Purpose of this manual

LP gas, like any combustible fuel can be dangerous if not used correctly.  If you attempt to construct your own Nitrous Oxide injection system, be aware of the hazards present when you use Nitrous Oxide fuel. Use proper fittings and fixtures, and be aware of the high pressure present at the output of a NITROUS storage tank. Upon expansion, Nitrous Oxide gas reaches extremely low temperatures and can freeze the skin almost instantly.  Also, gaseous Nitrous Oxide is heavier than air, and can collect in enclosed places. Any containment of a tank must be properly vented. Even though Nitrous Oxide is not combustible, it is a source of oxygen and supports combustion.  Never check for gas leaks using a flame.

In addition, while adding Nitrous Oxide injection equipment to a gasoline engine is becoming a commonly accepted practice, keep in mind that doing so may void your warranty, negate any emissions certifications your engine has and/or violate local or state vehicle codes. It is not impossible that, done incorrectly, adding NITROUS to your gasoline engine will cause damage to its operation or construction.  So, be careful.

This manual is intended to be used for educational and informational purposes only.  You are ultimately responsible for any and all actions that you take after reading this document.  Should you actually decide to construct a working Nitrous Oxide injection system, we (Rudy Axelrod Publications) will not be responsible for any damage to your property or person, or that of any others as a result of anything you do with the information contained here.

Laughing Gas

N2O Nitrous oxide, almost odorless, is a colorless gas that was first discovered by the English scientist and clergyman Joseph Priestley (who was also famous for being the first to isolate other important gases such as oxygen, carbon monoxide, carbon dioxide, ammonia, and sulfur dioxide) in 1793. He made Nitrous Oxide by heating ammonium nitrate in the presence of iron filings, and then passing the gas that came off (NO) through water to remove toxic by-products. The reaction he observed was:

2NO + H20 + Fe N2O + Fe(OH)2


After his initial trials, Priestley thought that Nitrous could be used as a preserving agent, but this proved unsuccessful.

Following his discovery, Humphrey Davy of the Pneumatic Institute in Bristol, England, experimented with the physiological properties of the gas, such as its effects upon respiration. He even administered the gas to visitors to the institute, and after watching the amusing effects on people, who inhaled it, coined the term 'laughing gas'! Davy even noted the anesthetic effects of the gas: "As nitrous oxide in its extensive operation appears capable of destroying physical pain, it may probably be used with advantage during surgical operations in which no great effusion of blood takes place".

However, despite this observation, for the next 40 years or so the primary use of Nitrous Oxide was for recreational enjoyment and public shows. So called nitrous oxide capers took place in traveling medicine shows and carnivals, where the public would pay a small price to inhale a minute's worth of the gas. People would laugh and act silly until the effect of the drug came to its abrupt end, when they would stand about in confusion. Many famous people (of their time) and dignitaries from Clifton and Bristol came to inhale Davy's purified nitrous oxide for recreational purposes.

Nitrous Oxide Injection

Nothing equals the potential power increase provided by Nitrous Oxide injection in an internal combustion engine.  If you look at a nitrous oxide system on a dollar-per-horsepower basis, you'll find that a nitrous system can provide the greatest value for each dollar you invest. Enthusiasts and racers alike are impressed by the ability to add 10 to 200 horsepower within a period of just a few hours. By choosing the correct system for your application, you'll be assured of a performance increase and reliability factor that could only be compared to doubling the size of your engine!

Fuels, used in internal combustion engines, require oxygen in order to burn. If you want to burn more fuel, you need to also put in more oxygen. Virtually all engine performance products increase power by increasing the fuel and oxygen flow. Camshafts, larger carburetors or valves, porting, intake manifolds, exhaust headers, superchargers, turbochargers, and nitrous oxide are clear examples of how improved engine breathing (putting in more oxygen in order to burn more fuel) will give you an increase in horsepower. That's the basic reason why nitrous systems produce such large horsepower increases.  It is the most efficient way to increase the flow of oxygen and fuel.

Another basic power factor is vaporization of the fuel. Gasoline, as with other liquid fuels, will not burn in a liquid state. The gasoline must be turned into a vapor for it to burn. This process of turning gasoline into a vapor is simple evaporation. It is basically no different than setting a glass of water outside and waiting for it to dry up. In the engine, of course, evaporation happens very quickly. Engine heat and fuel atomization are the keys to accelerating the evaporation process enough to turn raw gasoline into a vapor at 8000 RPM. The process of atomization turns raw fuel flow into tiny droplets which then evaporate faster due to the larger amount of surface area presented for evaporation. The size of the fuel droplets is very important. Take a large droplet of gasoline, break it up into 10 smaller droplets, and you've increased the surface area for more efficient evaporation. The result is more fuel available to be burned and do work during combustion. A well-designed nitrous system will produce very small droplet sizes in the supplemental fuel that flows into the engine with nitrous.

