The more I research this matter the more I'm convinced that we aren't talking injecting Nitrous and/or Alcohol here, given suggestion of injecting it through an automotive injector. I think we are probably thinking nitromethane as used in 2 stroke RC applications. Wherein pretty much everything herein becomes irrelevant, because that application depends upon a glow plug in the cylinder to generate the heat for combustion, not a spark plug. Everything I've been able to find on that application indicated ntiromethane does not work real well in normally aspirated 4 stroke combustion engines. So that's kinda out of the question.
My comments above indicate that Alcohol is a drier burning fuel, which it is, although comments to the effect that the engine would run hotter were maybe incorrect... although it burns cooler, Alcohol robs lubrication. No maybe it doesn't generate more heat as a result of combustion and cause melt down, but it does contribute a significant number of other concerns from a point of lubrication. Especiallly in this instance where we're talking extremely primative lubrication in lawn mower engines compared to Sprint Cars Mike.
In respect to 2 strokes:
http://www.ultralightnews.com/features/fuelrec.htmlThe following is taken from Rotax Service bulletin UL's 13 94
Using auto fuel in Rotax two cycle aircraft engines.
Also, the alcohol competes directly with the lubrication, and depending on your oil's ability to combat such, could cause engine damage.Alcohol carries water which on shutdown and storage can create corrosion on vital engine parts such as crank, main, and rod bearings as well as pins. Once corrosion has started the bearings will fail.
Seasonal blend crossovers can affect your fuels volatility, if you use a winter blend fuel during hot summer days. This is a common occurrence with people who buy a fuel blend in colder climates in March, but don't use it in the Rotax engine until June. Evaporation temperatures of your fuel must be low enough to minimize crankcase and combustion chamber deposits as well as spark plug fouling without fear of vapour locking of boiling. Always make sure you buy your fuel from a high volume user, and avoid fuel which is been in storage for long periods of time, especially between seasons.
Loss of octane rating is a common problem on fuel stored incorrectly which could lead directly to engine failure.
http://www.whybike.com/motorcycle81.htmFuelThe two stroke engine needs to be run on a mixture of petrol and two stroke oil. This is so that the engine is kept lubricated whilst in use.
99% of all starting problems are caused by fuel problems. These can stem from bad or old fuel and improperly mixed fuel (please see mixing chart).
Do not use fuels that contain alcohol, as the can cause you bike to run ‘lean’. Be advised some racing fuels contain alcohol and are best avoided... We recommend that you use normal petrol from a garage and a quality two stroke oil.
A mixture that is too lean i.e not enough two stroke oil can damage your mini moto’s engine as the moving parts are not properly lubricated. This can cause the engine to seize. However a mixture that is too rich can choke the engine and effect the performance and cause starting problems.
Issues are also suspected with lubrication, even in automobile engines...
http://www.deh.gov.au/atmosphere/fuelquality/publications/review-non-automotive/engine-durability.html7.1 Wear on Engines and LubricationVarious studies investigating wear on engines using ethanol-blended fuels have been performed on four-stoke and two-stroke engines. The majority of work on four-stroke engines is of automotive background.
There have been studies completed on the metal to metal wear differences due to the impact of using alcohol and alcohol gasoline blends.
The evidence reported by Black is that ethanol blends offer less lubrication to metal parts. The same paper also reports that should long cranking periods be required to start the engine, metal to metal contact occurs due to the alcohol washing away the lubrication film. It should be noted that though it is not clear, this might be based on straight alcohol fuels.
7.2 Deposit FormationVarious studies investigating deposit formation on engines using ethanol-blended fuels have been performed on four-stoke and two-stroke engines. The majority of work on four-stroke engines is of automotive background.
Four-stroke engines may experience intake system deposits (ISD). ISDs are the deposits discussed in any significant detail by the various authors of the literature reviewed.
In particular, deposits on the back of the intake valve is referenced as the area of most concern. This concern is clear due to the intake valve and seat area presenting the flow restriction point in the intake tract of modern engines.Intake system deposits are reported by (13,14) to be more prevalent with fuels containing alcohol. The authors14 explain that gasoline contains two types of additive packages to control deposits. The two different additive packages are formulated to control deposits on the pintle of the fuel injector to ensure accurate fuel metering and to control the deposits on the surfaces of the intake system, particularly the intake valve, to ensure the engines charge airflow is not compromised.
Their detailed testing has shown that adding 10% by volume neat ethanol to gasoline with adequate ISD additive increased intake valve deposits by more than 350%. This is not only due to the dilution effect but also due to an antagonistic effect since neat ethanol blended at 10% by volume with gasoline without ISD additive increased intake valve deposits by 37% over the gasoline base without ISD additive. Increasing the ISD additive by 50% over the normal concentration in gasoline was found necessary with 10% ethanol blends in order to achieve the same deposit control as with normal ISD additive levels in gasoline. Some of the experiences reported by (14) are confirmed by (11). Firstly that intake system deposits have been found in the intake valve area, and also includes the intake manifold area; and secondly that the deposits can be controlled with higher additive levels than would be required for gasoline only11.
