Nitrous, juice, squeeze... the very words are loaded with rebellious implications, suggesting that someone'spushing the limits, even getting away with something they shouldn't be. They do call them cheater plates, right? We, on the other hand, say that when it comes to making power, why shouldn't you get away with it? Nitrous oxide is power in a bottle, and it's hands-down the most cost-effective way to make more power and go faster. There is a wide variety of systems available, and with one bolted in place and properly set up, horsepower gains of anywhere from 50 to 600-plus with the multistage systems are available at the tap of a button. Our first goal here will be to cover the basics of how nitrous works as well as what you need to know to use it safely and effectively. Second, we've picked the minds of some expert nitrous tuners and manufacturers so that you can reap the benefits of their experience. And last but not least, we've also filled this nitrous extravaganza with several informative mini-tech articles, all in the name of giving you the most bang for your buck-which is what nitrous is all about, after all.
Why Nitrous Oxide?
We know you've heard it before, but we're gonna say it one more time: An internal combustion engine needs fuel, air (oxygen), and spark (ignition) to run and make power. The more air/fuel mixture you can get into an engine, burn, and get out, the more power you can make. Which leads us to nitrous oxide, or N2O as it's known in chemical shorthand. First of all, nitrous is not a fuel, and it's not flammable. Nitrous consists of two atoms of nitrogen joined to one atom of oxygen, and contains about 36 percent oxygen. The air we-and our engines-breathe is only about 23 percent oxygen. So by injecting nitrous into an engine, we're essentially filling the cylinder with concentrated oxygen.
When kept under pressure in a bottle and through the system, nitrous oxide exists in liquid form. As soon as it's injected into the intake tract, it becomes a gas. Once this gas makes it into the combustion chamber, many things happen. First and foremost, the heat and pressure of an engine's compression stroke break down the nitrous molecule into its components, freeing all that oxygen and allowing much more fuel to be burned than would normally be possible. Second, the force of this molecular breakdown improves fuel atomization-you not only get more fuel into the combustion chamber, but you also get it in a form that's easier to burn. And finally, because nitrous gas is very cold-we're talking -125 degrees F here-the intake charge is chilled, creating a denser charge, which leads to better combustion and increased power.
With significantly more air/fuel mixture on hand for the burning on the power stroke, the result is a significant gain in cylinder pressure, which translates into substantial power gains. In theory, it's actually pretty simple, and if you pay attention to some important details, it can be fairly simple in practice as well.
Although their basic internal components are the same, nitrous and fuel solenoids come in a wide variety of sizes, each with internal orifices designed to deliver specific amounts of nitrous and fuel. Amperage draws also vary, depending on the pressure being dealt with. Manufacturers tailor solenoids to specific setups. For example, a small solenoid may not have the power and capacity to deal with a big shot. It's not a good idea to mix and match them.
Wet or Dry?
There are literally hundreds of nitrous systems on the market, but they all fall into two basic categories: wet and dry. Wet systems deliver both nitrous and fuel into the intake manifold. The most common wet system, by far, is the carburetor plate setup, which is mounted below the carburetor to facilitate injection of fuel and nitrous into the intake plenum. In fuel-injected applications, a plate or nozzle is usually mounted just behind the throttle body to accomplish the same task. Plate systems are popular for good reason-they're easy to install, and the level of power being added-the shot, as it's called-is easy to adjust via a jet change. Another advantage to this setup is that the plates are calibrated to provide a proper air/fuel ratio, making it less likely you'll run lean and damage your engine.
The top-of-the-line wet system is a direct-port arrangement, which you'll usually find on drag cars. We've gotten indepth in the subject elsewhere, so we'll only touch on the basics here, but the great advantage to this setup is that nitrous and fuel are injected directly into each intake runner. This means that copious quantities of squeeze can be fed into each cylinder for maximum power production. These systems are also very accurate, since the amounts of fuel and nitrous being delivered can be individually tuned for each cylinder. Installation, on the other hand, is much more involved.
Dry nitrous systems differ from their wet brethren in that they only provide nitrous, which is sprayed into the inlet tract (which stays dry of fuel, hence the name). The extra fuel needed is added through the engine's existing fuel injectors. One common way to do this is to revise the fuel curve in the factory's ECM; another is to bleed off a bit of nitrous to trick the factory fuel regulator into providing more fuel. But since there's only a single nozzle to install in the inlet tract, dry systems tend to be pretty simple to install.
