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By: Jason Giacchino

April 2010 - Off The Pegs

Nitrous Versus Methanol

Dear ATV Source:

Nitrous Express

I’ve been out of the scene for about 15 years thanks to the family thing and dabbled a bit in automotive tuning during that time away from ATVs.  Now, I’m thinking of picking up an ATV (either the Honda TRX700 or the Yamaha Raptor 700) and wondered why, unlike the street tuning scene, Nitrous Oxide boost isn’t at all common in the performance ATV world.  I remember the dune guys used to go as far as to convert their Banshees to burn alcohol but wouldn’t simply adding NOS have accomplished the same objective?

Great question and the answer requires a closer look at the gas that divides its popularity between dentist offices and performance tuners alike.  Believe it or not, nitrous oxide isn’t flammable at room temperature (which is probably a good thing considering smoking in public used to be allowed; yes, even while waiting to be seen by the dentist).  Nitrous oxide requires a great deal of heating before its explosive properties become realized; to the tune of just short of 570 degrees Fahrenheit.  Even at this high temperature, contrary to common misconception, the gas is not a combustible so much as it is an oxidizer.  What this means is that in the fiery instant where fuel and spark meet, nitrous can provide much more oxygen to the process than air can alone (a little over 35% more to be specific).

Since, as the name implies, nitrous oxide consists of both nitrogen atoms (2 of them) and oxygen (1), what actually happens within the engine’s combustion chamber is that the nitrogen atoms split apart, freeing the oxygen to do what it does best in the situation: oxygenize the fuel molecules.  More oxygen enriched fuel burns more efficiently, and you feel this in the form of a power boost throughout the duration of the nitrous oxide’s injection.

There’s an added power boost often overlooked as well in that the nitrous stored in that little can is in liquid state and under a great deal of pressure (1000 psi isn’t uncommon).  Once exposed to the atmosphere, the liquid instantly vaporizes (the process of liquid turning into gas).  As this happens, heat in the surrounding area becomes absorbed as well and hence the vapor benefits from an instantaneous drop in temperature.  In plain terms this means that intake charge itself is cooler and hence denser than if you were drawing in ambient air.  A denser charge packs even more oxygen, which, of course,only further compliments the power boost you feel.

Since nitrous allows for a much denser charge into the cylinder it simultaneously dramatically increases cylinder pressures. The increased pressure results in heat, so ironically a colder intake charge results in a surge of heat. The most common problems resulting from prolonged cylinder heat include piston deformation, valve damage or warping or cracking of the head or predetonation (pinging).

Just like in the car world, nitrous oxide injection systems come in either “dry” or “wet” configurations.  The difference is simple and really quite logical: A dry kit relies only upon the gaseous form of the nitrous oxide for an increased boost while a wet kit combines the nitrous oxide with pressurized fuel (gasoline) to accomplish the same task.  Interestingly enough, the Banshee-days you reference in your question most all relied upon wet kit nitrous injection on account of the fact that carburetors demand a specific air/ fuel ratio to function properly.  These days, with the move to electronic fuel injection in most ATVs, the choice of running either kit exists.

General rule of thumb: A dry kit is cheaper as it requires fewer parts, less complexity, and there are some kits that require no engine modification whatsoever by instead injecting the N2O into the air box to be “inhaled” by the motor rather than into the cylinder directly.

Many companies (such as NX: Nitrous Express) offer small engine nitrous kits for jet skis, snowmobiles, motorcycles, and ATVs that, depending on the engine (from one to four cylinders), can provide a boost of from 5 to 50 horsepower.

Alcohol, in this case methanol, is recommended for short duration racing as an engine will consume roughly twice the amount of alcohol fuel for any given output compared to gasoline!  And like brake fluid, methanol is hygroscopic meaning it absorbs water the moment it is exposed to the atmosphere and it is corrosive to metals, gaskets and seals. In four stroke engines it is recommended that a methanol fuel treatment (lube) be used in order to combat corrosion.  Plus, methanol should be completely drained from the fuel system at the end of the day, every time.

Also, because alcohol burns so much cooler than gasoline, meth-burning ATVs usually require an increase in compression.  Methanol is less tolerant of a lean air/fuel ratio than gasoline and will detonate quite violently.

So in conclusion, nitrous oxide and methanol may both accomplish similar end results (increased power for short duration racing); the means in which they accomplish this are quite different with nitrous getting the nod for less maintenance despite a steeper initial cost.

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