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.JPG) Compucar nitrous bottle mounted in my '95 GT's trunk Nitrous - what is it? is it safe? does it really make the world go by like warp drive? Thats a bunch of material to cover, but I see so much information floating around that is just plain wrong, I decided to go write up an article to cover everything I could think of about nitrous. Lets start off with the all important "What is nitrous and how/why does it work?" I recommend anyone running nitrous on a straight gear to check out the section at the bottom on that subject. It may save you some broken parts. What is Nitrous and How/Why Does it Add Horsepower? Well, nitrous is a gas (not gas as in gasoline...gas as in state of matter) that is made of two parts nitrogen and one part oxygen, forming NČO. The only thing that matters for making horsepower in a gasoline engine is how much oxygen and how much gasoline can be burned. Granted, the air to fuel ratio needs to be held at a certain rate, not just stuffed in without any regards to amounts. This being said, nitrous oxide contains roughly 3 times more oxygen per part than the air we breath does. Problem is, that oxygen isn't allowed to break free of the compound without some pretty intense heat (500°+). Well, guess what...when your engine is running, the temperatures inside the combustion chamber are well over the required heat range. This frees the oxygen, allowing it to be used for the combustion process. "What about the nitrogen that was left?" you may ask. Well, it helps to slow the combustion process, as all that extra gasoline and oxygen will want to explode in a wild, explosive matter. The nitrogen helps ensure that the combustion is controlled and keeps from damaging engine components. In addition to providing the extra oxygen (which allows the engine to burn more gasoline), nitrous oxide also cools the air coming into the engine. Nitrous is stored under a lot of pressure (typically between 700-1300psi inside the bottle), and that pressure forces the nitrous that is usually a gas into a liquid state. This liquid state nitrous is extremely cold, and thus will cool down the air coming into the engine as well as the intake manifold on the engine. Cooler air is more dense, and the more dense the air, the more air the engine can take in, allowing for more gas to be burned! Its like having your cake and eating it too. Is Nitrous Safe? I see a lot of people saying that nitrous is unsafe, uncontrolled, explosive, or any number of other bad things. Is it really? Well, in a sense it is, BUT (before you go saying superchargers or turbos are so much safer) keep in mind it is only unsafe when it is used incorrectly. What do I mean by that? Well, lets start first by explaining the three main types of nitrous kits: Wet kits: Wet kits are the nitrous systems that inject the nitrous as well as extra fuel into the intake, as such, the nozzle is placed AFTER the mass air sensor in engines so equipped. These are the #1 recommended kits for Mustangs, and for good reason. We'll get more in depth as to why later in this article. Dry kits: Dry kits are the systems that inject only nitrous before the mass air sensor, or by increasing fuel pressure so that the injectors supply the extra gasoline. These kits can't be used with carburetors. These kits are recommended a lot as well, and again, for good reason. Well, which is better? Keep reading. Direct port kits: Direct port kits are, in a way, wet kits. They differ in that instead of having a single nozzle that injects the nitrous/fuel mixture before the throttle body, they have a nozzle for each cylinder that injects the mixture in the intake manifold directly into each cylinder's runner just before the runner meets the head. These kits are excellent choices for large shots (200+) because they almost eliminate nitrous backfires that are associated with wet kits (again, more on this later). Now, back to what I meant by "it is only unsafe when it is used incorrectly": In most cases, Nitrous kits come designed for different applications. This means that your Honda Civic kit is completely different from the Ford Mustang GT kit, and that even the Ford Mustang GT 5.0 and Ford Mustang GT 4.6 kits are different. They are tailored to each vehicle, which is meant to keep enthusiasts from damaging their engines with too large of shots or what not. Lets say your kit for your car comes with the 100shot jets as the biggest. Well, you run that for a while, but you're wanting more go, so you purchase a set of 150shot jets. Well, now you're stepping over the "safe" bounds that the kit manufacturer set for your car. Sometimes you'll get away with it, and more times that not, you'll get away with it for a little while...long enough to get hooked. Lets say you run those 150shot jets for 1/2 a bottle, then decide to go even further with a 175shot. You run that 175 shot twice and *boom* your intake explodes, blow a head gasket, or much much worse, you overstress a piston or rod, and now you've got a mess waiting in your oil pan. Time for a rebuild. Well, was that the kit's fault, or was that your fault for stepping over the bounds? Of course it was your fault. The manufacturer makes it clear that its not safe to go further than the kit is designed for. Next on the list of reasons why nitrous can be unsafe? Guys that activate the nitrous too soon. In the instructions that comes with your kit, there is a certain rpm they do not recommend you spray below. This is usually 2500-3000 rpms. There