Which system is for you? If you're running a carb, it's really a matter of what your goals are. For the vast majority of street/ strip cars, a plate system is gonna be your best bet. If you're looking to run bigger shots (350-plus, according to our sources) and plan on spending more time at the strip than on the street, it may be time to avail yourself of the benefits of a direct-port system. When it comes to EFI, a wet system takes a little more work to install, but it is easier to tune for higher horsepower levels since you're controlling both fuel and nitrous levels. Dry systems are simple to install, but you must have a return-style fuel system to use one. As with anything else, it pays to be honest about your goals and intended usage and do plenty of research before purchasing a system.
Jets are pretty simple devices, but since they do determine how much nitrous and fuel you're injecting into your engine, it's a good idea to make sure yours are in good shape-the bores can wear over time-and that the sizes are clearly marked. NOS' Precision SS jets are made from stainless steel for accuracy and durability, and the size is laser-etched into them.
How Much Can I Run?
It's a loaded question, and the one we all want answered the most: How much nitrous can I run? We all want the most bang for our buck without literally going bang, right? So the answer is...it depends. The biggest thing is to know what you have in your engine. Is it bone stock, with a cast crank and pistons? What kind of cam and heads do you have? What kind of shape is your motor in? Is your motor properly tuned for non-nitrous operation? According to NOS, a small-block should be able to take about a 140hp shot, while big-blocks can handle 125-200 extra. If you're looking for more than that, it's time to start looking into forged pistons and an overall stouter bottom end. Our man Steve Brul at Westech Performance recommends not going higher than 35 percent of your engine's power output; in other words, the limit on a 300hp engine would be 105 hp extra. "You're rolling the dice at 50 percent," Brul tells us. "And I've never seen someone run 50 percent and not blow something up." This may sound conservative to some, but given that most of you will want to run your engine on nitrous more than once, we think it's advice worth considering, especially when dealing with stock engines. One of the best tips we've heard, however, is this: If you're planning to run nitrous on a regular basis, build your engine as if it will run at all times at the power level you intend to reach with juice. For example, if you're cooking up a 450hp small-block and want to hit it with a 150-shot, build the engine as if it will always be making 600 hp.
What You Must Do
Despite all the talk about whether engine internals can handle a certain amount of squeeze, most nitrous mishaps come from improper tuning, especially failure to pay attention to those most crucial of factors, spark and fuel. "People don't take enough care about their timing," says Zex's Matt Patrick. With nitrous, cylinder pressure isn't just higher, but it peaks earlier as well, meaning ignition timing must be retarded-if it isn't, detonation can quickly ruin your day. Each manufacturer will provide guidelines (they're in your instruction booklet), but reducing advance by 1.5- 2 degrees per 50 hp is a good rule of thumb. And while you're working to fight detonation, don't forget your spark plugs. In general, plugs that are one to two heat ranges colder than normal should be used when nitrous shots up to 150 hp are in play, and the gap should be reduced to 0.025-0.030 inch to help the spark travel across in this high-pressure atmosphere. Remember, by adding nitrous to an engine, you're really adding enormous amounts of oxygen-and without the proper amount of fuel mixed in, an engine can go lean and disaster can result. A nitrous system will need a minimum amount of fuel pressure to work properly-usually 6-10 psi for carburetor systems. The instruction manual for your kit will spell how much pressure is needed, and you really should make sure you have it. You also need to make sure your fuel system has enough capacity to support your goals-we'll give you a formula elsewhere, but the engine-building guidelines above work here too: If you have a 450-horse engine you plan to squeeze with a 150 shot, your fuel system must be able to support 600 hp.
For many, nitrous comes off as a risky proposition. But if we learned anything from this investigation, it's that a properly installed-and tuned-system can provide the huge power gains we all crave without making engines go boom. And the way to get there, according to every manufacturer and tuner we talked to, is to read the directions and follow their recommendations. Remember, it's all about air, fuel, and spark. If you take the time to control these factors as the experts suggest, chances are you'll quickly get addicted to the instantly gratifying, kick-in-the-pants power that comes from hitting the juice
You've got to arm your nitrous system before you run it-a covered toggle switch like the NOS piece here does the job with a bit of flair. Because it increases cylinder pressure rapidly, nitrous should only be engaged when an engine is over 2,500 rpm and at wide open throttle. A WOT ensures activation at the proper time. A simple switch like the one up front will get the job done, but beefier pieces, such as NOS' Billet Microswitch and Nitrous Pro-Flow's laser-cut piece keep the switch in place and look trick. The item at the back is an NOS waterproof microswitch, which may come in handy in marine applications.
Q&A: Matt Patrick, Zex Performance Products
CHP: What is Zex's main market?