This is one of the reasons that nitrous oxide injection can make more horsepower than many other systems. The third basic power factor we will look at is air/fuel mixture density. Ever try to jog on top of a 10,000 foot pass in the Rockies? Leaves you gasping for breath, doesn't it? That's because the air is thinner, less dense, and higher up in the atmosphere than it is at sea level. It is also why you would run slower on a track in Denver than you would near sea level in New Jersey. Density is affected by atmospheric pressure (the weight of the atmosphere above you), heat, and humidity. We can't change the pressure of the atmosphere; but we can regulate the heat of our intake charge to some extent. Cool cams and intercoolers make extra power by cooling the fuel and air/fuel mixture to make it denser. And, the denser the mixture is, the more the cylinder is packed with fuel and air to burn and make power. When nitrous oxide is injected, it turns from a liquid to a gas instantly and becomes very cold. This cold nitrous vapor drops the temperature of the whole intake charge in the manifold by as much as 65 degrees F. The denser mixture that results helps an engine produce even more extra horsepower.

Nitrous Oxide is a source of oxygen.

Nitrous oxide is a convenient form of oxygen. Since we are only interested in the oxygen the air contains, nitrous oxide provides a simple tool for manipulating how much oxygen will be present when you add additional fuel in an attempt to release more power. The power always comes from the fuel source. Nitrous oxide is not a fuel. Nitrous oxide is a convenient way to add the additional oxygen required to burn more fuel. If you add only nitrous oxide and do not add additional fuel, you would just speed up the rate at which your engine is burning the fuel that it normally uses.

This, more often than not, leads to destructive detonation. The energy comes from the fuel, not the nitrous. Nitrous oxide simply allows you to burn a greater quantity of fuel in the same time period; thus, the overall effect is a tremendous increase in the total amount of energy, or power, released from the fuel and available for accelerating your vehicle.

There is no black magic involved in nitrous oxide. In effect, using nitrous is no different from using a bigger carburetor, a better manifold, a supercharger, or a turbocharger. Understand that the air you and your engine breathe is made up, at sea level, of 78% nitrogen, 21% oxygen, and just 1% other gases. Nitrous oxide (N2O) is made by simply taking the 2 major components of earth's atmosphere (in this case 2 molecules of nitrogen and 1 molecule of oxygen) and attaching them together with a chemical bond. When the nitrous oxide goes into your engine the heat of combustion breaks the chemical bond to provide your engine more oxygen with which to burn fuel. As you've read, all race engines operate under the same principles: more air (better breathing, supercharging, turbocharging, or nitrous) plus more fuel in a denser vapor equals more power.

Nitrous Oxide Compared to other Performance Products

You cannot buy more performance, dollar for dollar, with any system other than a nitrous injection system.  You could spend thousands of dollars on carburetion, a manifold, valve train components, exhaust, pistons, porting, supercharging, or turbo charging to get the same amount of extra horsepower that a nitrous system would provide for just a few hundred dollars. But this doesn't mean you won't benefit if you also install other performance parts. Once you have installed a nitrous system, all those other performance parts just increase the nitrous power. If you just have a few dollars and want lots of extra power, the best choice is a nitrous system.

Only nitrous is a part time power increaser. All of the standard performance parts put additional stress on the engine and burn more fuel all the time; not to mention what a pain it is to ride around town with a lumpy idle from a camshaft that is barely usable on the street. Power on demand is one of the great things about a nitrous system; it only works when the driver wants it. All the rest of the time, the engine operates normally; no extra stress, no extra fuel use, and no driveline problems.

Types of Nitrous Oxide Injection Systems

The two most popular types of nitrous oxide systems are spray bar plate systems, such as the Powershot, Cheater, and Big Shot automotive systems (which use a spacer plate between the carburetor and manifold) and direct port. The plate adds nitrous and supplemental fuel to the intake air stream through built-in spray bars. Plate systems are used on automotive engines on the street and in many racing classes.

Direct port systems use specially designed injectors, Fogger nozzles, to add the nitrous and supplemental fuel to each individual intake runner. These systems can flow huge amounts of nitrous and fuel while distributing it evenly to every cylinder. Multiple stage direct port systems have produced much more than 500 extra horsepower on some pro racing engines. All Direct Port systems feature changeable nitrous and fuel jets for horsepower adjustments and system tuning. Direct port systems are used in both street and racing applications on virtually every kind of engine. Some nitrous systems for fuel injection are a variation of Direct Port technology.

Tuning a Nitrous System: Important Points to Remember

Although this may seem like a very basic factor, failure to thoroughly understand what is happening in your engine is the number one reason your system installations may not be successful. Always start conservative. Follow the recommended jet combinations and start with the lowest level if you have an adjustable system. It only takes a few moments to change the jets so don't take unnecessary risks by starting at the highest level.

