TECHNICAL  ARTICLES!

Index

-What is octane?

-The magic of methanol

-The promise of ethanol

-Engines that might go into a tractor

-Supercharging overview

-Cub Cadet gear ratios

-Rod length chart overview

What is octane?

When crude oil is cracked in a refinery, it creates different length hydrocarbons, just ask Cy when the breeze is blowing in from the west, anyway these can be separated and blended to make different fuels.

The fuels octane is made up of eight carbon atoms chained together. The octane rating of gas tells you how much the fuel can be compressed before it ignites. When gas ignites by compression instead of by a spark plug, it can damage an engine (ping-pre-ignition), not all oil compresses well, but octane can be compressed a lot and nothing will happen. Lower-octane gas can handle the lowest amount of compression before igniting. higher-octane fuel is used in a high-performance engines, which needs higher compression.

The Magic of Methanol

Methanol = CH3OH
Ethanol = C2H5OH

Methanol, also known as wood alcohol, because it was originally produced from distilling wood and now is made primarily from natural gas. It’s a dense and safe fuel as well as inexpensive and a plentiful one – especially in the United States, which produces almost one quarter of the worlds supply, and is the best high performance fuel available. Far better than any expensive "racing" petroleum fuel. It'll help any 4-stroke high performance engine produce more power and run cooler. Methanol is a safe fuel to use. But if anyone feels uncomfortable using or converting an engine for use with of methanol, please consult with a professional engine builder first..

Methanol will mix equally with water and it evaporates quickly. The important thing to remember when storing methanol is the keep it in an air tight container in a dry place. Because it can easily draw moisture when stored for a long period, especially in a metal container. (Unlike plastic, steel gets cold, which draws condensation.) If one suspects that water had gotten into the methanol, it can be separated easily by using a chamois. (The chamois will absorb the water and allow the methanol to pass through.)

If your club's sanctioning rules say that the methanol fuel must be able to pass a water test, then just use 100% pure methanol with no oil. (To some clubs, oil is also known as a "contaminant.") Pure methanol will remain clear in water, but turn cloudy in water when mixed with oil. And it's important that the main fuel mixture on the carburetor be richened slightly, to keep from burning the piston (because of the lack of oil in the fuel).

Methanol has no effect on rubber, neoprene or OEM carburetor or fuel system parts nor does it get stale like gas does. But it will corrode aluminum as plain water does if it is not drained and allowed to evaporate from the fuel system over an extended length of time.

Because methanol will ignite only in a narrow range of high temperatures, it is less likely to catch on fire should an accident occur. If methanol does catch on fire, water can extinguish the flames, unlike a gasoline fire.

Methanol burns much slower than the highest octane gasoline. (It has about a 135 octane rating.) Therefore, the ignition timing must be advanced more than for gas when burning methanol. If the timing isn't advanced enough, some of the methanol will go unburned and little will be gained. Modifications to the point lobe on the camshaft may need to be made in order to achieve the full ignition timing setting. Methanol also requires a hotter spark. Therefore, a high-voltage/high performance ignition coil is needed, along with a wide spark plug gap (.060"). NOTE - Never run over-advanced ignition timing with any petroleum-based fuel (gas) just to try to get "more power." All that does is seriously overheat the engine and could weaken (collapse) the piston rings, shrink the piston, warp the cylinder head and exhaust valve and it could even cause the engine block to crack.

As methanol burns, it produces tremendous combustion chamber pressures under full throttle (even more so on cooler days). To prevent possible cylinder/crankcase separation, the cylinder must be "strapped" to the crankcase. Especially on 12 hp engines and up. So strap it now, or scrap it later! Methanol works best in a high compression engine, too.

Moreover, if you had a 10hp block bored for a 12hp piston, or a 12hp block bored for a 14hp piston, and you use your tractor to push snow, definitely strap the cylinder to the crankcase! Because it now has a much thinner cylinder wall, and the cold winter air is more dense (like the air is thicker or there's more of it). Dense air will build up the compression pressure within the combustion chamber, causing the engine to produce more power. But what also happens is at full throttle, this high compression is pushing upward on the cylinder head, and pulling upward on the cylinder wall. And sometimes the cylinder wall will break, ruining the whole engine. I know, I've had this happen to me before. No joke.

Methanol produces a "cooling effect" as it enters an engine at high velocity (high rpms). And, it's a clean burning fuel, it won't carbon up the combustion chamber, foul-out the spark plug or even harm the ozone layer. The crankcase motor oil may need to be changed periodically though.

IMPORTANT! It's always a good idea to use a special upper cylinder lubricant to be mixed with methanol to prevent possible piston-to-cylinder scoring. If a lubricant isn't used and if the fuel is ran too lean, it could ruin a good high-dollar piston and cylinder wall! But I realize that some clubs don't allow any additives (lubricant) in methanol (it boosts the octane and will probably fail in a fuel test).

