NITROUS: WHAT IS IT?
Nitrous oxide (N20) is a cryogenic gas composed of nitrogen and oxygen molecules. At roughly 570 degrees Fahrenheit, the oxygen molecules separate from the nitrogen molecules and the oxygen becomes available for combustion. In other words, nitrous artificially crams more oxygen into the combustion chamber of an internal combustion engine. Nothing more, nothing less.
Nitrous oxide is so efficient because it has a higher percentage of oxygen per cubic foot than even the atmosphere does. The atmo-sphere we live in is about 20 percent oxygen and 80 percent nitrogen, whereas nitrous is 36 percent oxygen and 66 percent nitrogen. In lay terms, this means nitrous contains more than twice as much oxygen per cubic foot. Another plus is nitrous' cooling effect. When the pressurized nitrous leaves the bottle, it changes from its liquid state (in the bottle) to a gas (when it's sprayed into the engine). During this process, it absorbs heat and the effect reduces the temperature of the nitrous to approximately 127 degrees below zero. We know horsepower is normally increased by about 1 percent for every 10- degree drop in inlet air-charge temperature, and nitrous can drop the inlet temperature by 50-70 degrees.
Nitrous exists in two grades, U.S.P. and Nitrous Plus. U.S.P. is the medical grade and commonly used as a mild anesthesia, especially in dentistry, and is not available to the public. Nitrous Plus differs only in the fact that it contains small amounts of sulfur dioxide to prevent substance abuse.
NITROUS TUNING
OK, you've purchased your nitrous kit, installed it, and you're ready to play. You expect to go faster, but here are a few things you should know. Before you crack open the bottle and hit the button, we recommend you read the instructions not once, but twice. Almost all the kits sold today offer basic starting points for jetting and timing, as well as some additional tuning tips. And according to the pros, one of the biggest mistakes people make is not following instructions.
That said, let's get to some tuning. As we stated earlier, the theory is to add nitrous and additional fuel, then burn the mixture efficiently. Maintaining the proper air/fuel is critical in a nitrous engine, because the additional oxygen can cause a lean condition in a hurry. The good news is that the nitrous companies have done the homework for you and if you stick to the recommended settings, you'll stay within a safe margin.
All the experts we spoke with agreed that nitrous newcomers should stick to the manufacturers' recommendations. However, you should also realize many basic kits are designed for stock applications and modified engines will require a different tune-up. "It's important to know that every engine is different, so each combination will have a different baseline tune-up," says nitrous guru Steve Johnson of Edelbrock (and formerly of NOS). "Naturally, you'll be reading the spark plugs, and one mistake people make is trying to tune the engine based off of one plug. Read them all. Different plugs and different fuel will leave different trace marks, so I recommend sticking with one fuel and one type of plug. Generally, I can look at the ground strap and see the bluish coloration." If the strap is getting too much heat the whole thing may be blue; however, if the strap is very thick or very thin the readings will differ. "The bluish tint normally relates to the timing advance," Johnson continued. "I believe the old rule of timing retard vs. level of nitrous is skewed because it really depends on the engine combination and the cylinder heads. Generally, the more efficient the head, the more timing needs to be removed. Both Johnson and Brandon Switzer of Nitrous Pro Flow agree bottle pressure plays a big role in any nitrous tune-up. "My recommendation is that you should tune your engine to a single bottle pressure. Heating the bottle raises the bottle pressure and has a great effect on the flow and how much nitrous will get to the engine," says Switzer.
"One of the most important items to have in any nitrous system is a pressure gauge," added Johnson. "If you have varied pressure you will not maintain consistency, and if the pressure gets high, like more than 25 psi above your normal setting, you run the risk of having a lean condition, and that can tear stuff up." Johnson recommended running between 900 and 950 psi.NMRA Drag Radial champion Chris Little was also kind enough to offer up some helpful advice: "I generally go by the rule that you take out 2 1/2 degrees of timing for every 50 hp of nitrous. At the track I look at the weather conditions and then tune accordingly. I don't really mess with the jets, but I'll adjust the timing based on the weather. In cool weather you need to take out more timing than in hot, humid air. When it's humid there's water in the air, and you can't burn water. The water actually cools the mixture so you can keep more timing in there."
Little speaks from experience, as his '90 Mustang LX has been as quick as 8.46 at 160-plus mph. It's powered by a 406 built by Bennett Racing and wears TFS High Port heads, a Wilson-prepped intake and a BG 1,000-cfm carb. Internals include aluminum rods, 13.5:1 pistons, and a COMP Cams camshaft.
"When it comes to tuning nitrous I have to say that avoiding detonation is the key. I use VP 121-octane gas and I run the same fuel pressure all the time. Some people make mistakes by having the timing too high and not having enough fuel, but you can hurt an engine by doing the opposite, even though you think too much fuel and too little timing is safe."
"Every nitrous user should have a magnifying glass to read plugs, and they should check the plugs at the end of the run, not after you drive back to the pits. My plugs look totally different when I click it at the end of a run and in the pits after I've driven back," Little added. "Always go with plugs that are two heat ranges colder than stock, because sometimes stock plugs will melt down even if the engine is not lean. "A clean plug should have some bluish coloration on the strap, but not be totally blue. Note the shape of the electrode when new. Then look at it after a run. The electrode tip should retain its square shape and not be rounded off. Lastly, the porcelain should be discolored with a brownish or yellowish tint. Not totally white, but not totally brown either, and it should not have any specks. Specks that look like glitter could be bits from aluminum pistons, and that means detonation."
Like most automotive topics, nitrous is one that could fill a book-and it has, many times. This article was designed to offer the basics in regards to operation, theory, and tuning. We hope you learned a bit and can put your newly found nitrous knowledge into practice. KC
 Nitrous racer Chris Little...  Nitrous racer Chris Little uses this nifty box stuffed with a spare regulator and all his nitrous jets. |
 Rather than heating his bottles...  Rather than heating his bottles with a wraparound electric heater or a torch, Little employs a water bath because it heats the bottle in a uniform fashion. This allows him better control of the bottle pressure, since the temperature of the nitrous directly relates to the pressure. |
 Little's engine is a 406 by...  Little's engine is a 406 by Bennett Racing and makes about 970 hp with both stages cooking. That power translates into mid-8s at 160 mph. |
 In order to tune nitrous,...  In order to tune nitrous, you will need to learn how to read plugs. The plug above shows an overly rich condition, but that is better than overly lean. A lean plug will have a bluish tint to the strap and may have speckles on the porcelain. If the plugs are lean you may also see that the center electrode is rounded off or melted. As a rule, always check all the plugs and set plug gap between .032 and .035 inch. |
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 The Nitrous Works also makes...  The Nitrous Works also makes some pretty cool stuff for EFI Fords, like this two-stage plate kit. |
 Nitrous Pro Flow sells a complete...  Nitrous Pro Flow sells a complete line of nitrous equipment, including kits and these solenoids. |
 Edelbrock is in the nitrous...  Edelbrock is in the nitrous market, too, with plenty of components, such as this EFI plate to fit their Performer series manifolds. |
 This is a Nitrous Pro Flow...  This is a Nitrous Pro Flow dual-stage kit. |
 Edelbrock sells nitrous in...  Edelbrock sells nitrous in kit form, too. |