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File:E85 logo.png
Logo used in the United States for E85 fuel

E85 is an alcohol fuel mixture of 85% ethanol (ethyl alcohol, i.e., grain alcohol) and 15% gasoline (petrol) (proportioned by volume rather than mass).

Availability

The fuel is widely used in Sweden and is becoming increasingly common in the United States, mainly in the Midwest where corn is a major crop and is the primary source material for ethanol fuel production. Minnesota has the largest number of E85 fuel pumps of any U.S. state, with 158 of the 580+ pumps in the country. As of July 2005, Illinois has the second-greatest number of E85 pumps (about 60); most other states have fewer than two dozen. Even in Minnesota, the ethanol pumps represent a tiny fraction of the fuel outlets—there are about 4,000 gas stations in the state, each with several individual pumps (however, all stations there are required to carry E10, a 10% mixture of ethanol and gasoline).

Concerns about rising gasoline prices and energy dependence have led to a resurgence of interest in E85 fuel; for example, Nebraska mandated the use of E85 in state vehicles whenever possible in May 2005. Similarly, whereas selling any fuel containing more than 10% ethanol is still currently illegal in some states, even this is rapidly changing. For example, Florida proposed changing state law to permit the sale of alternative fuels such as E85 at an October 7, 2005 meeting, and held public hearings on October 24th. The expected outcome of having held this hearing is the changing of Florida state law to permit the selling of alternative fuels such as E85 by the end of 2005 to the general public. (Currently, only county, state, and Federal fleet vehicles may purchase E85 in Florida, from only 3 pumps in the state.) Several other states have similar laws still on their books that prevent the sale of E85 to the general public. The expected general outcome, though, is the rapidly widening acceptance of E85 sales to the general public in all of the United States by the end of 2006.

US Federal fleet flex-fuel vehicles (FFVs) are required to operate on alternative fuels 100% of the time upon the signing of the Energy Policy Act of 2005 into law by President Bush on August 8, 2005. (See Section 701 for this requirement). Formerly, such FFVs were required to be operated by the end of 2005 on alternative fuels only 51% of the time (i.e., the majority of the time) by Executive Order 13149. (See Executive Order 13149 [1], dated April 21, 2000.) This means that the US Government's use of E85 is effectively doubled as of August 8, 2005 with the signing into law of the Energy Policy Act of 2005. This jump in consumption had the unintended effect of limiting public availability of E85 coincident with shortages of gasoline due to impacts of hurricanes in the Gulf of Mexico during the 2005 hurricane season. Although the price of corn had not changed greatly, the usage of E85 nonetheless jumped, thereby creating a shortage of E85, and causing E85 prices to rise coincident with gasoline prices during the 2005 Hurricane Season.

Cost

As of 2005, E85 is frequently sold for up to 35% lower cost per quantity than gasoline. Much of this discount can be attributed to various government subsidies, and, at least in the United States, the elimination of state taxes that typically apply to gasoline and can amount to 47 cents, or more, per gallon of fuel. The US federal tax exemption that keeps ethanol economically competitive with petroleum fuel products is due to expire in 2007, but this exemption may be extended through legislative action. In the aftermath of Hurricane Katrina in 2005, the price of E85 rose to nearly on par with the cost of 87 octane gasoline in many states in the United States, and was for a short time the only fuel available when gasoline was sold out, but within four weeks of Katrina, the price of E85 had fallen once more to a 20% to 35% lower cost than 87 octane gasoline.

The price of E85 has risen quickly during 2005 also due to additional factors. With the signing into law of the Energy Policy Act of 2005, US Federal consumption of E85 jumped, causing shortages of E85, along with a rise in prices.

Unfortunately, because ethanol contains less energy than gasoline, fuel economy is reduced for most 2002 and earlier FFVs (flexible-fuel vehicles) that are currently on the road by about 30% (most after 2003 lose only 15-17%, or less) when operated on pure E85 (summer blend.) Some of the newest vehicles can lessen this reduction to only 5-15%. A few cars actually claim to provide better fuel economy on E85 than on gasoline; for example, one Saab turbocharged car actually claims better fuel economy and higher power on E85 than gasoline through using a higher compression ratio engine. Still, for almost all FFVs, more E85 is typically needed to do the same work as can be achieved with a lesser volume of gasoline. This difference is sometimes offset by the lower cost of the E85 fuel, depending on E85's current price discount relative to the current price of gasoline. As described earlier, the best thing for drivers to do is to record fuel usage with both fuels and calculate cost/distance for them. Only by doing that, can the end-user economy of the two fuels be compared.