Here's another thing concerning methanol fuel - when it evaporates, it leaves behind some very small particles of white, flaky calcium deposits in the fuel system. Which is normal and unavoidable. These deposits can ruin a good fuel filter, but won't harm the engine or any other part of the fuel system. So to keep from having any [future] fuel flow problems, don't install a fuel filter. Instead, filter the fuel with a paint, coffee or a fine mesh filter of some sort before it is poured into the fuel tank. Just place the filter in a funnel, and pour the fuel through it into the tank. If there are any very small particles of dirt present in the fuel, they should pass right through, being the jets have been enlarged.

Fuel filters can only filter so much of a grain of dirt. Anything smaller will pass right through, most of time causing no harm. Sometimes a hair will pass through a wire mesh fuel filter, lodging in the float valve, keeping it closing all the way because it can't get past the bend. It'll cause the carburetor to flood overnight. I've seen this happen a few times. On certain small engines, the flooding gas will seep down into the motor oil, ruining it. Briggs & Stratton riding mower engines are notorious for this. All you can do is clean out the carburetor and hope it doesn't happen again. And if there's enough fresh gas in the crankcase, sometimes the crankcase will explode if the engine backfires through the carburetor. The backfire flame will sometimes travel through the valve cover & into the crankcase.

Most garden tractor carburetors can be easily converted for methanol use. The main thing to keep in mind is that methanol requires about twice the volume of fuel than gas. (Approximately a 5-6:1 ratio for methanol versus 10-12:1 ratio for gas). So to run methanol, the fuel passage holes will basically need to be enlarged to about twice their original size.

So the bottom line is that if you want a power gain of at least 13%, convert to methanol.

(Re-printed from Brian Miller’s tips and tricks)

The Promise of Ethanol

Ethanol can be derived from corn, wheat, potato wastes, cheese whey, rice straw, sawdust, urban wastes, paper mill wastes, yard clippings, molasses, sugar cane, seaweed, surplus food crops, and other cellulose waste. Petroleum is also used to make industrial ethanol.

Ethanol, which is the same chemical as the alcohol in alcoholic beverages, can approach 96% purity by distillation, and is as clear as water. Higher purities require different industrial processes. It is flammable and burns more cleanly than many other fuels. When fully combusted its combustion products are only carbon dioxide and water. For this reason, it is favored for environmentally conscious transport schemes and has been used to fuel public buses. However, pure ethanol attacks certain rubber and plastic materials and cannot be used in unmodified car engines. Additionally, ethanol has a much higher octane rating than ordinary gasoline, requiring changes to the spark timing in engines. To change a gasoline-fueled car into an ethanol-fueled car, larger carburetor jets (about 50% larger) are needed. Also, a system is added to inject a little warmed ethanol into the carburetor to solve the cold starting problem. If 10% - 30% ethanol is blended with gasoline, then no engine modification is needed.

A mixture containing gasoline with at least 10% ethanol is known as gasohol. It is commonly available in the Midwest of the United States and is required by the state of Minnesota. One common gasohol variant is "E15", containing 15% ethanol and 85% gasoline. These concentrations are generally safe for regular automobile engines, and some regions and municipalities mandate that the locally-sold fuels contain limited amounts of ethanol. One way to measure alternative fuels is the "gasoline-equivalent gallons" (GEG). In 2002, the U.S. used as fuel an amount of ethanol equal to the energy of 1.13 billion gallons of gasoline. This was less than one percent of the total fuel used that year.

The term "E85 ethanol" is used for a mixture of 15% gasoline and 85% ethanol. Beginning with the model year 1999, a number of vehicles in the U.S. were manufactured so as to be able to run on E85 fuel without modification. Most of the vehicles are officially classified as light trucks (a class containing minivans, SUVs, and pickup trucks). These vehicles are often labeled dual fuel or flexible fuel vehicles, since they can automatically detect the type of fuel and change the engine's behavior to compensate for the different ways that they burn in the engine cylinders.

When farmers distilled their own ethanol, they sometimes used radiators as part of the still. The radiators often contained lead, which would get into the ethanol. Lead entered the air during the burning of contaminated fuel, possibly leading to neural damage. However this was a minor source of lead since tetraethyl lead was used as a gasoline additive.

In Brazil and the United States, the use of ethanol from sugar cane and grain as car fuel has been promoted by government programs. Some individual U.S. states in the corn belt began subsidizing ethanol from corn (maize) after the Arab oil embargo of 1973. The Energy Tax Act of 1978 authorized an excise tax exemption for bio-fuels, chiefly gasohol. The excise tax exemption alone has been estimated as worth US$1.4 billion per year. Another U.S. federal program guaranteed loans for the construction of ethanol plants, and in 1986 the U.S. even gave ethanol producers free corn.

