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> The Nitrous FAQ:  FAQ (Frequently Asked Questions) Everything you wanted to know about N2O

John WilliamsonFAQ (Frequently Asked Questions)

There is more RUBBISH talked about Nitrous Injection than all the other types of tuning put together. Read ALL of this, because its all TRUE!

Do not listen to your pub or forum "expert" or "engine guy" or racer because most of these people know very little about this subject.  Especially when it comes to building your own systems or the shortcomings of the US based systems.


FAQ Simple:

This is a "Nitrous Oxide Injection F.A.Q." similar to ones found all over the net...
The difference is that this one is correct and accurate and more detailed than the typical FAQ found elsewhere. And it relates to MY systems much more than the rather agricultural US clones.

How Does Nitrous Oxide Work? 

Several ways at once. First, nitrous oxide is comprised of 2 parts nitrogen and one part oxygen (36% oxygen by weight). When the nitrous oxide is heated to approximately 572F (on compression stroke and during initial combustion), it breaks down and releases its load of extra oxygen, However, it is not this oxygen which creates more power, but the ability of this oxygen to burn more fuel.

Quick note here: Contrary to popular opinion DRY Nitrous systems ALSO add more fuel one way or another or they couldn't give more power and would in fact damage your engine very quickly. They do this normally by fooling the stock vehicles injection system into adding the extra fuel. Personally I think all dry systems are a liability and should be avoided at all costs! for a bunch of reasons.

By burning more fuel, higher cylinder pressures are created and this is where most of the additional power comes from.  Secondly, as pressurized nitrous oxide is injected into the intake manifold, it changes from a liquid to a gas as it expands. This boiling affect reduces the temperature of the nitrous oxide to minus 127 Degrees F or -88 Degrees C. This "cooling affect" in turn significantly reduces intake charge temperatures by approximately 60-75 Degrees F or over 20 Degrees C . This also helps create additional power. A general rule of thumb: For every 10 Degrees F. reduction in intake charge temperature, a 1% increase in power will be realized. Example: A 350 HP engine with an intake temperature drop of 70 Degrees F, would gain approximately 25 HP on the cooling affect alone. The nitrogen that was also released when the Nitrous split up performs an essential role. Nitrogen acts to absorb the heat and expand with the increased cylinder pressures leading to a controlled combustion process and better slower heat release. In other words you get more pressure to push down the piston. 

Quick note with ref to the above.... With a correctly set up system, the PEAK cylinder pressure wont be very much higher than the stock engine already had. The key here is that you MUST retard the timing sufficiently for this to be the case.

What we are trying to achieve (at least on a road car) is extra power with no engine problems. Retarding the ignition means that you get a much higher average cylinder pressure but a lower peak pressure. Retarding it a lot means huge doses of nitrous is "safe" on stock motors. This means your engine doesn't see much more stress or pressure than it did without nitrous.

Also if the Nitrous Fuel ratio is set adequately "over" rich then temperatures remain pretty low as well. Admittedly this isn't the most efficient use of the available nitrous but it keeps your road car or bike totally reliable whilst getting 80 percent as much power as a totally "leaned out" set up. Understanding this means you can set up your car or bike safely. This sort of accuracy isn't even possible with most commercial systems due to a large number of things not least being Why its jetted @ Solenoids


Why Nitrous Oxide (N20)? Not NOS! 

Nitrous oxide injection has become a very popular option for today's performance enthusiast for several reasons: 

  • N20 offers you more performance per / $ spent, than any other performance modification. 

  • N20 installations are relatively easy to accomplish. 

  • Since N20 is used only when needed, it offers you the advantages of complete drivability and normal gas mileage while not "on the button." 

  • Systems available for virtually any power need from 5 HP to over 500 extra HP. 

  • One of the few performance options available for today's computer controlled, fuel injected engines. 

  • Systems can easily be removed or transferred to another vehicle unlike conventional tuning parts.

Q: Why not oxygen?

Many serious reasons!  A whole page here explaining why... Why we cant use Oxygen!

Q: Will N20 affect engine reliability? 

A: Theoretically not.

In moderate doses, properly set up (see above) and used by someone that understands the system then it should not have any adverse effects. In some cases the opposite could be argued.  However someone using a cheap commercial dry kit with little knowledge of what's going on will likely break something sooner or later. Knowledge as always is power.