For example, an existing pre-2003 model year FFV vehicle that normally achieves, say, 30 MPG on pure gasoline will typically achieve about 20 MPG, or slightly better, on E85 (summer blend.) When operated on E85 winter blend, which is actually E70 (70% ethanol, 30% gasoline), fuel economy will be even better than when operating on the summer blend. To achieve any short-term operational fuel cost savings, the price of E85 should therefore be 30% or more below the price of gasoline to equalize short term fuel costs for most older pre-2003 FFVs for both winter and summer blends of E85. Life-cycle costs over the life of the FFV engine are theoretically lower for E85, as ethanol is a cooler and cleaner burning fuel than gasoline. Provided that one takes a longterm life-cycle operating cost view, a continuous price discount of only 20% to 25% below the cost of gasoline is probably about the break-even point in terms of vehicle life-cycle operating costs for operating most FFVs on E85 exclusively (for summer, spring/fall, and winter blends.)

Fuel economy in fuel-injected non-FFVs operating on a mix of E85 and gasoline varies greatly depending on the engine and fuel mix. For a 60:40 blend of gasoline to E85 (summer blend), a typical fuel economy reduction of around 23.7% resulted in one controlled experiment with a 1998 Chevrolet S10 pickup with a 2.2L 4-cylinder engine, relative to the fuel economy achieved on pure gasoline. Similarly, for a 50:50 blend of gasoline to E85 (summer blend), a typical fuel economy reduction of around 25% resulted for the same vehicle. (Fuel economy performance numbers were measured on a fixed commute of approximately 110 miles roundtrip per day, on a predominantly freeway commute, running at a fixed speed (62 mph), with cruise control activated, air conditioning ON, at sea level, with flat terrain, traveling to/from Kennedy Space Center, FL.)

Use in Flexible-fuel engines

E85 is best used in engines modified to accept higher concentrations of ethanol. Such flexible-fuel engines are designed to run on any mixture of gasoline or ethanol with up to 85% ethanol by volume. The primary differences from non-FFVs is the elimination of bare magnesium, aluminium, and rubber parts in the fuel system, the use of fuel pumps capable of operating with electrically-conductive (alcohol) instead of non-conducting dielectric (gasoline) fuel, specially-coated wear-resistant engine parts, fuel injection control systems having a wider range of pulse widths (for injecting approximately 30% more fuel), the selection of stainless steel fuel lines (sometimes lined with plastic), the selection of stainless steel fuel tanks in place of terne fuel tanks, and, in some cases, the use of acid-neutralizing motor oil. For vehicles with fuel-tank mounted fuel pumps, additional differences to prevent arcing, as well as flame arrestors positioned in the tank's fill pipe, are also sometimes used.

Historically, the first widely-sold flexible-fuel vehicle in the United States was a variant of Henry Ford's Model T intended for use by self-reliant farmers who could make their own ethanol. Surprisingly, it is capable even to this day of running on E85, or gasoline, as it was designed to operate on either ethanol or gasoline, at the user's choice. Henry Ford's subsequent 1927 Model A likewise was an early flex fuel vehicle. It, however, eased the driver's method of accommodating various blends of alcohol and gasoline through a driver's control on the dash with a knob that was turned to control air fuel mixture and pulled to choke the single-barrel Zenith carburetor. This dash-mounted control provided easy control of all the major adjustments required for easily burning alcohol and gasoline in varying proportions, including enough range for burning today's E85 blend of alcohol and gasoline in any mix of E85 and gasoline.

Modern flexible-fuel vehicles have come a long way since the Model T and Model A, and now automatically adapt themselves to burning changing percentages of alcohol and gasoline without any user intervention required. So far, most flexible-fuel vehicles that have been built in the United States have been sport-utility vehicles and other members of the "light truck" vehicle class, with smaller numbers of sedans, station wagons, and the like.

Swedish automobile maker Saab has developed a turbocharged flexible-fuel engine called the BioPower which takes special advantage of the high-octane fuel. This engine allows the vehicle to accelerate faster and attain higher speeds when running on E85 than when running on straight gasoline. Test done using older SAABs fitted with the APC system shows that they can run fine on up to 50% E85 mixed with ordinary petrol. However it may have long term effects as alcohol is more agressive on tubes and the petrol also acts as a lubricant.

General Motors subsidiary GM do Brazil adopted GM's Family II and Family 1 straight-4 engines with FlexPower technology that enables the use of ethanol, gasoline, or their mixture. The vehicles with FlexPower include the Chevrolet Corsa and the Chevrolet Astra.