Be realistic about how much power your engine will handle. Don't get carried away here. Only you know exactly which components are in your engine. If you are unsure about those components, you can call our tech line and one of our highly experienced tech personnel can help you to decide what is safe for your particular combination. If you don't know what's inside your engine, then you are most safe by assuming that the components are factory stock and choose the correct system for that application.

The power comes from fuel. The additional power is set by the amount of additional fuel your system supplies while the nitrous system is in operation. If the fuel isn't there, the power won't be either and no amount of nitrous or anything else can bring it back.

There are two controls typically available to manipulate the amount of fuel available during system use; the fuel jet size and the fuel pressure. The correct fuel pressure is read while the system is flowing fuel. Some fuel pressure regulators give false readings because the pressure reading will creep up when the system is not activated. When this happens, the actual flowing fuel pressure will be much lower than expected and can cause problems.

Reduce Nitrous Jets first

When problems with misfire or detonation are encountered, ALWAYS reduce the size of the nitrous jet first! Remember that the power comes from the fuel, not the nitrous, so trying to cool things down by adding fuel simply adds more power and complicates the problem. Carburetors jetted over-rich run cooler and release less power. Nitrous systems jetted over-rich will possibly just release more power, so if you run into problems, reduce the size of the nitrous jet(s) first.

When you check your spark plugs for signs of how your system is operating, check every sparkplug, not just the easiest plug to get to. No two cylinders ever run exactly alike. Nitrous has the unique characteristic of cleaning the spark plugs very well and leave them looking like you just installed them. If there are any signs of detonation such as tiny silver or black specks deposited on the porcelain, reduce the nitrous jet size. If the ground strap of the spark plug exhibits a bluish-rainbow coloring, reduce the nitrous jet size. If the ground electrode shows signs of melting, reduce the nitrous jet size and change to a spark plug with a shorter and thicker electrode.

Spark Plugs and Nitrous Oxide

Over the years there seems to have been a great amount of technical material written about the simple operation of a spark plug and what they can do in relation to the way an engine runs. There are a few basic characteristics about spark plugs that you need to know to make an intelligent choice about the correct spark plug for your application. First, and most important; a spark plug must be of the correct design to operate within the environment of your engine, not the other way around. This means that the spark plug has virtually no influence on how the engine burns fuel or runs in general. The correct spark plug will simply survive the conditions present in your engine. A spark plug must maintain a certain temperature to keep itself clean. The wrong heat range can cause an overheated plug or a fouled plug. The heat range refers to the temperature of the ceramic material surrounding the center electrode.

Lean air/fuel ratios are more difficult to light because there are less fuel molecules in the area of the plug gap when the plug is scheduled to fire; thus, projected e plugs were designed for late-model lean-burn engines. Modern high-energy ignition also allowed larger plug gaps. All the while this was happening something else happened. Something that no one seems to have really noticed as the real culprit when the issue of factory type plugs being used with nitrous comes up. Quite often, a factory type, wide-gap projected plug will produce a misfire condition after only a few seconds of nitrous use. The misfire is not due to the heat range. The misfire occurs because the spark plug becomes a glowing ember because it is too long to dissipate the extra heat produced by a nitrous-accelerated burn condition. The correct fix for this phenomenon is to replace the plugs with one that has a shorter ground electrode. By doing this, you will shorten the path for the heat being absorbed by the ground strap. You can use the same heat range, you just have to find a non-projected e plus with a shorter and preferably thicker ground electrode.

If you only change the heat range of the spark plug to a colder heat range, you may very well still have the misfire problem. Since the length of the ground electrode is the cause of the misfire, a colder spark plug may have the same length of ground strap as the hotter plug you replaced it with.

Spark plug gaps should generally be .030" to .035". Never try to gap a plug designed for an .060" gap down to .035". Find the correct spark plug designed for an .035" gap.


Types of Systems

The first type, called the "direct injection" system, you pick a value of Nitrous Oxide to feed to the engine, either by calculation or by trial-and-error, and you simply shoot it into the air intake. No provision is possible for correcting gas flow depending on engine load, so the system is probably only optimized for one type of load demand. The advantage is that this type of system is simplicity and cost.  The disadvantages are that you will probably need to design a system with caution to make sure that you aren't overloading your engine with too much gas, because the system doesn't compensate for variations in engine speed, load, etc.

In the second type, sensors and controls are used to monitor engine performance and load, and adjust the gas flow to suit the need at the moment.  Some commercially available systems will be of this type.

In order to determine the load on the engine in a normally aspirated system, a venturi must be placed in the air intake, as gasoline engines have no natural intake manifold vacuum. A sample of the vacuum produced by the venturi is fed to a metering system, either electronic or mechanical, which adjusts the gas flow to suit the circumstances.