But probably in any case... One day its inevitable your engine will break, they almost all do so if you drive it like you hate it!  No engine goes forever so just accept it! If it has N20 fitted it will inevitably get the blame!

And It may well be nothing to do with the nitrous and usually isn't!

Q: Can I simply bolt a N20 kit onto my stock engine? 

A: Yes. Provided its fit, healthy and one or two simple precautions are observed then no problem In fact Stock engines are often best!

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

A: Generally forged pistons are one of the best modifications you can make. Retard ignition timing by a few degrees.  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". 

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

Loads..... Depends on jetting. You simply choose! Literally 400 to 600 percent is easily possible. If you know what you are doing.

Q: How long will the bottle last? 

Approximately 10bhp per lb per min. You decide! You choose bottle size and power increase. So a 2.25 lb bottle on a bike will give just less than a minute with a 25BHP increase. That's a LONG time when it goes from zero to 150mph in ten seconds!

Q: How long can I hold the Nitrous button down? 

A: It is possible to hold the button down until the bottle is empty. However you will be lucky to find enough road...  I tried it several times in both the V8 powered Ford Sierra and my GSX 1100 Suzuki bikes. They run out of revs and gears before the bottle gets empty.

Q: When is the best time to use nitrous? 

A: At wide open throttle only.  Due to the tremendous amount of increased torque, you will generally find best results, traction permitting, at early activation off the line when drag racing.

Q: Will I have to re-jet my carburettor on my car when adding nitrous? 

A: No! The N20 system is independent of your carburettor 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 inside the engine. 

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. 

Q: Where can I get my bottle refilled? 

A: There are many performance shops that can refill your nitrous bottle.  There are many suppliers, see the "REFILL" page.

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

A: None! All the same, Medical grade simply does NOT have the bad smell chemical added that Race grade stuff does. I don't recommend sniffing it anyway as it gives you a headache...

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

A: Only if the chip had been designed specifically for use with nitrous oxide.  Its pointless anyway unless your vehicle is turbocharged.

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. 

But the richer you run it the less heat. So if you want more power use more of both. Do not just try to weaken the mixture to the limit as richer is safer!

You want pressure, its what makes the car/bike faster, but you don't want the heat. Go Richer and more retarded the more boost you add!

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 psi.  Or jet accordingly to correct the situation. Live in a cold place? Used a bigger nitrous Jet...

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 hugely. 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? 

Mileage is not an indication of engine condition. Some low mileage vehicles are technically worn badly. Stop Start motoring, lack of oil changes or bad manufacturing causes this. Some very high mileage cars and bikes that have spent their lives on motorways and serviced regularly are found to be almost as new when stripped down. Worn engines may be a problem, high mileage may well not be. If you are unsure have a Garage compression test, and oil pressure test it and get the Mechanics opinion of its condition.

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 and the extra heat may in fact clean it up and improve its performance.

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 kits are used in applications from relatively low compression stock type motors to Pro-Modified, which often exceed 15 to 1. Generally, the higher the compression ratio, the more ignition retard, as well as higher octane fuel, is required.

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 have 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. For road cars or bikes the stock cam is great!

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

A: Neither is better. The best system is whatever "suits" your induction system the best.

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 carburettor or fuel injected), as well as being able to supply the additional fuel required by the nitrous kit under full throttle conditions. It may be a good idea to dedicate a separate fuel pump to the nitrous kit if in doubt.  

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

A: DIY System?  Its almost free!  www.nitrous.info The cost of many other performance options can put you in the poorhouse. 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 important 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.  As a short term cheap fix if you have problems close the plug gap by 25 percent.

FAQ Technical Fact/Fallacy (Don't know where this one came from originally but now I have modified it, it's ALL true!)

Nitrous oxide injection has become one of the most popular methods of increasing the power output of an internal combustion engine, and justifiably so. Nitrous oxide (N2O) injection is simple precisely metered N2O and gasoline are force-fed into the engine, supplementing the normal air/fuel mixture to release more work-producing heat during the combustion process. The only equipment required is an N2O storage tank, a pair of solenoid-actuated valves to control the N2O and gasoline flow, nozzles (or spray bars) to distribute the N2O and gasoline, and the various hoses, lines and wiring to connect the system. Engine disassembly is not required for installation-and the system can be removed for resale or transfer to another car at any time. The cost of a new professionally prepared system is reasonable (between $400 and $600 US in most cases), and the power increase is dramatic (usually in excess of 100 hp for most street systems).