Experimental use in standard engines

E85 has a considerably higher octane rating than gasoline — about 110 — a difference significant enough that it does not burn as efficiently in traditionally-manufactured internal-combustion engines.

Use of E85 in non-FFV vechicles is generally experimental, with some users recommending light blends as low as 20%, while others have successfully run 100% E85. The main attraction of burning E85, of course, is the lower price per gallon at the pump of E85 versus gasoline. Other advantages include the common benefits of renewable energy sources, such as less environmental impact and less reliance on foreign energy.

Modern cars (i.e., most cars built after 1988) have fuel-injection engines with oxygen sensors that will attempt to adjust the air-fuel mixture for the extra oxygenation of E85, with variable effects on performance. All such cars can burn small amounts of E85 with no ill effects.

Operating fuel-injected non-FFVs on more than 50% E85 will generally cause the check engine light (CEL) to illuminate, indicating that the ECU can no longer maintain closed-loop control of the internal combustion process due to the presence of more oxygen in E85 than in gasoline. Once the CEL illuminates, adding more E85 to the fuel tank becomes rather inefficient. For example, running 90% E85 in a non-FFV will reduce fuel economy by 33% or more relative to what would be achieved running 100% gasoline. (This example is again for the same 1998 Chevy S10 pickup for which the fuel economy was studied in the controlled experiment mentioned previously.) Even more importantly, continuing to operate the non-FFV with the check engine light (CEL) illuminated may also cause damage to the catalytic converter as well as to the engine pistons if allowed to persist. It just does not make good economic sense to run a non-FFV with amounts of E85 high enough to cause the CEL to illuminate.

Under stoichiometric combustion conditions, ideal combustion occurs for burning pure gasoline as well as for various mixes of gasoline and E85 (at least until the CEL illuminates in the non-FFV) such that there is no significant amount of uncombined oxygen or unburned fuel being emitted in the exhaust. This means that no change in the exhaust manifold oxygen sensor is required for either FFVs or non-FFVs when burning higher percentages of E85. This also means that the catalytic converter on the non-FFV burning E85 mixed with gasoline is not being stressed by the presence of too much oxygen in the exhaust, which would otherwise reduce catalytic converter operating life.

Nonetheless, even when the CEL does not illuminate on the non-FFV burning E85, proper catalytic operation of the catalytic converter for a non-FFV burning higher percentages of E85 may not be achieved as soon as necessary to prevent the emission of some pollution products resulting from burning the gasoline contained in the mixture, especially upon initial cold engine start. This is because the catalytic converter needs to rise to an internal temperature of approximately 300 degrees C before it can 'fire off' and commence its intended catalytic function operation. When burning large amounts of E85 in a non-FFV, the cooler burning characteristics of alcohol fuel than gasoline fuel may delay reaching the 'fire-off' temperature in a non-FFV as quickly as when burning gasoline. Any additional pollution, however, is only going to be emitted for a very short distance when burning E85 in a non-FFV, as the catalytic converter will nonetheless still 'fire off' quite quickly and commence catalytic operation shortly. It is not known whether the small amount of pollution emitted prior to catalytic converter 'fire off' may actually be reduced even during the cold startup phase, as well as once catalytic operation commences, when burning E85 in a non-FFV. Likewise, even once the catalytic converter 'fires off', operation with the CEL illuminated will still result in excess amounts of nitrous oxide being released, greater than when operating the engine on gasoline. The solution is simply to add gasoline, and extinguish the check engine light (CEL), at which time exhaust pollutants will return to within normal limits .

For non-FFVs burning E85 once the CEL illuminates, it is the lessened amount of fuel injection than what is needed that causes the air fuel mixture to become too lean; that is, there is not enough fuel being injected into the combustion process, with the result that the oxygen content in the exhaust rises out of limits, and perfect (i.e., stoichiometric) combustion is lost if the percentage of E85 in the fuel tank becomes too high. It is the loss of near-stoichiometric combustion that causes the excessive loss of fuel economy in non-FFVs burning too high a percentage of E85 versus gasoline in their fuel mix.

