Note: This is mainly for V6 engines, but the information can be applied to V8s or any other engine, just adjust the size of the shots accordingly.
What is Nitrous Oxide? – The Basics
Nitrous oxide is a non-flammable gas that can be used to increase the amount of horsepower by delivering more oxygen into the combustion chamber. More oxygen equals more horsepower. Nitrous also burns cooler than the incoming air between 60-75°F to be exact. This is very beneficial to the engine and producing more power.
There are many brands of nitrous. Nitrous Oxide Systems (NOS), Nitrous Express (NX), Nitrous Works, Compucar, Edlebrock, Venom, Zex,etc are some of the larger companies.
Nitrous comes in bottles because it is a gas that when compressed to the pressure used in cars, it becomes a semi-liquid. The suggested pressure to use nitrous is between 900-1050psi. The bottle is mounted anywhere in the car, but most of the time, mounted in the trunk. The V6 mustang actually has a pre-drilled hole behind the passenger side backseat. This makes a perfect place to mount the bottle’s nitrous line.
Nitrous is plumbed into the intake and there it passes into the cylinder head where the combustion occurs. On “wet” kits, nitrous is mixed with fuel and then injected into the intake. On “dry” kits, nitrous is injected before the mass air sensor. (a.k.a. MAF) The maf records the amount of air coming into the engine, and then sends a signal to the fuel injectors to send the right amount of fuel to not be lean or rich.
Wet vs. Dry Kits
As stated above, wet kits mix nitrous with fuel before injecting into the intake. There are two types of wet kits, fogger, and direct port.
Fogger systems are the most common for the V6 mustang. A fogger nozzle (like the one in the picture above) is inserted into the intake tubing just before the throttle body. The fuel and nitrous mix inside of the nozzle to produce a fog that is sprayed into the intake hosing. The fog then mixes with the rest of the air going into the upper intake.
Direct port is the same premise, just with a fogger for each cylinder. These foggers inject the fog after the lower intake and right before the combustion chamber. The picture above is one on an LT1 lower intake. The reason to do direct port is safety, and larger shots. When running a large shot (125+ in the case for a V6 mustang) the nitrous/fuel mixture can easily pool in one cylinder. After all, it is just moving with the air, you cannot expect it to split exactly evenly in the upper intake. You want the nitrous to be spaced evenly to achieve the most power. The fogger systems are not generally recommended above a 150 shot. This also helps with the tuning aspect. Each cylinder can be tuned independently of each other.
Dry kits plumb the nitrous before the maf, as stated above. They do not mix nitrous with fuel before injecting into the intake. This type of system relies on the maf and the fuel injectors to compensate for the extra air in the system. The fogger nozzle is the only method of delivery for a dry kit. One cannot get a dry direct port kit.
Wet kits are presumed to be the safest kits. This is because you do not have to rely on your maf and your injectors. If the maf does not pick up the extra air, the injectors will not put extra fuel into the mix and you will run really lean. (bad news). On the V6, the models made in 1998 and prior can use the dry kits safer than the models made in 1999 and after. The reason is, in 1999, Ford switched from a return style fuel system (where the excess fuel not burned is returned to the fuel tank) to a returnless style fuel system. On the pre99s, the fuel pressure regulator can be adjusted to increase the amount of fuel. And since the fuel is just returned, it’s not a huge deal. On the 99+s however, the returnless style makes the maf calculate the exact amount needed. The fuel pressure cannot be changed very easily and you need a very good dynotune to run a dry kit on a 99+. The wet systems can be run safer on both styles because the fuel is already mixed with the nitrous in the proper amount. This eliminates the worry about the maf and the injectors. However, the worry for the fuel pressure is higher than in the dry system. The fuel that is mixed with the nitrous in the fogger nozzle is taken from the fuel rail. If there is a solenoid leak (will discuss solenoids later), the fuel would be exiting thru there and your fuel pressure would drop. This is very rare and can be countered by either a Fuel Safety Cut-Off Switch or a fuel pressure gauge (will discuss safety later). For the V6 mustangs, as well as all cars, I suggest wet kits over all dry kits.
The system will only really be used when racing, so there has to be ways to control when you want it on or not. A full 10lbs bottle will run out in about a minute if it is on all the time. The minimum things needed to run a nitrous system safely are an arming switch and a WOT (wide-open throttle) switch. The activation switch will make the nitrous work. The WOT switch is a check on the activation switch. With the WOT switch, the only way the nitrous will work if armed is if you are at full throttle. The button closes the electrical connection and thus allowing the electricity to pass and in turn, letting the nitrous work. Whenever nitrous is used, the nitrous and fuel will be going as much is allowed by the jets into the hosing unless a multiple stage shot is being used (which will not be discussed because the V6s don’t need it and can blow the engine)
There are many safety devices out to help make nitrous more safe for users. The first device is the window switch. A window switch overrides and helps the WOT switch at the same time. With just the WOT switch, it is possible to use nitrous at 1000RPMs. This is very unsafe. The window switch can be set to allow the nitrous only to work between certain RPMs. Generally, 3000RPMs are the minimum advised. The window needs an upper limit, which should be placed about 300 or so RPMs below your rev limiter. You do not want to hit your limiter because in most modern cars, when the rev limiter is reached, the fuel pump is cut off and that is detrimental to the nitrous system, wet or dry. So with the window switch and the WOT switch, the nitrous can only be used between 3000RPMs (or whatever you set your minimum at) and about 5300RPMs (whatever your max is. This is my recommended range for a V6 mustang) AND at wide-open throttle.