The load imposed on a turbocharged engine is in direct ratio to the boost pressure.  It's a simple process to take a sample of the boost pressure developed by the turbocharger and use it to control the metering system. Most commercially made systems are designed for turbocharged engines, both for this reason, and because of the greater power gain that the turbo realizes from Nitrous Oxide injection.

Since boost is such a reliable indicator of engine load, higher values of Nitrous Oxide injection can be realized, with tighter control over the results.  This is the type of system that will be fully explored in this text.

Direct Injection System

The direct injection system adds simply shoots the Nitrous Oxide into the air intake system at the turbocharger inlet.  The gas is thoroughly mixed with the incoming air in the turbocharger compressor and forced into the engine under pressure.  This is a simple system that works very well.

Parts Needed

The components needed to construct a Nitrous Oxide injection system can be obtained from RV dealers; Automotive parts suppliers and hardware stores.  The following list covers the major items needed to construct a working system.

1.      Nitrous Tank       

2.      Nitrous Hose

3.      Pressure Regulator      

4.      Solenoid Valve (12 volt)

5.      Pressure Switch to sense turbo boost.

6.      Master shutoff switch

7.      Indicator light to show "armed" condition

8.      Control orifice at turbocharger inlet

Wiring and Fuel Schematic


Nitrous Oxide Tank by Nitrous Oxide Systems (NOS), and range in size from 1-lb to 50-lb bottles. It is also possible to use industrial grade 50 lb tanks, but they aren't siphoned tanks, meaning they have to be turned upside down to be used. 

Nitrous Oxide Tank   Nitrous Tank by Zex

Nitrous Supply Bottle & Valve Assembly by Zex

Code: 82000

Any containment vessel you choose for your system should be properly and securely mounted to avoid damage to the equipment during driving. Any wiring or plumbing from the tank or associated components should likewise be properly secured out of harm's way.

How long will a tank of Nitrous Oxide last?

Just like your fuel tank it is not long enough between refills, especially when you first play with it as you would a new toy. However once you get past this playful stage you begin to realize what a useful boost Nitrous Oxide is, and only use it when necessary, then the Nitrous Oxide tank seems to last forever before needing a refill. It is impossible to put a time to how long a tank of Nitrous Oxide will last. It depends on the size of the tank; the size of the Nitrous Oxide jet which determines the amount of power increase, and consequently the rate of Nitrous Oxide usage.  Power increases can he changed from as little as 5 hp to as much as 100 hp.  Obviously the bigger jet uses Nitrous Oxide more rapidly.

With all this in mind, a big bottle with a small jet will last the longest.  In a real life situation some use a tank a day, some use a tank a week and some take more than 2 weeks to empty a tank.  It is only a BOOSTER to your normal engine power and consequently you can run the vehicle as normal if you don't want to use the Nitrous Oxide too quickly, or when the Nitrous Oxide tank is empty.


The regulator you use will depend on how much pressure and flow is needed. If your Nitrous Oxide injection system will be used on a turbocharged engine, or if your engine has a high displacement (Cu In), you may want to purchase a regulator that has an adjustable output pressure. Turbocharged engines generally require pressures of 4-6 PSI, at greater flow rates than a household low-pressure regulator can provide.  Make sure that any regulator you use is rated for the pressure of a Nitrous Oxide cylinder (approximately 250 PSI) and is rated for flammable gas duty. Two-stage regulators will be less affected by changes in altitude, barometric pressure and temperature.

Note that systems which demand a lot of vapor will need a regulator which can supply the specified flow without freezing up. At some point, large gas flows will require you to install an evaporator system similar to those used on NITROUS fueled spark-ignition engines that are used on forklifts and the tank will need to feed liquid NITROUS to the evaporator/regulator.

Solenoid Valve

A solenoid valve is an electrically actuated valve that is used to control the flow of gas into the engine. It needs to be rated for the pressure that it is being asked to control, and be safe for flammable gases. The electrical rating needs to be 12 volts DC, continuous duty.

Pressure Switch 

A suitable pressure switch must be used to sense the turbo output pressure.  If the turbo has a maximum boost of 16 lbs. a pressure switch that closes contacts at 75% or 12 lbs. is about right.  The engine will operate normally until the load reaches 75% of full load and then the pressure switch will apply power to the solenoid and allow Nitrous Oxide to flow into the turbine inlet.  This is a very effective way to apply Nitrous Oxide.  Nitrous

Oxide is only used on extreme loads and a tank full should last for weeks, maybe months, depending on driving habits.  A pressure switch with a 1/8” NPT as the one shown, can be mounted on the intake manifold by drilling and tapping a hole.   If you take the Nitrous Oxide system off later, you can plug the hole with a 1/8” pipe plug.  Be careful to retrieve any chips that fall into the intake manifold.  Chances are they won’t cause any problems but it is always good to drop a small magnet into the hole to catch loose chips.