E85 gives particularly good results in turbocharged cars due to its high octane [2]. It allows the ECU to run more favorable ignition timing and leaner fuel mixtures than are possible on normal premium gasoline. Users who have experimented with converting OBDII (i.e., On-Board Diagnostic System 2, that is for 1996 model year and later) turbocharged cars to run on E85 have had very good results. Experiments indicate that most OBDII-specification turbocharged cars can run up to approximately 39% E85 (33% ethanol) with no CEL's or other problems. (In contrast, most OBDII specification fuel-injected non-turbocharged cars and light trucks are more foregiving and can usually operate well with in excess of 50% E85 (42% ethanol) prior to having CEL's occur.) Fuel system compatibility issues have not been reported for any OBDII cars or light trucks running on high ethanol mixes of E85 and gasoline for periods of time exceeding two years. (This is likely to be the outcome justifiably expected of the normal conservative automotive engineer's predisposition not to design a fuel system merely resistant to ethanol in E10, or 10% percentages, but instead to select materials for the fuel system that are nearly impervious to ethanol.)

Fuel economy does not drop as much as might be expected in turbocharged engines based on the specific energy content of E85 compared to gasoline, in contrast to the previously-reported reduction of 23.7% reduction in a 60:40 blend of gasoline to E85 for one non-turbocharged, fuel-injected, non-FFV. Although E85 contains only 72% of the energy on a gallon for gallon basis compared to gasoline, experimenters have seen much better fuel mileage than this difference in energy content implies. Many automotive writers and columnists suggest that because of the lower energy content, you should expect an equivalent 39% increase in fuel usage. This has not been observed in practice when running gasoline and ethanol blends. Some of the newest model FFV's get only about 7% less mileage per gallon of fuel of E85 compared to their gasoline fuel mileage.

The reason for this non-intuitive difference is that the turbocharged engine seems especially well-suited for operation on E85, for it in effect has a variable compression ratio capability, which is exactly what is needed to accommodate varying ethanol and gasoline ratios that occur in practice in an FFV. At light load cruise, the turbocharged engine operates as a low compression engine. Under high load and high manifold boost pressures, such as accelerating to pass or merge onto a highway, it makes full use of the higher octane of E85. It appears that due to the better ignition timing and better engine performance on a fuel of 100 octane, the driver spends less time at high throttle openings, and can cruise in a higher gear and at lower throttle openings than is possible on 100% premium gasoline. In daily commute driving, mostly highway, 100% E85 in a turbocharged car can hit fuel mileages of over 90% of the normal gasoline fuel economy. Tests indicate approximately a 5% increase in engine performance is possible by switching to E85 fuel in high performance cars.

Experimenters who have made conversions to 100% E85 report that cold start problems at very cold temperatures can easily be avoided through adding 1 - 2 gallons of gasoline to the E85 in the tank, prior to the arrival of the cold weather.

No significant ignition timing changes are required for a gasoline engine running on E85.

Risks of use in standard engines

Prolonged exposure to high concentrations of ethanol may corrode metal and rubber parts in older engines (pre-1988) designed primarily for gasoline. The hydroxyl group on the ethanol molecule is an extremely weak acid, but it can enhance corrosion for some natural materials. For post-1988 fuel-injected engines, all the components are already designed to accommodate E10 (10% ethanol) blends through the elimination of exposed magnesium and aluminium metals and natural rubber and cork gasketed parts. Hence, there is a greater degree of flexibility in just how much more ethanol may be added without causing ethanol-induced damage, varying by automobile manufacturer. Anhydrous ethanol in the absence of direct exposure to alkali metals and bases is non-corrosive; it is only when water is mixed with the ethanol that the mixture becomes corrosive to some metals. Hence, there is no appreciable difference in the corrosive properties between E10 and a 50:50 blend of E10 gasoline and E85 (47.5% ethanol), provided there is no water present, and the design was done to accommodate E10. Nonetheless, operation with more than 10% ethanol has never been recommended by car manufacturers in non-FFVs.

Operation on up to 20% ethanol is generally considered safe for all post 1988 cars and trucks. This equates to running a blend of 23.5% of E85. Starting in 2010, at least one US state (Minnesota) already has legislatively mandated and planned to force E20 (20% ethanol) into their general gasoline fuel-distribution network. Details of how this will work for individual vehicle owners while maintaining automobile manufacturer warranties, despite exceeding the manufacturer's maximum warranted operation percentage of 10% of ethanol in fuel, are still being worked as of late-2005. However, the choice of transitioning to a 20% ethanol blend of gasoline is not without precedent; Brazil, in its conversion to an ethanol-fueled economy, determined that operation with up to 22% ethanol in gasoline was safe for the cars and trucks then on the road in Brazil at the time, and the conversion to a 20% blend was accomplished with only minor issues arising for older vehicles. Recently, conversion to a 24% blend was accomplished in Brazil.