As popular as N2O systems have become (industry estimates are that over 20,000 systems are now in use!), many enthusiasts still think of N2O as some sort of evil black magic. Honest and reliable information about the effects of nitrous oxide, the care and installation of N2O systems and tuning tips regarding N2O use has been practically nonexistent. Instead, the bench racers pass along inflated rumours of unbelievable power gains that rival a Saturn rocket, and incredible horror stories of vehicles supposedly erupting in fireballs that would make a hydrogen bomb seem small. 

FALLACY: N2O is explosive and a fire hazard.
FACT: N2O will not burn, nor is it a fuel. It is merely an oxygen-rich compound that supports the combustion of additional fuel. That's why additional fuel is injected along with the N2O on all N2O systems. It is true that if N2O is added to a combustion process already in progress, the extra oxygen may cause rapid, uncontrolled combustion, thus raising the peak temperatures produced.

FALLACY: N2O adds octane to the fuel being used and reduces detonation.
FACT: N2O does not increase the octane of the fuel being used. However, nitrous oxide injection may suppress detonation due to the intercooling effect of the depressurizing of the compressed N2O and by the introduction of extra gasoline. Most N2O systems intentionally add about 10 percent excess fuel as a safeguard against accidentally leaning the mixture. The extra fuel acts almost like water injection to cool the mixture and dampen detonation.

FALLACY: Premium fuel must be used with N2O injection.
FACT: The purpose of N2O injection is to support the combustion of extra fuel, thereby releasing more work-producing heat in the combustion chambers. Consequently, maximum cylinder pressures with N2O will be higher than when it isn't in use. Extra cylinder pressure does tend to cause pre-ignition and uncontrolled combustion, but as previously described, N2O injection also tends to suppress detonation. With most street N2O systems, these two opposing forces tend to cancel each other out, which means you can continue to use the same octane gas that was acceptable before the N2O was added. Because competition N2O systems inject a greater quantity of N2O and gasoline than do street N2O systems, cylinder pressure is frequently raised to the point where a higher octane fuel (or anti-detonation additives) must be used.

FALLACY: N2O will melt pistons, rings and valves.
FACT: If the N2O system has been properly designed to supply the correct amount of gasoline along with the N2O, combustion temperatures will actually be lower than when N2O isn't being used, so damage from elevated temperatures does not occur. Since the purpose of N2O injection is to make more heat, this may sound like a contradiction, but it isn't. With N2O, the total amount of heat energy released is greater, but the peak combustion temperature is lower. Think of it this way: A huge oil storage tank burning at an average temperature of 1000 degrees releases a lot more energy than a small acetylene torch with a tip temperature of 2000 degrees. That's a comparison by extremes, but in an engine with N2O injection, each cylinder might be burning 25 percent more fuel at a temperature of 1400 degrees than the engine would without N2O at 1460 degrees.
Claims of engine damage while using N2O are not totally fictitious, however, since if cylinder pressure does rise above the octane tolerance of the fuel being used, detonation occurs, and that will damage pistons, rings, etc.

FALLACY: Freezing the N2O tank increases N2O flow and the power output.
FACT: Whenever a pressure vessel is cooled, internal pressure drops. Most N2O systems are designed to work with tank pressures of 600-800 psi, which is the approximate pressure of a normal bottle at room temperature (approximately 72 degrees). If the bottle is cooled below room temperature, the pressure quickly falls, and flow would be reduced to the nozzles. For example, a bottle that had 800 psi at 75 degrees would fall to 450 psi at 30 degrees, and only 275 psi at O degrees.
On the other side of the coin, heating the bottle increases the pressure, but heat also tends to make the N2O vaporize in the line between the solenoid valve and the discharge nozzle, which upsets metering and reduces N2O flow. Ideally, the bottle and lines should be kept at room temperature. At the drags, some cooling of the bottle may be required to achieve this while the car sits in the staging lanes, but a damp cloth or towel wrapped around the bottle will generally be all that's required. If you really want to pursue additional cooling, chill the line between the solenoid
valve and the nozzle, and keep that line as short as possible to reduce the likelihood of vaporization before the discharge nozzles.

