Project Redheaded Step Child was finally going to get a serious power infusion in the form of nitrous oxide.
Project Redheaded Step Child is still going strong, but in our attempt to make 300 rwhp with a naturally aspirated 4.6, every last horsepower is getting harder and harder to come by. While there's a new, dedicated non-PI intake waiting in the wings, we decided what the motor really needed to play ball in the big leagues was a serious dose of steroids. With all the talk about juicing, we decided to jump on the bandwagon and let it flow.
Sure, some may see it as taking the easy way out, but we've just about run out of all-throttle-and-no-bottle options on our early Two-Valve 4.6. Remember, the plan was to achieve 300 rwhp without resorting to increasing displacement.
With a stroker out, we decided this was an excellent time to experiment with a powerful substance capable of providing super power to our otherwise mild-mannered Clark Kent of a mod motor. While much has been written about nitrous oxide in the pages of MM&FF, know that the chemical compound is actually not a true fuel, but rather an oxidizer. Other than in the mythical realms of TV and cinema, nitrous oxide does not explode into flaming fireballs of death, not unless your nitrous bottle happens to be sitting precariously close to a stack of C4 explosives.
In internal combustion applications, nitrous oxide was originally used when the Germans (and British) went searching for ways to improve the power output, and therefore effective ceiling, for their military aircraft during World War II. What better incentive can there be for the go-fast juice than having someone shooting at you? Today, the compound is most commonly used as a general anesthetic in the dental industry. Hot rodders-and many professional racers-know the substance for its effect on the power production of the internal combustion engine.
As indicated previously, nitrous oxide is a compound consisting of both nitrogen and oxygen, not unlike the air we currently breathe. From a performance standpoint, it is the oxygen molecule that we are most interested in, as oxygen supports the combustion process. Naturally the combustion must be supplied enrichment fuel, but this is taken care of by the nitrous system.
The Zex Wet EFI kit included everything needed to install the kit on our '96 4.6 Two-Valve engine. The only thing we had to do was fill the bottle (they must be shipped empty).
While it may seem that having the extra oxygen molecule makes nitrous flammable, the reality is that the extra molecule becomes available only once it has been released from the compound. This release takes place in the combustion chamber when the temperature exceeds 572F degrees. Once the temperature has released the oxygen molecules, they are free to support the combustion of the additional fuel. The result is a dramatic increase in power. It is possible to double the power output of your stock motor with the use of nitrous, but typical power gains are on the order of 75-125 hp for most street Mustangs.
The limiting factor will be the strength of the engine, the flow rate of the nitrous system itself, and the tune. Obviously the greater the desired power increase, the more critical the air/fuel and timing curves become. Run the motor a tad on the lean side when you add a 75hp shot to your 300hp motor, and you're likely to get away with it. The same mistake with a 200hp shot and say goodbye to your motor-forged pistons or not. Truth be told, missing the air/fuel ratio is a lot less detrimental than the timing curve, which is why companies like Zex supply recommendations to retard the timing for specific hp gains.
For Project RSC, we chose the Zex EFI Wet nitrous kit (PN 83023). The wet kit was so named because the system combined the nitrous and additional fuel enrichment into a single (common) fogger nozzle. The Zex wet kit is adjustable, with jetting available to increase the power increase from 75 hp to 125 hp. It came complete, offering everything from the 10-pound (empty) bottle down to the smallest mounting screw and electrical connector. Also included in the kit was the patented Zex Active Fuel Controller. The controller automatically adjusts the fuel enrich-ment supplied to compensate for the changing bottle pressure. Naturally, the higher the bottle pressure, the greater the nitrous flow.
Before installing the Zex kit, we ran the Mustang on the Super Flow chassis dyno at Westech to establish a baseline. The early Two-Valve motor pumped out 274 hp at 316 lb-ft of torque at the wheels. | 
The natural location for the nitrous bottle is hidden in the trunk. We secured the bottle brackets to the cover for the spare tire (make sure to remove the tire before drilling). | 
The Zex kit included this trick fuel controller that actually adjusted fuel flow to compensate for changes in nitrous-bottle pressure. |