are two reasons for this...the first (which applies to wet kits only) is below those rpms, the air inside your intake is moving slow, and the nitrous/fuel mixture isn't pulled into the engine as well, and can begin to puddle inside the intake. This puddled fuel can ignite (remember there is gasoline injected with wet kits) inside the intake if anything goes wrong. This is best demonstrated by methanol race cars at the drag strip. If you've ever seen a methanol car have a "nitrous backfire", you know how violent and explosive it can be. Keep in mind that gasoline is no where near as volatile as methanol, so don't think that if this happens to you that your car will burn to the ground, as 90% of the time a nitrous backfire will usually only take out your mass air sensor, air box, and maybe your throttle body. While this turns out to be expensive, if you follow the rules, you don't have to worry about anything. Also, keep in mind smaller shots (100 or less) are far less likely to puddle than the larger shots are. The second reason not to spray too early is the fact that nitrous creates so much more cylinder pressure, and this cylinder pressure is even higher at low rpms while the piston is moving slow. To help keep this cylinder pressure down, it is advised to never spray below 3000 rpms. I myself have had a nitrous backfire. I'll share the story here, as it was a lesson I learned, and hopefully it can keep you from making the same mistake. I had just finished installing my nitrous kit on my '95 Mustang GT, ran the small 50shot a few times, and then the 90 shot a few times as well. I decided to step up to the 125 shot jets included in the kit (150 being the largest included) and go out for a spin. I sprayed the 125 shot about 3 or 4 good times, and handed the keys to a really good friend of mine, unknowing that I had left the arm switch on. He proceeded to hop in the car and make a WOT (wide open throttle) run at low rpms (for those not knowing, the nitrous is activated at WOT) to get a baseline feel for the car. This run started out at ~1500rpm. Well, the kit immediately sprayed and due to the low rpms, there was a small nitrous backfire, which thankfully only claimed my stock air box. I was lucky. You might not be. Always spray after 3000rpms! The third reason nitrous can be unsafe is the fact that some guys do not monitor the bottle pressure, or try to get more out of their kits by spraying above the recommended pressure. All nitrous kits have a certain bottle pressure they are designed to operate at. this is usually between 900-1050 psi. My Compucar kit for example is designed for use from 1000-1050psi for getting the most horsepower from the shots, and 900-950 for those that are cautious. If the bottle pressure is too high, the engine can run lean, and running lean leads to detonation. Detonation leads to broken parts. Always monitor your bottle pressure and stay within the manufacturer's recommended range. A fourth reason? Fuel pressure and/or too small of fuel injectors. If your fuel pressure drops too far during a nitrous run, the kit will not have the additional fuel it needs to run at a safe air/fuel ratio. There are fuel pressure safety switches that are designed to turn the kit off if fuel pressure drops. I HIGHLY recommend these to be used in EVERY nitrous kit. Lastly there is incorrect installation. If you don't follow the manufacturer's directions for installation, you may have a problem down the road. Make sure to keep the lines clean, and blow them out before connecting them. Allowing trash in the lines could result in a sticking solenoid, and hopefully for your sake, it'll be the fuel solenoid, but its almost always the nitrous solenoid, which will cause a lean condition once you close the throttle. Keep those lines clean, and always, ALWAYS check for proper operation by spraying to the atmosphere in a test run before spraying into the intake. This will make sure that if you have a stuck solenoid, it will be vented to atmosphere and not into the intake, possibly destroying your engine. Its best to let that bit of nitrous you paid for escape into the atmosphere, than to cost yourself an engine if there was dirt in the lines. Don't think that these reasons are trying to discourage you from buying nitrous. I am simply trying to tell you how to prevent ever having any problems. Nitrous is very safe if you 1) run the recommended shots 2) spray above 3000rpms 3) spray at the appropriate bottle pressure 4) make sure your fuel pressure is good and 5) install the kit correctly. Now that we got the whole unsafe thing under our belts, lets move on, shall we? Should I Get a Wet Kit, Dry Kit, or Direct Port Kit? Well, lets explore this a bit, shall we, starting with the wet kit's advantages and disadvantages. Wet kit advantages: Wet kit disadvantages: Dry kit advantages: Dry kit disadvantages: Direct Port kit advantages: Direct Port kit disadvantages: Now, after reading some of the advantages and disadvantages, I will tell you that 9 out of 10 times I would recommend a wet kit for a beginner. The reason for this is the beginner isn't going to want to tune their car up for the dry kits, and could end up getting themselves in trouble. Dry kits are recommended for cars that have intakes that don't adapt well to nitrous and for those that don't mind putting the time and money in to tune their cars for the nitrous. Anytime a large shot is to be used, a direct port kit should be considered. Tuning for Nitrous? How Do I Do That? You might say "I don't