xorl %eax, %eax

Nitrous Oxide Performance Systems

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Believe it or not, I was asked to write about this! Anyway, assuming that you know the basics of internal combustion engines, you can read this and find it pretty straightforward (at least this was my intention). Nowadays there are many companies producing ready to use kits for most engines such as the most popular NOS

and NX

or less popular like ZEX.

No matter what the company is, the design remains the same. Strangely enough most people know nothing about this even if this is actively used at least since 1914 when Robert H. Goddard suggested this as liquid fuel along with gasoline in rocket motors. So, with no further introduction let’s have a look at this technology as it was adopted in internal combustion engines.

Nitrous Oxide (N2O)
This is an oxide of nitrogen chemical compound which is a colorless, non-flammable gas that is widely used in medicine as anesthetic for surgeries. As I have mentioned above, it can be used as oxidizer due to its behavior at high temperatures where its chemical compound acts similarly to molecular oxygen. More specifically, an internal combustion engine uses air to obtain the required oxygen to ignite the mixture inside the combustion chamber. However, earth’s air has about 21% oxygen. On the other hand, at high temperatures nitrous oxide breaks down and due to exothermic reaction the nitrogen atom is freed from the oxygen ones releasing 0.5 Mole for each oxygen Mole. This results in roughly 33% of oxygen. Given the appropriate amount of fuel, the ignition can produce amazing power increase because of the pressure released in the combustion chamber. Moreover, during its release from the nitrous bottle, nitrous vaporizes and the change of the mixture’s temperature increases its density allowing greater amounts of mixture being delivered to the cylinder.

Dry Nitrous System
This is the most basic system. Here is a kit by NOS that includes all the parts required to set it up.

Basically, what you’re doing here is installing an electrically controlled switch to a valve and driving a line from the NOS bottle to the engine’s intake manifold. You finally place a NOS nozzle into the air intake (which sprays at a 90 angle) and connect it to the valve. When the valve is opened the nitrous will be sprayed into the intake manifold. Of course, in order to have increased performance you will also need sufficient fuel. There are two solutions to this issue when using dry nitrous.
1) Reprogram car’s computer (ECU) to increase the amount of fuel provided by the fuel injectors
2) Place the NOS nozzle before the intake’s Mass Flow Sensor (MFS). By doing this, the sensor will detect colder air (higher density) and instruct the ECU to provide more fuel.
This is a great kit for people who are just getting their hands dirty and want to try something new. It’s easy to install in a couple of hours and it’s very unlikely that you will be able to damage your engine with such a low (but definitely noticeable) power increase.

Wet Nitrous System
This is what you will probably see being used most of the time.

As you can see from the above picture of a ZEX nitrous system, it has a new nozzle that takes two input lines. Obviously, one is the nitrous valve but the second one is used to spray additional fuel. For carburetor engines there is a plate system to perform the same task such as the one you see here:

The installation is similar to the dry kit apart from the additional fuel line that is placed in the new nozzle. The nozzle is placed behind the throttle body. However, this system is ideal for engines that have intake manifold designed for wet flow such as turbo and supercharged ones. It could cause problems on intake manifolds not designed to handle wet flow.

Direct Port Nitrous System
This system has the exact similar operation as the wet system but as you can see in the following NX kit it contains more nozzles.

So, instead of spraying behind the throttle body, it sprays directly into each cylinder using a separate two-line nozzles for each one. This solves the problem of not equally distributing the mixture in all cylinders that the previous two systems had and it’s direct injection results in massive increase of horsepower. Consequently, this is usually installed in engines modified to be able to handle that power.
Because of its power, this system is usually set up in stages which are electronically controlled. This means that it provides less nitrous flow on stage one, more on the second, etc. Here is a photo of NOS Progressive Nitrous Controller that does exactly this electronic management.

There are more options to do this but most people choose ready to use microcontrollers like the above one.

Nitrous Damage
Well, if used properly it cannot damage your engine. But remember that since the use of nitrous could increase the power of your engine, some parts of it should be upgraded to be able to handle it. For example have a look at this piston and cylinder header.

This is a classic example of “more power that it could handle”. In extreme cases such as for example using multi-stage direct port nitrous injection you would almost certainly need to replace your stock pistons, rods, fuel pump, etc.

Engine Modifications
On most (if not any) dry nitrous kits you don’t have to perform any modifications to have a noticeable increase of your horsepower. However, when wet (single or multi-stage) systems are used, it’s a little bit more complex. In the following sections I will discuss a few components that have critical impact after such a modification.

Fuel Pump
This is a pump stored inside the gas tank of your vehicle and looks like this:

As its name suggests, its purpose is to pump fuel from the tank and drive it to the engine’s fuel injectors. When a direct port nitrous system is installed is important to upgrade your fuel pump with a higher output aftermarket one in order to have the best possible mixture to avoid lean mixtures that would damage your engine.

Spark Plugs
This is the most common modification in nitrous powered engines.

Despite what most people think about spark plugs, their task isn’t to simply ignite the mixture inside the combustion chamber. If you have a look at the image below, you will notice a part named insulator tip.

The aim of this component along with the metal body of the spark plug is to transfer the heat from the combustion chamber to the cylinder head that has cooling system and absorbs the heat. So, spark plugs have a property known as heat range that describes exactly this. Its ability to transfer the heat. A so-called cold spark plug will be able to transfer more heat but on the other hand, you should consider that it has to support all the heat range of your combustion chamber to avoid any misfiring. If you choose a hot spark plug, it is very likely that it would overheat and fail during mixture ignition in high temperatures. This roughly translates to power loss and possible engine damage.

