Words And Photos: Richard Holdener

It doesn’t matter whether you run your car in the NHRA Winternationals or on “National Street” in a small town called Winters, chances are you have heard of nitrous oxide. Though it has been used for decades to enhance the power output of internal combustion engines, only in the last decade has it become the darling of both the big and small screen. Success stories like Street Outlaws have put the substance in front of countless enthusiasts, while The Fast and Furious franchise has introduced it to literally millions of movie-goers.

Not everything you see depicted in the silver screen is 100 percent accurate, but the core message remains consistent. Push the button on a nitrous system, and your performance request is answered instantaneously. That immediate surge of torque remains as long as the nitrous is engaged. It might not help foil an international smuggling ring, but it will make your vehicle one heck of a lot faster!

Before getting to the test on our tunnel-rammed 572 BBC, it might be a good idea to get a better understanding how nitrous works and the different ways it can be applied to a motor.

Nitrous oxide is often depicted as an explosive substance in the movies, but the reality is nitrous oxide isn’t even flammable. It takes a team of special effects guys to get a system to explode, and the fireball is the result of C4 or some other explosive and not the nitrous itself. Open up the valve on a nitrous bottle and apply a match (or even a torch), and you will be sadly disappointed at the result. The sub-zero temperature of the nitrous mixture will simply extinguish the flame. Considerably less exciting than the crash-scene infernos we all watch and love on film, but if nitrous oxide doesn’t explode, how does it add power?

Nitrous oxide is a compound consisting primarily of nitrogen and oxygen (very similar to the air we breathe). The extra power offered by the nitrous oxide actually comes from the oxygen molecule portion of the compound, but first it must be separated from its nitrogen partner. Heat is required to release the oxygen molecule, but the supplied heat must exceed 572 degrees. The best place to find heat of this magnitude is in the combustion process of an internal combustion engine.

Though often thought of as a fuel, nitrous oxide is actually defined as an oxidizing agent. Once released, the liberated oxygen molecules are free to support or enhance the combustion process. When you combine the extra oxygen present in the system with extra fuel (like gasoline), the results are push-button power.

The release of the power-producing oxygen molecules is impressive enough, but the benefits offered by nitrous oxide also include a substantial reduction in inlet charge temperature. For performance use, nitrous is stored (under pressure) as a liquid, and when the injected, the nitrous is converted into a gas — a simple process known as boiling.

This liquid-to-gas conversion absorbs a great deal of heat from the surrounding area (the inlet air). The average enthusiast often associates a boiling point with heat (converting liquid water to steam at 212 degrees), but the boiling point of nitrous oxide is a chilly -129 degrees. In addition to the heat absorbed during the boiling process itself, the introduction of a compound registering -129 degrees has an additional positive (chilling) effect on the inlet charge temperature. Since cooler inlet air is rich in oxygen molecules, this chilling effect can further increase power. The combination of extra oxygen molecules and sub-zero injection temperatures produce some pretty impressive power gains.

Nitrous oxide systems can be very complex and include computer-controlled solenoid activation, but most systems include the following major components. The first is a high-pressure, containment bottle. Nitrous is fed from the bottle through high-pressure lines to a solenoid. The solenoid is electronically activated to allow nitrous flow. The fuel system shares this design, with fuel from the engine’s fuel pump flowing to the fuel solenoid. The fuel and nitrous solenoids are activated simultaneously to allow the introduction of both into the engine.

From the solenoids, nitrous and fuel are delivered to some type of injection point. The injection points can include a single fogger nozzle placed upstream of the throttle body, an injection plate located under the carburetor (or throttle body), and even multiple fogger nozzles drilled and tapped into the intake manifold to feed each individual cylinder. It is also possible to combine these systems to provide multiple stages of nitrous. The nitrous and fuel flow from the solenoids to the injection point is regulated through jetting to adjust the power gains offered by the kit.

To illustrate just how cool adding a mixture hovering around -129 degrees is, we subjected a big-block Chevy to a NOS nitrous kit. Not just any big-block and not just any simple plate system. The Rat motor in question was sporting no less than 572c.i. and was chock full of go-fast goodies even before adding the squeeze.

The 572 started out life as a Dart Big-M block. The stout foundation ensured plenty of strength, to which we could add plenty of nitrous. The four-bolt block was stuffed with a forged rotating that included components from Lunati, CP, and Total Seal. The short block was also home to a COMP roller cam, Moroso oiling system, and AFR 345 heads. Topping the mix was a Dart tunnel ram given the once over by the flow wizards at Wilson manifolds. The dual-quad, tunnel ram featured a pair of Holley 1050 Ultra Dominators. The tunnel ram required use of a crab-cap distributor and crank trigger from MSD.

The great thing about running the tunnel ram on our big-block was it allowed us to run a pair of nitrous plates; after all, if a single is good, two NOS plates are twice as nice! The Pro Shot system supplied by NOS included one fuel and one nitrous solenoid, but the system can be upgraded with additional solenoids for increased flow. The single solenoids were more than enough for our power needs, as we set up jetting to provide 300hp (150hp per plate). We made sure to heat the bottle to ensure adequate bottle pressure before hitting the power button.

The 572 was no slouch even before the nitrous, posting peaks of 883hp and 767 lb-ft of torque. After engaging the NOS system, the peaks jumped to 1,168hp and 1,006 lb-ft of torque. With each plate centered over four cylinders, the dual-plate system offered even better nitrous/fuel distribution than a single system. The dual-plate NOS system pushed our pachyderm well into the four-digit power zone. Imagine hitting the button on this baby in an early Chevelle, Camaro, or C10 truck.

Nitrous not only adds a serious chunk of power but does so instantly. Push the button and you are immediately rewarded with almost 300 lb-ft of torque and an extra 300hp. Making this all the more impressive was the fact the BBC was already thumping out 883hp and 767 lb-ft of torque. Any time you get four-digit power levels, you know you are doing something right. This nitrous-injected big-block produced 1,168hp and 1,006 lb-ft of torque on the squeeze.

Sources

ARP
arp-bolts.com

ATI
atiracing.com

COMP Cams
compcams.com

CP Pistons/Carrillo Rods
cp-carillo.com

Holley/Hooker/NOS
holley.com

Lucas Oil
lucasoil.com

Lunati
lunatipower.com

Moroso
moroso.com

MSD
msdignition.com

Total Seal Rings
totalseal.com