Richard Holdener
May 3, 2011

Right off the bat, know that nitrous oxide is cool and potentially powerful. Unfortunately for the uninitiated, television and movies (especially Fast and Furious) are to blame for most of the silly conversations that take place about nitrous oxide. The most common of the misconceptions is that nitrous oxide is highly explosive (or that it's even flammable). It would take a nitrous bottle stuffed to the regulator with C4 explosives to produce the kind of blasts seen on the big screen.

Contrary to popular belief, touching a match to the stream of nitrous oxide will result in very little drama. In point of fact, the match will simply go out. Noticeably absent will be the door-blowing explosions and eyebrow-singing fireballs that send the aforementioned street racer's ride to a fiery grave.

It should, however, be noted that the oxygen contained within the nitrous oxide compound is extremely flammable--it is just that the compound itself is not. Only after the oxygen molecules have been released from the compound will they be allowed to burn. Fortunately for enthusiasts, it requires a great deal of heat (to the tune of 572 degrees) to liberate the oxygen molecules. In the internal combustion engine, this tremendous (oxygen-liberating) temperature is supplied by the combustion process.

Technically speaking, however, nitrous oxide is not a fuel, but rather an oxidizing agent. Once released, the free oxygen molecules support (or enhance) the combustion process, which requires the burning of some other fuel--in this case gasoline.

As if the release of the power-producing oxygen molecules isn't enough to win you over, additional power gains are realized by the reduction in inlet charge temperature. For automotive use, nitrous is stored (under pressure) as a liquid, and when injected, the nitrous is converted into a gas (a process called boiling). The liquid-to-gas conversion absorbs a great deal of heat from the surrounding area (the inlet air). Though we normally associate a boiling point with heat (converting liquid water to steam at 212 degrees), the boiling point of nitrous oxide is a chilly -129 degrees.

In addition to the heat absorbed during the boiling process, introducing a compound at -129 degrees has an additional positive (chilling) effect on the inlet charge temperature. Cooler inlet air is rich in oxygen molecules. Basically speaking, the cooler the air, the greater the number of oxygen molecules present. Nitrous oxide is about as cold a substance as you can ever deliver to your motor. Not surprisingly, the combination of extra oxygen molecules and additional cooling can produce some pretty impressive power gains.

One of the great things is that the additional power supplied by nitrous injection is nearly independent of the power output of the original motor. You don't need a dedicated nitrous motor, or even anything more exotic than a stock motor, to enjoy the benefits of nitrous.

We mentioned that the nitrous oxide is responsible for cooling the inlet charge, something that both improves power output and helps suppress harmful detonation. The separation of the nitrogen and oxygen molecules (during combustion) into individual components also helps to minimize detonation. This built-in detonation control allows impressive power gains without fear of damage to the motor, even a stock motor with cast pistons. Of course the power gains and life expectancy of the motor are directly related to the tune, as proper air/fuel mixture and (especially) ignition timing are critical on a powerful nitrous motor. Applied and tuned properly (as per the supplied instructions), a modern nitrous system can provide safe, effective, reliable power gains.

While nitrous oxide will definitely wake up a stock 5.0L Ford, there are ways to further improve the power of a nitrous motor. With that many additional oxygen molecules finding their way into the combustion chamber, they naturally have to find a way out. This is where things like cylinder heads, cam timing, and even the exhaust system can play a part. Remember, the extra power offered by nitrous is on top of the power offered by the normally aspirated combination--the more power before the nitrous, the more power after the nitrous.

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To illustrate the gains offered by a good nitrous kit, we set up a test on the engine dyno using a typical 347 stroker. The idea was to build a suitable test motor, then subject it to a healthy dose of squeeze. With high horsepower in mind, we stuffed a stock block with a forged stroker crank and 5.4-inch rods from ProComp Motorsports, and forged slugs from Probe Racing, as well as a Speed Pro ring package designed to maximize sealing under harsh conditions.

Topping the 347 is a set of Twisted Wedge Track Heat 185 heads from Trick Flow Specialties, a Comp XFI Stroker cam from Comp Cams, and a Holley SysteMax upper and lower intake system, including a 75mm throttle body. Additional components included a set of Hooker long-tube headers, Meziere electric water pump, and ProComp Motorsprots 28-ounce damper. This 347 stroker was machined and assembled by L&R Automotive. For tuning, we relied on a FAST management system and 36-lb/hr injectors. Prior to running, the motor was treated to Lucas break-in oil and a pair of break-in cycles.

Once tuned, the 347 stroker produced 463 hp and 343 lb-ft of torque, with torque production exceeding 400 lb-ft from below 3,500 rpm to 6,000 rpm. Waiting in the wings was our Zex wet EFI nitrous kit, with a jetting set to provide an extra 150 hp. We made sure to warm the bottle to optimize the bottle pressure (above 900 psi), and once activated, the peak numbers jumped to 617 hp and 616 lb-ft of torque. That is serious power at the push of a button, and though the Zex kit can be configured to provide even more, concern for the strength of the production 5.0L block kept us from further squeezing. Once activated, the peak numbers jumped to 617 hp and 616 lb-ft of torque.

Fresh Squeezed 347-NA vs. Zex Nitrous

The graph illustrates that the 347 stroker was a healthy combination to start with, but really got with the program once we pressed the fun button. In normally aspirated trim, the 347 produced 463 hp and 434 lb-ft of torque, but these numbers jumped to an amazing 617 hp and a like amount of peak torque once the Zex nitrous kicked in. Given the power offered by the normally aspirated combination, we wouldn't think twice about running a 175hp shot, but we have some concern for the stock block at those elevated power levels.

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