Long before we were spraying nitrous oxide into motorcycle engines for its power boosting characteristics, it had another life. In the late 1700s an English chemist named Joseph Priestly discovered the near odorless, colorless non-flammable gas; at that time it was originally intended to be a preservative for food. Then some years later fellow Englishman Humphrey Davy experimented with the physiological uses of nitrous oxide and its anesthetic and analgesic qualities. By 1840 it was used commonly in dentistry, childbirth, and even during heart attacks to relieve pain, and is still used today to a limited extent.
A typical internal combustion...
A typical internal combustion engine mixes oxygen and hydrocarbons for a chemical reaction that creates energy. Here we show a simple hydrocarbon molecule-methane (CH4 , composed of one carbon atom and four hydrogen atoms)-mixing with two oxygen molecules (O2 , composed of two oxygen atoms). The process is similar for other hydrocarbons, which are all molecules with more numbers of carbon and hydrogen atoms. When the reaction takes place, the hydrogen atoms move from the carbon atom to two of the oxygen atoms, and two of the oxygen atoms latch onto the carbon atom. The result is two water molecules (H2O, two hydrogen atoms and one oxygen atom) and one carbon dioxide molecule (CO2 , one carbon atom and two oxygen atoms), along with energy. Note that the total number of atoms remains constant, they are simply shuffled around to form new molecules.
The World War II German Luftwaffe was probably the first to use nitrous oxide as an internal combustion engine performance booster. Thousands of German aircraft were fitted with the system known as "GM-1" that provided the engine with extra oxygen that was otherwise scarce at high altitudes. However, by the end of WWII, jet engines were becoming the powerplant of choice, thus interest in nitrous-boosted piston engines waned considerably.
Moving forward to the 1950s, it was Smokey Yunick in the USA who rediscovered nitrous oxide injection. Yunick was racing in the budding NASCAR series at the time, using every possible trick to gain a competitive edge; NASCAR promptly outlawed his secret after discovering it. After another lull, nitrous oxide caught on once again in the late 1970s with dragracers, and from then on nitrous has been a part of both automotive and motorcycle racing. It offers the most economical route to more power in an internal combustion engine than any other option available. Of course there are limitations and issues with using nitrous such as bottle capacity, proper setup, and engine longevity, but it remains one of the most popular bolt-on engine performance enhancers on the market. Nitrous oxide has many names such as laughing gas or happy gas, but on the street it is more commonly called dope, spray or NOS, the most popular brand name.
Nitrous oxide is a non-flammable gas (at room temperature), but when heated to about 570 degrees F, it acts as an oxidizer by making more oxygen available. Made up of two nitrogen atoms and one oxygen atom (about 36 percent more oxygen by weight than the same volume of air), the nitrous molecules split in the heat of the combustion chamber, making the oxygen available to combine with more fuel to provide extra power. Also providing more power is the fact that nitrous oxide is kept in a liquid state inside the pressurized bottle (usually between 800-1000 psi)-but once released into the atmosphere it vaporizes, absorbing heat. The resulting temperature drop at the point of injection (usually the intake manifold) paves the way for a denser intake charge that contains more oxygen and can now support more fuel-and thus more power.
Nitrous systems are divided into two major categories known as "wet nitrous" or "dry nitrous" kits. A wet nitrous kit means that the system is also spraying or injecting additional fuel (gasoline) along with the nitrous oxide. As the name implies, a dry nitrous kit only injects nitrous oxide into the engine, without the use of another system to add fuel.
Prior to the proliferation of electronic fuel injection in motorcycles, wet nitrous kits were the most common type used. Since carburetors have no easy way of precisely changing their fuel delivery when spraying nitrous, engine builders had to utilize other ways of adding the necessary gasoline into the intake charge to maintain a proper air/fuel ratio. These wet nitrous kits use one delivery system consisting of fuel lines and solenoids to regulate the flow of gasoline, and another system to meter and distribute the nitrous oxide. Small brass jets mounted inside the fuel and nitrous oxide lines are used to precisely meter the amount fed to each solenoid. Then the gasoline and nitrous oxide are combined in a nozzle that is usually drilled into the cylinder head to directly inject the nitrous/gasoline into the intake port.