In reality, the technical difference between a cold and hot spark plug is at its insulator tip’s length. Hot spark plugs have longer ones that absorb more heat but this might not be ideal for all cases. However, it’s a wise choice for everyday driving (low temperatures inside combustion chamber). Cold ones have shorter insulator tips and you may find them as aftermarket racing spark plugs. They transfer the heat quicker and remain cold. That said, you can easily deduce that if your combustion chamber doesn’t produce high temperatures it could be an overkill having cold spark plugs.

By now you should be aware that a hardcore nitrous system will definitely produce more exhaust gas than the stock engine. This is simply because it burns more fuel/air. Since camshafts are responsible for the timing of valves it might be needed to upgrade your camshaft with a different one that leaves the exhaust valves open for more time so that it can release the exhaust gas from the combustion chamber.

Other Upgrades
Of course, there are more upgrades which basically have to do with the materials’ ability to handle the additional power. For example, more exhaust gas would most likely require a new exhaust system. The high temperatures and pressure inside the combustion chamber would result in needing higher quality pistons, cylinder headers, etc. The higher needs for intake air require performance intake manifolds and air filters, etc.

Now that we know a couple of things regarding nitrous oxide, let’s have a look at various accessories that can assist in performance tuning.

Bottle Heater
This looks like this:

And it’s a battery powered warmer that wraps the nitrous bottle to provide the appropriate temperature in order to have the correct pressure inside the bottle.

Remote Bottle Valve Opener
It’s a device like the one shown below

Which can be remotely activated to open the nitrous bottle which is very convenient since most installations have the bottles installed in the car’s trunk.

Bottle Pressure Gauge
Probably the most important accessory.

You should always check the pressure of nitrous bottle.

Nitrous Purge Kit
To prevent backfires you might want to use something like this:

What this does is checking that the lines are clear of power robbing vapor.

Fuel Pressure Safety Switch (FPSS)
This is another neat device that looks like this:

This nice gadget will stop spraying nitrous if the fuel pressure drops (meaning that it doesn’t provide the required fuel).

RPM Activated Switch
It’s pretty obvious by its name.

It is used to activate “something” (you can wire almost anything to it) when it hits the specified RPMs. This is used in most modern car nitrous installations when using the manufacturer’s computer (ECU). Its purpose is to eliminate a very common nitrous damage because of the rev limiter.
Rev limiters are nothing more than a virtual upper bound RPM limit. When this is reached, the vehicle’s ECU sends a signal to cut off the fuel injection and thus slow down engine’s RPMs. Most manufacturers use this to protect stupid drivers from damaging their vehicles. However, in a nitrous powered car this could be devastating. Imagine spraying nitrous and suddenly leaving the engine with a lean mixture with almost no fuel. It could cause serious damage.
The solutions are to either use an aftermarket ECU, reprogram your ECU (if possible) or use a simple RPM activated switch and automatically shut down the nitrous injection at an RPM lower than vehicle’s rev limiter.

Nitrous Jets Upgrade
The nitrous nozzles (on wet and direct port systems) take two lines. One from nitrous bottle and another from a fuel line.

Using these jets you can change the amount of nitrous and/or fuel being passed through that line. You simply place them between the incoming line and the nozzle’s input. You can use them to have the best result by providing the appropriate amount of nitrous/fuel.

There are countless gauges for keeping an eye on everything that’s going on in your car. When installing some heavy nitrous system it would be wise to at least have an AFR (Air/Fuel Ratio) gauge to avoid the bad outcomes of a lean mixture.

Also, an Exhaust Gas Temperature (EGT) gauge is extremely useful for quickly detecting any damages. For example, a fast temperature increase would almost certainly mean that something inside the combustion chamber doesn’t work as expected. In most cases this is spark plugs, exhaust valves and piston rings that have melted.

I hope I covered most of the aspects around nitrous systems. If however I missed something or you have any questions please let me know. :)

Thanks to Google Image search for the images.

Written by xorl

March 6, 2011 at 17:00

Posted in motorcycles & cars

7 Responses

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  1. Great blog post for introduction to nitrous oxide systems. Thank you! Looking for more blog posts about the subject. Maybe, as a hacker, how to program ECU, or how to find programable ECU? :) It would be really good to know something about hacking car-systems.


    March 6, 2011 at 19:09

  2. Thank you. I had that subject in mind too. ECUs are very interesting. :)


    March 6, 2011 at 19:47

  3. Get back to public warez!!!


    March 6, 2011 at 22:03

  4. Good post!! btw, Don’t you think it’s preferable to use other modifications to gain power like turbo/compressor kits (with the necessary upgrades) against N2O kits? they provide a lot of power with less maintenance. I know you wrote this post without giving any opinion but i’d like to hear it :)



    March 7, 2011 at 02:56

  5. @Skye: Well, my intention was to provide an informative post about nitrous. Not suggesting anything.
    In my opinion, N2O isn’t the best option for performance upgrade. I agree with you that turbo and superchargers are more “complete” solutions. However, it is useful if someone needs a some additional horsepower for a limited amount of time.
    That said, I don’t think that it can be compared with turbo or supercharger. But on the other hand, it’s a tiny modification compared to installing a turbo or supercharger and costs less money.


    March 7, 2011 at 13:06

  6. :) totally agree with you. Thanks for your answer and your posts.


    March 7, 2011 at 13:15

  7. How much it cost the backfire kit

    John d de leon

    September 2, 2012 at 16:22

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