Next safety mechanism is a fuel pressure safety switch. This was mentioned in the discussion about wet vs. dry systems. This prevents your fuel pressure from dropping too low and thus resulting in a lean condition. This works to shut off the nitrous flow (by opening a circuit) if the fuel pressure drops below a specified amount. This can override all other systems, as it requires the nitrous to be flowing for the switch to turn it off.
Nitrous pressure gauge is the next safety item. There are several types and can be mounted anywhere from the bottle to your a-pillar. This tells you how much pressure is in your bottle. The optimal pressure is between 900-1100psi.
Air/Fuel Gauge is next. This is a gauge to visualize if you are running lean, rich, or just right. This will tell you if you are not getting enough fuel mixed with the nitrous or too much. If you run too lean, you can damage your engine. If you run too lean, then you lose a lot of horsepower. This gauge helps to maximize horsepower.
The blow-down tube is the final safety measure. This is usually required for cars who run at a track. This is a pressure reliever if the pressure in the bottle gets too high. This prevents the bottle from bursting under high stress and heat (remember, nitrous itself is nonflammable, the fuel is flammable and its right over the gas tank, so you don’t want have the bottle blow thru the gas tank).
One question often asked is “I have a chip, can I use nitrous?” The answer is yes, and it is no. Let me explain. Stock timing is fine to run up to a 100 shot on a V6 mustang. However, if your chip advances your timing (for more hp and run a higher octane gas) then you cannot use the chip and nitrous. You want the most timing to be stock while using nitrous. Nitrous increases the burn rate in the cylinder and adding timing can lead to detonation and pinging. The best way to run a chip with nitrous is to get one of those multi-position chips. These can have more than one setting burned into the chip. That way, you can run advanced timing when not using the spray, and then switch it to stock timing (or retarded timing) when using nitrous.
Fuel
Always run the highest octane possible when running nitrous oxide. This will help to prevent detonation in the cylinder. It is best to use AT LEAST 92 octane pump gas while spraying. Race gas is good, but 92 works just fine for 100 shots and lower on the V6. Those advertised fuel octane boosters are hype. They raise the octane by tenths of points, not whole points. Therefore, when it says it can raise it by three, it means 0.3 or 92.3 octane afterwards. Just remember to run 92 octane when spraying.
Remember that you cannot have a safe nitrous system without fuel. Make sure you have a large enough fuel pump to supply the shot you are running. Make sure you have large enough fuel injectors to compensate for the shot if you are running a dry system.
Spark Plugs
Remember to run colder spark plugs with nitrous. This means copper plugs. For the V6 mustang, Autolite 764s work perfectly. Also, remember to gap them correctly too. The stock gap is 0.050” and you want to run 0.035” when running nitrous. The reason is that nitrous increases the cylinder pressure, which can result in spark blowout (the spark of the plug not staying lit to combust the air and gas resulting in lost hp). Gapping your plugs smaller will make it harder to prevent spark blowout.
Other Upgrades
There are other upgrades that you can add to your nitrous setup to make it more convenient and easier to use. These include a purge, remote bottle opener, and bottle heater.
A purge is a solenoid that purges the nitrous line. After a while, air will seep into the nitrous line and fill it up between the nitrous bottle and the nitrous solenoid. Purging gets rid of that air and fills the line with nitrous. This helps so when you spray before purging, the added fuel does not bog you down because of the lack of nitrous. My sentiments on the purge are that it is not worth the money it costs. The reason is that you can just floor the car in neutral and flip the activation switch for about one second. You will be able to tell when the line has been purged by watching your tachometer.
The remote bottle opener is a convenient way to open the bottle in the trunk without having to get out of your seat and crawl back there. It is also great for quick lineups out on the street when you’re not expecting to use nitrous, so the bottle is closed. One flip of this switch and the bottle is open and the nitrous is ready to be used. It is a great way to help keep your system stealthy.
The bottle heater is a must. As stated above, the recommended pressure is about 1000psi. However, the only time when you will be at this pressure just opening the bottle is right after it is filled. If you have a bottle heater, the heater will heat the bottle and the pressure will increase. There are even bottle heaters with built-in transponders that act as pressure gauges. These turn the heater on when the bottle pressure is below 900psi and turn off when it reaches 1100psi. This is the ultimate in not having to worry about your bottle going too high.