In addition to corrosion, there is also a risk of increased engine wear for non-FFV engines that are not specifically designed for operation on high levels (i.e., for greater than 10%) of ethanol. The risk primarily comes in the rare event that the E85 fuel ever becomes contaminated with water. For water levels below approximately 0.5% to 1.0% contained in the ethanol, no phase separation of gasoline and ethanol occurs. For contamination with 1% or more water in the ethanol, phase separation occurs, and the ethanol and water mixture will separate from the gasoline. This can be simply observed by pouring a mixture of suspected water-contaminated E85 fuel in a clear glass tube, waiting roughly 30 minutes for the separation to occur (if it does), and then inspecting the sample. If there is water contamination of above 1% water in the ethanol, a clear separation of alcohol (with water) and gasoline will be clearly visible, with the colored gasoline floating above the clear alcohol and water mixture.

For a badly-contaminated amount of water in the ethanol and water mixture that separates from the gasoline (i.e., approximately 11% water, 89% ethanol, equivalent to 178 proof alcohol), considerable engine wear will occur, especially during times while the engine is heating up to normal operating temperatures, as for example just after starting the engine, when low temperature partial combustion of the water-contaminated ethanol mixture is taking place. This wear, caused by water-contaminated E85, is the result of the combustion process of ethanol, water, and gasoline producing considerable amounts of formic acid (HCOOH, also known as methanoic acid, and sometimes written as CH2O2).

In addition to the production of formic acid occurring for water-contaminated E85, smaller amounts of acetaldehyde (CH3CHO) and acetic acid (C2H4O2) are also formed for water-contaminated ethanol combustion. Nonetheless, it is the formic acid that is responsible for the majority of the rapid increase in engine wear.

Engines specifically designed for FFVs employ soft nitride coatings on their internal metal parts to provide formic acid wear resistance in the event of water contamination of E85 fuel. Also, the use of lubricant oil (motor oil) containing an acid neutralizer is necessary to prevent the damage of oil-lubricated engine parts in the event of water contamination of fuel. Such lubricant oil is required by at least one manufacturer of FFVs even to this day (Chrysler).

For non-FFVs burning E85 in greater than 23.5% E85 mixtures (20% ethanol), the remedy for accidentally getting a tank of water-contaminated E85 (or gasoline) while preventing excessive engine wear is to change the motor oil as soon as possible after either burning the fuel and replacing it with non-contaminated fuel, or after immediately draining and replacing the water-contaminated fuel. The risk of burning slightly water-contaminated fuel with low percentages of water (less than 1%) on a long commute is minimal; after all, it is the low temperature combustion of water contaminated ethanol and gasoline that causes the bulk of the formic acid to form; burning a slightly-contaminated mix of water (less than 1%) and ethanol quickly, in one long commute, will not likely cause any appreciable engine wear past the first 15 miles of driving, especially once the engine warms up and high temperature combustion occurs exclusively.

For those making their own E85, the risk of introducing water unintentionally into their homemade fuel is relatively high unless adequate safety precautions and quality control procedures are taken. Ethanol and water form an azeotrope such that it is impossible to distill ethanol to higher than 95.6% ethanol purity by weight (roughly 190 proof), regardless of how many times distillation is repeated. Unfortunately, this proof ethanol contains too much water to prevent separation of a mixture of such proof ethanol with gasoline, or to prevent the formation of formic acid during low temperature combustion. Therefore, when making E85, it becomes necessary to remove this residual water. It is possible to break the ethanol and water azeotrope through adding benzene or another hydrocarbon prior to a final rectifying distillation. This takes another distillation (energy consuming) step. However, it is possible to remove the residual water more easily, using 3 angstrom (3A) synthetic zeolite pellets to adsorb the water from the mix of ethanol and water, prior to mixing the now anhydrous ethanol with gasoline in an 85% to 15% by volume mixture to make E85. This absorption process is also known as a molecular sieve. The benefit of using synthetic zeolite pellets is that they are essentially comparable to using a catalyst, in being infinitely reusable and in not being consumed in the process, and the pellets require only re-heating (perhaps on a backyard grill, in a solar reflector furnace, or with heated carbon dioxide gas collected and saved from the fermentation process) to drive off the water molecules adsorbed into the zeolite. Research has also been done at Purdue University on using corn grits as a dessicant. [3] Once the ground corn becomes water logged, the corn grits can be processed much as the zeolite pellets, at least for a number of drying cycles before the grits lose their effectiveness. Once this occurs, it is possible to run the now water-logged corn grits through the natural fermentation process and convert them into even more ethanol fuel.