Adding Nitrous Oxide to the Engine

While it is possible to connect the orifice(s) directly to the intake of the engine, it is better to locate the jet at the solenoid and supply the metered gas to the engine through a length of NITROUS-rated rubber hose.   The hose is terminated at the turbocharger inlet. 

Nitrous Oxide must be added to the inlet of the turbocharger.  Adding the gas after the turbine output is possible, but you will need to account for the boost pressure, raising the NITROUS regulator to a value greater than the turbochargers output, typically 6-18 psi.




Mounting the Components on the Engine

Metering systems for gas pressure devices generally include an orifice, or jet to control flow. The size of the supply jet can be fixed, or adjustable. Fixed orifices must be drilled out to increase the flow for a given pressure, while adjustable units can be manipulated with a wrench or similar tool to change the quantity of gas that passes.

The supply jet can be made my drilling a small hole in the end of a 1/8” pipe plug.  The table below is a guide to the hole size needed.



Nitrous Nozzle Kit Zex   Code: NS6549


Replacement Nitrous/Fuel Jets  by Zex  Code: NS6500


Guide to Orifice Flow Capacities

Caution: Orifice flow capacities are dependant on a variety of factors that cannot be included in a simple table. Capacities vary with the composition of the gas, specific gravity, orifice configuration, back pressure etc. This data is approximate.

Drill Size vs. Fuel Flow

If you make your own jet, or decide to change the flow of a jet the following table gives the drill size to achieve the proper fuel flow.




BTU/hr at 11" WC


BTU/hr at 11" WC


BTU/hr at 11" WC


BTU/hr at 11" WG


























































































































































































































































Electrical System

For any installed NITROUS system, you will need at least a basic electrical control system to activate the solenoid valve, as well as protection and interlocking circuits to make sure that the Nitrous Oxide is turned off when the engine is not running. Here's a description of how wire the system.

 1.   First and most important, the 12 volt power to run the solenoid valve is supplied from the switched side of the ignition system. This insures that the gas is always off when the ignition switch is off. The supply wiring to the rest of the circuit is protected by a fuse.

2.   An On/Off switch on the dashboard. It's a good idea to have one on any system, so that you can defeat the gas when the engine is cold, or in case a problem requires shutting down the gas.

3.   An interlock that prevents gas from entering the engine when it isn't running.  Even though the ignition switch interrupts the solenoid circuit what happens if the engine dies, or you turn on the ignition to listen to the radio, or you're having trouble getting it started and are holding the throttle open while your crank it, or any of 19 other "impossible" scenarios that can dump gas into the motor while it's not running and consuming the fuel?

On a normally aspirated engine, (no turbo) it is best to install a pressure switch in oil system.  A normally open switch is required.

On a turbocharged engine, a pressure switch mounted on the intake manifold will not allow Nitrous Oxide to flow unless the turbo is building pressure.  This is acts as a safety interlock as well as turns on the Nitrous Oxide when the engine load becomes high enough.

Tuning it up

Adjusting the orifice and/or gas flow for optimum performance could be tricky. Basically, increase the NITROUS flow incrementally until you see/hear detrimental effects. The first, and most noticeable is hard knocking, or pinging from the engine. If it sounds like someone threw a handful of ball bearings inside your motor when your turn on the gas, by all means TURN IT DOWN!!! The rattling you are hearing is the "colliding flame fronts", and is also the sound of your pistons being turned into molten aluminum. If anything, adding NITROUS to a gasoline engine's intake air should make the engine quieter.

Another thing to watch for if your engine has a pyrometer (exhaust gas temperature gauge), is EGT's dropping. NITROUS promotes more complete combustion, so some of the heat that used to escape through the exhaust pipe is now being converted into mechanical power and transferred to the wheels.

Gasoline engines do not react well to NITROUS fumigation when they are cold. Turning on the gas before the engine has warmed properly will result in rough idle and bogging, or lack of pulling power. Let the engine come up to something near operating temperature before turning on the gas.

 What will it do?

Turbocharged engines will realize a dramatic increase in power when fed an adequate quantity of gas. Large trucks can utilize the extra power when climbing long hills and steep grades.  The drive train will not always take the extra torque though.  Altering the boost pressure, installing a modified engine control management computer chip, and providing intake and exhaust flow enhancements are all a part of race-prep for gasoline engines. If you have a turbocharged vehicle, you are probably going to want to look into a commercially manufactured fumigation system to make sure that you get the most from your engine, with the least likelihood of engine damage.   

