrong means “what my opponents want”?
Still others see conversion of corn to ethanol as the institutionalizing of hunger in the form of “burning food.” Could it be, as claimed by some big-picture pundits, that the world-wide rise in food prices in part cause by conversion of corn to ethanol led to the social unrest and revolutions now referred-to as “Arab Spring”?
It’s giving me a headache. What do we do? We read and understand what it says on the pump before filling up. We write to our Congresspersons to let them know our concerns.
Happy motoring.