Running a non-FFV with too high of a percentage of ethanol will also cause a lean air fuel mixture. A lean mixture, if allowed to persist over considerable periods of time, will cause overheating of pistons and will eventually cause engine damage. It will also cause premature catalytic converter failure. This is also why the check engine light will illuminate if you mix more than around 50% to 60% E85 by volume with your gasoline in a non-FFV. If this happens, just add more 87 octane regular grade gasoline as soon as possible to correct the problem. (Some premium blends contain up to 10% ethanol; to correct the problem as quickly as possible, always add regular grade gasoline, not premium grade gasoline.) These lean mixture problems will not happen in a properly-converted vehicle.

After-market Conversion Kits and conversions

After-market conversion kits, for converting standard engines to operate on E85, are generally not legal in U.S. states subject to emissions controls unless you get your converted vehicle independently EPA certified. This is despite the fact that the exhaust emissions from any such converted cars are improved by utilizing higher percentages of ethanol in the gasoline blend. Unfortunately, EPA certification costs in excess of $23,000 and you additionally have to prove that your vehicle will maintain low emissions for at least 50,000 miles after the conversion. Most individuals won't give up their vehicles for the requisite 50,000 mile test period. Likewise, conversion kit manufacturers don't certify their kits any longer due to these overly protective laws, which by law must be tested with every model vehicle for which they are to be sold. If done in the US the Fees have already been paid though the original certification. The EPA Federal Test Procedure costs $750.00, but you can request the reduced payment of down to 1% of the car's added retail value of the conversion. A minimum fee may apply if the value added is not very high.

Similarly, U.S. Federal law prohibits the manufacture of such conversion kits for sale in the U.S. unless they are EPA certified, by a ban that dates to when conversion kits for converting vehicles to use compressed natural gas was enacted to prevent the sale of such conversion kits due to concern about the safety of such conversion kits being released among the general public. This is despite the fact that such kits are nonetheless legal in all states, but CA, and most states even offer a tax break for converting your vehicle (See tax breaks.)

Still, there is one Brazilian after-market kit available legally in U.S. states not subject to emission controls that will nonetheless permit the conversion of 4, 6, or 8 cylinder engines to operate from fuels ranging from pure gasoline to a mix of gasoline and ethanol to pure ethanol, including E85. It operates by modifying the fuel-injection pulses sent to the fuel injectors when in 'A', or alcohol mode instead of 'G', or gasoline mode. (In 'G' mode, no modification to the fuel-injection pulses is performed.) This conversion kit modification serves to extend the control range over which the ECU can adjust the air-fuel ratio to achieve an oxygen sensor reading measured before the catalytic converter that falls within nominal stoichometric ideal combustion limits. The general belief is that this conversion kit operates in its 'A' mode simply through lengthening the individual pulse-widths of fuel-injection pulses, thereby increasing fuel flow per injection pulse by roughly 30%, whereas in 'G' mode, it acts simply as a straight pass through for fuel-injection pulses.

Other than the one Brazilian after-market kit, no other pre-manufactured E85 conversion kits are known to exist. Nonetheless, it is still possible to modify existing non-FFV engines to operate on pure E85 without the use of this particular after-market kit.

The primary method used to convert non-fuel-injected cars is two-fold. First, any non-compatible rubber parts and gaskets and terne gas tanks and terne fuel lines are replaced. Then, it remains necessary to increase the fuel rate of flow by roughly 25% - 30%. This can be accomplished in one of any of several different ways, depending on the specific details of the fueling system. In the early 80's auto makers were required to make vehicles ethanol compatible, so most newer vehicles will handle E85 with no problem. If a car is converted though, the ethanol will clean out the gunk left over from the gasoline and plug the fuel filter. Replace your fuel filter after about 600 miles!

For non-fuel-injected engines, this may be accomplished through increasing the diameter of the carburetor running jets to a size that is slightly larger in diameter. The theoretical change is not to increase the hole diameter by 25% to 30%, but rather to increase the area and hence the fuel flow rate by 25%-30%. Hence, the diameter of the jets must be increased by to times their original diameters, while keeping the general shapes at the opening of the jets as close to nearly the same as possible. (The idling jet must also be increased in diameter in addition to the running jet, primarily to accomplish successful starting in colder weather.) An excellent starting point, if one doesn't want to experiment with multiple test trials over the 25% to 30% range, is simply to increase the fuel flow by 27%, which just requires increasing the diameter of the jets by a factor of times the original diameter.