Notes about air flow

Probably the single most important thing you can do for a gasoline engine besides the addition of Nitrous Oxide injection, is to improve the air flow in and out of the engine. This is particularly important in a normally aspirated engine.

Intake air

First and foremost, remove any and all possible flow restrictions.  Increasing the diameter of the intake ducting is also important. Converting to a larger pipe will mean that the engine has less pulling loss, resulting in more air per piston intake stroke, which means you can addf more fuel (and/or NITROUS) to the engine, resulting in more power

Temperature of the air is also important. Cooler is better. Cool air is more dense, more oxygen to aid in combustion. The intake end of the pipe leading into the air filter should be supplied with the coolest air possible. Usually, this means from either the grille, a hood scoop or under the front bumper of the car. What you don't want is air that has been warmed after coming through the radiator, in other words, hot engine compartment temperature air is not good.

Turbo engines benefit from installation of an intercooler, which is essentially an air-to-air heat exchanger that removes the heat produced when the intake air is compressed by the turbine. Cooler boost air will allow greater gains in power through increased fueling, either through adjustment of the injection pump, by fumigation, or both.

 Exhaust gases

Getting rid of exhaust gases quickly is also very important. Gasoline engines do not benefit from controlled back pressure like gasoline engines. In all cases, larger diameter exhaust pipes are better. Low restriction exhaust manifolds, down pipes and mufflers all add to power and performance, in dramatic ways.

Other Modifications

Most anything you do to enhance performance will result in the engine running outside of its design parameters. It may be necessary to compensate for this by adding high performance parts such as racing head bolts/studs, ceramic-coated pistons, additional cooling system enhancements, larger clutch disc and pressure plate, and even a locking differential transaxle to minimize wheel spin. It all depends on how far you intend to go.  Like anything, the only limit is what your wallet can handle!







Cole Hersee Company, 20  Old Colony Avenue, Boston Mass.  02127-2467, USA


Pressure Switch No. 8659 


Normally Open:  Closed at 9-16 PSI


Web Address:  www.colehersee.com


Zex   3418 Democrat Road, Memphis , TN 38118, US

Nitrous Supply Bottle & Valve Assembly
Code: 82000   

Nitrous Nozzle Kit
Code: NS6549

Replacement Nitrous/Fuel Jets
Code: NS6500

Web Address:  www.zex.com


Questions about Nitrous Systems.

Q: Will Nitrous affect engine reliability?

A: The key is choosing the correct H.P. for a given application. A Nitrous Oxide System that uses the correct factory calibration does not usually cause increased wear. As the energy released in the cylinder increases so do the loads on the various components that must handle them. If the load increases exceed the ability of the component to handle them, added wear takes place.  Nitrous Oxide Systems are designed for use on demand and only at wide open throttle. Nitrous can be extremely advantageous i that it is only used when you want it, not all the time. All  Nitrous Oxide Systems are designed for maximum power with reliability for a given application.

Q: Can I simply bolt a Nitrous Oxide System onto my stock engine?

A: Yes, the key is to choose the correct Nitrous Oxide System for a given application; i.e., 4 cyl. engines normally allow an extra 40-60 HP, 6 cyl. engines usually work great between 75-100 extra HP, small block V8's (302/350/400cid) can typically accept up to 140 extra HP, and big block V8's (427/454) might accept from 125-200 extra HP. These suggested ranges provide maximum reliability from most stock engines using cast pistons and cast crank with few or no engine modifications.

Q: What are some of the general rules for even higher H.P. gains?

A: Generally, forged aluminum pistons are one of the best modifications you can make. Retard ignition timing by 4-8 degrees (1 to 1½ degrees timing retard per 50 H.P. gain). In many cases a higher flowing fuel pump may be necessary. Higher octane (100+) racing type fuel may be required as well as spark plugs 1 to 2 heat ranges colder than normal with gaps closed to .025"-.030". For gains over 250 H.P., other important modifications could be necessary in addition to those mentioned above. These special modifications may include a forged crankshaft, a high quality race type connecting rod, a high output fuel pump dedicated to feeding the additional fuel demands of the nitrous system, and a racing fuel with high specific gravity and an octane rating of 110 or more.

Q: How much performance improvement can I expect with a nitrous system?

A: For many applications an improvement from 1 to 3 full seconds and 10 to 15 MPH in the quarter mile can be expected. Factors such as engine size, tires, jetting, gearing, etc. will effect the final results.

Q: How long will the bottle last?

A: This largely depends on the type of nitrous Nitrous Oxide System and jetting used. For example, a 125 HP Power Shot Nitrous Oxide System with a standard 10 lb. capacity bottle will usually offer up to 7 to 10 full quarter-mile passes. For power levels of 250 HP, 3 to 5 full quarter-mile passes may be expected. If nitrous is only used in 2nd and 3rd gears, the number of runs will be more.