Alcohol and hydrogen
There is an emerging view that current consumers of fossil fuels should move to using hydrogen as a fuel, creating a new so-called hydrogen economy. One theory holds that hydrogen should not be considered to be a fuel source in and of itself. In this view, hydrogen is merely an intermediate energy storage medium existing between an energy source (be it solar power, bio-fuels, and even fossil fuels) and the place where the energy will be used. Because hydrogen in its gaseous state takes up a very large volume when compared to other fuels, logistics becomes a very difficult problem. One possible solution is to use ethanol to transport the hydrogen, then liberate the hydrogen from its associated carbon in a hydrogen reformer and feed the hydrogen into a fuel cell. Alternatively, some fuel cells can be directly fed by ethanol.

In early 2004, researchers at the University of Minnesota announced that they had invented a simple ethanol reactor that would take ethanol, feed it through a stack of catalysts, and output hydrogen suitable for a fuel cell. The device uses a rhodium-cerium catalyst for the initial reaction, which occurs at a temperature of about 700°C. This initial reaction mixes ethanol, water vapor, and oxygen and produces good quantities of hydrogen. Unfortunately, it also results in the formation of carbon monoxide, a substance that "chokes" most fuel cells and must be passed through another catalyst to be converted into carbon dioxide. The ultimate products of the simple device are roughly 50% hydrogen gas and 30% nitrogen, with the remaining 20% mostly composed of carbon dioxide. Both the nitrogen and carbon dioxide are fairly inert when the mixture is pumped into an appropriate fuel cell. Once the carbon dioxide is released back into the atmosphere, it is reabsorbed by plant life.

Alternate sources
Sugar cane grows in the southern United States, but not in the cooler climates where corn is dominant. However, many regions that currently grow corn are also appropriate areas for growing sugar beets. Some studies indicate that using these sugar beets would be a much more efficient method for making ethanol in the U.S. than using corn.

In the 1980s, Brazil seriously considered producing ethanol from cassava, a major food crop with massive starchy roots. However yields were lower than sugarcane and the processing of cassava was considerably more complex, as it would require cooking the root to turn the starch into fermentable sugar. The babaçu plant was also investigated as a possible source of alcohol.

There is also growing interest in the use of biomass as a source for ethanol and other types of fuel. This is a broad-ranging idea, using various types of organic matter including purpose-grown crops of plants and trees as well as leftover waste products — even including animal waste.

At this time, most of the different processes for converting biomass into ethanol and other fuels are very complicated and not particularly efficient. A few processes have seen increasing buzz, including thermal depolymerization (though that process produces what is described as light crude oil).

Net fuel energy balance
To be viable, an alcohol-based fuel economy should have positive net fuel energy balance. Namely, the total fuel energy expended in producing the alcohol — including fertilizing, farming, harvesting, transportation, fermentation, distillation, and distribution, as well as the fuel used in building the farm and fuel plant equipment — should not exceed the energy contents of the product.

Switching to a system with negative fuel energy balance would only increase the consumption of non-alcohol fuels. Such a system would only be worth considering as a way of exploiting non-alcohol fuels that may not be suitable for transportation use, such as coal, natural gas, or bio-fuel from crop residues. (Indeed, many U.S. proposals assume the use of natural gas for distillation.) However, many of the expected environmental and sustainability advantages of alcohol fuels would not be realized in a system with negative fuel balance.

Even a positive but small energy balance would be problematic: if the net fuel energy balance is 50%, then, in order to eliminate the use of non-alcohol fuels, it would be necessary to produce two gallons of alcohol for each gallon of alcohol delivered to the consumer.

In this regard, geography is the decisive factor. In tropical regions with abundant water and land resources, such as Brazil, the viability of production of ethanol from sugarcane is no longer in question; in fact, the burning of sugarcane residues (bagasse) generates far more energy than needed to operate the ethanol plants, and many of them are now selling electric energy to the utilities. Also, in countries with abundant hydroelectric power, the net fuel energy balance of the cycle could be improved to some extent by using electricity in the production, e.g. for milling and distillation.

The picture is quite different for other regions, such as the United States, where the climate is too cool for sugarcane. In the U.S., agricultural ethanol is generally obtained from grain, chiefly maize, and the net fuel energy balance of that route is still critical.