For older vehicles, an even simpler non-conversion 'conversion' is possible once any non-compatible rubber gas hoses and cork gaskets and such are all replaced with ethanol-resistant materals. For older vehicles with a manual choke, it is possible simply to leave the choke slightly engaged even when the motor is warmed up, and the conversion is complete.

For converting later-model fuel-injected cars and trucks, fuel injection-pressure boosters can be installed, to increase fuel-injector fuel rate flow. It may be difficult to get your mixture right, plus there is a safety risk of more leaks in your fuel system. Likewise, if you do choose this method, you may loose some of your compatibility with running on pure gasoline, from moving the air fuel mix farther from optimum for what is needed for running on pure gasoline.

The disadvantage of most of these 'conversions' is the non-reversibility of the conversion, without changing out or removing added parts, unlike the Brazilian after-market kit which is completely reversible.

If any of these conversion techniques are used, especially in older vehicles in which there may be rust or other residue present in the fuel tank, it may be necessary additionally to replace the fuel filter within 400 to 600 miles, as ethanol has a tendency to release any trapped rust or gasoline fuel gum or residue, which can cause the fuel filter to become blocked. Once replaced, life expectancy of the new fuel filter should be normal, barring an exceptionally dirty gas tank or fuel system.

Interestingly enough, running E85 in a vehicle can actually improve fuel efficiency if the fuel delivery system was especially gummed up. This improvement remains if the vehicle is returned to operation on gasoline only.

Technical details on Air Fuel Ratios required for burning E85, gasoline, and ethanol

E85 fuel requires a richer air fuel mixture than gasoline for best results. Successful conversions generally require 27% - 30% more fuel flow than when the engine burns 100% gasoline. (In contrast, methanol conversions require even more fuel flow increase than ethanol conversions.) Flexible fuel vehicles additionally impose a wider range of air fuel ratios that must be achieved than what is required for vehicles that operate only on gasoline or alcohol. This is because a wider range of air fuel ratios is required to use all the varying percentages of ethanol and gasoline efficiently that may be present in the fuel tank at any given time.

The nominal (chemically correct) air fuel ratio is 14.64:1 by mass (not volume) for burning 100% gasoline, but in practice the nominal air fuel ratio for most 100% gasoline fuel injection systems ranges from about 14.6 to 14.7 for a typical nominal value, depending on manufacturer, with the ratio of 14.7 being slightly preferred for increasing fuel economy under light load conditions.

The following table shows the range of air fuel ratios typically used for burning gasoline, E85, and pure ethanol (E100) under an assortment of assumed operating conditions: 


Fuel                        AFRst      FARst      Equivalence   Lambda
----                        -----      -----        Ratio       -----
=========================================================================
Gasoline stoich             14.7       0.068        1           1
Gasoline Max power rich     12.5       0.08         1.176       0.8503
Gasoline Max power lean     13.23      0.0755       1.111       0.900

=========================================================================
E85 stoich                   9.765    0.10235       1           1
E85 Max power rich           6.975    0.1434        1.40        0.7143
E85 Max power lean           8.4687   0.118         1.153       0.8673  

=========================================================================
E100 stoich                  9.0078   0.111         1           1
E100 Max power rich          6.429    0.155         1.4         0.714
E100 Max power lean          7.8      0.128         1.15        0.870
=======================--================================================


The term AFRst refers to the Air Fuel Ratio under stoichiometric, or ideal air fuel ratio mixture conditions. (See stoichiometry.) FARst refers to the Fuel Air Ratio under stoichiometric conditions, and is simply the reciprocal of AFRst.

Equivalence Ratio is the ratio of actual Fuel Air Ratio to Stoichiometric Fuel Air Ratio; it provides an intuitive way to express richer mixtures. Lambda is the ratio of actual Air Fuel Ratio to Stoichiometric Air Fuel Ratio; it provides an intuitive way to express leaness conditions (i.e., less fuel, less rich) mixtures of fuel and air.

Air Fuel Ratio is always computed on the basis of ratios of mass (not volume). The following is a computation of the theoretical E100 (100% ethanol, C2H6O) Air Fuel Ratio, based on stoichiometric (perfect combustion) principles:

C2H6O + 3 O2 = 2 CO2 + 3 H2O

Adding up the molar mass for ethanol: (6 x 1.00794) + (2 x 12.0107) + (1 x 15.9994) = 46.0684 grams/mol of Ethanol

1 mol x 46.0684 g/mol Ethanol : 3 mol x 2 x 15.9994 g/mol Oxygen

46.0684 : 95.9964 = 1:2.0838 for the fuel:oxygen ratio for perfect (i.e., stoichiometric) combustion.

