Q:If nitrous oxide is not flammable, how does it add so much power to an engine? Also, can a snowmobile be equipped with nitrous?-Paul D., Maple Grove

 

A:An engine's power comes from its fuel, which expands with great force when it ignites. The more fuel you can burn, the more power you make - just like an M80 is much more powerful than a ladyfinger or Black Cat firecracker. A typical engine's power is not limited by fuel flow - a bigger carb or multiple carbs or fuel injection can dump in more gas than the engine can burn. When there is not enough oxygen present for the amount of fuel pumped in, the excess gas doesn't burn. The bottleneck is air, or more specifically, oxygen.

To burn and release its energy, gasoline requires enormous amounts of oxygen from the air. It's not so different from a human athlete, who also requires oxygen to keep muscles moving and the brain alert. When there isn't enough air, the inanimate and the human machine falter. Forced induction like turbocharging and supercharging is designed to add more air, more oxygen, to the engine so it can burn more fuel and make more power.

Nitrous oxide (which can be combined with those technologies) takes a different approach. Rather than pump air to move more of it into the engine, nitrous chills the air, making it much denser and greatly increasing the amount of oxygen by volume - the denser the air, the closer together its molecules, the more oxygen one has available. Hood scoops and ram air, etc., are designed to bring in cooler, more oxygen-rich air from beyond the engine compartment.

When drag racers - on the track or within the silver-screen-story of the "Fast and the Furious" movies - hit a nitrous shot, the flammable substance they're cramming into their engine intakes is not the nitrous itself but additional fuel that can be burned because of the huge rush of oxygen the supercooled air contains. All of that oxygen combines with the gas present, which burns to make power. Nitrous adds so much oxygen, in fact, that a nitrous-oxide system will provide supplemental fuel too, to avoid a lean condition. When there is too much oxygen for the fuel available, there will be too much flame and too much heat inside the cylinder, which can scorch pistons and create other problems.

While the compound nitrous oxide is not flammable, it breaks down at around 565 degrees Fahrenheit and the oxygen liberated at that point will help burn fuel like any other oxygen. Nitrous thus adds oxygen two ways - by supercooling the air that accompanies the nitrous-fuel mix, and by freeing oxygen itself when it reaches its dissociation temperature inside the much hotter combustion chamber. There are some complex discussions to be had about nitrous displacing air in the intake but everyone agrees there's a demonstrable gain from nitrous use so that's pretty academic stuff.

Yes, you can add nitrous to a snowmobile. Speed freaks have added it to just about every sort of engine you can name. Proceed with caution, though, because nitrous can damage engines if improperly fitted or used, and can hurt people if the vehicle fails catastrophically or the supercool nitrous gets on your skin. A quick Internet search on "snowmobile nitrous" reveals various companies and kits for this purpose. Do your research carefully to insure that the kit you buy suits your machine's engine. And remember that increased power also means increased stresses on engine components. Power is an addictive thing (human history proves it), and there's a tendency always to want a little more. Push your engine too hard or too often and you'll wear it out or break it.