Matt Patrick: We mostly sell to the modern-performance, late-model EFI guys. We've also got a whole new line of products for trucks. It's an emerging segment. If a guy doesn't want a used Camaro, a pickup truck is a convenient platform, and a Gen III-style truck motor can handle a lot of nitrous.
CHP: What kind of things do you look at when developing these kits?
MP: People tend to go for the thing that's engineered for their vehicle. When all cars had MAF systems, they ran 40 psi fuel pressure. That's not the case anymore, and GM uses 58 psi. If we don't adjust for that customer, they won't have an optimized tuneup. The OEM is also using crimped-together plastic lines, which has forced us to engineer more specific kits and adapters. We also size all our braided lines to the chassis, which is especially important on a late F-body.
CHP: What kind of power levels do you recommend?
MP: On average, most people run 100-125 hp. We think 125 hp is fairly safe on the stock long-block. When you push things to 150-175 hp, you've used up the safety margin and should consider better pistons, rods, etc.
CHP: What type of system do you sell more of, wet or dry?
MP: Eighty-five percent of what we sell is wet. The nice thing is that they supply their own source of fuel. They're very universal and bolt onto anything. And the charge takes care of itself. A dry kit is a simple install, with a different injector. We bleed off nitrous to trick the fuel regulator into thinking it has a stiffer spring. They don't fit newer cars that use returnless fuel systems, though.
CHP: Where else is Zex seeing action?
MP: Sales of our our perimeter-plate carb systems, which optimize distribution so you don't have lean cylinders, are through the roof. People want the latest in technology, but the great thing is seeing the performance gains.
CHP: What kind of problems do you commonly see?
MP: A number of customers aren't taking enough concern about timing. Our installation instructions say to retard the timing 2 degrees per 50 hp. But this is assuming the base timing has already been optimized without nitrous. You go as far as you can, then back off a few degrees. And it's best if you retard the timing only when the nitrous is engaged.
CHP: Anything else?
MP: Spark plugs-the gap needs to be closed 0.010-0.015, and the plugs need to be 1-2 step colder. But the biggest trend we see is too much timing.
Q&A: Steve Johnson, Induction Solutions
CHP: So, what does Induction Solutions do?
Steve Johnson: We are primarily into installing nitrous systems and plumbing intakes, and I blueprint and wet-flow the systems for proper calibration. I also provide a baseline tuneup and phone or racetrack support 24/7.
CHP: What do you do when you blueprint a system?
SJ: Whether it's a plate or direct-port system, the primary areas I focus on are the solenoids, nozzles, and jets, the three most important parts of the system.
CHP: Is that really necessary?
SJ: Even though things are brand-new, everyone's human; even a CNC machine can have programming errors or worn tooling. Solenoids are just like anything else; there's a tolerance, so I go through each one, measure the orifices, and correct them if necessary. With jets, I make sure each is properly marked, and check the orifice and consistency of machining. I don't take it for granted that everything's done right. When I'm trying to tune an engine, I want consistency.
Maintain proper nitrous and fuel pressure levels for optimum performance-and also to make sure air/fuel ratios stay in the safety zone. NOS' Racer's Nitrous and Fuel Pressure Gauge kits come with Schrader valve fittings, which can be plumbed into your system to facilitate quick and accurate pressure checks.
CHP: What's your advice about tuning a nitrous combo?
SJ: The one thing I'd say is to work your way up in steps, from smallest tune to largest. Guys bolt the thing on, try a 100-shot, then try 200, then jump all the way to 500 without learning key things like what timing each step really likes. With all the cylinder heads and engine combos, there's never two guys that have the same base timing. So start small and work your way up. Learn where it wants to be. Make a run, take out 2 more degrees, fine-tune fuel pressure, watch your e.t. and mph-especially mph-and see how it changes. Don't try to take a shortcut to the end of the tune-up sheet without going in the middle and learning, and watch your bottle pressure.
CHP: Why do you mention bottle pressure?
SJ: Any change over 25 psi will show a difference, but if pressure makes a dramatic difference, you really need to look at your tuneup. If a guy runs 900 psi, then raises it to 1,000 psi and it seems to help, it tells you the system may be too rich, since higher pressure moves more nitrous.
CHP: Any final words?
SJ: Nitrous, to a degree, is a balancing act, but guys tend to go overkill. The simpler you keep things the better off you'll be. Pay attention to the instructions provided with your kit or work with only one tuner-not everyone in the pits who will talk to you
Q&A: Jamie Wagner, Edelbrock Performance
CHP: Edelbrock is known for a lot of things, but how heavily involved is the company in nitrous?
