Nitrous Oxide

It is claimed that adding a nitrous kit to your car is the best bang for your buck that you can get. Well it's true. Read further and you may discover that nitrous might be the alternative aftermarket high performance product for you. The installation cost compared to other high performance modifications in a lot of cases is cheaper. Other mods are of a permanent nature with the resulting horsepower gain available to you 24/7 whether you want it or not. Nitrous on the other hand is only there if you want it by simply flicking a switch. It does however require further injection of money to keep using it. The bottle of nitrous doesn't last forever, so to keep using it will require you to keep filling the bottle, so it is a constant extra cost to keep running it on a regular basis, the more you use it the more it costs. A 10lb bottle will cost about $110, the last time I checked. Only using it every now and then to overtake another car, impress people or just to beat someone at the lights occassionaly, then it won't cost much at all. Another factor of course is how much extra horsepower does the system add. The higher the HP obviously the more gas will be used. As a rough guide an additional 100HP will consume 1.00lb of gas for a 10 second run. From this you can estimate how many shots you will get from a bottle. In saying all that, there are some great advantages of running nitrous compared to say fitting large duration, high lift cams, turbos or superchargers. Power on demand is one of the great advantages about a nitrous system; it only works when you want it to. The rest of the time, the engine operates normally with no extra stress on the engine and no extra fuel use. With the flick of a switch, you can suddenly unleash a monster. To get an extra 50HP from your engine any other way definately would involve at least a cam change and along with that the lumpy idle and poor driveability around town. The beauty also is that you can do your cam mod or turbo/supercharger and also add nitrous on top of that and have yourself an absolute terror. Nitrous is starting to catch on recently and it is no wonder. The technological improvements to the systems compared to what was available in the eighties is amazing. They are so much more reliable and safer to use on engines compared to my day when it was relatively easy to destroy an engine with poorly designed nitrous systems and inferior solenoid components.

So let's look very briefly at what makes horsepower. An engine operates by burning fuel, which then expands and pushes the pistons down. If you want to make more horsepower, you need to burn more fuel so it will exert more down force on the pistons. Fuel requires oxygen in order to burn. If you want to burn more fuel, you also need to put in more oxygen. All aftermarket engine performance accessories increase power by increasing the flow of fuel and oxygen. Camshafts, bigger valves, larger carburettors, intake manifolds, extractors, turbochargers and superchargers are all examples of improving engine performance by increasing the air and fuel flow which leads me to the next subject.

So what is this stuff? I'll keep this down to one paragrah because there is no need to get into to much depth over it. Nitrous oxide is not a fuel. Nitrous oxide is a way of adding the additional oxygen required to burn more fuel. The extra fuel is added with the nitrous by a separate fuel delivery system. The extra power comes from the fuel. If you add only nitrous and do not add additional fuel, you would in essence run very lean in mixture strength because the extra oxygen will be released in the combustion chamber creating an excess oxygen condition (lean mixture). Doing this whilst under full acceleration will lead to destructive detonation. Nitrous oxide (N2O) is made up of 2 molecules of Nitrogen and one of Oxygen. 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. The denser the mixture is, the more the cylinder is packed with fuel and air which results in more power. When nitrous oxide is injected, it turns from a liquid to a gas instantly and becomes very cold. This cold vapor drops the temperature of the intake air fuel mixture in the manifold by a considerable amount. The denser mixture that results helps an engine produce even more extra horsepower above and beyond what the nitrous system can. There, quick and easy.

In the performance aftermarket industry there is no equal to what nitrous oxide can provide in the way of extra horsepower and torque. Kits are available for all the popular V8 engines and various EFI engines  including 4 & 6 cyl variants and a kit that fits almost anything. You can add from 20 to 150 reliable horsepower on your street car easily within a day or two depending on the system and how much extra horsepower your going for. For serious racing there are kits that can produce in excess of 400 extra HP but that is beyond this article.

The are quite a few systems out there and choosing the right one is the challenge. Let me first break it down to two types of systems - WET & DRY These terms describe the method used to inject the extra fuel supplement required for the nitrous.

  • WET SYSTEM- This term mainly refers to an EFI engine but is also used on carburetted engines. The additional fuel and nitrous is delivered into the intake manifold either before the throttle butterfly for EFI or just under the throttle butterfly for carburetted engines, depending on the kit used. The term WET refers to the inlet manifold actually getting wet with the supplementary fuel. This is because with fuel injection the inlet manifold is used to control and distribute air only, with the fuel being injected directly into the inlet port of the cylinder head.

  • DRY SYSTEM- A dry system delivers the nitrous in the same way as a wet system however the fuel enrichment is delivered by the fuel injector and is achieved by either increasing the fuel pressure (limited increase in HP) or increasing the on time (duty cycle) of the injector. The later method requires a chip modification and is a better way to increase the fuel flow. However larger flow injectors will also need to be fitted to cater for kits larger than 50HP. It is a bit more complicated than this and I am sure you have read the manufactuerers speal on how good their dry systems are.

Wet systems do not require any sort of chip modifications when fitted to EFI engines which make them far more versatile. A wet systems can be easily jetted to increase or decrease the power gain and the basic kits can be removed and refitted to a different engines with similar configurations and layout. Now lets get into variations of wet systems. The three most popular types of nitrous oxide wet systems are:

Spray bar plate systems. A typical basic V8 set-up from the USA. These use a spacer plate under the carburettor that houses two spray bars, one for fuel and one for NOS. These kits are the cheaper of the systems that are available. They are easy to install and set-up and offer considerable HP gains. A kit is available without the carb plate and by simply purchasing a fogger nozzle and a few extra bits this kit can be adapted to suit other applications like the Single injector system below but much cheaper.

