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Of course it can't be as easy as saying it is 85% ethanol, that is the mixture as it arrives at the gas station. Just like gasoline, ethanol is reformulated depending on area and season so in winter the gas station may increase the concentration of gasoline to help cold starting and in places like Denver Colorado addatives my be used to adjust for altitude as it has an effect on how well the fuel vaporizes. With all of that going on the fuel going into your tank has something less than 85% ethanol content, then depending on what you filled up on last, pure gasoline, E10, E85, etc... and how much new fuel you are adding the actual mixture in your tank can be practically anything.
Basic Facts
The first fact to consider is that ethanol is not gasoline and almost all pre-made assumptions need to be forgotten. Because of the molecular structure of ethanol more fuel is required to get the proper stoichiometric ratio to burn efficiently. Because of the different molecular structure ethanol puts out less energy per pound compared to gasoline and an E85 converted engine will require 15-20% more fuel. The loss of energy per pound does not mean that the engine will produce less power though, consider that nitro-methane has about half the engergy content of gasoline but provides a 230% increase in power at stoichiometric ratio. One of the main reasons why heavy modification of the engine and fuel delivery systems must be performed is because ethanol is slightly corrosive and has good electrolytic properties. This means that it is recommended for many of the fuel system components be made out of different materials, or coated with a material that will resist the corrosion although this is much more critical if converting to methanol. If running carbureted seals in the carb should be upgraded to viton where possable this also applies to fuel injector o-rings and other seals which come in contact with the fuel.E85 also has a higher equivlant octane so will require higher compression for the best combustion and power.
Conversion Factors
The first things to consider are, can you afford to do a conversion? Is E85 readilly available? If it is not readilly available do you want to build the engine with dual compatability? Depending on your location most people have access to 1-3 locations that have E85 within a practicle distance. Of course if the nearest station with E85 is 50 miles away from your normal routines of driving it isn't practicle to attempt a conversion unless you forsee it becomming more easily available in your area.
Fuel Tank
Since an E85 engine would require about 20% more fuel it is recommended your fuel tank size to be increased by about this percentage. The selected fuel tank must also be made of a material that will not degrade with ethanol. A race equipment supplier for dirt track or sprint car racing would probably be the easiest source and would already be safety rated for methanol which would exceed the ratings for ethanol.
Fuel Filter and Lines
Of course an application specific filter will be needed. This are often made for racing applicatons and have a micromesh stainless steel filtering media. Most of the time these filters are made to connect with AN fittings, these fittings will either need to be made of stainless steel or anodized with a special coating. Stainless steel hardline can be used for the fuel lines. Teflon lined stainless steel braided lines may also be used. Any seales needed should be viton or another compatable material. Filter and fuel line size may need to be larger then their gasoline equivlants to accomodate the extra 20% of volume needed. Most car manufacturers have atleast one or two models which are E85 compatable (not just GM) so if components are hard to locate parts from these vehicles would be an easy source.
Internal Seals
Where possable seals inside the engine that are exposed to fuel or oil should be changed where possable for Viton seals. Why change the ones exposed to oil? Blowby over time will cause small amounts of ethanol to get into the oil. Viton valve stem seals will help make sure the engine will last as long as possable. The O-rings in and around the distributor shaft should be swapped for viton, for Mazda trucks camshaft seals Might already be Viton as it is brown in color. High performance piston rings should be considered, high carbon steels do not handle ethanol very well. They capacity of the oil system may want to be increased to decrease ethanol concentration over time. A well functioning PCV system will help insure that ethanol in the oil evaporates off and gets pulled back into the intake. Most oils today can withstand atleast 5,000 miles of operation in an engine but the old recommendation of changing your oil every 3,000 miles will also be a good way to keep ethanol concentration low, especially if internal seals cannot be replaced with Viton.
Fuel Rail, Intake, Pistons, Aluminum Parts
Although aluminum resists corrosion from ethanol fairly well compared to other metals it is extremly poor at resisting electrolysis. For this reason the fuel rail should be made out of stainless steel or anodized with a resistant coating. Depending on intake manifold design, engine warm up components, and emission devices it may be recommended to anodize aluminum intake manifolds as well if they are exposed to fuel. Again some sort of permanent coating will need to be applied to the tops of the pistons and combustion chambers, one may look into the coatings applied to nitro pistons since nitro-methane is also highly corrosive. Platinum physical vapor deposition has also proved to be effective because of the many good qualities of platinum. Platinum is highly resistant to weathering effects such as corrosion, heat expansion, and abrasion. This makes it durable against ethanol and carbon build up. Platinum plating also causes a catalytic effect which internally reduces NOx emissons.
Here are links to search for E85 stations in your area:
U.S. Epartment of Energy Alternate Fuel Locator
National Ethanol Vehicle Coalition
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