have a dyno to tune for nitrous, and don't care to pay someone a lot of money to tune my car for nitrous." Well, that's fine, but I'd recommend to stay with small jets unless you have a dyno run with air/fuel readout to verify the curve is safe. What is "safe" with nitrous? Most consider 11.5:1 to be very safe with nitrous. Higher numbers such as 12:1 is considered safe lean, 12.5:1 and higher is too lean, and below 11:1 is considered rich. Its best to aim for 11.5-12:1 for best power and safest operation. Smaller shots can get away with a leaner (higher #) than larger shots. Tuning for nitrous isn't just verifying air/fuel ratio, but also includes tuning the ignition timing as well. Different engines react different when it comes to ignition timing with nitrous. Some engines want 10* initial timing with a 125 shot, while some engines won't like anything more than 6-8* with even a 50 shot. The best way to start tuning is to start with a 50shot and running stock timing. From there its best to start pulling timing, say 1.5* for every 50hp above the 50shot. For example, with a 150 shot, you'd remove 3* of timing. If your car doesn't have a distributor, a timing adjuster can usually be added to adjust timing. If not, be careful as you proceed going to the higher jets, making sure there is NO detonation. Detonation kills head gaskets and pistons or rods faster than anything. Another item that will need to be addressed with nitrous is spark plugs. Always use copper spark plugs with nitrous. Also, use 1 step colder plugs for up to a 125 shot, and 2 steps colder for 150 and over. This may need to be adjusted, depending on your engine (I.E. v6s should use 1 step colder for up to 75 shots and 2 steps for anything over) and the results you get after using the nitrous. Learn to read your spark plugs. I suggest reading different manuals on this, as its a lot to cover, and I don't want to attempt it here. Check the plugs after several runs on the nitrous, and also check them every time you step the jets up. Never take the manufacturer's suggestions as being carved in stone. If they say 8-12* of initial timing is safe with their kit, start at the small side, and work up. Remember, its easier to play it safe and sneak up on your tune than it is to start on the edge and mess something up, only to have to start over. ALWAYS start conservative. Nitrous Kit Components Lets start out first with the solenoids. They are the master control of the nitrous system.
The solenoids will have two wires coming from the top of them and two ports one labeled "in" and one labeled "out". The "in" side of the solenoid is plumbed to the nitrous bottle for the nitrous solenoid or fuel rail for the fuel solenoid, and the out side will be plumbed to the nitrous nozzle. The solenoids actually cut off the supply of nitrous and fuel, which shuts the system down. If they stick open due to dirt or some foreign object, then the system will continue to spray. Next, we have the nozzle itself and the jets:
Here are three different styles of nozzles on the left and right hand sides and two different styles of jets in the middle. The nozzles on the left have ports for both nitrous and gasoline, and require the jets on the top that screw into place. The brass nozzle on the left is for a dry kit, with only one port for the nitrous. This nozzle also requires the top jets that screw into place. The jets on the bottom are used with carbureted plate systems. Here we have the all important gauge.
Without a gauge, you can't monitor the bottle pressure, and you're gambling every time you spray. Always run a gauge, and always spray at recommended pressures. The other nitrous components are the nitrous filter, which goes inline between the bottle and solenoid, fuel pressure safety switch, WOT switch, activation switch, bottle, and stainless steel lines. How do I Install My Nitrous Kit? That's a very good question, and one that you should consult your kit's manufacturer for the answer to. Keep in mind that you ALWAYS want to fuse any power wires you install. Also, its best to use a switched power source so you can't spray the nitrous while the car is off. And always install an activation switch so you can turn the nitrous system off when you don't want to use it. Are There Any Ways to Make My Kit Safer? Glad you asked. Yes, there are ways to make nitrous kits safer. The first I always recommend is the Fuel Pressure Safety Switch. This item will turn your nitrous kit off in case there is a drop in fuel pressure. Next on the list is a Window Switch. What this switch does is only allow the kit to activate between two rpms that you choose. The most commonly used rpms are 3000 and 6000 rpms, but depending on your car, you may want to change this. Third is a blow down tube. Every nitrous bottle is fitted with a pressure relief fitting that bursts, releases the nitrous to atmosphere if the bottle pressure rises above 3000psi. The blow down tube fits over this burst valve that redirects the escaping nitrous outside of the cabin. It is required for use at NHRA sanctioned tracks. Any Other Accessories I Should Know About? But of course! Bottle Warmer - A bottle warmer will allow you to heat the nitrous bottle, increasing the bottle pressure. Many warmers come with pressure switches to automatically turn the warmer off once the bottle reaches a pre-selected pressure. Purge valve - A purge valve will purge the nitrous lines of air, and allow liquid nitrous to fill the lines all the way up to the nitrous solenoid. This will eliminate