This page explains some of the features and benefits of running nitrous oxide on your car. Hopefully, these will be useful for those considering a nitrous installation, or just wanting to know what’s up.

There are many different philosophies and opinions regarding the proper nitrous system. Please e-mail if you have positive question or suggestion that could improve safety or contribute to quality and performance.

It is a colorless, odorless gas composed of two (2) nitrogen atoms bonded to one (1) oxygen atom. The scientific abbreviation for nitrogen is N, and O for oxygen. The proper abbreviation for one nitrous oxide molecule is N2O. This where the familiar phrase “N-2-O” comes from.

Nitrous Oxide is an oxidizer that is used as a carrier for oxygen. Mixed with the right ratios of fuel, and fed into the intake, it provides additional combustible material into the cylinders, creating more power. There are many ways to get the nitrous and fuel into the engine, the following describes typical applications that have proven successful.

THE BASICS

The nitrous is compressed to high pressure (900-1100psi) in a tank, in liquid form. From the tank (typically fastened down tightly in your trunk), a hose runs up to the engine bay. From there, an electrically controlled (like, by a button you push) valve called a solenoid is used to release the nitrous into the motor when you request it. At the same time, a fuel line in a "wet system," is controlled by another solenoid, and releases fuel into the motor. This provides the basic mechanism for the nitrous system.

A "wet system" is a nitrous system that mixes both nitrous and fuel, and feeds it (in a "Spray") into the intake. A "dry system" only feeds nitrous into the intake, and tricks the existing fuel system to add the fuel.

As mentioned, there are several ways to feed the nitrous and fuel into your motor. Here are brief descriptions of them.

This is a 1/2" thick plate that's mounted between your throttle body and intake manifold. Both nitrous and fuel lines are connected to it (so it's a wet setup) and the plate combines them and sprays into the intake.

Of course, you don't want the system to be running all the time - a 10lb bottle will last you less than a minute, if it's open. Typically, you want the system triggered on while you're at the track, at WOT (wide open throttle), and at relatively high rpm's (see "Safety" for why). To make that happen, you'll typically want to wire, in sequence, several switches. I won't describe the specific wiring here, but you'll have some or all of the following:

1. Arming (On/Off ) switch.
2. WOT switch is a micro switch installed on the throttle system, that activates the circuit only when your foot is on the floorboard. 3)pushbutton in the car, probably on the shifter 4)"Window Switch" (see "Safety" for details) that closes the circuit only when the engine RPM is between a certain range (like 3000-6000) that you decide is acceptable 5) Fuel Pressure Safety Switch

The system to trigger described above is a basic "single stage" setup. The nitrous is either on or off, and when it's on, the full volume dictated by the jets is sprayed into the engine. There are other applications that are full race or multiple stage nitrous system that require more detailed management at higher rpm, with time-based systems, which delay the nitrous flow for some time after you launch, etc.

These Nitrous controllers are a great addition to any nitrous system and can help to safeguard the engine from Lean-Condition.

Well, a lot can go wrong, but hopefully you'll have adequate safety mechanisms built in to protect your motor when it does. The main thing that can go wrong is adding nitrous into your engine without compensating fuel. This extreme lean condition is disaster for the engine, and you're not likely to get a second chance - at least with the same engine. Conversely, adding extra fuel without nitrous is not particularly bad for the engine, so you can imagine, it's safer to start with the car running rich (too much fuel), then lean it back from there. Some examples of problems you might encounter include:

• Ignition RPM Limiter
  The rev limiter is implemented by cutting the signal to the fuel injectors so the cylinders have no combustion. If you're running a dry system, which depends on the fuel injectors to provide compensating fuel for the nitrous, losing fuel this way is the ultimate disaster. An after market ignition will typically implement the rev limit by cutting off spark rather than fuel, which is a much safer implementation of the rev limit. Typically, you'd get your stock PCM programmed to set the rev limit up higher than you'll ever expect to go (like 7000RPM), and use the setting on the after market ignition as your actual rev limit.

This electrical device provides an open or closed circuit based on the engine being between two RPM values (hence "window") that you chose, so that you'll only flow nitrous in this range. Why would you do that? Well, for two very different reasons.

1. At low RPM, think about what's going on: you're spraying nitrous into the intake at a constant flow. That is, the nitrous bottle and solenoids have no idea what RPM you're at, and they're just pushing it into the intake at a constant volume. Inside the engine, though, the nitrous and fuel combination is being sucked into the cylinders during every stroke. The net result is that at low RPM, you're getting far more of the mixture into the cylinders. At 3000 RPM, for example, you're getting twice the amount as at 6000 RPM. So, you can imagine that running nitrous at, say 1000 RPM, is far more stressful on the motor as at 3000 RPM, and typically causes a "nitrous backfire" - meaning that the nitrous/fuel combination can explode in the intake manifold (rather than the cylinders) - a bad thing. So that's why you don't want the system triggered at low RPM.
2. At high RPM, the situation is easier to explain. Given the discussion of the rev limit above, you may just want the nitrous system to cut off before hitting that rev limit. If you've got a stock ignition, you certainly want a window switch. If your rev limit is implemented by an aftermarket ignition, it's perfectly safe for the motor to run nitrous during the rev limit. It's not particularly easy though, on your transmission or clutch to have all that power during the shift, which may be a reason to keep the window switch set a bit before you shift.

This is a device that's plumbed into the fuel system, and provides an open or closed circuit based on availability of fuel pressure. It can be used in the triggering circuit to make sure the system isn't on when you've got a fuel problem. Typically, you only use it to switch off the nitrous solenoid; turning off the fuel solenoid as well can start a cycle of switching the solenoids on and off while the pressure raises and drops in the fuel system when you're switching the solenoid on and off. Let the pressure build up in the fuel lines when you open that solenoid, and when it's high enough, the nitrous solenoid will open. The switch can be used whether you've got a wet or a dry system. You can adjust the pressure at which it triggers by using an allen wrench on the back of the switch (loosen the screw lowers the pressure threshold).