Energy balance in the United States
Many early studies concluded that the use of corn ethanol for fuel would have a negative net energy balance. Namely, the total energy needed to produce ethanol from grain — including fermentation, fertilizing, fuel for farm tractors, harvesting and transporting the grain, building and operating an ethanol plant, and the natural gas used to distill corn sugars into alcohol — exceeds the energy content of ethanol. Critics have argued that since production energy comes mostly from fossil fuels, gasohol isn't just wasting money but hastening the depletion of nonrenewable resources. Most such studies were based on data collected in the 1970s and early 1980s, but some analyses in 2001, continued to indicate that ethanol has a negative energy balance. A peer-reviewed study by Cornell University ecology professor David Pimentel seemed to confirm this conclusion. Pimentel's study was disputed by other specialists, forcing him to revise his figures. Still, in August 2003, he stated in a Cornell bulletin that production of ethanol from corn only takes 29% more energy than it produces.

However, continuous refinements to ethanol production procedures have much improved the benefit/cost ratio, and most studies of modern systems indicate that they now have a positive net energy balance.

Many other studies of corn ethanol production have been conducted, with greatly varied net energy estimates. Most indicate that production requires energy equivalent to 1/2, 2/3, or more of the fuel produced is required to run the process. A 2002 report by the United States Department of Agriculture concluded that corn ethanol production in the U.S. has a net energy value of 1.34, meaning 34% more energy was produced than what went in. This means that 75% (1/1.34) of each unit produced is required to replace the energy used in production. MSU Ethanol Energy Balance Study: Michigan State University, May 2002. This comprehensive, independent study funded by MSU shows that there is 56% more energy in a gallon of ethanol than it takes to produce it.

Here are some current and non-current engines that might go in a garden tractor, check your club rules for details.

SUPERCHARGING-IS IT FOR YOU?

There are several ways to increase the power of an engine, all of which involve increasing the amount of fuel and air we move into the engine and getting rid of the exhaust as quickly and easily as possible. If we are starting from scratch, the easiest and least expensive way to increase power is simply to build a bigger engine. Increasing the number of cylinders, increasing the cylinder bore and increasing the crankshaft stroke are all methods used to increase displacement and make the engine capable of moving more air, burning more fuel and producing more power. Weight and physical size are often the limiting factors in this approach. We can also turn the engine faster, the faster it cranks the more fuel, air and exhaust it moves. Unfortunately we soon reach the physical limitations of the components. Reversing the direction of a piston 10,000 times a minute or more can be tough on bearings, rods and crankshafts. Spring tension on valves must be strong enough to keep the valve following the cam profile, but not so strong as to beat the valve seat to pieces when the valve closes. Another solution is to fiddle with the mechanics of the engine to increase its volumetric efficiency. Typical hot rod techniques include increasing compression (requires the use of high octane fuel, see the above article on octane) and changing the cam or cams (controlling how high a valve lifts and how long it stays open). Again the purpose is to get more fuel and air into the engine and exhaust the combusted fuel out. These techniques often result in a power increase over a narrow portion of the balance of the RPM range (power band), and with a resulting loss in power in the balance of the RPM range. In more sophisticated engines, the use of three, four or five valves per cylinder and variable valve timing has improved the useable RPM range and volumetric efficiency of engines with limited physical size.

Properly designed all of the above methods work, but horsepower gains are generally limited and and rely on atmospheric pressure to force air into the combustion chamber. For truly impressive power gains, pressurizing the intake is most effective. Supercharging is one way to do this, turbo charging is another way, a supercharger is nothing more than an air pump that is generally belt driven from the crankshaft of the engine . It packs more air into the combustion chamber allowing the engine to burn more fuel and create more power. The increased pressure is called boost, and generally ranges from 3-5 PSI for mildly boosted automotive engines to 15 PSI or more , depending on the application. If the engine can withstand the mechanical stress, horsepower can be doubled or more with just a modest increase in the physical size of the engine. The advantages of a supercharger are that they can provide a significant amount of boost at low engine RPMs. Because of the direct connection between the supercharger and the engine, boost pressures are directly related to RPMs. The simplest set up limits the boost by selecting drive ratios that limit maximum boost at maximum engine RPM. With this set up, boost decreases as engine RPM decreases. A more sophisticated system turns the supercharger faster, creating a higher amount of boost at lower RPM, enhancing low end power. As boost pressures increase beyond the desired limits as the engine RPMs increase a bled valve lets out excess pressure. With modern electronic engine controls, optimum boost pressures can be maintained over a broad operating range (wide power band).

While supercharging is a way to gain sizeable horsepower gains, there are some disadvantages also. For best results the engine should be designed from the ground up to be supercharged. The increased power means increased heat and raised levels of compression require the appropriate fuels or adjustments in compression ratios. Long term durability is also an issue as supercharging, particularly with high boost pressures, put significant stress on an engine.

So the bottom line may be to think carefully about your application before bolting on a supercharger.

For small engine superchargers check out: http://www.hscsupercharger.com/