Jamie Wagner: We've got a pretty decent nitrous program, and it's increasing every year. Our direct-port and plate systems are doing pretty well.
CHP: So how much nitrous can you use on an engine?
JW: It's more of what you know. If you're shaky on tuning the car, you could hurt the engine. You should talk to somebody familiar with tuning nitrous-and follow the directions. You can call us for help, but you have to go through the steps.
CHP: So is there a guideline as far as a number?
JW: We say about 100 hp on a street car. Then you need to get the proper components, like forged pistons, and get the ignition timing worked out. You need to make sure you're matching the engine components with performance level.
CHP: Can you give us an example?
JW: If you've got a 350 and you want to do a 150-shot on it, you should have decent pistons, the correct timing and spark-plug range, and the correct fuel delivery, whether you tap into your existing system or mount an external pump. If you have hypereutectic pistons, you have an issue. You should leave a margin for error. With a good set of pistons, you can rattle the engine and not hurt it. But as long as the tune-up is right, go 150 or more.
CHP: You mentioned fuel delivery in particular.
JW: All our jetting specs our based on 6.5 psi for carbureted systems; with a wet system, you're working off the base fuel pressure. But what you want is consistent, stable pressure. If you've got a 400hp motor that uses 80 percent of your fuel system's capacity and you want to do a 200-shot, you have to make it up. It's the same thing if a fuel system is marginal at best to begin with. Overcapacity is better than undercapacity.
CHP: What are the considerations when choosing between a plate and a direct-port system?
JW: It depends on what you're after. A direct-port system provides max gains and better individual tuning regardless of power level. You could do a 100-shot direct-port and have much better control. The benefit of a plate system is simplicity. They're easy to plumb in, easy to get up and running, and easy to tune, but not as efficient.
If you're gonna play with nitrous, you'll want good tools when you're disconnecting bottles for changes and refills. NOS' bottle nut wrench makes quick work of line adapters; Nitrous Pro-Flow's Nutbuster attaches to the line fitting with a set screw for quick line removal and comes in AN-4 and AN-6 sizes. Edelbrock's slick Bottle Nut Combo Wrench can handle three AN sizes and standard 1 1/4-inch bottle nuts.
CHP: What advice do you have for tuning a system?
JW: Always do your initial jet on the rich side, meaning use a larger fuel jet. It's easier to cut back than to go bigger. Also, be sure to change the heat range of plugs; if it's too hot, you can have detonation issues. We recommend that you retard the timing 2 degrees for the first 100 hp, and 2 degrees per 50 after that.
CHP: That sounds pretty straightforward.
JW: It's easy to get carried away with overexpectations, letting your eyes overwhelm your senses. Don't outrun your fuel system; start slow and ease your way into it. On the dyno, we start with small jetting. Like all modifications, it's about air/fuel and what the engine can stand.
CHP: Can we assume you recommend dyno tuning?
JW: If you have the ability to run on a chassis dyno, it can save some time and agony. In the scheme of money we spend on these cars, it's worth it to be able to tell when things go sideways
Q&A: Brandon Switzer, Speedtech Nitrous
CHP: How long has Speedtech Nitrous been in business?
Brandon Switzer: We're about three years old; we were involved with Shannon Jenkins and Mike Castellana, helping them on their race teams, and one day at the track just decided to open. Most companies start at the street level and try to work up; we started the opposite way, in the most premier nitrous class (Pro Mod), and are working our way to street.
CHP: Does the race experience apply to the street/strip realm?
BS: It applies directly. It may not be one-to-one, but there's a huge trickle-down effect, improving manufacturing and how to make cars better. What we learn helps with feedback to our customers in different areas.
CHP: So where is Speedtech doing most of its business?
BS: We primarily sell to racers, because that's what we do-we're out there with them every weekend. Most of these systems are direct-port setups, but we're working to expand into the street market, so we sell a lot of plate systems too. Our Diffuser Plate System has two inserts, so it sprays a 360-degree cone of nitrous at a 45-degree angle. It's an equal umbrella, creating perfect distribution around the plenum.
CHP: What should our readers know about nitrous?
BS: One of the major things is that nitrous is a two-phase gas. If you incorrectly size any area of the system, it changes phase (or boils) and you lose all metering capabilities. The second it changes, it loses density. Area calculation is one of the biggest things to look at when creating a nitrous system.
CHP: How do you know this is happening?
BS: Nitrous gets cold when it expands; it's ambient until then. All you have to do is turn the system on and run it. Anywhere it freezes, from the bottle to the nozzle, it's changing phase.
