Nitrous Oxide injection
How it works: The key is in the oxide part of this power adder's name. Nitrous oxide, when sprayed into an engine's intake tract, introduces more oxygen into the combustion process than is found in the atmosphere. Because there's more oxygen in the chamber, more fuel can be added, since burning more air and fuel equals more power. Nitrous has an added benefit: When it vaporizes, it's extremely cold.
That temperature change acts on the air around it, makes it denser, so more air can pack into the combustion chamber per cycle.
Nitrous oxide systems are typically sold per horsepower as a "shot." For example, a "50-shot" system will deliver 50 units of additional horsepower. Nitrous systems are also either "wet" or "dry," depending on whether the nitrous is mixed with fuel prior to entering the combustion chamber (wet) or not (dry).
Nitrous systems can be set to activate in several different ways. The simplest method is with a switch that introduces the nitrous only during WOT conditions. Or you can inject nitrous via the "happy button" that's gotten so much attention in movies. The most complex systems introduce nitrous to the engine in several stages, or with a progressive controller. Drag racers use this method to deliver a modulated amount of nitrous at launch (so the power delivery doesn't induce tire spin) and then increase the nitrous as speed builds. Activating each stage with a gear change, for example, will deliver maximum nitrous flow - and therefore horsepower - at the top end.
Nitrous is the only part-time power adder in this bunch. It only works when it's activated. When the system's off, the engine operates normally.
A nitrous system's packaging is different than that of either a turbo or supercharger. The nozzles, solenoids, lines and additional underhood parts can be routed in the engine compartment, but you'll have to make room for the bottle which stores the nitrous oxide.
Nitrous' inherent limitation: boost for only as long as the bottle is full. Nitrous Express' formula to calculate nitrous use is: 0.8 pounds of nitrous oxide times 10 seconds, equals 100 horsepower. So if your system is jetted to produce 100 horsepower, you'll use just under a pound of nitrous every 10 seconds and drain that 10-pound bottle in less than two minutes.
Where it works best:
Drag racing.
Bang for the Buck rating:
"Nitrous Express has a nitrous system that retails for $399 that will provide up to 250 wheel horsepower. Name another power adder that can provide a $1.60 per horsepower ratio!"
- Mike Wood, Nitrous Express
Dope:
"Nitrous provides instant torque at any rpm. This tremendous torque boost carries on unabated throughout the rpm range of the engine. No waiting; it's right now!"
- Mike Wood, Nitrous Express
"It's the most cost-effective way to add horsepower to any engine, from stock to highly modified. It's easy to install. There's less heat under the hood and less heat in the engine. It's only on when you need it to be. And in most cases, it requires little to zero upgrades to the fuel system or engine to use. Nitrous works great on turbo cars because it will also help cool the intake charge and the turbo."
- Matt Held, Nitrous Oxide Systems
"They're flying in those [naturally aspirated K-series Hondas] right now, absolutely flying. It works exceptionally well for road racing. The only problem is, if you have exceptionally long straights, a little squeeze will make you that much faster."
- Brian Gillespie, Hasport
Nope:
"You might as well start tossing sticks of dynamite onto your cylinders and lighting them."
- Tyler Tanaka, Turbonetics
"No one really runs nitrous that much anymore in this industry. If you visit the message boards , or go to the races, you don't see that many people doing full-blown nitrous builds anymore. It's either a turbo setup or an all-motor setup. "
- Tony Shagday, Skunk2 Racing
"Nitrous cars may have cost covered at the front end, but after the sting of each bottle refill, those savings up front seem to dwindle. Not to mention the need to keep a watchful eye on bottle temperature, pressure and fuel for optimal performance and safety. Once the bottle is empty, you are forced to deal with a lower power level until the next refill."
- Michael Ullrich, Stillen