Single Injector system. This Wizard of NOS kit from the UK is probably the best & pricey kit available. It is the simplest on the market and uses only one nozzle mounted in the intake just before the throttle butterfly on an EFI engine. This kit uses poly hoses rather than steel braded hose or steel tubing. The solenoids or pulsoids as they are known carry a liftime warranty. The pulsoids are perfectly suited for progressive NOS injection should you decide to add this extra feature to the kit. They are pulsed just like a fuel injector to deliver precise amounts of NOS and fuel. I highly recommend the progressive kit if more than 50HP is going to be used especially to a 4 cylinder. Things break when a sudden jolt of HP hits the running gear. With a progressive kit more HP can be applied gradually without causing wheel spin, clutch and engine problems. This kit can be used on any 4 & 6 cyl engine, EFI or carburettored. This kit can also be expanded to a direct port set-up by simply purchasing distribution blocks and more injector nozzles, but it is cheaper to buy direct port in the first place.

Direct Port: This is a USA kit and uses fogger nozzles to add the nitrous and extra fuel to each individual intake runner. When you want big HP, direct port is the way to go. Set-up correctly it goes extremely hard. These systems flow huge amounts of nitrous and fuel while distributing it evenly to every cylinder. But if you want the looks rather than huge power gains, it can be easliy tamed down simply by matching the components and jets to suit. To get these systems to work properly, each NOS & fuel line must be equal in length from the distribution block to each nozzle as well as keeping the pipe lengths as short as practical. The picture to the right shows one way of setting it up.

The direct port system was the only nitrous system that I have had some dealings with. It was a 200HP kit on a supercharged 350 Chev, fitted into a 1957 Chevy. It was an absolute picture, not that well designed but looked good anyway. It had 16 chrome lines neatly places around the supercharger. Eight lines for the nitrous and eight for the fuel. Definately show car presentation. It was an awesome street legal, lethal machine without the nitrous. Holly crap, when the switch was flicked it was one huge handful of car to control. 200 extra HP hits so hard and for a street machine this kit would have been better set-up as a 2 stage. It was to much excitement for me to handle. The bloke that bought my business bought the engine in pieces. I rebuilt the engine with a further injection of $10,000 to strengthen the block and add an MSD pro race ignition system. The engine eventually ended up in a drag car. This Direct Port system had changeable nitrous and fuel jets as all systems do for horsepower adjustments, so I could reduce the power output if needed, but why would anyone want to. Another point on such a big system is that for street use it is obviously a ridiculous set-up to use a hard shot of such magnitude. The sudden power surge just makes controlling the vehicle very difficult. If only they had progressive shot control back in the eighties. Alright I have made a big jump here going to a 200HP kit but it is just awesome and deserved a mention. One thing to mention though when we talk about nitrous and that is the additional fuel delivery. Fuel pressure and flow is paramount when you start to get serious about HP gains. Remember the extra fuel will need to be supplied by an extra fuel pump to ensure adequate fuel supply to the nitrous system. Run out of supplementary fuel on a high HP kit during a nitrous run under full power and the engine is gone before you can lift your foot off the accelerator. For small gains in HP the standard fuel pump might be adequate.

I put up a PDF article from NGK plugs on spark plugs and nitrous. It is in the Ignition Section under spark plugs. It deserves a read but I will just add a bit to it here. On smaller nitrous kits, changing the plugs to one heat range colder will be sufficient and in some cases not even necessary.

On larger, big HP systems you also have to go one heat range or even two colder but also have to find a plug with a shorter earth electrode. A wide gap projected plug will misfire after only a short burst of nitrous. The misfire is caused by the earth electrode of the spark plug becoming red hot from the extra heat produced from the nitrous burn. The easy fix is to find a plug with a short earth electrode. Also on big kits, if your not using the nitrous during the week then you need to re-install your standard plugs. Two heat ranges colder will foul the plug under normal use. On lesser HP kits you may get away with the stock plugs if you don't use the nitrous for continued periods. If you go on the strip regularly, then fit the colder plugs and remove them after the meet.

If your interested in what a NOS kit can do for you then rush down to your NOS distributor and check out what kits are available for your machine. There should be a dealer in your town somewhere, just look up the telephone directory for high performance accessories. Oh and by the way you may find that NOS might be illegal to use on your machine on the street. Your risk, but I have heard that by disconnecting or removing the bottle you will avoid getting in trouble with the law.

Just like choosing a camshaft wisely, let the nitrous experts guide you to purchasing the right kit for your application, but find someone that knows what their talking about. Probably the best way to do that is to buy yourself a book on nitrous and read up on the subject. You may not understand it all, but you will get enough out of it, to know when someone is talking crap and trying to sell you something that will not be suitable.

In summary, there are many ways to get NOS on your car, single injector nozzle, spray bar, direct port multiple nozzles, 2 stage injection, progressive injection and the list goes on. In all cases, reliable supplementary fuel supply is paramount to your engines life. All kits are not the same, some deliver the power very harshly while some deliver it softly without the need in some cases of using progressive injection. Do your home work and plan the gain you want. Keep your expectation in line with what the engine is capable of before you go installing that 150HP kit on your Corolla. The rough rule on a stock engine is no more than 50% increase in HP. If you want more then engine strength improvements are required.