Now, oxygen is 20.9% of air by volume, or equivalently, 23.133% of air by mass, assuming that atmospheric gases behave as ideal gases. (See Earth's atmosphere.)

Hence, the theoretical air fuel ratio for E100 (100% ethanol) is:

(2.0838/0.23133) : 1 = 9.0078 : 1

So, for E85 (summer blend), the required air fuel ratio can be estimated as:

0.85 x 9.0078 + 0.15 x 14.64 = 9.8526

Likewise, for E85 (winter blend), the required air fuel ratio can be estimated as:

0.70 x 9.0078 + 0.30 x 14.64 = 10.6975, which is closer to the gasoline air fuel ratio.

The estimated required E85 summer blend air fuel ratio compares very closely to the value of 9.765 given in the table. In practice, though, the exact stoichiometric air fuel ratio for gasoline varies as a function of the exact blend of gasoline, which, in turn, is varied by time of year by refineries to increase or decrease volatility, prevent vapor locking, etc., for better matching seasonal climatic changes.

Deviations from stoichiometric combustion computed values are required during non-standard operating conditions such as heavy load, or cold weather operation, in which case the mixture ratio can range from 10:1 to 18:1 for burning 100% gasoline. Slightly wider ranges than even this on the low end of the air fuel ratio, dropping to below 8:1, are required for burning all possible blends of E85 and gasoline efficiently under all conditions of engine loads and inlet air temperatures.

At inlet air temperatures below 15 C (59 F), it is likewise not possible to start the typical internal combustion engine on pure ethanol (E100); for cold engine starts, starting the engine on gasoline and then transitioning to E100 can be done. Similarly, for starting a vehicle on E85 summer blend in extremely cold weather, it is likewise required to add additional gasoline during at least the starting of the engine, before transitioning to burning the E85 summer blend. In practice, it is easier simply to add more pure gasoline to the fuel tank when extremely cold weather is expected, prior to the arrival of the cold weather, to avoid cold engine start difficulties.

Fortunately for those converting non-FFVs to operate on E85, the wide range of inherent air fuel control required for burning pure gasoline is very nearly the same range required for burning many blends of E85 with gasoline up to approximately 60% E85, at least for non-extreme engine loads and non-extreme weather conditions. Hence, the common success seen in practice for burning many blends of E85 with gasoline even in non-FFVs at blends in excess of 50% E85, especially under light engine loads cruising under benign weather conditions.

All of these theoretical stoichiometric combustion estimated values should be taken only as approximations to what may really be required for achieving perfect combustion. The lambda sensor is what ultimately confirms whether stoichiometric combustion is taking place in practice.

Additionally, the ideal "stoich" (common shorthand way to indicate stoichiometric) mixture typically burns too hot for any situation other than light load cruise. This is the target mixture that the ECU attempts to achieve in closed-loop fueling to get the best possible emissions and fuel mileage at light load cruise conditions. This mixture typically can give approximately 95% of the engine's best power, provided the fuel has sufficient octane to prevent damaging detonation (i.e., knock).

The "Max Power Rich" condition is the richest air fuel mixture (more fuel than best power) that gives both good drivability and power levels, within approximately 1% of the absolute best power on that fuel.

The "Max Power Lean" condition is the leanest air fuel mixture (less fuel than best power) that gives good drivability, acceptable exhaust gas temperatures to prevent engine damage, and power levels within approximately 1% of the absolute best power on that fuel.

Lambda, typically used for referring to lean versus rich air fuel mixtures, is normally measured by the so-called lambda sensor (also known as an oxygen sensor.)

Depending on seasonal blend variations E85 will weigh approximately 6.5 pounds per U.S. Gallon, having a liquid density of approximately 0.77 - 0.79 compared to gasoline which has typical values of 6.0 - 6.5 pounds per U.S. gallon and a density of 0.72 - 0.78.

Examples of currently-produced E85 flexible fuel vehicles

Europe

USA

Brazil

Note: the flexible fuel engines in Brazil are built to run on gasoline (which is always mixed with 20% to 25% of ethanol in Brazil), hydrated ethyl alcohol (96% ethanol, 4% water), or any mix of those fuels. That would make them "E96-like" cars. See Flexible-fuel vehicles for more information.

See also

References

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