Craig S. Walker

Nitrous oxide is quite possibly the most eligible candidate for red headed stepchild of the performance world. Often misunderstood, nitrous has been the subject of name calling, mistaken identity, and has been many times the child unjustly accused of wrongdoing.

"How so" you ask? Consider how many names other performance enhancements go by. Turbos are a type of supercharger, I once heard them called hair dryers, but that's pushing it. Rotary vane superchargers might get called blowers but I have trouble coming up with other names. Nitrous has a number of names, not all of which are kind: Nitrous oxide, Nitrous, Laughing gas, N2O, Squeeze, Juice, the list goes on and on. Sometimes it is referred to as Nitro. This is not technically correct, as nitro is the shorthand for nitromethane, a colorless liquid fuel from the nitro-paraffin family with a low latent heat of evaporation. Nitrous is a gas at room temperature. It can be compressed into a liquid form or chilled to -127 degrees Fahrenheit where it changes phase to a liquid.

Unfortunately nitrous has also had to bare the brunt of many hot rodder's gory stories of melted motors, bent - thrown-and missing connecting rods, and dislodged head gaskets. I think myths get perpetuated by our fascination with the horrors of others misfortunes in the reciprocating piston engine department. Nitrous it self is not predisposed with a propensity to attack the unlikely and unwitting speed demon. It has no pre-conceived notions or prejudices. It is only as useful and as harmful as the Einstein or Gump using it.

Nitrous Oxide is known by its chemical name N2O. It is a molecule comprised of two parts nitrogen and one part oxygen. It is colorless and odorless and non-flammable. Yes, that's right, non-flammable. Nitrous does not burn. It mostly just likes to sink to the floor, as it is heavier than air and not harmful to humans unless inhaled in mass quantities. Yes, it's the very same stuff the dentist gives the patient with the root canal. No pain, no memory, just stupid laughter. Can you guess where the name laughing gas came from?

To understand nitrous we must look back to World War Two aviation and the engineers who sought to better the armed forces' military air strength. It is somewhat sad but true; that all the hot rodding we see in internal combustion engines today was performed back in the world of aviation during this unsettled time. For valve heads, trick port work, wild combustion chamber shapes, sodium filled valves and even screw in valve seats were experimented with. To get the extra edge engineers toyed with the limitations of the engine's efficiency. It was thought that if the engine's environment could be improved so could the output.

With a nitrous bottle on the side, a merely fast street bike becomes

a monster. It's all in the perception.

The air around us is mostly nitrogen (about 78%) a small amount of argon mixed with trace gasses (2%) and the remainder (20%) is good old oxygen. Scientists figured if an engine made 100hp on air at one atmosphere of pressure (only 20%) oxygen, it could make 5 times that if it ingested pure oxygen at the same pressure. Unfortunately the amount of oxygen in the ingested gas blend not only determines how much fuel can be burned it also dictates under how much control. It's easy to assume a good many engines were lost to oxygen tests that resulted in run-away detonation and massive uncontrolled explosions of fuel. Pure oxygen was soon abandoned as a power enhancer. Hydrogen peroxide was tried with favorable results in the power multiplier department, but problems with packaging (H2O2 is a liquid at room temperature) and difficulty with atomization relegated it simply a memory in the "interesting tests" logbook. N20 was one of the last things on the list. Its relatively low oxygen content was expected to hamper its performance.

Amazingly, even with its relatively low oxygen content (compared to the "favorable power enhancers") nitrous oxide gave tremendous improvement and a controlled burn rate. When exposed to the heat of combustion, nitrous breaks down into its molecular subsidiaries, nitrogen and oxygen. Nitrous changes phase from molecule to atomic compounds at 572 deg F. The nitrogen released in the combustion process provided a damper for the flame front preventing the run away that occurred with pure oxygen. The other benefit was the phase change temperature where nitrous changed from liquid to gas at -127 deg F. This induced an additional cooling effect in the intake, allowing test engines to ingest even more air and fuel (denser charge as a result). It is well known by now that an engine develops an addition 1% more HP for every 10-deg drop in intake temp. The charge cooling effect of nitrous changing state added another dimension to the capabilities of N2O.

Not finished yet!!! More to come