Installing a WOT switch in vehicle without a mechanical throttle linkage, aka drive-by-wire (DBW) system, used to be problematic. NOS has addressed the issue with its DBW/Wide Open Throttle window switch. Designed primarily for use with nitrous systems on DBW vehicles, it features adjustable low- and high-rpm set points to turn the system on and then off, and throttle position sensor (TPS) activation. Don't have a DBW vehicle but still want an rpm window switch? Hook up the power and an rpm signal from your ignition, and you're good to go.
CHP: What kinds of problems do you see people having with nitrous systems?
BS: One of the main reasons people have problems is the electrical system. A gearhead is into the engine and trans and doesn't think it applies to him much. But a nitrous system has more electronics than anything else. What'll happen is that a system tests fine in the shop, but then it's very rich at the track, when other electrical accessories are running. The nitrous solenoid won't open. A guy will have a 10-gauge power wire to the system, but no ground or a 16-gauge ground. Remember with a DC setup, the ground has to return what it brings.
CHP: What else should nitrous users look out for?
BS: The heat range of a plug is critical to controlling detonation. A stock, efficient, hot plug with too much nitrous and not enough octane can turn into a glow plug and cause preignition. You can tear up a motor with a 100-shot if you're off.
CHP: So we should pay more attention to our spark plugs.
BS: It's the only window to see what's going on in the engine. A spark plug isn't going to lie to you. Most nitrous guys need to learn to read spark plugs better than they do.
You wouldn't think of running your vehicle without a fuel filter, but N2O filters are equally important. Contaminants in a nitrous system can clog jets and damage solenoids, so including a filter with a cleanable element, like this billet setup from NOS, is a good idea.
There's nothing wrong with getting out of your car, opening the trunk, and turning the knob to open your nitrous bottle before making a run, but why be obvious? Edelbrock's Remote Arming Valve Kit (left) and Zex's Remote Bottle Valve Opener both allow you to open the bottle valve without leaving the driver seat.
Although a bare-bones nitrous system will get the job done, a number of accessories help provide optimum performance, consistency, and even safety. Zex puts them all together in its Racer's Tuning Kit.
*A bottle heater keeps the nitrous inside at a consistent pressure, which in turn helps maintain a consistent N2O-to-fuel ratio. A gauge is included to monitor pressure.
*A purge valve ensures best performance by freeing the system of any trapped air so it delivers nothing but liquid nitrous to the plate or nozzles.
*If you're gonna go racing, you'll have to have a blowdown tube that vents to the outside of your vehicle if the bottle becomes overheated and the safety disk ruptures.
Bottle heaters are essential to maintaining bottle pressure, as we mentioned, but they're not much on looks. Zex's new Plug-in Bottle Heater plugs into a cigarette lighter or power point, so you can flash the bottle at the show, then hook up the heater when it's time to race.
* The bottle should be mounted at a 15-degree angle with the valve at the higher end. On almost all bottles, this means the logo will be facing up and the bottle nut facing down. This also properly positions the nitrous pickup tube.
* A good bottle will use a high-flow bottle valve as opposed to a medical-grade valve.
* A nice set of quick-release bottle brackets, like the NOS pieces pictured, make bottle changes a lot easier.
* How long will a bottle last? It depends on bottle capacity and the shot size. According to Zex, a 10-pound bottle will last about 10 quarter-mile runs spraying a 75hp shot; up it 125 hp and you'll get about 6 runs.
* The best way to measure how much nitrous you have left is to weigh the bottle. A 10-pound bottle weighs about 25 pounds when full of juice-each bottle will have specific figures on the label.
* Best performance is achieved with a bottle that's at least half full.
* When using a bottle heater, pressure should be kept in the 900-1,000 psi range unless your manufacturer specifies otherwise.
Because nitrous oxide adds oxygen to the combustion process, you must make sure your vehicle's fuel pump and regulator can supply the extra fuel needed to go with it. Fuel pressure should be 6-10 pounds for a carbureted application; EFI systems should follow the manufacturer's recommendations. In addition to pressure, you must make sure your system flows enough to support your horsepower goals. How much do you need? Follow this formula: hp 2 = pounds per hour (lb/hr)
lb/hr 6 = gallons per hour (gph)
gph x 1.15 = minimum gph
So let's think big here. If you've got a 500hp engine you intend to hit with a 200hp shot:700 2 = 350 lb/hr
350 6 = 58.3 gph
58.3 x 1.15 = 67.05 minimum gph
The BG220 pump shown here flows more than 220 gph, more than enough to handle the job.