Crankcase scavenged two-stroke engines may experience detrimental deposits in the piston ring land area as documented by Kasperson and Reynolds28. The piston ring land deposits tended to cause ring stick, where the piston ring becomes stuck in the pistons ring groove. These ring land deposits are common in engines operating on gasoline; solvents and detergents in the fuel and oil control the severity of the deposits.
And, the lower temperature causes problems in itself does it not? Like the need to run hotter plugs to generate enough heat to properly utilize the fuel. Wherein a lawn mower engine probably doesn't run at the temperatures a Sprint Car engine does, so additional concerns exist in respect to decreased efficiency in burn rate.
http://journeytoforever.org/biofuel_library/ethanol_manual/manual1-2.htmlVOLATILITYAnother important quality in a motor fuel is "volatility", or the ability to be vaporized. As previously noted, methyl alcohol contains less than half the heat value of gasoline and ethyl alcohol contains only about 60%. The next higher alcohol, propyl alcohol with three carbon atoms, contains only 26.6% oxygen and thus about 74% of the heat value of gasoline. It is apparent that the more complex the alcohol, the closer its heat value comes to that of gasoline. Cetyl alcohol (Figure 2-1), for example, contains only about 6.6% oxygen and thus has about 90% of the heat value of gasoline. However, this alcohol is a solid wax! It can't be conveniently vaporized and mixed with air in an engine and so is useless as a motor fuel. Consequently, in considering alcohol fuels, a compromise must be made between heat value and volatility.
Closely related to volatility is a quality called "latent heat of vaporization". When a liquid is at its boiling point, a certain amount of additional heat is needed to change the liquid to a gas. This additional heat is the latent heat of vaporization, expressed in Btu/lb in Figure 2-2. This effect is one of the principles behind refrigeration and the reason that water evaporating from your skin feels cool.
Referring to Figure 2-2, gasoline has a latent heat of about 140 Btu/lb; methanol, 474 Btu/lb; and ethanol, 361 Btu/lb. In an engine, vaporization of the gasoline fuel/air mixture results in a temperature drop of about 40 degrees Fahrenheit. Under similar conditions, the temperature drop for ethyl alcohol will be more than twice that of gasoline, and for methanol the drop will be over three times as great. These temperature drops result in a considerably greater "mass density" of the fuel entering the engine for alcohol as compared to gasoline. The result is a greatly increased efficiency for alcohol fuels. To visualize why, remember that at a given pressure, the amount of space a gas occupies is directly proportional to the temperature. For example, if one pound of a gas fits into a certain container at a given pressure and the temperature is cut in half, the container will now hold two pounds of the gas at the same pressure. In an engine, a stoichiometric mixture of methanol and air would be over three times colder than the same gasoline/air mixture. This means that there is now over three times (by weight) as much methanol in the cylinder. Now, even though methanol has only half the heat value of gasoline, the net gain in "volumetric mass efficiency" is over three times.
So, for example, if the gasoline/air mixture in a given engine cylinder produces 100 Btu on each stroke, the same engine would produce 150 Btu per stroke with methanol. This power gain due to increased volumetric mass efficiency is the primary reason for the popularity of methyl alcohol as a racing fuel. With ethanol the effect isn't quite as dramatic, but the greater heat value partially offsets the lower latent heat. Overall, this power increase with alcohol fuels considerably mitigates the liability of low heat value.
However, the increased cooling due to latent heat sometimes creates a problem in an engine converted to run on alcohol. Once vaporized, a certain amount of heat is required to keep the fuel from condensing back to the liquid state before it reaches the cylinder. To accomplish this, an engine is designed to provide this heat to the intake manifold. Alcohol, because of its greater latent heat, requires more heat than gasoline. This is one of the reasons that racing engines have short path manifolds and multiple carburetors. The shorter the distance the fuel must travel to the cylinder, the less chance of condensation and fuel distribution problems. On a practical level, most engines that have been converted to alcohol supply enough heat once they are warmed up. The main problem, as with high performance racing engines, is in starting a cold engine. This problem and the related fuel distribution problem will be discussed later in more detail.
A few more interesting links on the conversion from gasoline to alcohol. Each indicating that without considerable thought in modification of the engine to run alcohol, it can in fact be counter productive, since the engine really isn't designed to run it, in any respect, not simply from a point of carburetion.
http://journeytoforever.org/biofuel_library/ethanol_motherearth/me2.htmlhttp://www.hpt-sport.com/gasclass.htmIt should also be noted that irrelevant to discussion here because the initial post suggests installation of fuel injection, the typical Lawn Mower Engine doesn't really have the ability to properly atomize fuel to begin with, and if you reduce temperatures and run alcohol in a normally aspirated set up, you're very likely going reduce efficiency, wherein it would be very wise to read the recommend the Octane Test at the end of the last link provided there folks. It might save you a dollar, and make you a little faster around the track.
Otherwise, the whole ball of wax isn't worth arguing over, and that isn't my point in posting all of this. I simply found it all very enlightening and having seen more than one question around here, and having heard more than a question or two in circles outside the forum here concerning the use of alcohol blended fuels, Octane ratings etc., I thought others might enjoy reading some of it.