Q: When is the best time to use nitrous?

A: At wide open throttle only (unless a progressive controller is used). Due to the tremendous amount of increased torque, you will generally find best results, traction permitting, at early activation. Nitrous can be safely applied above 2,500 RPM under full throttle conditions.

Q: Will I have to rejet my carburetor on my car when adding nitrous?

A: No! The  system is independent of your carburetor and injects its own mixture of fuel and nitrous.

Q: Is nitrous oxide flammable?

A: No. Nitrous oxide by itself is non-flammable. However, the oxygen present in nitrous oxide causes combustion of fuel to take place more rapidly.

Q: Will nitrous oxide cause detonation?

A: Not directly. Detonation is the result of too little fuel present during combustion (lean) or too low of an octane of fuel. Too much ignition advance also causes detonation. In general, most of our Nitrous Oxide Systems engineered for stock type engines will work well with premium type fuels and minimal decreases of ignition timing. In racing applications where higher compression ratios are used, resulting in higher cylinder pressures, a higher fuel octane must be used as well as more ignition retard.

Q: Where can I get my bottle refilled?

A: There are many performance shops that can refill your nitrous bottle generally for around $20.

Q: Is there any performance increase in using medical grade nitrous oxide?

A: None!

Q: Is it a good idea to use an aftermarket computer chip in conjunction with an  System?

A: Only if the chip had been designed specifically for use with nitrous oxide. Most aftermarket chips use more aggressive timing advance curves to create more power. This can lead to potential detonation. You may wish to check with the manufacturer of the chip before using it. The top manufacturers, such as Hypertech do make special chips for use with nitrous.

Q: How long does it generally take to install a Nitrous System?

A: A Nitrous system can be installed using common hand tools in approximately 3 to 5 hours.

Q: Which type of manifold is better suited for a plate injector type of nitrous system, single or dual plane manifold?

A: As long as he manifold doesn't interfere with the spray pattern of the bars, either will work fine in most cases. The distribution is better with a single plane at high RPM. If your goal is to increase power by more than 200 HP, the single plane manifold is better.

Q: Does nitrous oxide raise cylinder pressures and temperatures?

A: Yes. Due to the ability to burn more fuel, this is exactly why nitrous makes so much power.

Q: Are there any benefits to chilling the nitrous bottle?

A: No. Chilling the bottle lowers the pressure dramatically and will also lower the flow rate of the nitrous causing a fuel rich condition and reducing power. On cold evenings you might run on the rich side. For optimal running conditions, keep bottle pressure at approximately 800-900 psi.  has a nitrous pressure gauge that allows you to monitor this. If you live or operate a nitrous system in colder climates, it may also be a good idea to purchase a bottle heater Nitrous Oxide System, part #14161. Generally, ambient temperatures of 70-90 degrees F. will allow for best power potential of  Nitrous Oxide Systems.

Q: Are there benefits to using nitrous with turbo or supercharger applications?

A: Absolutely! In turbo applications, turbo lag is completely eliminated with the addition of a nitrous system. In addition, both turbo and superchargers compress the incoming air, thus heating it. With the injection of nitrous, a tremendous intercooling effect reduces intake charge temperatures by 75 degrees or more. Boost is usually increased as well; adding to even more power.

Q: What effect does nitrous have on an engine with considerable miles on it?

A: This depends largely on the actual condition of the engine components. Any performance modification to an engine that is worn out or poorly tuned will have detrimental effects. However, an engine in good condition, with good ring and head gasket sealing, should be able to use nitrous without any abnormal wear.

Q: Will the use of nitrous oxide affect the catalytic converter?

A: No. The increase in oxygen present in the exhaust may actually increase the efficiency of the converter. Since the use of nitrous is normally limited to 10-20 seconds of continuous use, there usually are no appreciable effects. Temperatures are typically well within acceptable standards.

Q: Will the percentage of performance increase be the same in a highly modified engine compared to a stock engine when using the same  Nitrous Oxide System and jetting?

A: Not really. In most cases the percentage of increase is greater from a stock engine because it is not as efficient as the modified engine in a normal non-nitrous mode. However, since the effects of nitrous oxide magnify the output of any engine, the total power output will be much higher in the modified engine.

Q: Can high compression engines utilize nitrous oxide?

A: Absolutely. High or low compression ratios can work quite suitably with nitrous oxide provided the proper balance of nitrous and fuel enrichment is maintained.  Nitrous Oxide Systems are used in applications from relatively low compression stock type motors to Pro-Modifieds, which often exceed 15 to 1. Generally, the higher the compression ratio, the more ignition retard, as well as higher octane fuel, is required. For more specific information talk to one of our technicians.

Q: Can service station fuel be used for street/strip nitrous oxide applications?

