Nitrous oxide needs no introduction. Despite the hoards of racers jumping on the forced induction bandwagon, nitrous remains one of the most devastatingly effective and incredibly affordable performance modifications in existence. For a measly $600, a basic nitrous oxide kit can add 150 hp to a typical small-block V-8. That's enough to push a 12-second street car deep into the 11s and potentially into the 10s.
Dollar per dollar, no other performance modification comes close. With the potential for these tremendous performance gains, however, come certain risks. Although nitrous kits are completely safe if installed correctly, the greedy and uninformed racer can get himself into a lot of trouble in a hurry as well. To make sure that doesn't happen, we recently had a chat with Kyle Smith of Nitrous Oxide Systems.
Like Coke and Xerox, the company has been around for so long that "NOS" has evolved into a generic name racers often use to describe all nitrous systems. In addition to offering tips to stay out of trouble, NOS divulged heaps of helpful information for maximizing nitrous performance including what types of fuel to run; whether a plate system or fogger is right for your application, selecting the right pistons and rods for heavy-duty nitrous use, and how to manage power coming out of the hole at the track.
Every hot rodder knows that nitrous oxide injection kits add silly heaps of horsepower for not a lot of money, but why is it so effective? A nitrous oxide molecule contains two parts nitrogen, and one part oxygen. "Nitrous oxide by itself is non-flammable, but when combined with gasoline, its oxygen content accelerates the combustion process and increases horsepower," Kyle explains. Furthermore, the nitrogen content acts as a buffer to dampen and control the combustion of oxygen. Nitrous oxide does not break down into nitrogen and oxygen until it reaches 572 degrees Fahrenheit. This means that it absorbs a tremendous amount of heat from the incoming air charge, reducing inlet air temperature by 60-75 degrees, further increasing power.
It wasn't too long ago when plate nitrous systems were limited to 300 hp. Thanks to steady improvements in nitrous technology; plate systems can now move 500 hp worth of nitrous to a hungry engine. "The increased horsepower capability of plate nitrous systems in recent years stems from plates being built with multiple sets of spray bars or diffusers combined with larger orifice solenoids. The NOS Big Shot system employs orifices that are strategically placed in the plate for improved atomization and efficient nitrous/fuel mixture distribution," says Kyle. Nitrous Oxide Systems' Double Cross system ups the ante even more with a plate design that incorporates spray bars intersecting at a 90-degree angle. This creates a highly efficient distribution of fuel and nitrous, which is particularly advantageous in engines with intake manifold that have long runners or divided plenums.
Plates vs. Foggers
As its name implies, a plate nitrous system utilizes a plate that bolts between the intake manifold and carburetor to deliver nitrous oxide and fuel into an engine. A direct-port nitrous system, on the other hand, relies on injector nozzles plumbed directly into each individual intake runner. Plate systems are much easier to install, but in the past, were limited to 250-300 hp of nitrous. In contrast, while direct port systems can handle in excess of 600 horsepower of nitrous, they require drilling and tapping the intake manifold for fogger nozzles, and bending up hard lines for both the fuel and nitrous side of the system. Considering the latest crop of plate systems are now capable of adding 500 hp, what are the advantages of a direct-port system? "No matter how big a plate system is, it is never as good a direct-port system," Kyle explains. "A plate system lacks the cylinder to cylinder tuning ability of a direct-port system, and does not distribute the nitrous/fuel mixture as evenly. Likewise, direct-port nozzles put the mixture directly in the path of the intake valve for quicker response on the bottle. This is very important because uneven distribution can load the crankshaft and accelerate engine wear."
Wet or Dry?
In both a plate and direct-port nitrous system, a mixture of nitrous oxide and fuel is injected into incoming air intake charge. As such, they're referred to as wet kits. Conversely, dry nitrous systems inject nitrous oxide only, relying on the factory fuel injectors to provide the additional fuel flow. This is accomplished by applying additional pressure to the factory fuel pressure regulator using the nitrous solenoid, which in turn increases fuel flow. Alternately, the EFI system's computer can be re-tuned to increase fuel flow as well. Since dry systems rely on the factory fuel injectors, whereas wet systems supply their own fuel through a dedicated fuel solenoid, the volume of nitrous they can handle are limited by injector size. However, dry systems offer several advantages. Considering that EFI intake manifolds are not designed to distribute fuel, dry systems are said to distribute nitrous more evenly to the cylinders than a plate system. Dry nitrous systems offer tuning advantages as well. "The biggest advantage of a dry system is that the operator has ultimate control of the fuel delivery at nearly any point in the run. This allows you to lean out or richen up the nitrous/fuel mixture point during a pass at the dragstrip, depending on track conditions," says Kyle.