You want to set the pressure on the FPSS, such that if the pressure drops about 10psi the nitrous system will shut off. On a wet EFI system, this will be around 33psi, and on a dry system I'd leave the switch just above stock, say 45psi.

To set the threshold pressure, you've got a couple options:

1. Connect enough plumbing so that you can have the FPSS installed at the same time as a fuel pressure gauge. Turn the key on to pressurize the fuel system, then turn it off. As the fuel pressure bleeds down, monitor the continuity across the FPSS contacts (disconnect them from the rest of the nitrous system) and when the pressure reaches the level you're interested in, adjust the screw on the back so it just balances back and forth between the continuity signal.
2. You could use an air compressor, with the appropriate fitting for the FPSS. Remove the FPSS from the car, and thread it onto the compressor. Set the compressor for the pressure of interest, and measure continuity as above.

If you can't do option #1 above because you don't have two available ports, first thread in the pressure gauge, and cycle the key. Then time how long it takes for the pressure to bleed down to the correct level. Then disconnect the pressure gauge, install the FPSS, and do the process against the clock rather than the pressure.

HIGH OCTANE FUEL

High octane gas (e.g. 100 or more, unleaded) will also slow the burn rate in the cylinder. This will provide another way, similar to retarding timing, to avoid knock. I only use nitrous on a 50/50 mix of 92 octane pump gas and 100 octane racing gas. Make sure it's unleaded, of course, or you'll destroy your O2 sensors.

By the way, watch out for Octane Boost claims. Typical claims are "8-10 points of octane boost for a tank of gas." You should be aware that these "points" are tenths of a point of octane as you'd purchase at a gas station. So the above example will raise your octane from 92 to 92.8 or 93, not 100-102 as you might think.

Don't assume that if high octane fuel helps on nitrous motors, that it'll help your naturally aspirated motor too. A naturally aspirated motor is tuned for a particular octane of gas; adding more doesn't help one bit. Save your money.

Your fuel system is the most important part of the system. As I hope is clear by now, the worst scenario in a nitrous system is a lean air/fuel mixture. The solutions to a good fuel system depend on the type of nitrous system you're using.

On a wet system, you simply need to ensure that your fuel system can supply adequate fuel, at standard (~45psi at WOT) pressure. A stock f-body fuel pump can usually supply enough fuel for around 450 total horsepower to the motor; any more and you want to get a larger pump. Much more than 650hp and you'll want larger fuel lines as well.

On a dry system, not only do you want adequate fuel like the wet system, but on an typical setup the fuel is added by raising the fuel pressure, which forces more gas through the injectors. In this scenario, it's typically recommended that you replace the stock fuel injectors with better quality (not higher rating, just better, like Bosch) injectors. These injectors are able to handle the increased fuel pressures necessary.

I'm not going to go through a bunch of details on tuning here, other than to mention some ideas. You've got a plumbing system to test, as well as an electrical system. You'd like to test each component of both systems, to verify that it's correctly doing it's job. I suggest doing most of this in your garage, with the nitrous and fuel lines removed from the intake, and pointing (or held) into a rag. Keep in mind the nitrous line will give a good kick under pressure, so don't just leave it loose to whip around. You can test your WOT switch easily enough, your window switch (maybe set the window range at a lower rpm for the test, so you don't have to rev up to your red line). To test your fuel pressure switch, you'll need to verify it's got a closed circuit when the engine is running (showing adequate pressure), but you'll also want to verify that it opens the circuit as fuel pressure drops. There are a couple ways to do this. On my car, the fuel pressure bleeds off at about 2psi per hour. So if I switch the engine off, I can use an ohm meter to check continuity across the FPSS connections, and within a couple hours it should switch off. You can also test the FPSS on an air compressor, by generating the pressure you want for the FPSS, and monitoring that it switches at the right point.

For the plumbing, you of course want to verify that there are no fuel or nitrous leaks in the system. You should be able to leave your nitrous bottle open for hours without losing bottle pressure. On the fuel side, of course a fuel leak may be the most disastrous possibility, so check this first by pressurizing the system (turn the key to "acc" but don't start the car) and feel around all the fittings.

I haven't listed all possibilities, but hopefully given you an idea of where to start testing. Once everything seems to check out, put in a set of 50hp jets, and move out on the track.

All nitrous systems use "jets" inserted in the fuel or nitrous lines to limit the flow. These jets have openings of a specific size, measured in thousandths of an inch. So a "35 jet" is a jet with a hole drilled 0.035" through it. Increasing a nitrous jet size will make the system run more lean, increasing the fuel jet size will make the system run more rich.

There's also a good web site with a jet size calculator on it for a wet setup (where you're metering the fuel and nitrous yourself). It will give you jet sizes based on desired horsepower, fuel and nitrous pressure. I recommend you use these as a target, maybe start a bit richer than shown.

I don't have information here on the use of a jet to apply vacuum pressure to a fuel pressure regulator, as in the NOS 5176 kit. The use of jets for this purpose, and calling them "fuel jets" is NOT related in any way to the normal use of fuel jets in a wet system, and I'm not aware of algorithms that would allow you to select these jets in combination with nitrous jets, to create a certain amount of horsepower. Contact the nitrous kit vendor for recommendations.

Miscellaneous Options

PURGE

Not unique to nitrous, but certainly a common failure on high horsepower cars, is the rear end. A 4th generation f-body, with a stock 10-bolt rear end, is not going to last long on nitrous. Plan for an expensive (~$2,000) upgrade at some point.