What is included in the kit?
In most kits, the necessities are only included. This includes the bottle, the hosing, the electrical wiring, WOT switch, the solenoids, the nozzle, jets, and instructions.
The bottle is usually a 10lb bottle and holds the nitrous. They will ship it empty. Nitrous is usually $3/lb to get filled, but check around. Stainless steel braided hoses come with the kit to run the fuel and the nitrous. Nitrous requires electrical wiring for one giant circuit. All of the safety devices open the circuit at some point to deactivate nitrous and that is how it turns off. The WOT switch is standard. The solenoids are the things that block the nitrous from entering the second set of hosing until an electrical current passes thru them. This opens them up and allows the nitrous and fuel to pass thru and on into the engine. It is a good idea to check them periodically by connecting wiring to the battery to them to make sure they still open and close properly. You don’t want one opening and the other not. (run rich if fuel opens or lean if nitrous opens). When electricity passes thru them, a clicking sound will be made as the solenoids open. The nozzle is what is inserted in the intake tubing and connects the nitrous line, fuel line, and had the jets in it. The jets are what regulates the amount of nitrous and fuel that enter into the engine. Everything that is included in the standard system is good enough to install and run nitrous on your car. I just do not advise doing so without some of the safety measures listed above.
Possible Damage to Other Systems?
Nitrous adds horsepower to the engine usually in the amount of the shot used. NX (nitrous express) and Nitrous Works rate their horsepower gains at the rear wheels. NOS, Compucar and some others rate their horsepower gains at the crankshaft. Nitrous also adds a lot more torque than it does horsepower. As all other modifications, a lot of torque and horsepower require some stronger than stock parts. The clutch can go out on manual cars very quickly. The rear end can go out, especially the stock 7.5 rear in V6 mustangs. This is a very temperamental rear end. Other things might be the non-forged crankshaft if you run too large of a shot. The instant gain in torque could prove to be too much. As with any new toy, you have to play with it a lot after you get it. This will wreak havoc on your tires. You may be going thru a set quicker than you thought. Now that I Know about Nitrous, What do You Suggest?
I think NX is one of the best brands out there. I was very happy with their quality. Nitrous Works is a great company too. Personally, I would not trust a dry kit on a V6 mustang, or any car for that matter. The safety devices I would get are: a window switch if you have a manual. Automatic cars do not drop below 3000RPMs when shifting generally and the computer will shift them before the rev limiter. I would also get a nitrous pressure gauge. It is just very beneficial to know the bottles pressure. The blow-down tube is nice, but if you can hide it from the track officials then you don’t need one. Just be sure to keep your pressure under control. They are nice for extra security though. Lastly, I would get a bottle heater.
What is the Largest Shot I Can Run on a V6?
100 is the largest shot. 75 is the largest shot safely. On single port engines, 100 can be used easier because there are only 6 runners, so nitrous distribution is a little more even. On the split port engines, 100 is okay, but I would stick to 75 because there are now 12 runners for the nitrous to choose from. It is best to start with a smaller shot to learn how nitrous feels and so you know when 3000RPMs is. A smaller shot will not do the damage a larger shot would do while practicing.
Why wait until 3000RPMs?
The engine is working harder up top, and there are more revolutions per minute, which means the same amount of nitrous can be in more rotations causing less stress on the engine over time. At lower RPMs, the engine is working harder to compensate for the now, ton more hp the engine is making. Another reason is if you spray before that the nitrous can puddle on the intake valves and blow the valves and backfire up throught the intake. Nitrous if done inproperly, can be dangerous.
How hard is the Install? Can I do it myself?
Absolutely! The nitrous is not that hard to install. The hardest part is the wiring and that just takes a lot of patience. Just be sure to follow the instructions supplied with the kit. Remember, there is the pre-drilled hole in the trunk that goes all the way to the ground. This will help to show you a great place to mount the bottle. Make sure the nitrous line goes thru the hole and is not tangled. The best part about nitrous installation is that no two set-ups look the same. There are many ways to set up the solenoids, where to put your switches, where to put your nozzle, where your bottle is, etc. Also, NX sells a fuse that can be sequenced in so that if a short occurs, it blows the fuse and not starts a fire on your engine. Be creative and have fun with it. Install usually takes about 4-5 hours.
Is Nitrous Worth It?
You bet it is! Nitrous is the most horsepower for the least amount of money, PERIOD. Some people say it is cheating and they do not like the power that is not always there. I am not a 100% racer. I like the feeling of daily driving too. The supercharger or turbochargers are always on and always making more power, and sometimes you don’t want that power. (See future article about turbos vs. superchargers vs. nitrous). In addition, with that extra power comes lower gas mileage. It is great for the weekend warrior or someone who just likes to have fun occasionally. If you’re going to use it all the time and get a bottle refill every week, save up for a supercharger. That means that you want the power there all the time.