A: Yes. Use of a premium type leaded or unleaded fuel of 92, or greater, octane is recommended for most applications. Many systems are designed for use with service station pump gas. However, when higher compression or higher horsepower levels are used, a racing fuel of 100 octane, or more, must be used.

Q: What type of cam is best suited for use with nitrous oxide?

A: Generally, cams that have more exhaust overlap and duration. However, it is best to choose a cam tailored to normal use (when nitrous is not activated) since 99% of most vehicle operation is not at full throttle. There are special cam grinds available for nitrous competition which has more aggressive exhaust profiles etc. Since cam selection depends largely on vehicle weight, gearing, etc., it is best to stick to cam manufacturer's recommendations for your particular goal.

Q: What type of nitrous system is better; a plate injection system or a direct port injection system?

A: The advantages of a plate system are ease of installation and removal, ability to transfer easily to another vehicle, ability to change jetting combinations quickly, and, in most cases, provide you with all the extra HP you will ever need (75 to 350 more HP). In some cases, such as in-line type engines with long runners, a direct port type system is advisable for maximizing distribution. Also, where more than 350 HP is needed, our direct port Fogger systems will provide the ultimate in distribution and power (up to 500+ HP). Direct port injection is also desirable when the system is hidden under the manifold.

Q: Should I modify my fuel system to use nitrous oxide?

A: Most stock fuel pumps will work adequately for smaller nitrous applications. It is important to check to see if your pump can flow enough fuel to your existing fuel system (whether carburetor or fuel injected), as well as being able to supply the additional fuel required by the nitrous Nitrous Oxide System under full throttle conditions. It may be a good idea to dedicate a separate fuel pump to the nitrous Nitrous Oxide System.

Q: Which is the best position to mount a nitrous bottle?

A:  bottles come with siphon tubes and, in order to maintain proper nitrous pickup, it is important to mount the bottle correctly. We recommend mounting the bottle at a 15 degree angle with the valve end higher than the bottom of the bottle. The valve end of the bottle should point to the front of the vehicle and the valve knob and label should face straight up.

Q: How important is it to use nitrous and fuel filters in a Nitrous Oxide System?

A: Some of the most important components of any nitrous system are nitrous and fuel filters that keep contaminants from attacking the solenoid or plugging up a jet. A stuck solenoid means trouble!

Q: What are the advantages of using nitrous compared to other performance options?

A: The cost of many other performance options can put you in the poorhouse. Dollar for dollar, you can't buy more performance with less money than nitrous. With a nitrous system, performance and reliability can be had for a much more reasonable price while retaining the advantages of a stock engine during normal driving. And, nitrous offers tremendous gains in torque without having to rev the engine to excessive rpm's. These factors help your engine last longer than many other methods of boosting horsepower.

Q: How do I know how much nitrous is left in the bottle?

A: The most reliable way is to weigh the bottle to determine how many pounds remain. When a bottle is near empty (about 20% or less nitrous remaining) a surging effect is normally felt.

Q: What is the function of the blow-off safety valve on the bottle?

A: It is very importent not to overfill a bottle; i.e., a 10 lb. capacity bottle should not be filled with more than 10 lb. of nitrous oxide by weight. Over-filling and/or too much heat can cause excessive bottle pressures forcing the safety seal to blow and releasing all the contents out of the bottle.

Q:Will I have to change my ignition system?

A: Most late model ignition systems are well suited for nitrous applications. In some higher HP cases, it may be advisable to look into a high quality high output ignition system.




Nitrous Oxide










C8 H18





Research Octane Number








Motor Octane Number








Cetane Number








Density of Liquid Fuel(kg/lt)








Density of Gas (kg/m3)








Boiling Point (C)








Lower Heating Value (kj/kg)








Energy Content (Volume) (kj/lt)








Energy Compared to Gasoline








Energy Compared to Gasoline








Stoichometric A/F Ratio (mass)








Heat of Vaporization (kj/kg)








Energy of Stoich. Mixture (Mj/m3)








Wobbe Number (Mj/m3)








Auto ignition Temperature (C)









Peak Flame Temperature (C)








Spark Ignition Energy (mj)








Flammability Limits (vol %)

2.1- 10.4


1.4- 7.6

0.6- 5.5




Detonation Limits (vol %)

3.4- 35

6.3- 13.5






Flame Spread Rate (m/s)




0.02- 0.08




Max. Burning Velocity in NTP air (cm/s)








Specific Gravity at NTP (kg/m3)




4- 6




Reid Vapor Pressure (psi)








Diffusion Velocity in NTP air (cm/s)

~ 0.34

~ 0.51

~ 0.17





Diffusion Coefficients in NTP air (cm2/s)








Quenching gap in TNP Air (mm)








Flame Visibility, relative








Flash Point (F)








·          @ 3500 psi