Muscle Mustangs & Fast Fords
NOS Three-Valve Kit Test - Liquid Displacement
NOS 3-Valve Nitrous Test
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 will 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 about nitrous oxide 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 mention 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 on 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, and reliable power gains. In fact, a good nitrous kit (in this case, from NOS) will make your 4.6L motor feel like it just gained a few extra liters of displacement.
While nitrous oxide will definitely wake up a stock Three-Valve, there are ways to further improve the power of a nitrous motor. With so many additional oxygen molecules finding their way into the combustion chamber, they naturally have to find a way out. This is where cam timing can play a part, as altering the exhaust lift and duration relative to the intake will help aid in ridding the combustion chamber of all those previously beneficial oxygen molecules.
While a cam swap may well net additional power on a nitrous motor, the 4.6L Three-Valve came factory equipped with variable cam timing. This means it's possible to alter the cam timing to help improve the output once the nitrous is injected.
This is usually most beneficial with large doses of nitrous, and since our stock motor is only going to see a 75hp shot, we decided to simply run the system without altering the cam timing. This is how 99 percent of the users will run the system, so we want to illustrate the gains offered under these conditions.
Given the stock nature of the modular test motor, the fact that it doesn't belong to us, and our desire to perform all testing on 91-octane (California premium unleaded) pump gas, we kept the nitrous shot purposely conservative at 75 hp. We figure this combination is something that can easily be duplicated by your average (daily driven) street '05-up GT.
The motor was equipped for (engine) dyno use with a FAST engine management system and 36-pound injectors. The FAST XFI management system allows us to dial in the timing and fuel curves to optimize the power produced by stock trim with the nitrous.
Actually, there was very little tuning required with the wet nitrous system from NOS (PN 02121NOS). All we had to do was ensure that the bottle pressure was at 900 psi, and we were rewarded with slightly more than the advertised power gains. We tuned the combination to produce a 13.0:1 air/fuel ratio and 30 degrees of total timing (more or less timing produced less power). Equipped as such, the 4.6L produced 359 hp and 381 lb-ft of torque before activating the nitrous.