Thirty odd years ago, the handwriting appeared on the wall for the first time. After decades of abundant and cheap oil, an “Energy Crisis” arose. Actual supplies of both crude oil and refined products were never really in question—availability was the issue. For the next few years, oil shortages came and went, prices increased moderately and little else changed. In spite of the rise in prices, crude oil and products refined from it remained cheaper than alternatives and as soon as supply shortages eased, it was “business as usual”.
The current “Energy Crisis” is probably the first one with any justification. It’s certainly a result of on-going idiocy in the Middle East combined with increased world-wide consumption and diminishing supplies from oil fields not located in countries where sand and camels are prevalent. Given the fact that the Middle East will never be a bastion of stability, the quest for viable alternative fuels may finally have some muscle behind it. Considering the existing infrastructure and vehicle population, it’s highly unlikely that we’ll completely eliminate dependence on gasoline in the foreseeable future. The most appealing alternative fuels are consequently those that can be blended with gasoline because their use requires a minimal amount of modification to existing vehicles and fuel delivery systems. (Those used in a vehicle as well as the “pipeline” that brings fuel to the corner filling station.)
Currently, ethanol-based fuels offer the greatest potential to make a significant impact on our consumption of gasoline. In spite of a considerable amount of rhetoric concerning practicality of manufacturing, distributing and consuming ethanol-based fuels, use of E85, a mixture of 85% ethanol and 15% gasoline, has risen dramatically in the past few years. Uncertainty about the future of gasoline supplies and associated costs is likely to increase focus on E85 and other ethanol blends, and that raises questions regarding the rebuilding of engines designed for use in days when “a buck’s worth” would put enough gas in a tank for a full night of cruising.
In those days of plentiful gasoline, concerns about dependence on foreign oil didn’t exist. Interest in the ability of a vehicle to consume a fuel other than gasoline was stoked by a desire for energy independence and convenience. For many farmers, it was easier to manufacture ethanol than to drive several miles to the nearest gas station. For vehicle manufacturers, the flip side of their customers’ desire for energy independence was lack of fuel quality and mixture standards. As a result, they had to provide the vehicle operator with a means of tuning air/fuel ratio to be compatible with the fuel in the tank—whatever it might be. Some vehicles were already equipped with a sophisticated tuning device—it was called a cable choke. If the driver needed a richer mixture, he simply pulled the cable out a bit further.
That arrangement isn’t the best choice for optimum engine efficiency, but it does illustrate the ease with which an engine can be “tuned” to operate on a fuel other than gasoline. In theory, converting any traditional gasoline engine to consume E85 requires nothing more than a carburetor rejetting or EFI recalibration and an ignition advance curve modification. Obviously, things are never that simple, but the bulk of the required changes are actually necessitated by the fuel system, not the engine itself. That’s largely because of any ethanol-based fuel’s affinity for moisture and its cleaning and corrosive qualities.
Ethanol has a healthy appetite for cork, aluminum, magnesium, certain types of rubber and “gunk”. These materials must obviously be eliminated from any fuel system that will be handling E85. However, locating and replacing some of these components may require a “trial by fire”– a good reason to keep a watchful eye on the carburetor, fuel lines and gas tank, after the first few fill-ups with E85. Carburetor gaskets and rubber fuel lines are obvious components that should be inspected, tested or replaced. Not so obvious are items like a fuel pump diaphragm, fuel filter or gas tank sending unit gasket. Electronic fuel injection systems typically incorporate high grade materials to accommodate system pressures ranging from 15 to 58 psi and these materials tend to resist the effects of alcohol fairly well (tend being the operative term).
Whether a vehicle is carbureted or injected, the gas tank itself may be the biggest obstacle on the path to alcohol dependency. After the fuel system has been made fully compatible with E85, “gunk” is the issue to be contemplated. While gasoline is lolling around in a tank, it leaves a part of itself there. With the passage of time, these deposits oxidize and gel, have children and lead a happy, relaxed life. The onset of an E85 invasion changes a gas tank’s environment dramatically. Being a relatively strong solvent, ethanol dissolves the gunk, allowing it to leave its happy home en route to the carburetor. Along the way, it enters the fuel filter and some of it stays there, so after a switch to E85, fuel filter life will shorten significantly, until a gas tank is “gunk free”.
E85 requires a richer mixture because its nominal stoichiometric (chemically ideal) air/fuel ratio is 9.77:1, while that of gasoline is 14.7:1. (The actual stoichiometric ratio varies somewhat according the composition of the gasoline in the E85 blend.) Obviously, this richer air/fuel ratio results in E85 delivering poorer fuel economy than gasoline. Another mileage-reducing factor is E85’s lower energy content. A gallon of gasoline contains approximately 114,100 BTU; E85 contains 83,200 BTU per gallon. (For reference, a gallon of number 2 diesel fuel contains 138,000 BTU.) In spite of these factors, gas mileage with E85 drops only 15% to 25% compared to straight gasoline.
Ethanol doesn’t vaporize quite as easily as gasoline, so when cold weather sets in, it’s usually necessary to raise gasoline content. Typically a 70/30 ethanol/gasoline blend (E70) eliminates hard starting problems at lower temperatures and that’s what you find at the pump during the winter months in areas of the country where E85 is widely available.
On the plus side, E85 has an octane rating of 105, so spark timing can be advanced several degrees (compared to the maximum practical setting for gasoline) without experiencing spark knock. More aggressive spark settings can be used to increase power output, which in turn reduces the degree of throttle opening required for acceleration and hill climbing. As a result, fuel economy doesn’t fall off as dramatically as expected, considering E85’s stoichiometric ratio and reduced energy content.
For engine rebuilders, fuel composition doesn’t have much impact on machining or assembly procedures. The biggest challenge in dealing with E85 is communicating vehicle fuel system requirements to customers. Failure to address these can lead to issues with the potential to cause engine damage, and will certainly result in accusing fingers pointed at the engine builder.
Another consideration is the fact that you may not know which fuel will ultimately be used to fire the engines you so lovingly rebuild. That being the case, it might not be a bad idea to include a tag with each engine alerting the end user to make the necessary vehicle modifications if the engine is to be fueled with ethanol or E85.
With six technically oriented automotive books and over 1,500 magazine articles to his credit, Dave Emanuel is regarded as one of the nation’s most respected automotive journalists. During the past 20 years, his work has appeared in popular publications such as Motor Trend, Road & Track, Hot Rod, Corvette Fever and Popular Science to name only a few of the more than twenty magazines.Dave’s technical expertise and extensive hands-on experience, combined with his personal relationships with many of the nation’s top high performance engine builders and Detroit engineers, allows him to provide readers with unique insights into the high performance and racing aspects of engines and drivelines. Dave is also involved with private enterprise and offers insight on yet another possible power source. Go online for more information: www.randomtechnology.com.
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