any surge at activation, and eliminates a rich condition on initial activation. Remote bottle opener - Sometimes you just want to open the bottle from the driver's seat. This item allows you to do that with the flick of a switch! How Do I Drive With Nitrous? I see a lot of questions on "do I have to deactivate the nitrous to shift?" and other similar questions. I'll do my best to answer the majority of these. A lot of how you drive with the nitrous is car dependent. A Honda Civic with a 50 shot and a Mustang GT with a 150 shot are going to act completely different. When beginning doing your first nitrous run, start out in 3rd, as you're less likely to spin and lose control. Start out by going full throttle in third gear with the switch off. Once you're in the safe rpm range and your bottle pressure is good, turn the switch on while staying full throttle. You should be able to immediately feel the car pick up. On your first spray, turn the system off after just a few seconds. Keep going further and further with the run until you're doing complete 1/4 mile runs with the system activated. Now, to launch the car: On street tires: Leave the line on motor, and once the RPMs are up enough, you can try activating the system. If you spin, deactivate it and use first gear as all motor. Change into second and reactivate the nitrous if you deactivated it. Now drive like normal, shifting with the system armed. Just take note that if you power shift with nitrous, you are much more likely to spin and lose control. Be ready to let out at any moment. On drag radials: You should be able to drive the same as if you had street tires, except you *should* be able to spray in 1st gear, provided you don't have an insane amount of power. On my '95 Mustang GT, which should be pushing close to 400rwhp on the nitrous, I am able to spray in 1st gear with my drag radials. Granted, you have to be QUICK to shift or else you will hit your rev limiter. If you are unsure if you can shift fast enough, DO NOT SPRAY. If you hit the factory rev limiter, engine damage can occur while spraying. On slicks: If you normally launch at 6k RPMs, try launching at 4500rpm with the switch activated and going full throttle once the clutch is dropped. You will need to experiment with launch RPMs to see what works best for you. Using Nitrous with a Straight Gear... There are plenty of guys that use nitrous with a straight gear successfully, many of which do not have any special safety switches in place. I'm not trying to say that you can't run without them, or that its not safe to run without them. What I will say is that if you don't have much experience with nitrous, if you tend to miss gears, if you like to power shift, or a number of other reasons, you may want to use some of my advise on the setup of nitrous in a manual transmission equipped car. First, you have your base kit that only has a WOT and arming switch. What I like to add onto this kit is a clutch switch that deactivates the nitrous as soon as the clutch pedal is pressed in about 1" or so. I set mine up so that the clutch quadrant actually presses the switch in when the clutch is out, so that when you press it in, the switch is turned off. I also use this switch for my two step. Its a micro switch that has a common in (for 12v+), a normally closed (which sends 12v+ when the switch is released [clutch pressed]), and a normally open (which sends 12v+ when the switch is pressed in [clutch released]). The normally closed spade leads to a momentary push button by the shifter. When BOTH the clutch pedal is pressed and the momentary switch is pressed, the 2nd step rev limiter is activated for launching. If either is released, the rev limit goes back to the top end limiter. Next, I have a window switch in place so that the kit will not activate unless the engine is in the rpm "window" I specify. I generally have this set at about 3000-5800rpm, since I shift at about 5600rpm. This allows me some room for error in my shift point without losing the nitrous shot, but still turns the nitrous out before the rev limit at 6000rpm. The window switch also is backup on the starting line if you use slicks. I can tell you that more than once I have launched, bogged, and the window switch cut the nitrous off when the RPMs fall below 3000 rpm. Without it, I'm sure I would've had at least one backfire due to that reason. Past these two switches, the setup is really the same, though if you run street tires or drag radials and do not want to spray 1st gear, then you can get a 1st gear lockout window switch instead. However, I would really encourage you to get the car setup for some true slicks and spray 1st gear right off the line. This is where nitrous makes up the most time. Does Nitrous Really Make Lights Go By Like Warp Drive? No. That's just ridiculous. Where Can I Get Nitrous? What Brands Do You Recommend? There are MANY retailers that sell nitrous kits. The brand I recommend and run myself is Compucar Nitrous Systems. They have a nice, well rounded package as well as a good warranty and tech support. To order a Compucar Nitrous System, you can visit my performance shop's website at http://www.scsperformance.com. Other good brands are Nitrous Express, Nitrous Oxide Systems, ZEX, TNT, Nitrous Works, and Nitrous Pro-Flow. |
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*all articles on this site are written by Stephen Hastings, and not copied from other sources. Please do not copy this material without giving a link to this site and giving credit. |