FALLACY: N2O injection in the individual manifold runners, as close as possible to the cylinder head, is more effective than injection immediately below the carburettor.
FACT: Although it used to be thought that direct port injection improved performance by assuring equal distribution, subsequent vehicle and dyno tests have shown that under-the-carb injection seems to provide a greater power increase since the gasoline has more time to vaporize as it travels down the intake runners. But the difference is very small!

FALLACY: As long as there's still pressure in the N2O bottle, some N2O is left and the system will function properly.
FACT: An N2O system meters and discharges liquid N2O when everything is working properly. When filled, an N2O bottle is only 68 percent full of liquid. The remaining space is specified as an expansion area. Additionally, an N2O tank needs a siphon tube to assure that the pressure head in the expansion area forces liquid N2O out into the lines, rather than gaseous N2O. When the liquid N2O is expended, it is not uncommon for the tank to still have 600 psi pressure, so pressure alone is not an indicator of N2O. Gaseous N2O is clear, whereas liquid N2O, vaporizing as it leaves the nozzle, will be white in colour. This is a more accurate indication of whether there is still liquid N2O in the bottle.

FALLACY: You need a prescription to buy N2O.
FACT: A prescription is not required to buy industrial grade nitrous oxide for automotive use. Nitrous oxide is available at most compressed gas suppliers, such as welding gas supply houses, but we have heard of isolated cases where a particular dealer who doesn't want to be bothered servicing hot rodders will use the excuse that you must have a prescription. If medical grade N2O (the only difference is the sterilization of the bottles) was being sought, then a prescription would be required. To make the purchase of N2O even easier, many speed shops are now refilling N2O bottles. If you live in a really isolated area or are confronted by an uncooperative dealer, the N2O system manufacturers will refill your tank, but of course, shipping the bottle back and forth is an inconvenience.

FALLACY: N2O requires no special tuning adjustments.
FACT: Force feeding N2O and extra fuel into the combustion chambers increases the density of the mixture, which increases the burning rate of the mixture. Consequently, it is frequently necessary to retard the ignition timing slightly for optimum results. The greater charge density also imposes a heavier load on the ignition system, so a good high-energy ignition system, with good spark plug wires and clean spark plugs is essential. If a competition N2O system is being used, the plug gap should smaller, and plugs one or two heat ranges colder than stock are recommended to help dissipate the extra heat of combustion.

FALLACY: You can't build your own N2O system
FACT YES!!! If you're sharp enough, you can as LOADS of people have done using these pages!

FALLACY: If tank pressure exceeds 850 psi, the solenoid valves will leak, flooding the manifold with N2O.
FACT: The solenoid valves used on some systems are rated at 850 psi working pressure. Other systems have solenoids with even higher ratings. In truth, the ratings are conservative and even the lowest rated solenoids being used will work at pressures up to 1500 psi. The working pressure has nothing to do with the pressure at which the solenoid will leak, since pressure actually helps close the valve, so the higher the pressure, the more tightly it seals. The working pressure or rating only refers to the solenoid's ability to open the valve against the pressure in the system.

FALLACY: N2O will blow up your engine.
FACT: If the N2O solenoid valve leaks or malfunctions while the engine is off, the manifold can become charged with a very lean mixture of N2O and gasoline. When the ignition is first turned on, a spark impulse may occur in a cylinder where the intake valve is standing open, igniting the mixture, which will virtually explode. Carburettors have been blown off manifolds in such situations. Consequently, it is advisable to turn off the main valve on the N2O tank whenever the car is going to be parked for several hours. If a leak is ever suspected, simply remove the coil wire and crank the engine for about 10 seconds to clear any N2O contamination.

FALLACY: You can smell leaking N2O.
FACT: Nitrous oxide is an odourless, colourless gas.

FALLACY: There's no limit to how much power you can make with N2O.
FACT: More N2O and more fuel equates to more power, but there's a definite limit to how much any engine will stand. It all comes down to: How fast do you want to go? And at what price?

*Technically the term NOS is incorrect as this refers to an specific company (called Nitrous Oxide Systems, in the US)




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